Initial import

1 files changed, 4731 insertions, 0 deletions

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
new file mode 100644
index 000000000..f55c3f35b
--- /dev/null
+++ b/drivers/md/raid10.c
@@ -0,0 +1,4731 @@
+/*
+ * raid10.c : Multiple Devices driver for Linux
+ *
+ * Copyright (C) 2000-2004 Neil Brown
+ *
+ * RAID-10 support for md.
+ *
+ * Base on code in raid1.c.  See raid1.c for further copyright information.
+ *
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * You should have received a copy of the GNU General Public License
+ * (for example /usr/src/linux/COPYING); if not, write to the Free
+ * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/blkdev.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/ratelimit.h>
+#include <linux/kthread.h>
+#include "md.h"
+#include "raid10.h"
+#include "raid0.h"
+#include "bitmap.h"
+
+/*
+ * RAID10 provides a combination of RAID0 and RAID1 functionality.
+ * The layout of data is defined by
+ *    chunk_size
+ *    raid_disks
+ *    near_copies (stored in low byte of layout)
+ *    far_copies (stored in second byte of layout)
+ *    far_offset (stored in bit 16 of layout )
+ *    use_far_sets (stored in bit 17 of layout )
+ *
+ * The data to be stored is divided into chunks using chunksize.  Each device
+ * is divided into far_copies sections.   In each section, chunks are laid out
+ * in a style similar to raid0, but near_copies copies of each chunk is stored
+ * (each on a different drive).  The starting device for each section is offset
+ * near_copies from the starting device of the previous section.  Thus there
+ * are (near_copies * far_copies) of each chunk, and each is on a different
+ * drive.  near_copies and far_copies must be at least one, and their product
+ * is at most raid_disks.
+ *
+ * If far_offset is true, then the far_copies are handled a bit differently.
+ * The copies are still in different stripes, but instead of being very far
+ * apart on disk, there are adjacent stripes.
+ *
+ * The far and offset algorithms are handled slightly differently if
+ * 'use_far_sets' is true.  In this case, the array's devices are grouped into
+ * sets that are (near_copies * far_copies) in size.  The far copied stripes
+ * are still shifted by 'near_copies' devices, but this shifting stays confined
+ * to the set rather than the entire array.  This is done to improve the number
+ * of device combinations that can fail without causing the array to fail.
+ * Example 'far' algorithm w/o 'use_far_sets' (each letter represents a chunk
+ * on a device):
+ *    A B C D    A B C D E
+ *      ...         ...
+ *    D A B C    E A B C D
+ * Example 'far' algorithm w/ 'use_far_sets' enabled (sets illustrated w/ []'s):
+ *    [A B] [C D]    [A B] [C D E]
+ *    |...| |...|    |...| | ... |
+ *    [B A] [D C]    [B A] [E C D]
+ */
+
+/*
+ * Number of guaranteed r10bios in case of extreme VM load:
+ */
+#define	NR_RAID10_BIOS 256
+
+/* when we get a read error on a read-only array, we redirect to another
+ * device without failing the first device, or trying to over-write to
+ * correct the read error.  To keep track of bad blocks on a per-bio
+ * level, we store IO_BLOCKED in the appropriate 'bios' pointer
+ */
+#define IO_BLOCKED ((struct bio *)1)
+/* When we successfully write to a known bad-block, we need to remove the
+ * bad-block marking which must be done from process context.  So we record
+ * the success by setting devs[n].bio to IO_MADE_GOOD
+ */
+#define IO_MADE_GOOD ((struct bio *)2)
+
+#define BIO_SPECIAL(bio) ((unsigned long)bio <= 2)
+
+/* When there are this many requests queued to be written by
+ * the raid10 thread, we become 'congested' to provide back-pressure
+ * for writeback.
+ */
+static int max_queued_requests = 1024;
+
+static void allow_barrier(struct r10conf *conf);
+static void lower_barrier(struct r10conf *conf);
+static int _enough(struct r10conf *conf, int previous, int ignore);
+static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
+				int *skipped);
+static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio);
+static void end_reshape_write(struct bio *bio, int error);
+static void end_reshape(struct r10conf *conf);
+
+static void * r10bio_pool_alloc(gfp_t gfp_flags, void *data)
+{
+	struct r10conf *conf = data;
+	int size = offsetof(struct r10bio, devs[conf->copies]);
+
+	/* allocate a r10bio with room for raid_disks entries in the
+	 * bios array */
+	return kzalloc(size, gfp_flags);
+}
+
+static void r10bio_pool_free(void *r10_bio, void *data)
+{
+	kfree(r10_bio);
+}
+
+/* Maximum size of each resync request */
+#define RESYNC_BLOCK_SIZE (64*1024)
+#define RESYNC_PAGES ((RESYNC_BLOCK_SIZE + PAGE_SIZE-1) / PAGE_SIZE)
+/* amount of memory to reserve for resync requests */
+#define RESYNC_WINDOW (1024*1024)
+/* maximum number of concurrent requests, memory permitting */
+#define RESYNC_DEPTH (32*1024*1024/RESYNC_BLOCK_SIZE)
+
+/*
+ * When performing a resync, we need to read and compare, so
+ * we need as many pages are there are copies.
+ * When performing a recovery, we need 2 bios, one for read,
+ * one for write (we recover only one drive per r10buf)
+ *
+ */
+static void * r10buf_pool_alloc(gfp_t gfp_flags, void *data)
+{
+	struct r10conf *conf = data;
+	struct page *page;
+	struct r10bio *r10_bio;
+	struct bio *bio;
+	int i, j;
+	int nalloc;
+
+	r10_bio = r10bio_pool_alloc(gfp_flags, conf);
+	if (!r10_bio)
+		return NULL;
+
+	if (test_bit(MD_RECOVERY_SYNC, &conf->mddev->recovery) ||
+	    test_bit(MD_RECOVERY_RESHAPE, &conf->mddev->recovery))
+		nalloc = conf->copies; /* resync */
+	else
+		nalloc = 2; /* recovery */
+
+	/*
+	 * Allocate bios.
+	 */
+	for (j = nalloc ; j-- ; ) {
+		bio = bio_kmalloc(gfp_flags, RESYNC_PAGES);
+		if (!bio)
+			goto out_free_bio;
+		r10_bio->devs[j].bio = bio;
+		if (!conf->have_replacement)
+			continue;
+		bio = bio_kmalloc(gfp_flags, RESYNC_PAGES);
+		if (!bio)
+			goto out_free_bio;
+		r10_bio->devs[j].repl_bio = bio;
+	}
+	/*
+	 * Allocate RESYNC_PAGES data pages and attach them
+	 * where needed.
+	 */
+	for (j = 0 ; j < nalloc; j++) {
+		struct bio *rbio = r10_bio->devs[j].repl_bio;
+		bio = r10_bio->devs[j].bio;
+		for (i = 0; i < RESYNC_PAGES; i++) {
+			if (j > 0 && !test_bit(MD_RECOVERY_SYNC,
+					       &conf->mddev->recovery)) {
+				/* we can share bv_page's during recovery
+				 * and reshape */
+				struct bio *rbio = r10_bio->devs[0].bio;
+				page = rbio->bi_io_vec[i].bv_page;
+				get_page(page);
+			} else
+				page = alloc_page(gfp_flags);
+			if (unlikely(!page))
+				goto out_free_pages;
+
+			bio->bi_io_vec[i].bv_page = page;
+			if (rbio)
+				rbio->bi_io_vec[i].bv_page = page;
+		}
+	}
+
+	return r10_bio;
+
+out_free_pages:
+	for ( ; i > 0 ; i--)
+		safe_put_page(bio->bi_io_vec[i-1].bv_page);
+	while (j--)
+		for (i = 0; i < RESYNC_PAGES ; i++)
+			safe_put_page(r10_bio->devs[j].bio->bi_io_vec[i].bv_page);
+	j = 0;
+out_free_bio:
+	for ( ; j < nalloc; j++) {
+		if (r10_bio->devs[j].bio)
+			bio_put(r10_bio->devs[j].bio);
+		if (r10_bio->devs[j].repl_bio)
+			bio_put(r10_bio->devs[j].repl_bio);
+	}
+	r10bio_pool_free(r10_bio, conf);
+	return NULL;
+}
+
+static void r10buf_pool_free(void *__r10_bio, void *data)
+{
+	int i;
+	struct r10conf *conf = data;
+	struct r10bio *r10bio = __r10_bio;
+	int j;
+
+	for (j=0; j < conf->copies; j++) {
+		struct bio *bio = r10bio->devs[j].bio;
+		if (bio) {
+			for (i = 0; i < RESYNC_PAGES; i++) {
+				safe_put_page(bio->bi_io_vec[i].bv_page);
+				bio->bi_io_vec[i].bv_page = NULL;
+			}
+			bio_put(bio);
+		}
+		bio = r10bio->devs[j].repl_bio;
+		if (bio)
+			bio_put(bio);
+	}
+	r10bio_pool_free(r10bio, conf);
+}
+
+static void put_all_bios(struct r10conf *conf, struct r10bio *r10_bio)
+{
+	int i;
+
+	for (i = 0; i < conf->copies; i++) {
+		struct bio **bio = & r10_bio->devs[i].bio;
+		if (!BIO_SPECIAL(*bio))
+			bio_put(*bio);
+		*bio = NULL;
+		bio = &r10_bio->devs[i].repl_bio;
+		if (r10_bio->read_slot < 0 && !BIO_SPECIAL(*bio))
+			bio_put(*bio);
+		*bio = NULL;
+	}
+}
+
+static void free_r10bio(struct r10bio *r10_bio)
+{
+	struct r10conf *conf = r10_bio->mddev->private;
+
+	put_all_bios(conf, r10_bio);
+	mempool_free(r10_bio, conf->r10bio_pool);
+}
+
+static void put_buf(struct r10bio *r10_bio)
+{
+	struct r10conf *conf = r10_bio->mddev->private;
+
+	mempool_free(r10_bio, conf->r10buf_pool);
+
+	lower_barrier(conf);
+}
+
+static void reschedule_retry(struct r10bio *r10_bio)
+{
+	unsigned long flags;
+	struct mddev *mddev = r10_bio->mddev;
+	struct r10conf *conf = mddev->private;
+
+	spin_lock_irqsave(&conf->device_lock, flags);
+	list_add(&r10_bio->retry_list, &conf->retry_list);
+	conf->nr_queued ++;
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+
+	/* wake up frozen array... */
+	wake_up(&conf->wait_barrier);
+
+	md_wakeup_thread(mddev->thread);
+}
+
+/*
+ * raid_end_bio_io() is called when we have finished servicing a mirrored
+ * operation and are ready to return a success/failure code to the buffer
+ * cache layer.
+ */
+static void raid_end_bio_io(struct r10bio *r10_bio)
+{
+	struct bio *bio = r10_bio->master_bio;
+	int done;
+	struct r10conf *conf = r10_bio->mddev->private;
+
+	if (bio->bi_phys_segments) {
+		unsigned long flags;
+		spin_lock_irqsave(&conf->device_lock, flags);
+		bio->bi_phys_segments--;
+		done = (bio->bi_phys_segments == 0);
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+	} else
+		done = 1;
+	if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
+		clear_bit(BIO_UPTODATE, &bio->bi_flags);
+	if (done) {
+		bio_endio(bio, 0);
+		/*
+		 * Wake up any possible resync thread that waits for the device
+		 * to go idle.
+		 */
+		allow_barrier(conf);
+	}
+	free_r10bio(r10_bio);
+}
+
+/*
+ * Update disk head position estimator based on IRQ completion info.
+ */
+static inline void update_head_pos(int slot, struct r10bio *r10_bio)
+{
+	struct r10conf *conf = r10_bio->mddev->private;
+
+	conf->mirrors[r10_bio->devs[slot].devnum].head_position =
+		r10_bio->devs[slot].addr + (r10_bio->sectors);
+}
+
+/*
+ * Find the disk number which triggered given bio
+ */
+static int find_bio_disk(struct r10conf *conf, struct r10bio *r10_bio,
+			 struct bio *bio, int *slotp, int *replp)
+{
+	int slot;
+	int repl = 0;
+
+	for (slot = 0; slot < conf->copies; slot++) {
+		if (r10_bio->devs[slot].bio == bio)
+			break;
+		if (r10_bio->devs[slot].repl_bio == bio) {
+			repl = 1;
+			break;
+		}
+	}
+
+	BUG_ON(slot == conf->copies);
+	update_head_pos(slot, r10_bio);
+
+	if (slotp)
+		*slotp = slot;
+	if (replp)
+		*replp = repl;
+	return r10_bio->devs[slot].devnum;
+}
+
+static void raid10_end_read_request(struct bio *bio, int error)
+{
+	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct r10bio *r10_bio = bio->bi_private;
+	int slot, dev;
+	struct md_rdev *rdev;
+	struct r10conf *conf = r10_bio->mddev->private;
+
+	slot = r10_bio->read_slot;
+	dev = r10_bio->devs[slot].devnum;
+	rdev = r10_bio->devs[slot].rdev;
+	/*
+	 * this branch is our 'one mirror IO has finished' event handler:
+	 */
+	update_head_pos(slot, r10_bio);
+
+	if (uptodate) {
+		/*
+		 * Set R10BIO_Uptodate in our master bio, so that
+		 * we will return a good error code to the higher
+		 * levels even if IO on some other mirrored buffer fails.
+		 *
+		 * The 'master' represents the composite IO operation to
+		 * user-side. So if something waits for IO, then it will
+		 * wait for the 'master' bio.
+		 */
+		set_bit(R10BIO_Uptodate, &r10_bio->state);
+	} else {
+		/* If all other devices that store this block have
+		 * failed, we want to return the error upwards rather
+		 * than fail the last device.  Here we redefine
+		 * "uptodate" to mean "Don't want to retry"
+		 */
+		if (!_enough(conf, test_bit(R10BIO_Previous, &r10_bio->state),
+			     rdev->raid_disk))
+			uptodate = 1;
+	}
+	if (uptodate) {
+		raid_end_bio_io(r10_bio);
+		rdev_dec_pending(rdev, conf->mddev);
+	} else {
+		/*
+		 * oops, read error - keep the refcount on the rdev
+		 */
+		char b[BDEVNAME_SIZE];
+		printk_ratelimited(KERN_ERR
+				   "md/raid10:%s: %s: rescheduling sector %llu\n",
+				   mdname(conf->mddev),
+				   bdevname(rdev->bdev, b),
+				   (unsigned long long)r10_bio->sector);
+		set_bit(R10BIO_ReadError, &r10_bio->state);
+		reschedule_retry(r10_bio);
+	}
+}
+
+static void close_write(struct r10bio *r10_bio)
+{
+	/* clear the bitmap if all writes complete successfully */
+	bitmap_endwrite(r10_bio->mddev->bitmap, r10_bio->sector,
+			r10_bio->sectors,
+			!test_bit(R10BIO_Degraded, &r10_bio->state),
+			0);
+	md_write_end(r10_bio->mddev);
+}
+
+static void one_write_done(struct r10bio *r10_bio)
+{
+	if (atomic_dec_and_test(&r10_bio->remaining)) {
+		if (test_bit(R10BIO_WriteError, &r10_bio->state))
+			reschedule_retry(r10_bio);
+		else {
+			close_write(r10_bio);
+			if (test_bit(R10BIO_MadeGood, &r10_bio->state))
+				reschedule_retry(r10_bio);
+			else
+				raid_end_bio_io(r10_bio);
+		}
+	}
+}
+
+static void raid10_end_write_request(struct bio *bio, int error)
+{
+	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct r10bio *r10_bio = bio->bi_private;
+	int dev;
+	int dec_rdev = 1;
+	struct r10conf *conf = r10_bio->mddev->private;
+	int slot, repl;
+	struct md_rdev *rdev = NULL;
+
+	dev = find_bio_disk(conf, r10_bio, bio, &slot, &repl);
+
+	if (repl)
+		rdev = conf->mirrors[dev].replacement;
+	if (!rdev) {
+		smp_rmb();
+		repl = 0;
+		rdev = conf->mirrors[dev].rdev;
+	}
+	/*
+	 * this branch is our 'one mirror IO has finished' event handler:
+	 */
+	if (!uptodate) {
+		if (repl)
+			/* Never record new bad blocks to replacement,
+			 * just fail it.
+			 */
+			md_error(rdev->mddev, rdev);
+		else {
+			set_bit(WriteErrorSeen,	&rdev->flags);
+			if (!test_and_set_bit(WantReplacement, &rdev->flags))
+				set_bit(MD_RECOVERY_NEEDED,
+					&rdev->mddev->recovery);
+			set_bit(R10BIO_WriteError, &r10_bio->state);
+			dec_rdev = 0;
+		}
+	} else {
+		/*
+		 * Set R10BIO_Uptodate in our master bio, so that
+		 * we will return a good error code for to the higher
+		 * levels even if IO on some other mirrored buffer fails.
+		 *
+		 * The 'master' represents the composite IO operation to
+		 * user-side. So if something waits for IO, then it will
+		 * wait for the 'master' bio.
+		 */
+		sector_t first_bad;
+		int bad_sectors;
+
+		/*
+		 * Do not set R10BIO_Uptodate if the current device is
+		 * rebuilding or Faulty. This is because we cannot use
+		 * such device for properly reading the data back (we could
+		 * potentially use it, if the current write would have felt
+		 * before rdev->recovery_offset, but for simplicity we don't
+		 * check this here.
+		 */
+		if (test_bit(In_sync, &rdev->flags) &&
+		    !test_bit(Faulty, &rdev->flags))
+			set_bit(R10BIO_Uptodate, &r10_bio->state);
+
+		/* Maybe we can clear some bad blocks. */
+		if (is_badblock(rdev,
+				r10_bio->devs[slot].addr,
+				r10_bio->sectors,
+				&first_bad, &bad_sectors)) {
+			bio_put(bio);
+			if (repl)
+				r10_bio->devs[slot].repl_bio = IO_MADE_GOOD;
+			else
+				r10_bio->devs[slot].bio = IO_MADE_GOOD;
+			dec_rdev = 0;
+			set_bit(R10BIO_MadeGood, &r10_bio->state);
+		}
+	}
+
+	/*
+	 *
+	 * Let's see if all mirrored write operations have finished
+	 * already.
+	 */
+	one_write_done(r10_bio);
+	if (dec_rdev)
+		rdev_dec_pending(rdev, conf->mddev);
+}
+
+/*
+ * RAID10 layout manager
+ * As well as the chunksize and raid_disks count, there are two
+ * parameters: near_copies and far_copies.
+ * near_copies * far_copies must be <= raid_disks.
+ * Normally one of these will be 1.
+ * If both are 1, we get raid0.
+ * If near_copies == raid_disks, we get raid1.
+ *
+ * Chunks are laid out in raid0 style with near_copies copies of the
+ * first chunk, followed by near_copies copies of the next chunk and
+ * so on.
+ * If far_copies > 1, then after 1/far_copies of the array has been assigned
+ * as described above, we start again with a device offset of near_copies.
+ * So we effectively have another copy of the whole array further down all
+ * the drives, but with blocks on different drives.
+ * With this layout, and block is never stored twice on the one device.
+ *
+ * raid10_find_phys finds the sector offset of a given virtual sector
+ * on each device that it is on.
+ *
+ * raid10_find_virt does the reverse mapping, from a device and a
+ * sector offset to a virtual address
+ */
+
+static void __raid10_find_phys(struct geom *geo, struct r10bio *r10bio)
+{
+	int n,f;
+	sector_t sector;
+	sector_t chunk;
+	sector_t stripe;
+	int dev;
+	int slot = 0;
+	int last_far_set_start, last_far_set_size;
+
+	last_far_set_start = (geo->raid_disks / geo->far_set_size) - 1;
+	last_far_set_start *= geo->far_set_size;
+
+	last_far_set_size = geo->far_set_size;
+	last_far_set_size += (geo->raid_disks % geo->far_set_size);
+
+	/* now calculate first sector/dev */
+	chunk = r10bio->sector >> geo->chunk_shift;
+	sector = r10bio->sector & geo->chunk_mask;
+
+	chunk *= geo->near_copies;
+	stripe = chunk;
+	dev = sector_div(stripe, geo->raid_disks);
+	if (geo->far_offset)
+		stripe *= geo->far_copies;
+
+	sector += stripe << geo->chunk_shift;
+
+	/* and calculate all the others */
+	for (n = 0; n < geo->near_copies; n++) {
+		int d = dev;
+		int set;
+		sector_t s = sector;
+		r10bio->devs[slot].devnum = d;
+		r10bio->devs[slot].addr = s;
+		slot++;
+
+		for (f = 1; f < geo->far_copies; f++) {
+			set = d / geo->far_set_size;
+			d += geo->near_copies;
+
+			if ((geo->raid_disks % geo->far_set_size) &&
+			    (d > last_far_set_start)) {
+				d -= last_far_set_start;
+				d %= last_far_set_size;
+				d += last_far_set_start;
+			} else {
+				d %= geo->far_set_size;
+				d += geo->far_set_size * set;
+			}
+			s += geo->stride;
+			r10bio->devs[slot].devnum = d;
+			r10bio->devs[slot].addr = s;
+			slot++;
+		}
+		dev++;
+		if (dev >= geo->raid_disks) {
+			dev = 0;
+			sector += (geo->chunk_mask + 1);
+		}
+	}
+}
+
+static void raid10_find_phys(struct r10conf *conf, struct r10bio *r10bio)
+{
+	struct geom *geo = &conf->geo;
+
+	if (conf->reshape_progress != MaxSector &&
+	    ((r10bio->sector >= conf->reshape_progress) !=
+	     conf->mddev->reshape_backwards)) {
+		set_bit(R10BIO_Previous, &r10bio->state);
+		geo = &conf->prev;
+	} else
+		clear_bit(R10BIO_Previous, &r10bio->state);
+
+	__raid10_find_phys(geo, r10bio);
+}
+
+static sector_t raid10_find_virt(struct r10conf *conf, sector_t sector, int dev)
+{
+	sector_t offset, chunk, vchunk;
+	/* Never use conf->prev as this is only called during resync
+	 * or recovery, so reshape isn't happening
+	 */
+	struct geom *geo = &conf->geo;
+	int far_set_start = (dev / geo->far_set_size) * geo->far_set_size;
+	int far_set_size = geo->far_set_size;
+	int last_far_set_start;
+
+	if (geo->raid_disks % geo->far_set_size) {
+		last_far_set_start = (geo->raid_disks / geo->far_set_size) - 1;
+		last_far_set_start *= geo->far_set_size;
+
+		if (dev >= last_far_set_start) {
+			far_set_size = geo->far_set_size;
+			far_set_size += (geo->raid_disks % geo->far_set_size);
+			far_set_start = last_far_set_start;
+		}
+	}
+
+	offset = sector & geo->chunk_mask;
+	if (geo->far_offset) {
+		int fc;
+		chunk = sector >> geo->chunk_shift;
+		fc = sector_div(chunk, geo->far_copies);
+		dev -= fc * geo->near_copies;
+		if (dev < far_set_start)
+			dev += far_set_size;
+	} else {
+		while (sector >= geo->stride) {
+			sector -= geo->stride;
+			if (dev < (geo->near_copies + far_set_start))
+				dev += far_set_size - geo->near_copies;
+			else
+				dev -= geo->near_copies;
+		}
+		chunk = sector >> geo->chunk_shift;
+	}
+	vchunk = chunk * geo->raid_disks + dev;
+	sector_div(vchunk, geo->near_copies);
+	return (vchunk << geo->chunk_shift) + offset;
+}
+
+/**
+ *	raid10_mergeable_bvec -- tell bio layer if a two requests can be merged
+ *	@mddev: the md device
+ *	@bvm: properties of new bio
+ *	@biovec: the request that could be merged to it.
+ *
+ *	Return amount of bytes we can accept at this offset
+ *	This requires checking for end-of-chunk if near_copies != raid_disks,
+ *	and for subordinate merge_bvec_fns if merge_check_needed.
+ */
+static int raid10_mergeable_bvec(struct mddev *mddev,
+				 struct bvec_merge_data *bvm,
+				 struct bio_vec *biovec)
+{
+	struct r10conf *conf = mddev->private;
+	sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
+	int max;
+	unsigned int chunk_sectors;
+	unsigned int bio_sectors = bvm->bi_size >> 9;
+	struct geom *geo = &conf->geo;
+
+	chunk_sectors = (conf->geo.chunk_mask & conf->prev.chunk_mask) + 1;
+	if (conf->reshape_progress != MaxSector &&
+	    ((sector >= conf->reshape_progress) !=
+	     conf->mddev->reshape_backwards))
+		geo = &conf->prev;
+
+	if (geo->near_copies < geo->raid_disks) {
+		max = (chunk_sectors - ((sector & (chunk_sectors - 1))
+					+ bio_sectors)) << 9;
+		if (max < 0)
+			/* bio_add cannot handle a negative return */
+			max = 0;
+		if (max <= biovec->bv_len && bio_sectors == 0)
+			return biovec->bv_len;
+	} else
+		max = biovec->bv_len;
+
+	if (mddev->merge_check_needed) {
+		struct {
+			struct r10bio r10_bio;
+			struct r10dev devs[conf->copies];
+		} on_stack;
+		struct r10bio *r10_bio = &on_stack.r10_bio;
+		int s;
+		if (conf->reshape_progress != MaxSector) {
+			/* Cannot give any guidance during reshape */
+			if (max <= biovec->bv_len && bio_sectors == 0)
+				return biovec->bv_len;
+			return 0;
+		}
+		r10_bio->sector = sector;
+		raid10_find_phys(conf, r10_bio);
+		rcu_read_lock();
+		for (s = 0; s < conf->copies; s++) {
+			int disk = r10_bio->devs[s].devnum;
+			struct md_rdev *rdev = rcu_dereference(
+				conf->mirrors[disk].rdev);
+			if (rdev && !test_bit(Faulty, &rdev->flags)) {
+				struct request_queue *q =
+					bdev_get_queue(rdev->bdev);
+				if (q->merge_bvec_fn) {
+					bvm->bi_sector = r10_bio->devs[s].addr
+						+ rdev->data_offset;
+					bvm->bi_bdev = rdev->bdev;
+					max = min(max, q->merge_bvec_fn(
+							  q, bvm, biovec));
+				}
+			}
+			rdev = rcu_dereference(conf->mirrors[disk].replacement);
+			if (rdev && !test_bit(Faulty, &rdev->flags)) {
+				struct request_queue *q =
+					bdev_get_queue(rdev->bdev);
+				if (q->merge_bvec_fn) {
+					bvm->bi_sector = r10_bio->devs[s].addr
+						+ rdev->data_offset;
+					bvm->bi_bdev = rdev->bdev;
+					max = min(max, q->merge_bvec_fn(
+							  q, bvm, biovec));
+				}
+			}
+		}
+		rcu_read_unlock();
+	}
+	return max;
+}
+
+/*
+ * This routine returns the disk from which the requested read should
+ * be done. There is a per-array 'next expected sequential IO' sector
+ * number - if this matches on the next IO then we use the last disk.
+ * There is also a per-disk 'last know head position' sector that is
+ * maintained from IRQ contexts, both the normal and the resync IO
+ * completion handlers update this position correctly. If there is no
+ * perfect sequential match then we pick the disk whose head is closest.
+ *
+ * If there are 2 mirrors in the same 2 devices, performance degrades
+ * because position is mirror, not device based.
+ *
+ * The rdev for the device selected will have nr_pending incremented.
+ */
+
+/*
+ * FIXME: possibly should rethink readbalancing and do it differently
+ * depending on near_copies / far_copies geometry.
+ */
+static struct md_rdev *read_balance(struct r10conf *conf,
+				    struct r10bio *r10_bio,
+				    int *max_sectors)
+{
+	const sector_t this_sector = r10_bio->sector;
+	int disk, slot;
+	int sectors = r10_bio->sectors;
+	int best_good_sectors;
+	sector_t new_distance, best_dist;
+	struct md_rdev *best_rdev, *rdev = NULL;
+	int do_balance;
+	int best_slot;
+	struct geom *geo = &conf->geo;
+
+	raid10_find_phys(conf, r10_bio);
+	rcu_read_lock();
+retry:
+	sectors = r10_bio->sectors;
+	best_slot = -1;
+	best_rdev = NULL;
+	best_dist = MaxSector;
+	best_good_sectors = 0;
+	do_balance = 1;
+	/*
+	 * Check if we can balance. We can balance on the whole
+	 * device if no resync is going on (recovery is ok), or below
+	 * the resync window. We take the first readable disk when
+	 * above the resync window.
+	 */
+	if (conf->mddev->recovery_cp < MaxSector
+	    && (this_sector + sectors >= conf->next_resync))
+		do_balance = 0;
+
+	for (slot = 0; slot < conf->copies ; slot++) {
+		sector_t first_bad;
+		int bad_sectors;
+		sector_t dev_sector;
+
+		if (r10_bio->devs[slot].bio == IO_BLOCKED)
+			continue;
+		disk = r10_bio->devs[slot].devnum;
+		rdev = rcu_dereference(conf->mirrors[disk].replacement);
+		if (rdev == NULL || test_bit(Faulty, &rdev->flags) ||
+		    test_bit(Unmerged, &rdev->flags) ||
+		    r10_bio->devs[slot].addr + sectors > rdev->recovery_offset)
+			rdev = rcu_dereference(conf->mirrors[disk].rdev);
+		if (rdev == NULL ||
+		    test_bit(Faulty, &rdev->flags) ||
+		    test_bit(Unmerged, &rdev->flags))
+			continue;
+		if (!test_bit(In_sync, &rdev->flags) &&
+		    r10_bio->devs[slot].addr + sectors > rdev->recovery_offset)
+			continue;
+
+		dev_sector = r10_bio->devs[slot].addr;
+		if (is_badblock(rdev, dev_sector, sectors,
+				&first_bad, &bad_sectors)) {
+			if (best_dist < MaxSector)
+				/* Already have a better slot */
+				continue;
+			if (first_bad <= dev_sector) {
+				/* Cannot read here.  If this is the
+				 * 'primary' device, then we must not read
+				 * beyond 'bad_sectors' from another device.
+				 */
+				bad_sectors -= (dev_sector - first_bad);
+				if (!do_balance && sectors > bad_sectors)
+					sectors = bad_sectors;
+				if (best_good_sectors > sectors)
+					best_good_sectors = sectors;
+			} else {
+				sector_t good_sectors =
+					first_bad - dev_sector;
+				if (good_sectors > best_good_sectors) {
+					best_good_sectors = good_sectors;
+					best_slot = slot;
+					best_rdev = rdev;
+				}
+				if (!do_balance)
+					/* Must read from here */
+					break;
+			}
+			continue;
+		} else
+			best_good_sectors = sectors;
+
+		if (!do_balance)
+			break;
+
+		/* This optimisation is debatable, and completely destroys
+		 * sequential read speed for 'far copies' arrays.  So only
+		 * keep it for 'near' arrays, and review those later.
+		 */
+		if (geo->near_copies > 1 && !atomic_read(&rdev->nr_pending))
+			break;
+
+		/* for far > 1 always use the lowest address */
+		if (geo->far_copies > 1)
+			new_distance = r10_bio->devs[slot].addr;
+		else
+			new_distance = abs(r10_bio->devs[slot].addr -
+					   conf->mirrors[disk].head_position);
+		if (new_distance < best_dist) {
+			best_dist = new_distance;
+			best_slot = slot;
+			best_rdev = rdev;
+		}
+	}
+	if (slot >= conf->copies) {
+		slot = best_slot;
+		rdev = best_rdev;
+	}
+
+	if (slot >= 0) {
+		atomic_inc(&rdev->nr_pending);
+		if (test_bit(Faulty, &rdev->flags)) {
+			/* Cannot risk returning a device that failed
+			 * before we inc'ed nr_pending
+			 */
+			rdev_dec_pending(rdev, conf->mddev);
+			goto retry;
+		}
+		r10_bio->read_slot = slot;
+	} else
+		rdev = NULL;
+	rcu_read_unlock();
+	*max_sectors = best_good_sectors;
+
+	return rdev;
+}
+
+static int raid10_congested(struct mddev *mddev, int bits)
+{
+	struct r10conf *conf = mddev->private;
+	int i, ret = 0;
+
+	if ((bits & (1 << BDI_async_congested)) &&
+	    conf->pending_count >= max_queued_requests)
+		return 1;
+
+	rcu_read_lock();
+	for (i = 0;
+	     (i < conf->geo.raid_disks || i < conf->prev.raid_disks)
+		     && ret == 0;
+	     i++) {
+		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
+		if (rdev && !test_bit(Faulty, &rdev->flags)) {
+			struct request_queue *q = bdev_get_queue(rdev->bdev);
+
+			ret |= bdi_congested(&q->backing_dev_info, bits);
+		}
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
+static void flush_pending_writes(struct r10conf *conf)
+{
+	/* Any writes that have been queued but are awaiting
+	 * bitmap updates get flushed here.
+	 */
+	spin_lock_irq(&conf->device_lock);
+
+	if (conf->pending_bio_list.head) {
+		struct bio *bio;
+		bio = bio_list_get(&conf->pending_bio_list);
+		conf->pending_count = 0;
+		spin_unlock_irq(&conf->device_lock);
+		/* flush any pending bitmap writes to disk
+		 * before proceeding w/ I/O */
+		bitmap_unplug(conf->mddev->bitmap);
+		wake_up(&conf->wait_barrier);
+
+		while (bio) { /* submit pending writes */
+			struct bio *next = bio->bi_next;
+			bio->bi_next = NULL;
+			if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+			    !blk_queue_discard(bdev_get_queue(bio->bi_bdev))))
+				/* Just ignore it */
+				bio_endio(bio, 0);
+			else
+				generic_make_request(bio);
+			bio = next;
+		}
+	} else
+		spin_unlock_irq(&conf->device_lock);
+}
+
+/* Barriers....
+ * Sometimes we need to suspend IO while we do something else,
+ * either some resync/recovery, or reconfigure the array.
+ * To do this we raise a 'barrier'.
+ * The 'barrier' is a counter that can be raised multiple times
+ * to count how many activities are happening which preclude
+ * normal IO.
+ * We can only raise the barrier if there is no pending IO.
+ * i.e. if nr_pending == 0.
+ * We choose only to raise the barrier if no-one is waiting for the
+ * barrier to go down.  This means that as soon as an IO request
+ * is ready, no other operations which require a barrier will start
+ * until the IO request has had a chance.
+ *
+ * So: regular IO calls 'wait_barrier'.  When that returns there
+ *    is no backgroup IO happening,  It must arrange to call
+ *    allow_barrier when it has finished its IO.
+ * backgroup IO calls must call raise_barrier.  Once that returns
+ *    there is no normal IO happeing.  It must arrange to call
+ *    lower_barrier when the particular background IO completes.
+ */
+
+static void raise_barrier(struct r10conf *conf, int force)
+{
+	BUG_ON(force && !conf->barrier);
+	spin_lock_irq(&conf->resync_lock);
+
+	/* Wait until no block IO is waiting (unless 'force') */
+	wait_event_lock_irq(conf->wait_barrier, force || !conf->nr_waiting,
+			    conf->resync_lock);
+
+	/* block any new IO from starting */
+	conf->barrier++;
+
+	/* Now wait for all pending IO to complete */
+	wait_event_lock_irq(conf->wait_barrier,
+			    !conf->nr_pending && conf->barrier < RESYNC_DEPTH,
+			    conf->resync_lock);
+
+	spin_unlock_irq(&conf->resync_lock);
+}
+
+static void lower_barrier(struct r10conf *conf)
+{
+	unsigned long flags;
+	spin_lock_irqsave(&conf->resync_lock, flags);
+	conf->barrier--;
+	spin_unlock_irqrestore(&conf->resync_lock, flags);
+	wake_up(&conf->wait_barrier);
+}
+
+static void wait_barrier(struct r10conf *conf)
+{
+	spin_lock_irq(&conf->resync_lock);
+	if (conf->barrier) {
+		conf->nr_waiting++;
+		/* Wait for the barrier to drop.
+		 * However if there are already pending
+		 * requests (preventing the barrier from
+		 * rising completely), and the
+		 * pre-process bio queue isn't empty,
+		 * then don't wait, as we need to empty
+		 * that queue to get the nr_pending
+		 * count down.
+		 */
+		wait_event_lock_irq(conf->wait_barrier,
+				    !conf->barrier ||
+				    (conf->nr_pending &&
+				     current->bio_list &&
+				     !bio_list_empty(current->bio_list)),
+				    conf->resync_lock);
+		conf->nr_waiting--;
+	}
+	conf->nr_pending++;
+	spin_unlock_irq(&conf->resync_lock);
+}
+
+static void allow_barrier(struct r10conf *conf)
+{
+	unsigned long flags;
+	spin_lock_irqsave(&conf->resync_lock, flags);
+	conf->nr_pending--;
+	spin_unlock_irqrestore(&conf->resync_lock, flags);
+	wake_up(&conf->wait_barrier);
+}
+
+static void freeze_array(struct r10conf *conf, int extra)
+{
+	/* stop syncio and normal IO and wait for everything to
+	 * go quiet.
+	 * We increment barrier and nr_waiting, and then
+	 * wait until nr_pending match nr_queued+extra
+	 * This is called in the context of one normal IO request
+	 * that has failed. Thus any sync request that might be pending
+	 * will be blocked by nr_pending, and we need to wait for
+	 * pending IO requests to complete or be queued for re-try.
+	 * Thus the number queued (nr_queued) plus this request (extra)
+	 * must match the number of pending IOs (nr_pending) before
+	 * we continue.
+	 */
+	spin_lock_irq(&conf->resync_lock);
+	conf->barrier++;
+	conf->nr_waiting++;
+	wait_event_lock_irq_cmd(conf->wait_barrier,
+				conf->nr_pending == conf->nr_queued+extra,
+				conf->resync_lock,
+				flush_pending_writes(conf));
+
+	spin_unlock_irq(&conf->resync_lock);
+}
+
+static void unfreeze_array(struct r10conf *conf)
+{
+	/* reverse the effect of the freeze */
+	spin_lock_irq(&conf->resync_lock);
+	conf->barrier--;
+	conf->nr_waiting--;
+	wake_up(&conf->wait_barrier);
+	spin_unlock_irq(&conf->resync_lock);
+}
+
+static sector_t choose_data_offset(struct r10bio *r10_bio,
+				   struct md_rdev *rdev)
+{
+	if (!test_bit(MD_RECOVERY_RESHAPE, &rdev->mddev->recovery) ||
+	    test_bit(R10BIO_Previous, &r10_bio->state))
+		return rdev->data_offset;
+	else
+		return rdev->new_data_offset;
+}
+
+struct raid10_plug_cb {
+	struct blk_plug_cb	cb;
+	struct bio_list		pending;
+	int			pending_cnt;
+};
+
+static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
+{
+	struct raid10_plug_cb *plug = container_of(cb, struct raid10_plug_cb,
+						   cb);
+	struct mddev *mddev = plug->cb.data;
+	struct r10conf *conf = mddev->private;
+	struct bio *bio;
+
+	if (from_schedule || current->bio_list) {
+		spin_lock_irq(&conf->device_lock);
+		bio_list_merge(&conf->pending_bio_list, &plug->pending);
+		conf->pending_count += plug->pending_cnt;
+		spin_unlock_irq(&conf->device_lock);
+		wake_up(&conf->wait_barrier);
+		md_wakeup_thread(mddev->thread);
+		kfree(plug);
+		return;
+	}
+
+	/* we aren't scheduling, so we can do the write-out directly. */
+	bio = bio_list_get(&plug->pending);
+	bitmap_unplug(mddev->bitmap);
+	wake_up(&conf->wait_barrier);
+
+	while (bio) { /* submit pending writes */
+		struct bio *next = bio->bi_next;
+		bio->bi_next = NULL;
+		if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+		    !blk_queue_discard(bdev_get_queue(bio->bi_bdev))))
+			/* Just ignore it */
+			bio_endio(bio, 0);
+		else
+			generic_make_request(bio);
+		bio = next;
+	}
+	kfree(plug);
+}
+
+static void __make_request(struct mddev *mddev, struct bio *bio)
+{
+	struct r10conf *conf = mddev->private;
+	struct r10bio *r10_bio;
+	struct bio *read_bio;
+	int i;
+	const int rw = bio_data_dir(bio);
+	const unsigned long do_sync = (bio->bi_rw & REQ_SYNC);
+	const unsigned long do_fua = (bio->bi_rw & REQ_FUA);
+	const unsigned long do_discard = (bio->bi_rw
+					  & (REQ_DISCARD | REQ_SECURE));
+	const unsigned long do_same = (bio->bi_rw & REQ_WRITE_SAME);
+	unsigned long flags;
+	struct md_rdev *blocked_rdev;
+	struct blk_plug_cb *cb;
+	struct raid10_plug_cb *plug = NULL;
+	int sectors_handled;
+	int max_sectors;
+	int sectors;
+
+	/*
+	 * Register the new request and wait if the reconstruction
+	 * thread has put up a bar for new requests.
+	 * Continue immediately if no resync is active currently.
+	 */
+	wait_barrier(conf);
+
+	sectors = bio_sectors(bio);
+	while (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
+	    bio->bi_iter.bi_sector < conf->reshape_progress &&
+	    bio->bi_iter.bi_sector + sectors > conf->reshape_progress) {
+		/* IO spans the reshape position.  Need to wait for
+		 * reshape to pass
+		 */
+		allow_barrier(conf);
+		wait_event(conf->wait_barrier,
+			   conf->reshape_progress <= bio->bi_iter.bi_sector ||
+			   conf->reshape_progress >= bio->bi_iter.bi_sector +
+			   sectors);
+		wait_barrier(conf);
+	}
+	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
+	    bio_data_dir(bio) == WRITE &&
+	    (mddev->reshape_backwards
+	     ? (bio->bi_iter.bi_sector < conf->reshape_safe &&
+		bio->bi_iter.bi_sector + sectors > conf->reshape_progress)
+	     : (bio->bi_iter.bi_sector + sectors > conf->reshape_safe &&
+		bio->bi_iter.bi_sector < conf->reshape_progress))) {
+		/* Need to update reshape_position in metadata */
+		mddev->reshape_position = conf->reshape_progress;
+		set_bit(MD_CHANGE_DEVS, &mddev->flags);
+		set_bit(MD_CHANGE_PENDING, &mddev->flags);
+		md_wakeup_thread(mddev->thread);
+		wait_event(mddev->sb_wait,
+			   !test_bit(MD_CHANGE_PENDING, &mddev->flags));
+
+		conf->reshape_safe = mddev->reshape_position;
+	}
+
+	r10_bio = mempool_alloc(conf->r10bio_pool, GFP_NOIO);
+
+	r10_bio->master_bio = bio;
+	r10_bio->sectors = sectors;
+
+	r10_bio->mddev = mddev;
+	r10_bio->sector = bio->bi_iter.bi_sector;
+	r10_bio->state = 0;
+
+	/* We might need to issue multiple reads to different
+	 * devices if there are bad blocks around, so we keep
+	 * track of the number of reads in bio->bi_phys_segments.
+	 * If this is 0, there is only one r10_bio and no locking
+	 * will be needed when the request completes.  If it is
+	 * non-zero, then it is the number of not-completed requests.
+	 */
+	bio->bi_phys_segments = 0;
+	clear_bit(BIO_SEG_VALID, &bio->bi_flags);
+
+	if (rw == READ) {
+		/*
+		 * read balancing logic:
+		 */
+		struct md_rdev *rdev;
+		int slot;
+
+read_again:
+		rdev = read_balance(conf, r10_bio, &max_sectors);
+		if (!rdev) {
+			raid_end_bio_io(r10_bio);
+			return;
+		}
+		slot = r10_bio->read_slot;
+
+		read_bio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+		bio_trim(read_bio, r10_bio->sector - bio->bi_iter.bi_sector,
+			 max_sectors);
+
+		r10_bio->devs[slot].bio = read_bio;
+		r10_bio->devs[slot].rdev = rdev;
+
+		read_bio->bi_iter.bi_sector = r10_bio->devs[slot].addr +
+			choose_data_offset(r10_bio, rdev);
+		read_bio->bi_bdev = rdev->bdev;
+		read_bio->bi_end_io = raid10_end_read_request;
+		read_bio->bi_rw = READ | do_sync;
+		read_bio->bi_private = r10_bio;
+
+		if (max_sectors < r10_bio->sectors) {
+			/* Could not read all from this device, so we will
+			 * need another r10_bio.
+			 */
+			sectors_handled = (r10_bio->sector + max_sectors
+					   - bio->bi_iter.bi_sector);
+			r10_bio->sectors = max_sectors;
+			spin_lock_irq(&conf->device_lock);
+			if (bio->bi_phys_segments == 0)
+				bio->bi_phys_segments = 2;
+			else
+				bio->bi_phys_segments++;
+			spin_unlock_irq(&conf->device_lock);
+			/* Cannot call generic_make_request directly
+			 * as that will be queued in __generic_make_request
+			 * and subsequent mempool_alloc might block
+			 * waiting for it.  so hand bio over to raid10d.
+			 */
+			reschedule_retry(r10_bio);
+
+			r10_bio = mempool_alloc(conf->r10bio_pool, GFP_NOIO);
+
+			r10_bio->master_bio = bio;
+			r10_bio->sectors = bio_sectors(bio) - sectors_handled;
+			r10_bio->state = 0;
+			r10_bio->mddev = mddev;
+			r10_bio->sector = bio->bi_iter.bi_sector +
+				sectors_handled;
+			goto read_again;
+		} else
+			generic_make_request(read_bio);
+		return;
+	}
+
+	/*
+	 * WRITE:
+	 */
+	if (conf->pending_count >= max_queued_requests) {
+		md_wakeup_thread(mddev->thread);
+		wait_event(conf->wait_barrier,
+			   conf->pending_count < max_queued_requests);
+	}
+	/* first select target devices under rcu_lock and
+	 * inc refcount on their rdev.  Record them by setting
+	 * bios[x] to bio
+	 * If there are known/acknowledged bad blocks on any device
+	 * on which we have seen a write error, we want to avoid
+	 * writing to those blocks.  This potentially requires several
+	 * writes to write around the bad blocks.  Each set of writes
+	 * gets its own r10_bio with a set of bios attached.  The number
+	 * of r10_bios is recored in bio->bi_phys_segments just as with
+	 * the read case.
+	 */
+
+	r10_bio->read_slot = -1; /* make sure repl_bio gets freed */
+	raid10_find_phys(conf, r10_bio);
+retry_write:
+	blocked_rdev = NULL;
+	rcu_read_lock();
+	max_sectors = r10_bio->sectors;
+
+	for (i = 0;  i < conf->copies; i++) {
+		int d = r10_bio->devs[i].devnum;
+		struct md_rdev *rdev = rcu_dereference(conf->mirrors[d].rdev);
+		struct md_rdev *rrdev = rcu_dereference(
+			conf->mirrors[d].replacement);
+		if (rdev == rrdev)
+			rrdev = NULL;
+		if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+			atomic_inc(&rdev->nr_pending);
+			blocked_rdev = rdev;
+			break;
+		}
+		if (rrdev && unlikely(test_bit(Blocked, &rrdev->flags))) {
+			atomic_inc(&rrdev->nr_pending);
+			blocked_rdev = rrdev;
+			break;
+		}
+		if (rdev && (test_bit(Faulty, &rdev->flags)
+			     || test_bit(Unmerged, &rdev->flags)))
+			rdev = NULL;
+		if (rrdev && (test_bit(Faulty, &rrdev->flags)
+			      || test_bit(Unmerged, &rrdev->flags)))
+			rrdev = NULL;
+
+		r10_bio->devs[i].bio = NULL;
+		r10_bio->devs[i].repl_bio = NULL;
+
+		if (!rdev && !rrdev) {
+			set_bit(R10BIO_Degraded, &r10_bio->state);
+			continue;
+		}
+		if (rdev && test_bit(WriteErrorSeen, &rdev->flags)) {
+			sector_t first_bad;
+			sector_t dev_sector = r10_bio->devs[i].addr;
+			int bad_sectors;
+			int is_bad;
+
+			is_bad = is_badblock(rdev, dev_sector,
+					     max_sectors,
+					     &first_bad, &bad_sectors);
+			if (is_bad < 0) {
+				/* Mustn't write here until the bad block
+				 * is acknowledged
+				 */
+				atomic_inc(&rdev->nr_pending);
+				set_bit(BlockedBadBlocks, &rdev->flags);
+				blocked_rdev = rdev;
+				break;
+			}
+			if (is_bad && first_bad <= dev_sector) {
+				/* Cannot write here at all */
+				bad_sectors -= (dev_sector - first_bad);
+				if (bad_sectors < max_sectors)
+					/* Mustn't write more than bad_sectors
+					 * to other devices yet
+					 */
+					max_sectors = bad_sectors;
+				/* We don't set R10BIO_Degraded as that
+				 * only applies if the disk is missing,
+				 * so it might be re-added, and we want to
+				 * know to recover this chunk.
+				 * In this case the device is here, and the
+				 * fact that this chunk is not in-sync is
+				 * recorded in the bad block log.
+				 */
+				continue;
+			}
+			if (is_bad) {
+				int good_sectors = first_bad - dev_sector;
+				if (good_sectors < max_sectors)
+					max_sectors = good_sectors;
+			}
+		}
+		if (rdev) {
+			r10_bio->devs[i].bio = bio;
+			atomic_inc(&rdev->nr_pending);
+		}
+		if (rrdev) {
+			r10_bio->devs[i].repl_bio = bio;
+			atomic_inc(&rrdev->nr_pending);
+		}
+	}
+	rcu_read_unlock();
+
+	if (unlikely(blocked_rdev)) {
+		/* Have to wait for this device to get unblocked, then retry */
+		int j;
+		int d;
+
+		for (j = 0; j < i; j++) {
+			if (r10_bio->devs[j].bio) {
+				d = r10_bio->devs[j].devnum;
+				rdev_dec_pending(conf->mirrors[d].rdev, mddev);
+			}
+			if (r10_bio->devs[j].repl_bio) {
+				struct md_rdev *rdev;
+				d = r10_bio->devs[j].devnum;
+				rdev = conf->mirrors[d].replacement;
+				if (!rdev) {
+					/* Race with remove_disk */
+					smp_mb();
+					rdev = conf->mirrors[d].rdev;
+				}
+				rdev_dec_pending(rdev, mddev);
+			}
+		}
+		allow_barrier(conf);
+		md_wait_for_blocked_rdev(blocked_rdev, mddev);
+		wait_barrier(conf);
+		goto retry_write;
+	}
+
+	if (max_sectors < r10_bio->sectors) {
+		/* We are splitting this into multiple parts, so
+		 * we need to prepare for allocating another r10_bio.
+		 */
+		r10_bio->sectors = max_sectors;
+		spin_lock_irq(&conf->device_lock);
+		if (bio->bi_phys_segments == 0)
+			bio->bi_phys_segments = 2;
+		else
+			bio->bi_phys_segments++;
+		spin_unlock_irq(&conf->device_lock);
+	}
+	sectors_handled = r10_bio->sector + max_sectors -
+		bio->bi_iter.bi_sector;
+
+	atomic_set(&r10_bio->remaining, 1);
+	bitmap_startwrite(mddev->bitmap, r10_bio->sector, r10_bio->sectors, 0);
+
+	for (i = 0; i < conf->copies; i++) {
+		struct bio *mbio;
+		int d = r10_bio->devs[i].devnum;
+		if (r10_bio->devs[i].bio) {
+			struct md_rdev *rdev = conf->mirrors[d].rdev;
+			mbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+			bio_trim(mbio, r10_bio->sector - bio->bi_iter.bi_sector,
+				 max_sectors);
+			r10_bio->devs[i].bio = mbio;
+
+			mbio->bi_iter.bi_sector	= (r10_bio->devs[i].addr+
+					   choose_data_offset(r10_bio,
+							      rdev));
+			mbio->bi_bdev = rdev->bdev;
+			mbio->bi_end_io	= raid10_end_write_request;
+			mbio->bi_rw =
+				WRITE | do_sync | do_fua | do_discard | do_same;
+			mbio->bi_private = r10_bio;
+
+			atomic_inc(&r10_bio->remaining);
+
+			cb = blk_check_plugged(raid10_unplug, mddev,
+					       sizeof(*plug));
+			if (cb)
+				plug = container_of(cb, struct raid10_plug_cb,
+						    cb);
+			else
+				plug = NULL;
+			spin_lock_irqsave(&conf->device_lock, flags);
+			if (plug) {
+				bio_list_add(&plug->pending, mbio);
+				plug->pending_cnt++;
+			} else {
+				bio_list_add(&conf->pending_bio_list, mbio);
+				conf->pending_count++;
+			}
+			spin_unlock_irqrestore(&conf->device_lock, flags);
+			if (!plug)
+				md_wakeup_thread(mddev->thread);
+		}
+
+		if (r10_bio->devs[i].repl_bio) {
+			struct md_rdev *rdev = conf->mirrors[d].replacement;
+			if (rdev == NULL) {
+				/* Replacement just got moved to main 'rdev' */
+				smp_mb();
+				rdev = conf->mirrors[d].rdev;
+			}
+			mbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+			bio_trim(mbio, r10_bio->sector - bio->bi_iter.bi_sector,
+				 max_sectors);
+			r10_bio->devs[i].repl_bio = mbio;
+
+			mbio->bi_iter.bi_sector	= (r10_bio->devs[i].addr +
+					   choose_data_offset(
+						   r10_bio, rdev));
+			mbio->bi_bdev = rdev->bdev;
+			mbio->bi_end_io	= raid10_end_write_request;
+			mbio->bi_rw =
+				WRITE | do_sync | do_fua | do_discard | do_same;
+			mbio->bi_private = r10_bio;
+
+			atomic_inc(&r10_bio->remaining);
+			spin_lock_irqsave(&conf->device_lock, flags);
+			bio_list_add(&conf->pending_bio_list, mbio);
+			conf->pending_count++;
+			spin_unlock_irqrestore(&conf->device_lock, flags);
+			if (!mddev_check_plugged(mddev))
+				md_wakeup_thread(mddev->thread);
+		}
+	}
+
+	/* Don't remove the bias on 'remaining' (one_write_done) until
+	 * after checking if we need to go around again.
+	 */
+
+	if (sectors_handled < bio_sectors(bio)) {
+		one_write_done(r10_bio);
+		/* We need another r10_bio.  It has already been counted
+		 * in bio->bi_phys_segments.
+		 */
+		r10_bio = mempool_alloc(conf->r10bio_pool, GFP_NOIO);
+
+		r10_bio->master_bio = bio;
+		r10_bio->sectors = bio_sectors(bio) - sectors_handled;
+
+		r10_bio->mddev = mddev;
+		r10_bio->sector = bio->bi_iter.bi_sector + sectors_handled;
+		r10_bio->state = 0;
+		goto retry_write;
+	}
+	one_write_done(r10_bio);
+}
+
+static void make_request(struct mddev *mddev, struct bio *bio)
+{
+	struct r10conf *conf = mddev->private;
+	sector_t chunk_mask = (conf->geo.chunk_mask & conf->prev.chunk_mask);
+	int chunk_sects = chunk_mask + 1;
+
+	struct bio *split;
+
+	if (unlikely(bio->bi_rw & REQ_FLUSH)) {
+		md_flush_request(mddev, bio);
+		return;
+	}
+
+	md_write_start(mddev, bio);
+
+	do {
+
+		/*
+		 * If this request crosses a chunk boundary, we need to split
+		 * it.
+		 */
+		if (unlikely((bio->bi_iter.bi_sector & chunk_mask) +
+			     bio_sectors(bio) > chunk_sects
+			     && (conf->geo.near_copies < conf->geo.raid_disks
+				 || conf->prev.near_copies <
+				 conf->prev.raid_disks))) {
+			split = bio_split(bio, chunk_sects -
+					  (bio->bi_iter.bi_sector &
+					   (chunk_sects - 1)),
+					  GFP_NOIO, fs_bio_set);
+			bio_chain(split, bio);
+		} else {
+			split = bio;
+		}
+
+		__make_request(mddev, split);
+	} while (split != bio);
+
+	/* In case raid10d snuck in to freeze_array */
+	wake_up(&conf->wait_barrier);
+}
+
+static void status(struct seq_file *seq, struct mddev *mddev)
+{
+	struct r10conf *conf = mddev->private;
+	int i;
+
+	if (conf->geo.near_copies < conf->geo.raid_disks)
+		seq_printf(seq, " %dK chunks", mddev->chunk_sectors / 2);
+	if (conf->geo.near_copies > 1)
+		seq_printf(seq, " %d near-copies", conf->geo.near_copies);
+	if (conf->geo.far_copies > 1) {
+		if (conf->geo.far_offset)
+			seq_printf(seq, " %d offset-copies", conf->geo.far_copies);
+		else
+			seq_printf(seq, " %d far-copies", conf->geo.far_copies);
+	}
+	seq_printf(seq, " [%d/%d] [", conf->geo.raid_disks,
+					conf->geo.raid_disks - mddev->degraded);
+	for (i = 0; i < conf->geo.raid_disks; i++)
+		seq_printf(seq, "%s",
+			      conf->mirrors[i].rdev &&
+			      test_bit(In_sync, &conf->mirrors[i].rdev->flags) ? "U" : "_");
+	seq_printf(seq, "]");
+}
+
+/* check if there are enough drives for
+ * every block to appear on atleast one.
+ * Don't consider the device numbered 'ignore'
+ * as we might be about to remove it.
+ */
+static int _enough(struct r10conf *conf, int previous, int ignore)
+{
+	int first = 0;
+	int has_enough = 0;
+	int disks, ncopies;
+	if (previous) {
+		disks = conf->prev.raid_disks;
+		ncopies = conf->prev.near_copies;
+	} else {
+		disks = conf->geo.raid_disks;
+		ncopies = conf->geo.near_copies;
+	}
+
+	rcu_read_lock();
+	do {
+		int n = conf->copies;
+		int cnt = 0;
+		int this = first;
+		while (n--) {
+			struct md_rdev *rdev;
+			if (this != ignore &&
+			    (rdev = rcu_dereference(conf->mirrors[this].rdev)) &&
+			    test_bit(In_sync, &rdev->flags))
+				cnt++;
+			this = (this+1) % disks;
+		}
+		if (cnt == 0)
+			goto out;
+		first = (first + ncopies) % disks;
+	} while (first != 0);
+	has_enough = 1;
+out:
+	rcu_read_unlock();
+	return has_enough;
+}
+
+static int enough(struct r10conf *conf, int ignore)
+{
+	/* when calling 'enough', both 'prev' and 'geo' must
+	 * be stable.
+	 * This is ensured if ->reconfig_mutex or ->device_lock
+	 * is held.
+	 */
+	return _enough(conf, 0, ignore) &&
+		_enough(conf, 1, ignore);
+}
+
+static void error(struct mddev *mddev, struct md_rdev *rdev)
+{
+	char b[BDEVNAME_SIZE];
+	struct r10conf *conf = mddev->private;
+	unsigned long flags;
+
+	/*
+	 * If it is not operational, then we have already marked it as dead
+	 * else if it is the last working disks, ignore the error, let the
+	 * next level up know.
+	 * else mark the drive as failed
+	 */
+	spin_lock_irqsave(&conf->device_lock, flags);
+	if (test_bit(In_sync, &rdev->flags)
+	    && !enough(conf, rdev->raid_disk)) {
+		/*
+		 * Don't fail the drive, just return an IO error.
+		 */
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+		return;
+	}
+	if (test_and_clear_bit(In_sync, &rdev->flags))
+		mddev->degraded++;
+	/*
+	 * If recovery is running, make sure it aborts.
+	 */
+	set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+	set_bit(Blocked, &rdev->flags);
+	set_bit(Faulty, &rdev->flags);
+	set_bit(MD_CHANGE_DEVS, &mddev->flags);
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+	printk(KERN_ALERT
+	       "md/raid10:%s: Disk failure on %s, disabling device.\n"
+	       "md/raid10:%s: Operation continuing on %d devices.\n",
+	       mdname(mddev), bdevname(rdev->bdev, b),
+	       mdname(mddev), conf->geo.raid_disks - mddev->degraded);
+}
+
+static void print_conf(struct r10conf *conf)
+{
+	int i;
+	struct raid10_info *tmp;
+
+	printk(KERN_DEBUG "RAID10 conf printout:\n");
+	if (!conf) {
+		printk(KERN_DEBUG "(!conf)\n");
+		return;
+	}
+	printk(KERN_DEBUG " --- wd:%d rd:%d\n", conf->geo.raid_disks - conf->mddev->degraded,
+		conf->geo.raid_disks);
+
+	for (i = 0; i < conf->geo.raid_disks; i++) {
+		char b[BDEVNAME_SIZE];
+		tmp = conf->mirrors + i;
+		if (tmp->rdev)
+			printk(KERN_DEBUG " disk %d, wo:%d, o:%d, dev:%s\n",
+				i, !test_bit(In_sync, &tmp->rdev->flags),
+			        !test_bit(Faulty, &tmp->rdev->flags),
+				bdevname(tmp->rdev->bdev,b));
+	}
+}
+
+static void close_sync(struct r10conf *conf)
+{
+	wait_barrier(conf);
+	allow_barrier(conf);
+
+	mempool_destroy(conf->r10buf_pool);
+	conf->r10buf_pool = NULL;
+}
+
+static int raid10_spare_active(struct mddev *mddev)
+{
+	int i;
+	struct r10conf *conf = mddev->private;
+	struct raid10_info *tmp;
+	int count = 0;
+	unsigned long flags;
+
+	/*
+	 * Find all non-in_sync disks within the RAID10 configuration
+	 * and mark them in_sync
+	 */
+	for (i = 0; i < conf->geo.raid_disks; i++) {
+		tmp = conf->mirrors + i;
+		if (tmp->replacement
+		    && tmp->replacement->recovery_offset == MaxSector
+		    && !test_bit(Faulty, &tmp->replacement->flags)
+		    && !test_and_set_bit(In_sync, &tmp->replacement->flags)) {
+			/* Replacement has just become active */
+			if (!tmp->rdev
+			    || !test_and_clear_bit(In_sync, &tmp->rdev->flags))
+				count++;
+			if (tmp->rdev) {
+				/* Replaced device not technically faulty,
+				 * but we need to be sure it gets removed
+				 * and never re-added.
+				 */
+				set_bit(Faulty, &tmp->rdev->flags);
+				sysfs_notify_dirent_safe(
+					tmp->rdev->sysfs_state);
+			}
+			sysfs_notify_dirent_safe(tmp->replacement->sysfs_state);
+		} else if (tmp->rdev
+			   && tmp->rdev->recovery_offset == MaxSector
+			   && !test_bit(Faulty, &tmp->rdev->flags)
+			   && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
+			count++;
+			sysfs_notify_dirent_safe(tmp->rdev->sysfs_state);
+		}
+	}
+	spin_lock_irqsave(&conf->device_lock, flags);
+	mddev->degraded -= count;
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+
+	print_conf(conf);
+	return count;
+}
+
+static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct r10conf *conf = mddev->private;
+	int err = -EEXIST;
+	int mirror;
+	int first = 0;
+	int last = conf->geo.raid_disks - 1;
+	struct request_queue *q = bdev_get_queue(rdev->bdev);
+
+	if (mddev->recovery_cp < MaxSector)
+		/* only hot-add to in-sync arrays, as recovery is
+		 * very different from resync
+		 */
+		return -EBUSY;
+	if (rdev->saved_raid_disk < 0 && !_enough(conf, 1, -1))
+		return -EINVAL;
+
+	if (rdev->raid_disk >= 0)
+		first = last = rdev->raid_disk;
+
+	if (q->merge_bvec_fn) {
+		set_bit(Unmerged, &rdev->flags);
+		mddev->merge_check_needed = 1;
+	}
+
+	if (rdev->saved_raid_disk >= first &&
+	    conf->mirrors[rdev->saved_raid_disk].rdev == NULL)
+		mirror = rdev->saved_raid_disk;
+	else
+		mirror = first;
+	for ( ; mirror <= last ; mirror++) {
+		struct raid10_info *p = &conf->mirrors[mirror];
+		if (p->recovery_disabled == mddev->recovery_disabled)
+			continue;
+		if (p->rdev) {
+			if (!test_bit(WantReplacement, &p->rdev->flags) ||
+			    p->replacement != NULL)
+				continue;
+			clear_bit(In_sync, &rdev->flags);
+			set_bit(Replacement, &rdev->flags);
+			rdev->raid_disk = mirror;
+			err = 0;
+			if (mddev->gendisk)
+				disk_stack_limits(mddev->gendisk, rdev->bdev,
+						  rdev->data_offset << 9);
+			conf->fullsync = 1;
+			rcu_assign_pointer(p->replacement, rdev);
+			break;
+		}
+
+		if (mddev->gendisk)
+			disk_stack_limits(mddev->gendisk, rdev->bdev,
+					  rdev->data_offset << 9);
+
+		p->head_position = 0;
+		p->recovery_disabled = mddev->recovery_disabled - 1;
+		rdev->raid_disk = mirror;
+		err = 0;
+		if (rdev->saved_raid_disk != mirror)
+			conf->fullsync = 1;
+		rcu_assign_pointer(p->rdev, rdev);
+		break;
+	}
+	if (err == 0 && test_bit(Unmerged, &rdev->flags)) {
+		/* Some requests might not have seen this new
+		 * merge_bvec_fn.  We must wait for them to complete
+		 * before merging the device fully.
+		 * First we make sure any code which has tested
+		 * our function has submitted the request, then
+		 * we wait for all outstanding requests to complete.
+		 */
+		synchronize_sched();
+		freeze_array(conf, 0);
+		unfreeze_array(conf);
+		clear_bit(Unmerged, &rdev->flags);
+	}
+	md_integrity_add_rdev(rdev, mddev);
+	if (mddev->queue && blk_queue_discard(bdev_get_queue(rdev->bdev)))
+		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
+	print_conf(conf);
+	return err;
+}
+
+static int raid10_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct r10conf *conf = mddev->private;
+	int err = 0;
+	int number = rdev->raid_disk;
+	struct md_rdev **rdevp;
+	struct raid10_info *p = conf->mirrors + number;
+
+	print_conf(conf);
+	if (rdev == p->rdev)
+		rdevp = &p->rdev;
+	else if (rdev == p->replacement)
+		rdevp = &p->replacement;
+	else
+		return 0;
+
+	if (test_bit(In_sync, &rdev->flags) ||
+	    atomic_read(&rdev->nr_pending)) {
+		err = -EBUSY;
+		goto abort;
+	}
+	/* Only remove faulty devices if recovery
+	 * is not possible.
+	 */
+	if (!test_bit(Faulty, &rdev->flags) &&
+	    mddev->recovery_disabled != p->recovery_disabled &&
+	    (!p->replacement || p->replacement == rdev) &&
+	    number < conf->geo.raid_disks &&
+	    enough(conf, -1)) {
+		err = -EBUSY;
+		goto abort;
+	}
+	*rdevp = NULL;
+	synchronize_rcu();
+	if (atomic_read(&rdev->nr_pending)) {
+		/* lost the race, try later */
+		err = -EBUSY;
+		*rdevp = rdev;
+		goto abort;
+	} else if (p->replacement) {
+		/* We must have just cleared 'rdev' */
+		p->rdev = p->replacement;
+		clear_bit(Replacement, &p->replacement->flags);
+		smp_mb(); /* Make sure other CPUs may see both as identical
+			   * but will never see neither -- if they are careful.
+			   */
+		p->replacement = NULL;
+		clear_bit(WantReplacement, &rdev->flags);
+	} else
+		/* We might have just remove the Replacement as faulty
+		 * Clear the flag just in case
+		 */
+		clear_bit(WantReplacement, &rdev->flags);
+
+	err = md_integrity_register(mddev);
+
+abort:
+
+	print_conf(conf);
+	return err;
+}
+
+static void end_sync_read(struct bio *bio, int error)
+{
+	struct r10bio *r10_bio = bio->bi_private;
+	struct r10conf *conf = r10_bio->mddev->private;
+	int d;
+
+	if (bio == r10_bio->master_bio) {
+		/* this is a reshape read */
+		d = r10_bio->read_slot; /* really the read dev */
+	} else
+		d = find_bio_disk(conf, r10_bio, bio, NULL, NULL);
+
+	if (test_bit(BIO_UPTODATE, &bio->bi_flags))
+		set_bit(R10BIO_Uptodate, &r10_bio->state);
+	else
+		/* The write handler will notice the lack of
+		 * R10BIO_Uptodate and record any errors etc
+		 */
+		atomic_add(r10_bio->sectors,
+			   &conf->mirrors[d].rdev->corrected_errors);
+
+	/* for reconstruct, we always reschedule after a read.
+	 * for resync, only after all reads
+	 */
+	rdev_dec_pending(conf->mirrors[d].rdev, conf->mddev);
+	if (test_bit(R10BIO_IsRecover, &r10_bio->state) ||
+	    atomic_dec_and_test(&r10_bio->remaining)) {
+		/* we have read all the blocks,
+		 * do the comparison in process context in raid10d
+		 */
+		reschedule_retry(r10_bio);
+	}
+}
+
+static void end_sync_request(struct r10bio *r10_bio)
+{
+	struct mddev *mddev = r10_bio->mddev;
+
+	while (atomic_dec_and_test(&r10_bio->remaining)) {
+		if (r10_bio->master_bio == NULL) {
+			/* the primary of several recovery bios */
+			sector_t s = r10_bio->sectors;
+			if (test_bit(R10BIO_MadeGood, &r10_bio->state) ||
+			    test_bit(R10BIO_WriteError, &r10_bio->state))
+				reschedule_retry(r10_bio);
+			else
+				put_buf(r10_bio);
+			md_done_sync(mddev, s, 1);
+			break;
+		} else {
+			struct r10bio *r10_bio2 = (struct r10bio *)r10_bio->master_bio;
+			if (test_bit(R10BIO_MadeGood, &r10_bio->state) ||
+			    test_bit(R10BIO_WriteError, &r10_bio->state))
+				reschedule_retry(r10_bio);
+			else
+				put_buf(r10_bio);
+			r10_bio = r10_bio2;
+		}
+	}
+}
+
+static void end_sync_write(struct bio *bio, int error)
+{
+	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct r10bio *r10_bio = bio->bi_private;
+	struct mddev *mddev = r10_bio->mddev;
+	struct r10conf *conf = mddev->private;
+	int d;
+	sector_t first_bad;
+	int bad_sectors;
+	int slot;
+	int repl;
+	struct md_rdev *rdev = NULL;
+
+	d = find_bio_disk(conf, r10_bio, bio, &slot, &repl);
+	if (repl)
+		rdev = conf->mirrors[d].replacement;
+	else
+		rdev = conf->mirrors[d].rdev;
+
+	if (!uptodate) {
+		if (repl)
+			md_error(mddev, rdev);
+		else {
+			set_bit(WriteErrorSeen, &rdev->flags);
+			if (!test_and_set_bit(WantReplacement, &rdev->flags))
+				set_bit(MD_RECOVERY_NEEDED,
+					&rdev->mddev->recovery);
+			set_bit(R10BIO_WriteError, &r10_bio->state);
+		}
+	} else if (is_badblock(rdev,
+			     r10_bio->devs[slot].addr,
+			     r10_bio->sectors,
+			     &first_bad, &bad_sectors))
+		set_bit(R10BIO_MadeGood, &r10_bio->state);
+
+	rdev_dec_pending(rdev, mddev);
+
+	end_sync_request(r10_bio);
+}
+
+/*
+ * Note: sync and recover and handled very differently for raid10
+ * This code is for resync.
+ * For resync, we read through virtual addresses and read all blocks.
+ * If there is any error, we schedule a write.  The lowest numbered
+ * drive is authoritative.
+ * However requests come for physical address, so we need to map.
+ * For every physical address there are raid_disks/copies virtual addresses,
+ * which is always are least one, but is not necessarly an integer.
+ * This means that a physical address can span multiple chunks, so we may
+ * have to submit multiple io requests for a single sync request.
+ */
+/*
+ * We check if all blocks are in-sync and only write to blocks that
+ * aren't in sync
+ */
+static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
+{
+	struct r10conf *conf = mddev->private;
+	int i, first;
+	struct bio *tbio, *fbio;
+	int vcnt;
+
+	atomic_set(&r10_bio->remaining, 1);
+
+	/* find the first device with a block */
+	for (i=0; i<conf->copies; i++)
+		if (test_bit(BIO_UPTODATE, &r10_bio->devs[i].bio->bi_flags))
+			break;
+
+	if (i == conf->copies)
+		goto done;
+
+	first = i;
+	fbio = r10_bio->devs[i].bio;
+
+	vcnt = (r10_bio->sectors + (PAGE_SIZE >> 9) - 1) >> (PAGE_SHIFT - 9);
+	/* now find blocks with errors */
+	for (i=0 ; i < conf->copies ; i++) {
+		int  j, d;
+
+		tbio = r10_bio->devs[i].bio;
+
+		if (tbio->bi_end_io != end_sync_read)
+			continue;
+		if (i == first)
+			continue;
+		if (test_bit(BIO_UPTODATE, &r10_bio->devs[i].bio->bi_flags)) {
+			/* We know that the bi_io_vec layout is the same for
+			 * both 'first' and 'i', so we just compare them.
+			 * All vec entries are PAGE_SIZE;
+			 */
+			int sectors = r10_bio->sectors;
+			for (j = 0; j < vcnt; j++) {
+				int len = PAGE_SIZE;
+				if (sectors < (len / 512))
+					len = sectors * 512;
+				if (memcmp(page_address(fbio->bi_io_vec[j].bv_page),
+					   page_address(tbio->bi_io_vec[j].bv_page),
+					   len))
+					break;
+				sectors -= len/512;
+			}
+			if (j == vcnt)
+				continue;
+			atomic64_add(r10_bio->sectors, &mddev->resync_mismatches);
+			if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
+				/* Don't fix anything. */
+				continue;
+		}
+		/* Ok, we need to write this bio, either to correct an
+		 * inconsistency or to correct an unreadable block.
+		 * First we need to fixup bv_offset, bv_len and
+		 * bi_vecs, as the read request might have corrupted these
+		 */
+		bio_reset(tbio);
+
+		tbio->bi_vcnt = vcnt;
+		tbio->bi_iter.bi_size = r10_bio->sectors << 9;
+		tbio->bi_rw = WRITE;
+		tbio->bi_private = r10_bio;
+		tbio->bi_iter.bi_sector = r10_bio->devs[i].addr;
+
+		for (j=0; j < vcnt ; j++) {
+			tbio->bi_io_vec[j].bv_offset = 0;
+			tbio->bi_io_vec[j].bv_len = PAGE_SIZE;
+
+			memcpy(page_address(tbio->bi_io_vec[j].bv_page),
+			       page_address(fbio->bi_io_vec[j].bv_page),
+			       PAGE_SIZE);
+		}
+		tbio->bi_end_io = end_sync_write;
+
+		d = r10_bio->devs[i].devnum;
+		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
+		atomic_inc(&r10_bio->remaining);
+		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(tbio));
+
+		tbio->bi_iter.bi_sector += conf->mirrors[d].rdev->data_offset;
+		tbio->bi_bdev = conf->mirrors[d].rdev->bdev;
+		generic_make_request(tbio);
+	}
+
+	/* Now write out to any replacement devices
+	 * that are active
+	 */
+	for (i = 0; i < conf->copies; i++) {
+		int j, d;
+
+		tbio = r10_bio->devs[i].repl_bio;
+		if (!tbio || !tbio->bi_end_io)
+			continue;
+		if (r10_bio->devs[i].bio->bi_end_io != end_sync_write
+		    && r10_bio->devs[i].bio != fbio)
+			for (j = 0; j < vcnt; j++)
+				memcpy(page_address(tbio->bi_io_vec[j].bv_page),
+				       page_address(fbio->bi_io_vec[j].bv_page),
+				       PAGE_SIZE);
+		d = r10_bio->devs[i].devnum;
+		atomic_inc(&r10_bio->remaining);
+		md_sync_acct(conf->mirrors[d].replacement->bdev,
+			     bio_sectors(tbio));
+		generic_make_request(tbio);
+	}
+
+done:
+	if (atomic_dec_and_test(&r10_bio->remaining)) {
+		md_done_sync(mddev, r10_bio->sectors, 1);
+		put_buf(r10_bio);
+	}
+}
+
+/*
+ * Now for the recovery code.
+ * Recovery happens across physical sectors.
+ * We recover all non-is_sync drives by finding the virtual address of
+ * each, and then choose a working drive that also has that virt address.
+ * There is a separate r10_bio for each non-in_sync drive.
+ * Only the first two slots are in use. The first for reading,
+ * The second for writing.
+ *
+ */
+static void fix_recovery_read_error(struct r10bio *r10_bio)
+{
+	/* We got a read error during recovery.
+	 * We repeat the read in smaller page-sized sections.
+	 * If a read succeeds, write it to the new device or record
+	 * a bad block if we cannot.
+	 * If a read fails, record a bad block on both old and
+	 * new devices.
+	 */
+	struct mddev *mddev = r10_bio->mddev;
+	struct r10conf *conf = mddev->private;
+	struct bio *bio = r10_bio->devs[0].bio;
+	sector_t sect = 0;
+	int sectors = r10_bio->sectors;
+	int idx = 0;
+	int dr = r10_bio->devs[0].devnum;
+	int dw = r10_bio->devs[1].devnum;
+
+	while (sectors) {
+		int s = sectors;
+		struct md_rdev *rdev;
+		sector_t addr;
+		int ok;
+
+		if (s > (PAGE_SIZE>>9))
+			s = PAGE_SIZE >> 9;
+
+		rdev = conf->mirrors[dr].rdev;
+		addr = r10_bio->devs[0].addr + sect,
+		ok = sync_page_io(rdev,
+				  addr,
+				  s << 9,
+				  bio->bi_io_vec[idx].bv_page,
+				  READ, false);
+		if (ok) {
+			rdev = conf->mirrors[dw].rdev;
+			addr = r10_bio->devs[1].addr + sect;
+			ok = sync_page_io(rdev,
+					  addr,
+					  s << 9,
+					  bio->bi_io_vec[idx].bv_page,
+					  WRITE, false);
+			if (!ok) {
+				set_bit(WriteErrorSeen, &rdev->flags);
+				if (!test_and_set_bit(WantReplacement,
+						      &rdev->flags))
+					set_bit(MD_RECOVERY_NEEDED,
+						&rdev->mddev->recovery);
+			}
+		}
+		if (!ok) {
+			/* We don't worry if we cannot set a bad block -
+			 * it really is bad so there is no loss in not
+			 * recording it yet
+			 */
+			rdev_set_badblocks(rdev, addr, s, 0);
+
+			if (rdev != conf->mirrors[dw].rdev) {
+				/* need bad block on destination too */
+				struct md_rdev *rdev2 = conf->mirrors[dw].rdev;
+				addr = r10_bio->devs[1].addr + sect;
+				ok = rdev_set_badblocks(rdev2, addr, s, 0);
+				if (!ok) {
+					/* just abort the recovery */
+					printk(KERN_NOTICE
+					       "md/raid10:%s: recovery aborted"
+					       " due to read error\n",
+					       mdname(mddev));
+
+					conf->mirrors[dw].recovery_disabled
+						= mddev->recovery_disabled;
+					set_bit(MD_RECOVERY_INTR,
+						&mddev->recovery);
+					break;
+				}
+			}
+		}
+
+		sectors -= s;
+		sect += s;
+		idx++;
+	}
+}
+
+static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
+{
+	struct r10conf *conf = mddev->private;
+	int d;
+	struct bio *wbio, *wbio2;
+
+	if (!test_bit(R10BIO_Uptodate, &r10_bio->state)) {
+		fix_recovery_read_error(r10_bio);
+		end_sync_request(r10_bio);
+		return;
+	}
+
+	/*
+	 * share the pages with the first bio
+	 * and submit the write request
+	 */
+	d = r10_bio->devs[1].devnum;
+	wbio = r10_bio->devs[1].bio;
+	wbio2 = r10_bio->devs[1].repl_bio;
+	/* Need to test wbio2->bi_end_io before we call
+	 * generic_make_request as if the former is NULL,
+	 * the latter is free to free wbio2.
+	 */
+	if (wbio2 && !wbio2->bi_end_io)
+		wbio2 = NULL;
+	if (wbio->bi_end_io) {
+		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
+		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(wbio));
+		generic_make_request(wbio);
+	}
+	if (wbio2) {
+		atomic_inc(&conf->mirrors[d].replacement->nr_pending);
+		md_sync_acct(conf->mirrors[d].replacement->bdev,
+			     bio_sectors(wbio2));
+		generic_make_request(wbio2);
+	}
+}
+
+/*
+ * Used by fix_read_error() to decay the per rdev read_errors.
+ * We halve the read error count for every hour that has elapsed
+ * since the last recorded read error.
+ *
+ */
+static void check_decay_read_errors(struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct timespec cur_time_mon;
+	unsigned long hours_since_last;
+	unsigned int read_errors = atomic_read(&rdev->read_errors);
+
+	ktime_get_ts(&cur_time_mon);
+
+	if (rdev->last_read_error.tv_sec == 0 &&
+	    rdev->last_read_error.tv_nsec == 0) {
+		/* first time we've seen a read error */
+		rdev->last_read_error = cur_time_mon;
+		return;
+	}
+
+	hours_since_last = (cur_time_mon.tv_sec -
+			    rdev->last_read_error.tv_sec) / 3600;
+
+	rdev->last_read_error = cur_time_mon;
+
+	/*
+	 * if hours_since_last is > the number of bits in read_errors
+	 * just set read errors to 0. We do this to avoid
+	 * overflowing the shift of read_errors by hours_since_last.
+	 */
+	if (hours_since_last >= 8 * sizeof(read_errors))
+		atomic_set(&rdev->read_errors, 0);
+	else
+		atomic_set(&rdev->read_errors, read_errors >> hours_since_last);
+}
+
+static int r10_sync_page_io(struct md_rdev *rdev, sector_t sector,
+			    int sectors, struct page *page, int rw)
+{
+	sector_t first_bad;
+	int bad_sectors;
+
+	if (is_badblock(rdev, sector, sectors, &first_bad, &bad_sectors)
+	    && (rw == READ || test_bit(WriteErrorSeen, &rdev->flags)))
+		return -1;
+	if (sync_page_io(rdev, sector, sectors << 9, page, rw, false))
+		/* success */
+		return 1;
+	if (rw == WRITE) {
+		set_bit(WriteErrorSeen, &rdev->flags);
+		if (!test_and_set_bit(WantReplacement, &rdev->flags))
+			set_bit(MD_RECOVERY_NEEDED,
+				&rdev->mddev->recovery);
+	}
+	/* need to record an error - either for the block or the device */
+	if (!rdev_set_badblocks(rdev, sector, sectors, 0))
+		md_error(rdev->mddev, rdev);
+	return 0;
+}
+
+/*
+ * This is a kernel thread which:
+ *
+ *	1.	Retries failed read operations on working mirrors.
+ *	2.	Updates the raid superblock when problems encounter.
+ *	3.	Performs writes following reads for array synchronising.
+ */
+
+static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10bio *r10_bio)
+{
+	int sect = 0; /* Offset from r10_bio->sector */
+	int sectors = r10_bio->sectors;
+	struct md_rdev*rdev;
+	int max_read_errors = atomic_read(&mddev->max_corr_read_errors);
+	int d = r10_bio->devs[r10_bio->read_slot].devnum;
+
+	/* still own a reference to this rdev, so it cannot
+	 * have been cleared recently.
+	 */
+	rdev = conf->mirrors[d].rdev;
+
+	if (test_bit(Faulty, &rdev->flags))
+		/* drive has already been failed, just ignore any
+		   more fix_read_error() attempts */
+		return;
+
+	check_decay_read_errors(mddev, rdev);
+	atomic_inc(&rdev->read_errors);
+	if (atomic_read(&rdev->read_errors) > max_read_errors) {
+		char b[BDEVNAME_SIZE];
+		bdevname(rdev->bdev, b);
+
+		printk(KERN_NOTICE
+		       "md/raid10:%s: %s: Raid device exceeded "
+		       "read_error threshold [cur %d:max %d]\n",
+		       mdname(mddev), b,
+		       atomic_read(&rdev->read_errors), max_read_errors);
+		printk(KERN_NOTICE
+		       "md/raid10:%s: %s: Failing raid device\n",
+		       mdname(mddev), b);
+		md_error(mddev, conf->mirrors[d].rdev);
+		r10_bio->devs[r10_bio->read_slot].bio = IO_BLOCKED;
+		return;
+	}
+
+	while(sectors) {
+		int s = sectors;
+		int sl = r10_bio->read_slot;
+		int success = 0;
+		int start;
+
+		if (s > (PAGE_SIZE>>9))
+			s = PAGE_SIZE >> 9;
+
+		rcu_read_lock();
+		do {
+			sector_t first_bad;
+			int bad_sectors;
+
+			d = r10_bio->devs[sl].devnum;
+			rdev = rcu_dereference(conf->mirrors[d].rdev);
+			if (rdev &&
+			    !test_bit(Unmerged, &rdev->flags) &&
+			    test_bit(In_sync, &rdev->flags) &&
+			    is_badblock(rdev, r10_bio->devs[sl].addr + sect, s,
+					&first_bad, &bad_sectors) == 0) {
+				atomic_inc(&rdev->nr_pending);
+				rcu_read_unlock();
+				success = sync_page_io(rdev,
+						       r10_bio->devs[sl].addr +
+						       sect,
+						       s<<9,
+						       conf->tmppage, READ, false);
+				rdev_dec_pending(rdev, mddev);
+				rcu_read_lock();
+				if (success)
+					break;
+			}
+			sl++;
+			if (sl == conf->copies)
+				sl = 0;
+		} while (!success && sl != r10_bio->read_slot);
+		rcu_read_unlock();
+
+		if (!success) {
+			/* Cannot read from anywhere, just mark the block
+			 * as bad on the first device to discourage future
+			 * reads.
+			 */
+			int dn = r10_bio->devs[r10_bio->read_slot].devnum;
+			rdev = conf->mirrors[dn].rdev;
+
+			if (!rdev_set_badblocks(
+				    rdev,
+				    r10_bio->devs[r10_bio->read_slot].addr
+				    + sect,
+				    s, 0)) {
+				md_error(mddev, rdev);
+				r10_bio->devs[r10_bio->read_slot].bio
+					= IO_BLOCKED;
+			}
+			break;
+		}
+
+		start = sl;
+		/* write it back and re-read */
+		rcu_read_lock();
+		while (sl != r10_bio->read_slot) {
+			char b[BDEVNAME_SIZE];
+
+			if (sl==0)
+				sl = conf->copies;
+			sl--;
+			d = r10_bio->devs[sl].devnum;
+			rdev = rcu_dereference(conf->mirrors[d].rdev);
+			if (!rdev ||
+			    test_bit(Unmerged, &rdev->flags) ||
+			    !test_bit(In_sync, &rdev->flags))
+				continue;
+
+			atomic_inc(&rdev->nr_pending);
+			rcu_read_unlock();
+			if (r10_sync_page_io(rdev,
+					     r10_bio->devs[sl].addr +
+					     sect,
+					     s, conf->tmppage, WRITE)
+			    == 0) {
+				/* Well, this device is dead */
+				printk(KERN_NOTICE
+				       "md/raid10:%s: read correction "
+				       "write failed"
+				       " (%d sectors at %llu on %s)\n",
+				       mdname(mddev), s,
+				       (unsigned long long)(
+					       sect +
+					       choose_data_offset(r10_bio,
+								  rdev)),
+				       bdevname(rdev->bdev, b));
+				printk(KERN_NOTICE "md/raid10:%s: %s: failing "
+				       "drive\n",
+				       mdname(mddev),
+				       bdevname(rdev->bdev, b));
+			}
+			rdev_dec_pending(rdev, mddev);
+			rcu_read_lock();
+		}
+		sl = start;
+		while (sl != r10_bio->read_slot) {
+			char b[BDEVNAME_SIZE];
+
+			if (sl==0)
+				sl = conf->copies;
+			sl--;
+			d = r10_bio->devs[sl].devnum;
+			rdev = rcu_dereference(conf->mirrors[d].rdev);
+			if (!rdev ||
+			    !test_bit(In_sync, &rdev->flags))
+				continue;
+
+			atomic_inc(&rdev->nr_pending);
+			rcu_read_unlock();
+			switch (r10_sync_page_io(rdev,
+					     r10_bio->devs[sl].addr +
+					     sect,
+					     s, conf->tmppage,
+						 READ)) {
+			case 0:
+				/* Well, this device is dead */
+				printk(KERN_NOTICE
+				       "md/raid10:%s: unable to read back "
+				       "corrected sectors"
+				       " (%d sectors at %llu on %s)\n",
+				       mdname(mddev), s,
+				       (unsigned long long)(
+					       sect +
+					       choose_data_offset(r10_bio, rdev)),
+				       bdevname(rdev->bdev, b));
+				printk(KERN_NOTICE "md/raid10:%s: %s: failing "
+				       "drive\n",
+				       mdname(mddev),
+				       bdevname(rdev->bdev, b));
+				break;
+			case 1:
+				printk(KERN_INFO
+				       "md/raid10:%s: read error corrected"
+				       " (%d sectors at %llu on %s)\n",
+				       mdname(mddev), s,
+				       (unsigned long long)(
+					       sect +
+					       choose_data_offset(r10_bio, rdev)),
+				       bdevname(rdev->bdev, b));
+				atomic_add(s, &rdev->corrected_errors);
+			}
+
+			rdev_dec_pending(rdev, mddev);
+			rcu_read_lock();
+		}
+		rcu_read_unlock();
+
+		sectors -= s;
+		sect += s;
+	}
+}
+
+static int narrow_write_error(struct r10bio *r10_bio, int i)
+{
+	struct bio *bio = r10_bio->master_bio;
+	struct mddev *mddev = r10_bio->mddev;
+	struct r10conf *conf = mddev->private;
+	struct md_rdev *rdev = conf->mirrors[r10_bio->devs[i].devnum].rdev;
+	/* bio has the data to be written to slot 'i' where
+	 * we just recently had a write error.
+	 * We repeatedly clone the bio and trim down to one block,
+	 * then try the write.  Where the write fails we record
+	 * a bad block.
+	 * It is conceivable that the bio doesn't exactly align with
+	 * blocks.  We must handle this.
+	 *
+	 * We currently own a reference to the rdev.
+	 */
+
+	int block_sectors;
+	sector_t sector;
+	int sectors;
+	int sect_to_write = r10_bio->sectors;
+	int ok = 1;
+
+	if (rdev->badblocks.shift < 0)
+		return 0;
+
+	block_sectors = roundup(1 << rdev->badblocks.shift,
+				bdev_logical_block_size(rdev->bdev) >> 9);
+	sector = r10_bio->sector;
+	sectors = ((r10_bio->sector + block_sectors)
+		   & ~(sector_t)(block_sectors - 1))
+		- sector;
+
+	while (sect_to_write) {
+		struct bio *wbio;
+		if (sectors > sect_to_write)
+			sectors = sect_to_write;
+		/* Write at 'sector' for 'sectors' */
+		wbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+		bio_trim(wbio, sector - bio->bi_iter.bi_sector, sectors);
+		wbio->bi_iter.bi_sector = (r10_bio->devs[i].addr+
+				   choose_data_offset(r10_bio, rdev) +
+				   (sector - r10_bio->sector));
+		wbio->bi_bdev = rdev->bdev;
+		if (submit_bio_wait(WRITE, wbio) == 0)
+			/* Failure! */
+			ok = rdev_set_badblocks(rdev, sector,
+						sectors, 0)
+				&& ok;
+
+		bio_put(wbio);
+		sect_to_write -= sectors;
+		sector += sectors;
+		sectors = block_sectors;
+	}
+	return ok;
+}
+
+static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
+{
+	int slot = r10_bio->read_slot;
+	struct bio *bio;
+	struct r10conf *conf = mddev->private;
+	struct md_rdev *rdev = r10_bio->devs[slot].rdev;
+	char b[BDEVNAME_SIZE];
+	unsigned long do_sync;
+	int max_sectors;
+
+	/* we got a read error. Maybe the drive is bad.  Maybe just
+	 * the block and we can fix it.
+	 * We freeze all other IO, and try reading the block from
+	 * other devices.  When we find one, we re-write
+	 * and check it that fixes the read error.
+	 * This is all done synchronously while the array is
+	 * frozen.
+	 */
+	bio = r10_bio->devs[slot].bio;
+	bdevname(bio->bi_bdev, b);
+	bio_put(bio);
+	r10_bio->devs[slot].bio = NULL;
+
+	if (mddev->ro == 0) {
+		freeze_array(conf, 1);
+		fix_read_error(conf, mddev, r10_bio);
+		unfreeze_array(conf);
+	} else
+		r10_bio->devs[slot].bio = IO_BLOCKED;
+
+	rdev_dec_pending(rdev, mddev);
+
+read_more:
+	rdev = read_balance(conf, r10_bio, &max_sectors);
+	if (rdev == NULL) {
+		printk(KERN_ALERT "md/raid10:%s: %s: unrecoverable I/O"
+		       " read error for block %llu\n",
+		       mdname(mddev), b,
+		       (unsigned long long)r10_bio->sector);
+		raid_end_bio_io(r10_bio);
+		return;
+	}
+
+	do_sync = (r10_bio->master_bio->bi_rw & REQ_SYNC);
+	slot = r10_bio->read_slot;
+	printk_ratelimited(
+		KERN_ERR
+		"md/raid10:%s: %s: redirecting "
+		"sector %llu to another mirror\n",
+		mdname(mddev),
+		bdevname(rdev->bdev, b),
+		(unsigned long long)r10_bio->sector);
+	bio = bio_clone_mddev(r10_bio->master_bio,
+			      GFP_NOIO, mddev);
+	bio_trim(bio, r10_bio->sector - bio->bi_iter.bi_sector, max_sectors);
+	r10_bio->devs[slot].bio = bio;
+	r10_bio->devs[slot].rdev = rdev;
+	bio->bi_iter.bi_sector = r10_bio->devs[slot].addr
+		+ choose_data_offset(r10_bio, rdev);
+	bio->bi_bdev = rdev->bdev;
+	bio->bi_rw = READ | do_sync;
+	bio->bi_private = r10_bio;
+	bio->bi_end_io = raid10_end_read_request;
+	if (max_sectors < r10_bio->sectors) {
+		/* Drat - have to split this up more */
+		struct bio *mbio = r10_bio->master_bio;
+		int sectors_handled =
+			r10_bio->sector + max_sectors
+			- mbio->bi_iter.bi_sector;
+		r10_bio->sectors = max_sectors;
+		spin_lock_irq(&conf->device_lock);
+		if (mbio->bi_phys_segments == 0)
+			mbio->bi_phys_segments = 2;
+		else
+			mbio->bi_phys_segments++;
+		spin_unlock_irq(&conf->device_lock);
+		generic_make_request(bio);
+
+		r10_bio = mempool_alloc(conf->r10bio_pool,
+					GFP_NOIO);
+		r10_bio->master_bio = mbio;
+		r10_bio->sectors = bio_sectors(mbio) - sectors_handled;
+		r10_bio->state = 0;
+		set_bit(R10BIO_ReadError,
+			&r10_bio->state);
+		r10_bio->mddev = mddev;
+		r10_bio->sector = mbio->bi_iter.bi_sector
+			+ sectors_handled;
+
+		goto read_more;
+	} else
+		generic_make_request(bio);
+}
+
+static void handle_write_completed(struct r10conf *conf, struct r10bio *r10_bio)
+{
+	/* Some sort of write request has finished and it
+	 * succeeded in writing where we thought there was a
+	 * bad block.  So forget the bad block.
+	 * Or possibly if failed and we need to record
+	 * a bad block.
+	 */
+	int m;
+	struct md_rdev *rdev;
+
+	if (test_bit(R10BIO_IsSync, &r10_bio->state) ||
+	    test_bit(R10BIO_IsRecover, &r10_bio->state)) {
+		for (m = 0; m < conf->copies; m++) {
+			int dev = r10_bio->devs[m].devnum;
+			rdev = conf->mirrors[dev].rdev;
+			if (r10_bio->devs[m].bio == NULL)
+				continue;
+			if (test_bit(BIO_UPTODATE,
+				     &r10_bio->devs[m].bio->bi_flags)) {
+				rdev_clear_badblocks(
+					rdev,
+					r10_bio->devs[m].addr,
+					r10_bio->sectors, 0);
+			} else {
+				if (!rdev_set_badblocks(
+					    rdev,
+					    r10_bio->devs[m].addr,
+					    r10_bio->sectors, 0))
+					md_error(conf->mddev, rdev);
+			}
+			rdev = conf->mirrors[dev].replacement;
+			if (r10_bio->devs[m].repl_bio == NULL)
+				continue;
+			if (test_bit(BIO_UPTODATE,
+				     &r10_bio->devs[m].repl_bio->bi_flags)) {
+				rdev_clear_badblocks(
+					rdev,
+					r10_bio->devs[m].addr,
+					r10_bio->sectors, 0);
+			} else {
+				if (!rdev_set_badblocks(
+					    rdev,
+					    r10_bio->devs[m].addr,
+					    r10_bio->sectors, 0))
+					md_error(conf->mddev, rdev);
+			}
+		}
+		put_buf(r10_bio);
+	} else {
+		for (m = 0; m < conf->copies; m++) {
+			int dev = r10_bio->devs[m].devnum;
+			struct bio *bio = r10_bio->devs[m].bio;
+			rdev = conf->mirrors[dev].rdev;
+			if (bio == IO_MADE_GOOD) {
+				rdev_clear_badblocks(
+					rdev,
+					r10_bio->devs[m].addr,
+					r10_bio->sectors, 0);
+				rdev_dec_pending(rdev, conf->mddev);
+			} else if (bio != NULL &&
+				   !test_bit(BIO_UPTODATE, &bio->bi_flags)) {
+				if (!narrow_write_error(r10_bio, m)) {
+					md_error(conf->mddev, rdev);
+					set_bit(R10BIO_Degraded,
+						&r10_bio->state);
+				}
+				rdev_dec_pending(rdev, conf->mddev);
+			}
+			bio = r10_bio->devs[m].repl_bio;
+			rdev = conf->mirrors[dev].replacement;
+			if (rdev && bio == IO_MADE_GOOD) {
+				rdev_clear_badblocks(
+					rdev,
+					r10_bio->devs[m].addr,
+					r10_bio->sectors, 0);
+				rdev_dec_pending(rdev, conf->mddev);
+			}
+		}
+		if (test_bit(R10BIO_WriteError,
+			     &r10_bio->state))
+			close_write(r10_bio);
+		raid_end_bio_io(r10_bio);
+	}
+}
+
+static void raid10d(struct md_thread *thread)
+{
+	struct mddev *mddev = thread->mddev;
+	struct r10bio *r10_bio;
+	unsigned long flags;
+	struct r10conf *conf = mddev->private;
+	struct list_head *head = &conf->retry_list;
+	struct blk_plug plug;
+
+	md_check_recovery(mddev);
+
+	blk_start_plug(&plug);
+	for (;;) {
+
+		flush_pending_writes(conf);
+
+		spin_lock_irqsave(&conf->device_lock, flags);
+		if (list_empty(head)) {
+			spin_unlock_irqrestore(&conf->device_lock, flags);
+			break;
+		}
+		r10_bio = list_entry(head->prev, struct r10bio, retry_list);
+		list_del(head->prev);
+		conf->nr_queued--;
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+
+		mddev = r10_bio->mddev;
+		conf = mddev->private;
+		if (test_bit(R10BIO_MadeGood, &r10_bio->state) ||
+		    test_bit(R10BIO_WriteError, &r10_bio->state))
+			handle_write_completed(conf, r10_bio);
+		else if (test_bit(R10BIO_IsReshape, &r10_bio->state))
+			reshape_request_write(mddev, r10_bio);
+		else if (test_bit(R10BIO_IsSync, &r10_bio->state))
+			sync_request_write(mddev, r10_bio);
+		else if (test_bit(R10BIO_IsRecover, &r10_bio->state))
+			recovery_request_write(mddev, r10_bio);
+		else if (test_bit(R10BIO_ReadError, &r10_bio->state))
+			handle_read_error(mddev, r10_bio);
+		else {
+			/* just a partial read to be scheduled from a
+			 * separate context
+			 */
+			int slot = r10_bio->read_slot;
+			generic_make_request(r10_bio->devs[slot].bio);
+		}
+
+		cond_resched();
+		if (mddev->flags & ~(1<<MD_CHANGE_PENDING))
+			md_check_recovery(mddev);
+	}
+	blk_finish_plug(&plug);
+}
+
+static int init_resync(struct r10conf *conf)
+{
+	int buffs;
+	int i;
+
+	buffs = RESYNC_WINDOW / RESYNC_BLOCK_SIZE;
+	BUG_ON(conf->r10buf_pool);
+	conf->have_replacement = 0;
+	for (i = 0; i < conf->geo.raid_disks; i++)
+		if (conf->mirrors[i].replacement)
+			conf->have_replacement = 1;
+	conf->r10buf_pool = mempool_create(buffs, r10buf_pool_alloc, r10buf_pool_free, conf);
+	if (!conf->r10buf_pool)
+		return -ENOMEM;
+	conf->next_resync = 0;
+	return 0;
+}
+
+/*
+ * perform a "sync" on one "block"
+ *
+ * We need to make sure that no normal I/O request - particularly write
+ * requests - conflict with active sync requests.
+ *
+ * This is achieved by tracking pending requests and a 'barrier' concept
+ * that can be installed to exclude normal IO requests.
+ *
+ * Resync and recovery are handled very differently.
+ * We differentiate by looking at MD_RECOVERY_SYNC in mddev->recovery.
+ *
+ * For resync, we iterate over virtual addresses, read all copies,
+ * and update if there are differences.  If only one copy is live,
+ * skip it.
+ * For recovery, we iterate over physical addresses, read a good
+ * value for each non-in_sync drive, and over-write.
+ *
+ * So, for recovery we may have several outstanding complex requests for a
+ * given address, one for each out-of-sync device.  We model this by allocating
+ * a number of r10_bio structures, one for each out-of-sync device.
+ * As we setup these structures, we collect all bio's together into a list
+ * which we then process collectively to add pages, and then process again
+ * to pass to generic_make_request.
+ *
+ * The r10_bio structures are linked using a borrowed master_bio pointer.
+ * This link is counted in ->remaining.  When the r10_bio that points to NULL
+ * has its remaining count decremented to 0, the whole complex operation
+ * is complete.
+ *
+ */
+
+static sector_t sync_request(struct mddev *mddev, sector_t sector_nr,
+			     int *skipped)
+{
+	struct r10conf *conf = mddev->private;
+	struct r10bio *r10_bio;
+	struct bio *biolist = NULL, *bio;
+	sector_t max_sector, nr_sectors;
+	int i;
+	int max_sync;
+	sector_t sync_blocks;
+	sector_t sectors_skipped = 0;
+	int chunks_skipped = 0;
+	sector_t chunk_mask = conf->geo.chunk_mask;
+
+	if (!conf->r10buf_pool)
+		if (init_resync(conf))
+			return 0;
+
+	/*
+	 * Allow skipping a full rebuild for incremental assembly
+	 * of a clean array, like RAID1 does.
+	 */
+	if (mddev->bitmap == NULL &&
+	    mddev->recovery_cp == MaxSector &&
+	    mddev->reshape_position == MaxSector &&
+	    !test_bit(MD_RECOVERY_SYNC, &mddev->recovery) &&
+	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
+	    !test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
+	    conf->fullsync == 0) {
+		*skipped = 1;
+		return mddev->dev_sectors - sector_nr;
+	}
+
+ skipped:
+	max_sector = mddev->dev_sectors;
+	if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||
+	    test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
+		max_sector = mddev->resync_max_sectors;
+	if (sector_nr >= max_sector) {
+		/* If we aborted, we need to abort the
+		 * sync on the 'current' bitmap chucks (there can
+		 * be several when recovering multiple devices).
+		 * as we may have started syncing it but not finished.
+		 * We can find the current address in
+		 * mddev->curr_resync, but for recovery,
+		 * we need to convert that to several
+		 * virtual addresses.
+		 */
+		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery)) {
+			end_reshape(conf);
+			close_sync(conf);
+			return 0;
+		}
+
+		if (mddev->curr_resync < max_sector) { /* aborted */
+			if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
+				bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
+						&sync_blocks, 1);
+			else for (i = 0; i < conf->geo.raid_disks; i++) {
+				sector_t sect =
+					raid10_find_virt(conf, mddev->curr_resync, i);
+				bitmap_end_sync(mddev->bitmap, sect,
+						&sync_blocks, 1);
+			}
+		} else {
+			/* completed sync */
+			if ((!mddev->bitmap || conf->fullsync)
+			    && conf->have_replacement
+			    && test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
+				/* Completed a full sync so the replacements
+				 * are now fully recovered.
+				 */
+				for (i = 0; i < conf->geo.raid_disks; i++)
+					if (conf->mirrors[i].replacement)
+						conf->mirrors[i].replacement
+							->recovery_offset
+							= MaxSector;
+			}
+			conf->fullsync = 0;
+		}
+		bitmap_close_sync(mddev->bitmap);
+		close_sync(conf);
+		*skipped = 1;
+		return sectors_skipped;
+	}
+
+	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
+		return reshape_request(mddev, sector_nr, skipped);
+
+	if (chunks_skipped >= conf->geo.raid_disks) {
+		/* if there has been nothing to do on any drive,
+		 * then there is nothing to do at all..
+		 */
+		*skipped = 1;
+		return (max_sector - sector_nr) + sectors_skipped;
+	}
+
+	if (max_sector > mddev->resync_max)
+		max_sector = mddev->resync_max; /* Don't do IO beyond here */
+
+	/* make sure whole request will fit in a chunk - if chunks
+	 * are meaningful
+	 */
+	if (conf->geo.near_copies < conf->geo.raid_disks &&
+	    max_sector > (sector_nr | chunk_mask))
+		max_sector = (sector_nr | chunk_mask) + 1;
+
+	/* Again, very different code for resync and recovery.
+	 * Both must result in an r10bio with a list of bios that
+	 * have bi_end_io, bi_sector, bi_bdev set,
+	 * and bi_private set to the r10bio.
+	 * For recovery, we may actually create several r10bios
+	 * with 2 bios in each, that correspond to the bios in the main one.
+	 * In this case, the subordinate r10bios link back through a
+	 * borrowed master_bio pointer, and the counter in the master
+	 * includes a ref from each subordinate.
+	 */
+	/* First, we decide what to do and set ->bi_end_io
+	 * To end_sync_read if we want to read, and
+	 * end_sync_write if we will want to write.
+	 */
+
+	max_sync = RESYNC_PAGES << (PAGE_SHIFT-9);
+	if (!test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
+		/* recovery... the complicated one */
+		int j;
+		r10_bio = NULL;
+
+		for (i = 0 ; i < conf->geo.raid_disks; i++) {
+			int still_degraded;
+			struct r10bio *rb2;
+			sector_t sect;
+			int must_sync;
+			int any_working;
+			struct raid10_info *mirror = &conf->mirrors[i];
+
+			if ((mirror->rdev == NULL ||
+			     test_bit(In_sync, &mirror->rdev->flags))
+			    &&
+			    (mirror->replacement == NULL ||
+			     test_bit(Faulty,
+				      &mirror->replacement->flags)))
+				continue;
+
+			still_degraded = 0;
+			/* want to reconstruct this device */
+			rb2 = r10_bio;
+			sect = raid10_find_virt(conf, sector_nr, i);
+			if (sect >= mddev->resync_max_sectors) {
+				/* last stripe is not complete - don't
+				 * try to recover this sector.
+				 */
+				continue;
+			}
+			/* Unless we are doing a full sync, or a replacement
+			 * we only need to recover the block if it is set in
+			 * the bitmap
+			 */
+			must_sync = bitmap_start_sync(mddev->bitmap, sect,
+						      &sync_blocks, 1);
+			if (sync_blocks < max_sync)
+				max_sync = sync_blocks;
+			if (!must_sync &&
+			    mirror->replacement == NULL &&
+			    !conf->fullsync) {
+				/* yep, skip the sync_blocks here, but don't assume
+				 * that there will never be anything to do here
+				 */
+				chunks_skipped = -1;
+				continue;
+			}
+
+			r10_bio = mempool_alloc(conf->r10buf_pool, GFP_NOIO);
+			r10_bio->state = 0;
+			raise_barrier(conf, rb2 != NULL);
+			atomic_set(&r10_bio->remaining, 0);
+
+			r10_bio->master_bio = (struct bio*)rb2;
+			if (rb2)
+				atomic_inc(&rb2->remaining);
+			r10_bio->mddev = mddev;
+			set_bit(R10BIO_IsRecover, &r10_bio->state);
+			r10_bio->sector = sect;
+
+			raid10_find_phys(conf, r10_bio);
+
+			/* Need to check if the array will still be
+			 * degraded
+			 */
+			for (j = 0; j < conf->geo.raid_disks; j++)
+				if (conf->mirrors[j].rdev == NULL ||
+				    test_bit(Faulty, &conf->mirrors[j].rdev->flags)) {
+					still_degraded = 1;
+					break;
+				}
+
+			must_sync = bitmap_start_sync(mddev->bitmap, sect,
+						      &sync_blocks, still_degraded);
+
+			any_working = 0;
+			for (j=0; j<conf->copies;j++) {
+				int k;
+				int d = r10_bio->devs[j].devnum;
+				sector_t from_addr, to_addr;
+				struct md_rdev *rdev;
+				sector_t sector, first_bad;
+				int bad_sectors;
+				if (!conf->mirrors[d].rdev ||
+				    !test_bit(In_sync, &conf->mirrors[d].rdev->flags))
+					continue;
+				/* This is where we read from */
+				any_working = 1;
+				rdev = conf->mirrors[d].rdev;
+				sector = r10_bio->devs[j].addr;
+
+				if (is_badblock(rdev, sector, max_sync,
+						&first_bad, &bad_sectors)) {
+					if (first_bad > sector)
+						max_sync = first_bad - sector;
+					else {
+						bad_sectors -= (sector
+								- first_bad);
+						if (max_sync > bad_sectors)
+							max_sync = bad_sectors;
+						continue;
+					}
+				}
+				bio = r10_bio->devs[0].bio;
+				bio_reset(bio);
+				bio->bi_next = biolist;
+				biolist = bio;
+				bio->bi_private = r10_bio;
+				bio->bi_end_io = end_sync_read;
+				bio->bi_rw = READ;
+				from_addr = r10_bio->devs[j].addr;
+				bio->bi_iter.bi_sector = from_addr +
+					rdev->data_offset;
+				bio->bi_bdev = rdev->bdev;
+				atomic_inc(&rdev->nr_pending);
+				/* and we write to 'i' (if not in_sync) */
+
+				for (k=0; k<conf->copies; k++)
+					if (r10_bio->devs[k].devnum == i)
+						break;
+				BUG_ON(k == conf->copies);
+				to_addr = r10_bio->devs[k].addr;
+				r10_bio->devs[0].devnum = d;
+				r10_bio->devs[0].addr = from_addr;
+				r10_bio->devs[1].devnum = i;
+				r10_bio->devs[1].addr = to_addr;
+
+				rdev = mirror->rdev;
+				if (!test_bit(In_sync, &rdev->flags)) {
+					bio = r10_bio->devs[1].bio;
+					bio_reset(bio);
+					bio->bi_next = biolist;
+					biolist = bio;
+					bio->bi_private = r10_bio;
+					bio->bi_end_io = end_sync_write;
+					bio->bi_rw = WRITE;
+					bio->bi_iter.bi_sector = to_addr
+						+ rdev->data_offset;
+					bio->bi_bdev = rdev->bdev;
+					atomic_inc(&r10_bio->remaining);
+				} else
+					r10_bio->devs[1].bio->bi_end_io = NULL;
+
+				/* and maybe write to replacement */
+				bio = r10_bio->devs[1].repl_bio;
+				if (bio)
+					bio->bi_end_io = NULL;
+				rdev = mirror->replacement;
+				/* Note: if rdev != NULL, then bio
+				 * cannot be NULL as r10buf_pool_alloc will
+				 * have allocated it.
+				 * So the second test here is pointless.
+				 * But it keeps semantic-checkers happy, and
+				 * this comment keeps human reviewers
+				 * happy.
+				 */
+				if (rdev == NULL || bio == NULL ||
+				    test_bit(Faulty, &rdev->flags))
+					break;
+				bio_reset(bio);
+				bio->bi_next = biolist;
+				biolist = bio;
+				bio->bi_private = r10_bio;
+				bio->bi_end_io = end_sync_write;
+				bio->bi_rw = WRITE;
+				bio->bi_iter.bi_sector = to_addr +
+					rdev->data_offset;
+				bio->bi_bdev = rdev->bdev;
+				atomic_inc(&r10_bio->remaining);
+				break;
+			}
+			if (j == conf->copies) {
+				/* Cannot recover, so abort the recovery or
+				 * record a bad block */
+				if (any_working) {
+					/* problem is that there are bad blocks
+					 * on other device(s)
+					 */
+					int k;
+					for (k = 0; k < conf->copies; k++)
+						if (r10_bio->devs[k].devnum == i)
+							break;
+					if (!test_bit(In_sync,
+						      &mirror->rdev->flags)
+					    && !rdev_set_badblocks(
+						    mirror->rdev,
+						    r10_bio->devs[k].addr,
+						    max_sync, 0))
+						any_working = 0;
+					if (mirror->replacement &&
+					    !rdev_set_badblocks(
+						    mirror->replacement,
+						    r10_bio->devs[k].addr,
+						    max_sync, 0))
+						any_working = 0;
+				}
+				if (!any_working)  {
+					if (!test_and_set_bit(MD_RECOVERY_INTR,
+							      &mddev->recovery))
+						printk(KERN_INFO "md/raid10:%s: insufficient "
+						       "working devices for recovery.\n",
+						       mdname(mddev));
+					mirror->recovery_disabled
+						= mddev->recovery_disabled;
+				}
+				put_buf(r10_bio);
+				if (rb2)
+					atomic_dec(&rb2->remaining);
+				r10_bio = rb2;
+				break;
+			}
+		}
+		if (biolist == NULL) {
+			while (r10_bio) {
+				struct r10bio *rb2 = r10_bio;
+				r10_bio = (struct r10bio*) rb2->master_bio;
+				rb2->master_bio = NULL;
+				put_buf(rb2);
+			}
+			goto giveup;
+		}
+	} else {
+		/* resync. Schedule a read for every block at this virt offset */
+		int count = 0;
+
+		bitmap_cond_end_sync(mddev->bitmap, sector_nr);
+
+		if (!bitmap_start_sync(mddev->bitmap, sector_nr,
+				       &sync_blocks, mddev->degraded) &&
+		    !conf->fullsync && !test_bit(MD_RECOVERY_REQUESTED,
+						 &mddev->recovery)) {
+			/* We can skip this block */
+			*skipped = 1;
+			return sync_blocks + sectors_skipped;
+		}
+		if (sync_blocks < max_sync)
+			max_sync = sync_blocks;
+		r10_bio = mempool_alloc(conf->r10buf_pool, GFP_NOIO);
+		r10_bio->state = 0;
+
+		r10_bio->mddev = mddev;
+		atomic_set(&r10_bio->remaining, 0);
+		raise_barrier(conf, 0);
+		conf->next_resync = sector_nr;
+
+		r10_bio->master_bio = NULL;
+		r10_bio->sector = sector_nr;
+		set_bit(R10BIO_IsSync, &r10_bio->state);
+		raid10_find_phys(conf, r10_bio);
+		r10_bio->sectors = (sector_nr | chunk_mask) - sector_nr + 1;
+
+		for (i = 0; i < conf->copies; i++) {
+			int d = r10_bio->devs[i].devnum;
+			sector_t first_bad, sector;
+			int bad_sectors;
+
+			if (r10_bio->devs[i].repl_bio)
+				r10_bio->devs[i].repl_bio->bi_end_io = NULL;
+
+			bio = r10_bio->devs[i].bio;
+			bio_reset(bio);
+			clear_bit(BIO_UPTODATE, &bio->bi_flags);
+			if (conf->mirrors[d].rdev == NULL ||
+			    test_bit(Faulty, &conf->mirrors[d].rdev->flags))
+				continue;
+			sector = r10_bio->devs[i].addr;
+			if (is_badblock(conf->mirrors[d].rdev,
+					sector, max_sync,
+					&first_bad, &bad_sectors)) {
+				if (first_bad > sector)
+					max_sync = first_bad - sector;
+				else {
+					bad_sectors -= (sector - first_bad);
+					if (max_sync > bad_sectors)
+						max_sync = bad_sectors;
+					continue;
+				}
+			}
+			atomic_inc(&conf->mirrors[d].rdev->nr_pending);
+			atomic_inc(&r10_bio->remaining);
+			bio->bi_next = biolist;
+			biolist = bio;
+			bio->bi_private = r10_bio;
+			bio->bi_end_io = end_sync_read;
+			bio->bi_rw = READ;
+			bio->bi_iter.bi_sector = sector +
+				conf->mirrors[d].rdev->data_offset;
+			bio->bi_bdev = conf->mirrors[d].rdev->bdev;
+			count++;
+
+			if (conf->mirrors[d].replacement == NULL ||
+			    test_bit(Faulty,
+				     &conf->mirrors[d].replacement->flags))
+				continue;
+
+			/* Need to set up for writing to the replacement */
+			bio = r10_bio->devs[i].repl_bio;
+			bio_reset(bio);
+			clear_bit(BIO_UPTODATE, &bio->bi_flags);
+
+			sector = r10_bio->devs[i].addr;
+			atomic_inc(&conf->mirrors[d].rdev->nr_pending);
+			bio->bi_next = biolist;
+			biolist = bio;
+			bio->bi_private = r10_bio;
+			bio->bi_end_io = end_sync_write;
+			bio->bi_rw = WRITE;
+			bio->bi_iter.bi_sector = sector +
+				conf->mirrors[d].replacement->data_offset;
+			bio->bi_bdev = conf->mirrors[d].replacement->bdev;
+			count++;
+		}
+
+		if (count < 2) {
+			for (i=0; i<conf->copies; i++) {
+				int d = r10_bio->devs[i].devnum;
+				if (r10_bio->devs[i].bio->bi_end_io)
+					rdev_dec_pending(conf->mirrors[d].rdev,
+							 mddev);
+				if (r10_bio->devs[i].repl_bio &&
+				    r10_bio->devs[i].repl_bio->bi_end_io)
+					rdev_dec_pending(
+						conf->mirrors[d].replacement,
+						mddev);
+			}
+			put_buf(r10_bio);
+			biolist = NULL;
+			goto giveup;
+		}
+	}
+
+	nr_sectors = 0;
+	if (sector_nr + max_sync < max_sector)
+		max_sector = sector_nr + max_sync;
+	do {
+		struct page *page;
+		int len = PAGE_SIZE;
+		if (sector_nr + (len>>9) > max_sector)
+			len = (max_sector - sector_nr) << 9;
+		if (len == 0)
+			break;
+		for (bio= biolist ; bio ; bio=bio->bi_next) {
+			struct bio *bio2;
+			page = bio->bi_io_vec[bio->bi_vcnt].bv_page;
+			if (bio_add_page(bio, page, len, 0))
+				continue;
+
+			/* stop here */
+			bio->bi_io_vec[bio->bi_vcnt].bv_page = page;
+			for (bio2 = biolist;
+			     bio2 && bio2 != bio;
+			     bio2 = bio2->bi_next) {
+				/* remove last page from this bio */
+				bio2->bi_vcnt--;
+				bio2->bi_iter.bi_size -= len;
+				__clear_bit(BIO_SEG_VALID, &bio2->bi_flags);
+			}
+			goto bio_full;
+		}
+		nr_sectors += len>>9;
+		sector_nr += len>>9;
+	} while (biolist->bi_vcnt < RESYNC_PAGES);
+ bio_full:
+	r10_bio->sectors = nr_sectors;
+
+	while (biolist) {
+		bio = biolist;
+		biolist = biolist->bi_next;
+
+		bio->bi_next = NULL;
+		r10_bio = bio->bi_private;
+		r10_bio->sectors = nr_sectors;
+
+		if (bio->bi_end_io == end_sync_read) {
+			md_sync_acct(bio->bi_bdev, nr_sectors);
+			set_bit(BIO_UPTODATE, &bio->bi_flags);
+			generic_make_request(bio);
+		}
+	}
+
+	if (sectors_skipped)
+		/* pretend they weren't skipped, it makes
+		 * no important difference in this case
+		 */
+		md_done_sync(mddev, sectors_skipped, 1);
+
+	return sectors_skipped + nr_sectors;
+ giveup:
+	/* There is nowhere to write, so all non-sync
+	 * drives must be failed or in resync, all drives
+	 * have a bad block, so try the next chunk...
+	 */
+	if (sector_nr + max_sync < max_sector)
+		max_sector = sector_nr + max_sync;
+
+	sectors_skipped += (max_sector - sector_nr);
+	chunks_skipped ++;
+	sector_nr = max_sector;
+	goto skipped;
+}
+
+static sector_t
+raid10_size(struct mddev *mddev, sector_t sectors, int raid_disks)
+{
+	sector_t size;
+	struct r10conf *conf = mddev->private;
+
+	if (!raid_disks)
+		raid_disks = min(conf->geo.raid_disks,
+				 conf->prev.raid_disks);
+	if (!sectors)
+		sectors = conf->dev_sectors;
+
+	size = sectors >> conf->geo.chunk_shift;
+	sector_div(size, conf->geo.far_copies);
+	size = size * raid_disks;
+	sector_div(size, conf->geo.near_copies);
+
+	return size << conf->geo.chunk_shift;
+}
+
+static void calc_sectors(struct r10conf *conf, sector_t size)
+{
+	/* Calculate the number of sectors-per-device that will
+	 * actually be used, and set conf->dev_sectors and
+	 * conf->stride
+	 */
+
+	size = size >> conf->geo.chunk_shift;
+	sector_div(size, conf->geo.far_copies);
+	size = size * conf->geo.raid_disks;
+	sector_div(size, conf->geo.near_copies);
+	/* 'size' is now the number of chunks in the array */
+	/* calculate "used chunks per device" */
+	size = size * conf->copies;
+
+	/* We need to round up when dividing by raid_disks to
+	 * get the stride size.
+	 */
+	size = DIV_ROUND_UP_SECTOR_T(size, conf->geo.raid_disks);
+
+	conf->dev_sectors = size << conf->geo.chunk_shift;
+
+	if (conf->geo.far_offset)
+		conf->geo.stride = 1 << conf->geo.chunk_shift;
+	else {
+		sector_div(size, conf->geo.far_copies);
+		conf->geo.stride = size << conf->geo.chunk_shift;
+	}
+}
+
+enum geo_type {geo_new, geo_old, geo_start};
+static int setup_geo(struct geom *geo, struct mddev *mddev, enum geo_type new)
+{
+	int nc, fc, fo;
+	int layout, chunk, disks;
+	switch (new) {
+	case geo_old:
+		layout = mddev->layout;
+		chunk = mddev->chunk_sectors;
+		disks = mddev->raid_disks - mddev->delta_disks;
+		break;
+	case geo_new:
+		layout = mddev->new_layout;
+		chunk = mddev->new_chunk_sectors;
+		disks = mddev->raid_disks;
+		break;
+	default: /* avoid 'may be unused' warnings */
+	case geo_start: /* new when starting reshape - raid_disks not
+			 * updated yet. */
+		layout = mddev->new_layout;
+		chunk = mddev->new_chunk_sectors;
+		disks = mddev->raid_disks + mddev->delta_disks;
+		break;
+	}
+	if (layout >> 18)
+		return -1;
+	if (chunk < (PAGE_SIZE >> 9) ||
+	    !is_power_of_2(chunk))
+		return -2;
+	nc = layout & 255;
+	fc = (layout >> 8) & 255;
+	fo = layout & (1<<16);
+	geo->raid_disks = disks;
+	geo->near_copies = nc;
+	geo->far_copies = fc;
+	geo->far_offset = fo;
+	geo->far_set_size = (layout & (1<<17)) ? disks / fc : disks;
+	geo->chunk_mask = chunk - 1;
+	geo->chunk_shift = ffz(~chunk);
+	return nc*fc;
+}
+
+static struct r10conf *setup_conf(struct mddev *mddev)
+{
+	struct r10conf *conf = NULL;
+	int err = -EINVAL;
+	struct geom geo;
+	int copies;
+
+	copies = setup_geo(&geo, mddev, geo_new);
+
+	if (copies == -2) {
+		printk(KERN_ERR "md/raid10:%s: chunk size must be "
+		       "at least PAGE_SIZE(%ld) and be a power of 2.\n",
+		       mdname(mddev), PAGE_SIZE);
+		goto out;
+	}
+
+	if (copies < 2 || copies > mddev->raid_disks) {
+		printk(KERN_ERR "md/raid10:%s: unsupported raid10 layout: 0x%8x\n",
+		       mdname(mddev), mddev->new_layout);
+		goto out;
+	}
+
+	err = -ENOMEM;
+	conf = kzalloc(sizeof(struct r10conf), GFP_KERNEL);
+	if (!conf)
+		goto out;
+
+	/* FIXME calc properly */
+	conf->mirrors = kzalloc(sizeof(struct raid10_info)*(mddev->raid_disks +
+							    max(0,-mddev->delta_disks)),
+				GFP_KERNEL);
+	if (!conf->mirrors)
+		goto out;
+
+	conf->tmppage = alloc_page(GFP_KERNEL);
+	if (!conf->tmppage)
+		goto out;
+
+	conf->geo = geo;
+	conf->copies = copies;
+	conf->r10bio_pool = mempool_create(NR_RAID10_BIOS, r10bio_pool_alloc,
+					   r10bio_pool_free, conf);
+	if (!conf->r10bio_pool)
+		goto out;
+
+	calc_sectors(conf, mddev->dev_sectors);
+	if (mddev->reshape_position == MaxSector) {
+		conf->prev = conf->geo;
+		conf->reshape_progress = MaxSector;
+	} else {
+		if (setup_geo(&conf->prev, mddev, geo_old) != conf->copies) {
+			err = -EINVAL;
+			goto out;
+		}
+		conf->reshape_progress = mddev->reshape_position;
+		if (conf->prev.far_offset)
+			conf->prev.stride = 1 << conf->prev.chunk_shift;
+		else
+			/* far_copies must be 1 */
+			conf->prev.stride = conf->dev_sectors;
+	}
+	spin_lock_init(&conf->device_lock);
+	INIT_LIST_HEAD(&conf->retry_list);
+
+	spin_lock_init(&conf->resync_lock);
+	init_waitqueue_head(&conf->wait_barrier);
+
+	conf->thread = md_register_thread(raid10d, mddev, "raid10");
+	if (!conf->thread)
+		goto out;
+
+	conf->mddev = mddev;
+	return conf;
+
+ out:
+	if (err == -ENOMEM)
+		printk(KERN_ERR "md/raid10:%s: couldn't allocate memory.\n",
+		       mdname(mddev));
+	if (conf) {
+		if (conf->r10bio_pool)
+			mempool_destroy(conf->r10bio_pool);
+		kfree(conf->mirrors);
+		safe_put_page(conf->tmppage);
+		kfree(conf);
+	}
+	return ERR_PTR(err);
+}
+
+static int run(struct mddev *mddev)
+{
+	struct r10conf *conf;
+	int i, disk_idx, chunk_size;
+	struct raid10_info *disk;
+	struct md_rdev *rdev;
+	sector_t size;
+	sector_t min_offset_diff = 0;
+	int first = 1;
+	bool discard_supported = false;
+
+	if (mddev->private == NULL) {
+		conf = setup_conf(mddev);
+		if (IS_ERR(conf))
+			return PTR_ERR(conf);
+		mddev->private = conf;
+	}
+	conf = mddev->private;
+	if (!conf)
+		goto out;
+
+	mddev->thread = conf->thread;
+	conf->thread = NULL;
+
+	chunk_size = mddev->chunk_sectors << 9;
+	if (mddev->queue) {
+		blk_queue_max_discard_sectors(mddev->queue,
+					      mddev->chunk_sectors);
+		blk_queue_max_write_same_sectors(mddev->queue, 0);
+		blk_queue_io_min(mddev->queue, chunk_size);
+		if (conf->geo.raid_disks % conf->geo.near_copies)
+			blk_queue_io_opt(mddev->queue, chunk_size * conf->geo.raid_disks);
+		else
+			blk_queue_io_opt(mddev->queue, chunk_size *
+					 (conf->geo.raid_disks / conf->geo.near_copies));
+	}
+
+	rdev_for_each(rdev, mddev) {
+		long long diff;
+		struct request_queue *q;
+
+		disk_idx = rdev->raid_disk;
+		if (disk_idx < 0)
+			continue;
+		if (disk_idx >= conf->geo.raid_disks &&
+		    disk_idx >= conf->prev.raid_disks)
+			continue;
+		disk = conf->mirrors + disk_idx;
+
+		if (test_bit(Replacement, &rdev->flags)) {
+			if (disk->replacement)
+				goto out_free_conf;
+			disk->replacement = rdev;
+		} else {
+			if (disk->rdev)
+				goto out_free_conf;
+			disk->rdev = rdev;
+		}
+		q = bdev_get_queue(rdev->bdev);
+		if (q->merge_bvec_fn)
+			mddev->merge_check_needed = 1;
+		diff = (rdev->new_data_offset - rdev->data_offset);
+		if (!mddev->reshape_backwards)
+			diff = -diff;
+		if (diff < 0)
+			diff = 0;
+		if (first || diff < min_offset_diff)
+			min_offset_diff = diff;
+
+		if (mddev->gendisk)
+			disk_stack_limits(mddev->gendisk, rdev->bdev,
+					  rdev->data_offset << 9);
+
+		disk->head_position = 0;
+
+		if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+			discard_supported = true;
+	}
+
+	if (mddev->queue) {
+		if (discard_supported)
+			queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
+						mddev->queue);
+		else
+			queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD,
+						  mddev->queue);
+	}
+	/* need to check that every block has at least one working mirror */
+	if (!enough(conf, -1)) {
+		printk(KERN_ERR "md/raid10:%s: not enough operational mirrors.\n",
+		       mdname(mddev));
+		goto out_free_conf;
+	}
+
+	if (conf->reshape_progress != MaxSector) {
+		/* must ensure that shape change is supported */
+		if (conf->geo.far_copies != 1 &&
+		    conf->geo.far_offset == 0)
+			goto out_free_conf;
+		if (conf->prev.far_copies != 1 &&
+		    conf->prev.far_offset == 0)
+			goto out_free_conf;
+	}
+
+	mddev->degraded = 0;
+	for (i = 0;
+	     i < conf->geo.raid_disks
+		     || i < conf->prev.raid_disks;
+	     i++) {
+
+		disk = conf->mirrors + i;
+
+		if (!disk->rdev && disk->replacement) {
+			/* The replacement is all we have - use it */
+			disk->rdev = disk->replacement;
+			disk->replacement = NULL;
+			clear_bit(Replacement, &disk->rdev->flags);
+		}
+
+		if (!disk->rdev ||
+		    !test_bit(In_sync, &disk->rdev->flags)) {
+			disk->head_position = 0;
+			mddev->degraded++;
+			if (disk->rdev &&
+			    disk->rdev->saved_raid_disk < 0)
+				conf->fullsync = 1;
+		}
+		disk->recovery_disabled = mddev->recovery_disabled - 1;
+	}
+
+	if (mddev->recovery_cp != MaxSector)
+		printk(KERN_NOTICE "md/raid10:%s: not clean"
+		       " -- starting background reconstruction\n",
+		       mdname(mddev));
+	printk(KERN_INFO
+		"md/raid10:%s: active with %d out of %d devices\n",
+		mdname(mddev), conf->geo.raid_disks - mddev->degraded,
+		conf->geo.raid_disks);
+	/*
+	 * Ok, everything is just fine now
+	 */
+	mddev->dev_sectors = conf->dev_sectors;
+	size = raid10_size(mddev, 0, 0);
+	md_set_array_sectors(mddev, size);
+	mddev->resync_max_sectors = size;
+
+	if (mddev->queue) {
+		int stripe = conf->geo.raid_disks *
+			((mddev->chunk_sectors << 9) / PAGE_SIZE);
+
+		/* Calculate max read-ahead size.
+		 * We need to readahead at least twice a whole stripe....
+		 * maybe...
+		 */
+		stripe /= conf->geo.near_copies;
+		if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
+			mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
+	}
+
+	if (md_integrity_register(mddev))
+		goto out_free_conf;
+
+	if (conf->reshape_progress != MaxSector) {
+		unsigned long before_length, after_length;
+
+		before_length = ((1 << conf->prev.chunk_shift) *
+				 conf->prev.far_copies);
+		after_length = ((1 << conf->geo.chunk_shift) *
+				conf->geo.far_copies);
+
+		if (max(before_length, after_length) > min_offset_diff) {
+			/* This cannot work */
+			printk("md/raid10: offset difference not enough to continue reshape\n");
+			goto out_free_conf;
+		}
+		conf->offset_diff = min_offset_diff;
+
+		conf->reshape_safe = conf->reshape_progress;
+		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
+		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
+		set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
+		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
+		mddev->sync_thread = md_register_thread(md_do_sync, mddev,
+							"reshape");
+	}
+
+	return 0;
+
+out_free_conf:
+	md_unregister_thread(&mddev->thread);
+	if (conf->r10bio_pool)
+		mempool_destroy(conf->r10bio_pool);
+	safe_put_page(conf->tmppage);
+	kfree(conf->mirrors);
+	kfree(conf);
+	mddev->private = NULL;
+out:
+	return -EIO;
+}
+
+static void raid10_free(struct mddev *mddev, void *priv)
+{
+	struct r10conf *conf = priv;
+
+	if (conf->r10bio_pool)
+		mempool_destroy(conf->r10bio_pool);
+	safe_put_page(conf->tmppage);
+	kfree(conf->mirrors);
+	kfree(conf->mirrors_old);
+	kfree(conf->mirrors_new);
+	kfree(conf);
+}
+
+static void raid10_quiesce(struct mddev *mddev, int state)
+{
+	struct r10conf *conf = mddev->private;
+
+	switch(state) {
+	case 1:
+		raise_barrier(conf, 0);
+		break;
+	case 0:
+		lower_barrier(conf);
+		break;
+	}
+}
+
+static int raid10_resize(struct mddev *mddev, sector_t sectors)
+{
+	/* Resize of 'far' arrays is not supported.
+	 * For 'near' and 'offset' arrays we can set the
+	 * number of sectors used to be an appropriate multiple
+	 * of the chunk size.
+	 * For 'offset', this is far_copies*chunksize.
+	 * For 'near' the multiplier is the LCM of
+	 * near_copies and raid_disks.
+	 * So if far_copies > 1 && !far_offset, fail.
+	 * Else find LCM(raid_disks, near_copy)*far_copies and
+	 * multiply by chunk_size.  Then round to this number.
+	 * This is mostly done by raid10_size()
+	 */
+	struct r10conf *conf = mddev->private;
+	sector_t oldsize, size;
+
+	if (mddev->reshape_position != MaxSector)
+		return -EBUSY;
+
+	if (conf->geo.far_copies > 1 && !conf->geo.far_offset)
+		return -EINVAL;
+
+	oldsize = raid10_size(mddev, 0, 0);
+	size = raid10_size(mddev, sectors, 0);
+	if (mddev->external_size &&
+	    mddev->array_sectors > size)
+		return -EINVAL;
+	if (mddev->bitmap) {
+		int ret = bitmap_resize(mddev->bitmap, size, 0, 0);
+		if (ret)
+			return ret;
+	}
+	md_set_array_sectors(mddev, size);
+	set_capacity(mddev->gendisk, mddev->array_sectors);
+	revalidate_disk(mddev->gendisk);
+	if (sectors > mddev->dev_sectors &&
+	    mddev->recovery_cp > oldsize) {
+		mddev->recovery_cp = oldsize;
+		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+	}
+	calc_sectors(conf, sectors);
+	mddev->dev_sectors = conf->dev_sectors;
+	mddev->resync_max_sectors = size;
+	return 0;
+}
+
+static void *raid10_takeover_raid0(struct mddev *mddev, sector_t size, int devs)
+{
+	struct md_rdev *rdev;
+	struct r10conf *conf;
+
+	if (mddev->degraded > 0) {
+		printk(KERN_ERR "md/raid10:%s: Error: degraded raid0!\n",
+		       mdname(mddev));
+		return ERR_PTR(-EINVAL);
+	}
+	sector_div(size, devs);
+
+	/* Set new parameters */
+	mddev->new_level = 10;
+	/* new layout: far_copies = 1, near_copies = 2 */
+	mddev->new_layout = (1<<8) + 2;
+	mddev->new_chunk_sectors = mddev->chunk_sectors;
+	mddev->delta_disks = mddev->raid_disks;
+	mddev->raid_disks *= 2;
+	/* make sure it will be not marked as dirty */
+	mddev->recovery_cp = MaxSector;
+	mddev->dev_sectors = size;
+
+	conf = setup_conf(mddev);
+	if (!IS_ERR(conf)) {
+		rdev_for_each(rdev, mddev)
+			if (rdev->raid_disk >= 0) {
+				rdev->new_raid_disk = rdev->raid_disk * 2;
+				rdev->sectors = size;
+			}
+		conf->barrier = 1;
+	}
+
+	return conf;
+}
+
+static void *raid10_takeover(struct mddev *mddev)
+{
+	struct r0conf *raid0_conf;
+
+	/* raid10 can take over:
+	 *  raid0 - providing it has only two drives
+	 */
+	if (mddev->level == 0) {
+		/* for raid0 takeover only one zone is supported */
+		raid0_conf = mddev->private;
+		if (raid0_conf->nr_strip_zones > 1) {
+			printk(KERN_ERR "md/raid10:%s: cannot takeover raid 0"
+			       " with more than one zone.\n",
+			       mdname(mddev));
+			return ERR_PTR(-EINVAL);
+		}
+		return raid10_takeover_raid0(mddev,
+			raid0_conf->strip_zone->zone_end,
+			raid0_conf->strip_zone->nb_dev);
+	}
+	return ERR_PTR(-EINVAL);
+}
+
+static int raid10_check_reshape(struct mddev *mddev)
+{
+	/* Called when there is a request to change
+	 * - layout (to ->new_layout)
+	 * - chunk size (to ->new_chunk_sectors)
+	 * - raid_disks (by delta_disks)
+	 * or when trying to restart a reshape that was ongoing.
+	 *
+	 * We need to validate the request and possibly allocate
+	 * space if that might be an issue later.
+	 *
+	 * Currently we reject any reshape of a 'far' mode array,
+	 * allow chunk size to change if new is generally acceptable,
+	 * allow raid_disks to increase, and allow
+	 * a switch between 'near' mode and 'offset' mode.
+	 */
+	struct r10conf *conf = mddev->private;
+	struct geom geo;
+
+	if (conf->geo.far_copies != 1 && !conf->geo.far_offset)
+		return -EINVAL;
+
+	if (setup_geo(&geo, mddev, geo_start) != conf->copies)
+		/* mustn't change number of copies */
+		return -EINVAL;
+	if (geo.far_copies > 1 && !geo.far_offset)
+		/* Cannot switch to 'far' mode */
+		return -EINVAL;
+
+	if (mddev->array_sectors & geo.chunk_mask)
+			/* not factor of array size */
+			return -EINVAL;
+
+	if (!enough(conf, -1))
+		return -EINVAL;
+
+	kfree(conf->mirrors_new);
+	conf->mirrors_new = NULL;
+	if (mddev->delta_disks > 0) {
+		/* allocate new 'mirrors' list */
+		conf->mirrors_new = kzalloc(
+			sizeof(struct raid10_info)
+			*(mddev->raid_disks +
+			  mddev->delta_disks),
+			GFP_KERNEL);
+		if (!conf->mirrors_new)
+			return -ENOMEM;
+	}
+	return 0;
+}
+
+/*
+ * Need to check if array has failed when deciding whether to:
+ *  - start an array
+ *  - remove non-faulty devices
+ *  - add a spare
+ *  - allow a reshape
+ * This determination is simple when no reshape is happening.
+ * However if there is a reshape, we need to carefully check
+ * both the before and after sections.
+ * This is because some failed devices may only affect one
+ * of the two sections, and some non-in_sync devices may
+ * be insync in the section most affected by failed devices.
+ */
+static int calc_degraded(struct r10conf *conf)
+{
+	int degraded, degraded2;
+	int i;
+
+	rcu_read_lock();
+	degraded = 0;
+	/* 'prev' section first */
+	for (i = 0; i < conf->prev.raid_disks; i++) {
+		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
+		if (!rdev || test_bit(Faulty, &rdev->flags))
+			degraded++;
+		else if (!test_bit(In_sync, &rdev->flags))
+			/* When we can reduce the number of devices in
+			 * an array, this might not contribute to
+			 * 'degraded'.  It does now.
+			 */
+			degraded++;
+	}
+	rcu_read_unlock();
+	if (conf->geo.raid_disks == conf->prev.raid_disks)
+		return degraded;
+	rcu_read_lock();
+	degraded2 = 0;
+	for (i = 0; i < conf->geo.raid_disks; i++) {
+		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
+		if (!rdev || test_bit(Faulty, &rdev->flags))
+			degraded2++;
+		else if (!test_bit(In_sync, &rdev->flags)) {
+			/* If reshape is increasing the number of devices,
+			 * this section has already been recovered, so
+			 * it doesn't contribute to degraded.
+			 * else it does.
+			 */
+			if (conf->geo.raid_disks <= conf->prev.raid_disks)
+				degraded2++;
+		}
+	}
+	rcu_read_unlock();
+	if (degraded2 > degraded)
+		return degraded2;
+	return degraded;
+}
+
+static int raid10_start_reshape(struct mddev *mddev)
+{
+	/* A 'reshape' has been requested. This commits
+	 * the various 'new' fields and sets MD_RECOVER_RESHAPE
+	 * This also checks if there are enough spares and adds them
+	 * to the array.
+	 * We currently require enough spares to make the final
+	 * array non-degraded.  We also require that the difference
+	 * between old and new data_offset - on each device - is
+	 * enough that we never risk over-writing.
+	 */
+
+	unsigned long before_length, after_length;
+	sector_t min_offset_diff = 0;
+	int first = 1;
+	struct geom new;
+	struct r10conf *conf = mddev->private;
+	struct md_rdev *rdev;
+	int spares = 0;
+	int ret;
+
+	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
+		return -EBUSY;
+
+	if (setup_geo(&new, mddev, geo_start) != conf->copies)
+		return -EINVAL;
+
+	before_length = ((1 << conf->prev.chunk_shift) *
+			 conf->prev.far_copies);
+	after_length = ((1 << conf->geo.chunk_shift) *
+			conf->geo.far_copies);
+
+	rdev_for_each(rdev, mddev) {
+		if (!test_bit(In_sync, &rdev->flags)
+		    && !test_bit(Faulty, &rdev->flags))
+			spares++;
+		if (rdev->raid_disk >= 0) {
+			long long diff = (rdev->new_data_offset
+					  - rdev->data_offset);
+			if (!mddev->reshape_backwards)
+				diff = -diff;
+			if (diff < 0)
+				diff = 0;
+			if (first || diff < min_offset_diff)
+				min_offset_diff = diff;
+		}
+	}
+
+	if (max(before_length, after_length) > min_offset_diff)
+		return -EINVAL;
+
+	if (spares < mddev->delta_disks)
+		return -EINVAL;
+
+	conf->offset_diff = min_offset_diff;
+	spin_lock_irq(&conf->device_lock);
+	if (conf->mirrors_new) {
+		memcpy(conf->mirrors_new, conf->mirrors,
+		       sizeof(struct raid10_info)*conf->prev.raid_disks);
+		smp_mb();
+		kfree(conf->mirrors_old);
+		conf->mirrors_old = conf->mirrors;
+		conf->mirrors = conf->mirrors_new;
+		conf->mirrors_new = NULL;
+	}
+	setup_geo(&conf->geo, mddev, geo_start);
+	smp_mb();
+	if (mddev->reshape_backwards) {
+		sector_t size = raid10_size(mddev, 0, 0);
+		if (size < mddev->array_sectors) {
+			spin_unlock_irq(&conf->device_lock);
+			printk(KERN_ERR "md/raid10:%s: array size must be reduce before number of disks\n",
+			       mdname(mddev));
+			return -EINVAL;
+		}
+		mddev->resync_max_sectors = size;
+		conf->reshape_progress = size;
+	} else
+		conf->reshape_progress = 0;
+	spin_unlock_irq(&conf->device_lock);
+
+	if (mddev->delta_disks && mddev->bitmap) {
+		ret = bitmap_resize(mddev->bitmap,
+				    raid10_size(mddev, 0,
+						conf->geo.raid_disks),
+				    0, 0);
+		if (ret)
+			goto abort;
+	}
+	if (mddev->delta_disks > 0) {
+		rdev_for_each(rdev, mddev)
+			if (rdev->raid_disk < 0 &&
+			    !test_bit(Faulty, &rdev->flags)) {
+				if (raid10_add_disk(mddev, rdev) == 0) {
+					if (rdev->raid_disk >=
+					    conf->prev.raid_disks)
+						set_bit(In_sync, &rdev->flags);
+					else
+						rdev->recovery_offset = 0;
+
+					if (sysfs_link_rdev(mddev, rdev))
+						/* Failure here  is OK */;
+				}
+			} else if (rdev->raid_disk >= conf->prev.raid_disks
+				   && !test_bit(Faulty, &rdev->flags)) {
+				/* This is a spare that was manually added */
+				set_bit(In_sync, &rdev->flags);
+			}
+	}
+	/* When a reshape changes the number of devices,
+	 * ->degraded is measured against the larger of the
+	 * pre and  post numbers.
+	 */
+	spin_lock_irq(&conf->device_lock);
+	mddev->degraded = calc_degraded(conf);
+	spin_unlock_irq(&conf->device_lock);
+	mddev->raid_disks = conf->geo.raid_disks;
+	mddev->reshape_position = conf->reshape_progress;
+	set_bit(MD_CHANGE_DEVS, &mddev->flags);
+
+	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
+	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
+	clear_bit(MD_RECOVERY_DONE, &mddev->recovery);
+	set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
+	set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
+
+	mddev->sync_thread = md_register_thread(md_do_sync, mddev,
+						"reshape");
+	if (!mddev->sync_thread) {
+		ret = -EAGAIN;
+		goto abort;
+	}
+	conf->reshape_checkpoint = jiffies;
+	md_wakeup_thread(mddev->sync_thread);
+	md_new_event(mddev);
+	return 0;
+
+abort:
+	mddev->recovery = 0;
+	spin_lock_irq(&conf->device_lock);
+	conf->geo = conf->prev;
+	mddev->raid_disks = conf->geo.raid_disks;
+	rdev_for_each(rdev, mddev)
+		rdev->new_data_offset = rdev->data_offset;
+	smp_wmb();
+	conf->reshape_progress = MaxSector;
+	mddev->reshape_position = MaxSector;
+	spin_unlock_irq(&conf->device_lock);
+	return ret;
+}
+
+/* Calculate the last device-address that could contain
+ * any block from the chunk that includes the array-address 's'
+ * and report the next address.
+ * i.e. the address returned will be chunk-aligned and after
+ * any data that is in the chunk containing 's'.
+ */
+static sector_t last_dev_address(sector_t s, struct geom *geo)
+{
+	s = (s | geo->chunk_mask) + 1;
+	s >>= geo->chunk_shift;
+	s *= geo->near_copies;
+	s = DIV_ROUND_UP_SECTOR_T(s, geo->raid_disks);
+	s *= geo->far_copies;
+	s <<= geo->chunk_shift;
+	return s;
+}
+
+/* Calculate the first device-address that could contain
+ * any block from the chunk that includes the array-address 's'.
+ * This too will be the start of a chunk
+ */
+static sector_t first_dev_address(sector_t s, struct geom *geo)
+{
+	s >>= geo->chunk_shift;
+	s *= geo->near_copies;
+	sector_div(s, geo->raid_disks);
+	s *= geo->far_copies;
+	s <<= geo->chunk_shift;
+	return s;
+}
+
+static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
+				int *skipped)
+{
+	/* We simply copy at most one chunk (smallest of old and new)
+	 * at a time, possibly less if that exceeds RESYNC_PAGES,
+	 * or we hit a bad block or something.
+	 * This might mean we pause for normal IO in the middle of
+	 * a chunk, but that is not a problem was mddev->reshape_position
+	 * can record any location.
+	 *
+	 * If we will want to write to a location that isn't
+	 * yet recorded as 'safe' (i.e. in metadata on disk) then
+	 * we need to flush all reshape requests and update the metadata.
+	 *
+	 * When reshaping forwards (e.g. to more devices), we interpret
+	 * 'safe' as the earliest block which might not have been copied
+	 * down yet.  We divide this by previous stripe size and multiply
+	 * by previous stripe length to get lowest device offset that we
+	 * cannot write to yet.
+	 * We interpret 'sector_nr' as an address that we want to write to.
+	 * From this we use last_device_address() to find where we might
+	 * write to, and first_device_address on the  'safe' position.
+	 * If this 'next' write position is after the 'safe' position,
+	 * we must update the metadata to increase the 'safe' position.
+	 *
+	 * When reshaping backwards, we round in the opposite direction
+	 * and perform the reverse test:  next write position must not be
+	 * less than current safe position.
+	 *
+	 * In all this the minimum difference in data offsets
+	 * (conf->offset_diff - always positive) allows a bit of slack,
+	 * so next can be after 'safe', but not by more than offset_disk
+	 *
+	 * We need to prepare all the bios here before we start any IO
+	 * to ensure the size we choose is acceptable to all devices.
+	 * The means one for each copy for write-out and an extra one for
+	 * read-in.
+	 * We store the read-in bio in ->master_bio and the others in
+	 * ->devs[x].bio and ->devs[x].repl_bio.
+	 */
+	struct r10conf *conf = mddev->private;
+	struct r10bio *r10_bio;
+	sector_t next, safe, last;
+	int max_sectors;
+	int nr_sectors;
+	int s;
+	struct md_rdev *rdev;
+	int need_flush = 0;
+	struct bio *blist;
+	struct bio *bio, *read_bio;
+	int sectors_done = 0;
+
+	if (sector_nr == 0) {
+		/* If restarting in the middle, skip the initial sectors */
+		if (mddev->reshape_backwards &&
+		    conf->reshape_progress < raid10_size(mddev, 0, 0)) {
+			sector_nr = (raid10_size(mddev, 0, 0)
+				     - conf->reshape_progress);
+		} else if (!mddev->reshape_backwards &&
+			   conf->reshape_progress > 0)
+			sector_nr = conf->reshape_progress;
+		if (sector_nr) {
+			mddev->curr_resync_completed = sector_nr;
+			sysfs_notify(&mddev->kobj, NULL, "sync_completed");
+			*skipped = 1;
+			return sector_nr;
+		}
+	}
+
+	/* We don't use sector_nr to track where we are up to
+	 * as that doesn't work well for ->reshape_backwards.
+	 * So just use ->reshape_progress.
+	 */
+	if (mddev->reshape_backwards) {
+		/* 'next' is the earliest device address that we might
+		 * write to for this chunk in the new layout
+		 */
+		next = first_dev_address(conf->reshape_progress - 1,
+					 &conf->geo);
+
+		/* 'safe' is the last device address that we might read from
+		 * in the old layout after a restart
+		 */
+		safe = last_dev_address(conf->reshape_safe - 1,
+					&conf->prev);
+
+		if (next + conf->offset_diff < safe)
+			need_flush = 1;
+
+		last = conf->reshape_progress - 1;
+		sector_nr = last & ~(sector_t)(conf->geo.chunk_mask
+					       & conf->prev.chunk_mask);
+		if (sector_nr + RESYNC_BLOCK_SIZE/512 < last)
+			sector_nr = last + 1 - RESYNC_BLOCK_SIZE/512;
+	} else {
+		/* 'next' is after the last device address that we
+		 * might write to for this chunk in the new layout
+		 */
+		next = last_dev_address(conf->reshape_progress, &conf->geo);
+
+		/* 'safe' is the earliest device address that we might
+		 * read from in the old layout after a restart
+		 */
+		safe = first_dev_address(conf->reshape_safe, &conf->prev);
+
+		/* Need to update metadata if 'next' might be beyond 'safe'
+		 * as that would possibly corrupt data
+		 */
+		if (next > safe + conf->offset_diff)
+			need_flush = 1;
+
+		sector_nr = conf->reshape_progress;
+		last  = sector_nr | (conf->geo.chunk_mask
+				     & conf->prev.chunk_mask);
+
+		if (sector_nr + RESYNC_BLOCK_SIZE/512 <= last)
+			last = sector_nr + RESYNC_BLOCK_SIZE/512 - 1;
+	}
+
+	if (need_flush ||
+	    time_after(jiffies, conf->reshape_checkpoint + 10*HZ)) {
+		/* Need to update reshape_position in metadata */
+		wait_barrier(conf);
+		mddev->reshape_position = conf->reshape_progress;
+		if (mddev->reshape_backwards)
+			mddev->curr_resync_completed = raid10_size(mddev, 0, 0)
+				- conf->reshape_progress;
+		else
+			mddev->curr_resync_completed = conf->reshape_progress;
+		conf->reshape_checkpoint = jiffies;
+		set_bit(MD_CHANGE_DEVS, &mddev->flags);
+		md_wakeup_thread(mddev->thread);
+		wait_event(mddev->sb_wait, mddev->flags == 0 ||
+			   test_bit(MD_RECOVERY_INTR, &mddev->recovery));
+		if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
+			allow_barrier(conf);
+			return sectors_done;
+		}
+		conf->reshape_safe = mddev->reshape_position;
+		allow_barrier(conf);
+	}
+
+read_more:
+	/* Now schedule reads for blocks from sector_nr to last */
+	r10_bio = mempool_alloc(conf->r10buf_pool, GFP_NOIO);
+	r10_bio->state = 0;
+	raise_barrier(conf, sectors_done != 0);
+	atomic_set(&r10_bio->remaining, 0);
+	r10_bio->mddev = mddev;
+	r10_bio->sector = sector_nr;
+	set_bit(R10BIO_IsReshape, &r10_bio->state);
+	r10_bio->sectors = last - sector_nr + 1;
+	rdev = read_balance(conf, r10_bio, &max_sectors);
+	BUG_ON(!test_bit(R10BIO_Previous, &r10_bio->state));
+
+	if (!rdev) {
+		/* Cannot read from here, so need to record bad blocks
+		 * on all the target devices.
+		 */
+		// FIXME
+		mempool_free(r10_bio, conf->r10buf_pool);
+		set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+		return sectors_done;
+	}
+
+	read_bio = bio_alloc_mddev(GFP_KERNEL, RESYNC_PAGES, mddev);
+
+	read_bio->bi_bdev = rdev->bdev;
+	read_bio->bi_iter.bi_sector = (r10_bio->devs[r10_bio->read_slot].addr
+			       + rdev->data_offset);
+	read_bio->bi_private = r10_bio;
+	read_bio->bi_end_io = end_sync_read;
+	read_bio->bi_rw = READ;
+	read_bio->bi_flags &= (~0UL << BIO_RESET_BITS);
+	__set_bit(BIO_UPTODATE, &read_bio->bi_flags);
+	read_bio->bi_vcnt = 0;
+	read_bio->bi_iter.bi_size = 0;
+	r10_bio->master_bio = read_bio;
+	r10_bio->read_slot = r10_bio->devs[r10_bio->read_slot].devnum;
+
+	/* Now find the locations in the new layout */
+	__raid10_find_phys(&conf->geo, r10_bio);
+
+	blist = read_bio;
+	read_bio->bi_next = NULL;
+
+	for (s = 0; s < conf->copies*2; s++) {
+		struct bio *b;
+		int d = r10_bio->devs[s/2].devnum;
+		struct md_rdev *rdev2;
+		if (s&1) {
+			rdev2 = conf->mirrors[d].replacement;
+			b = r10_bio->devs[s/2].repl_bio;
+		} else {
+			rdev2 = conf->mirrors[d].rdev;
+			b = r10_bio->devs[s/2].bio;
+		}
+		if (!rdev2 || test_bit(Faulty, &rdev2->flags))
+			continue;
+
+		bio_reset(b);
+		b->bi_bdev = rdev2->bdev;
+		b->bi_iter.bi_sector = r10_bio->devs[s/2].addr +
+			rdev2->new_data_offset;
+		b->bi_private = r10_bio;
+		b->bi_end_io = end_reshape_write;
+		b->bi_rw = WRITE;
+		b->bi_next = blist;
+		blist = b;
+	}
+
+	/* Now add as many pages as possible to all of these bios. */
+
+	nr_sectors = 0;
+	for (s = 0 ; s < max_sectors; s += PAGE_SIZE >> 9) {
+		struct page *page = r10_bio->devs[0].bio->bi_io_vec[s/(PAGE_SIZE>>9)].bv_page;
+		int len = (max_sectors - s) << 9;
+		if (len > PAGE_SIZE)
+			len = PAGE_SIZE;
+		for (bio = blist; bio ; bio = bio->bi_next) {
+			struct bio *bio2;
+			if (bio_add_page(bio, page, len, 0))
+				continue;
+
+			/* Didn't fit, must stop */
+			for (bio2 = blist;
+			     bio2 && bio2 != bio;
+			     bio2 = bio2->bi_next) {
+				/* Remove last page from this bio */
+				bio2->bi_vcnt--;
+				bio2->bi_iter.bi_size -= len;
+				__clear_bit(BIO_SEG_VALID, &bio2->bi_flags);
+			}
+			goto bio_full;
+		}
+		sector_nr += len >> 9;
+		nr_sectors += len >> 9;
+	}
+bio_full:
+	r10_bio->sectors = nr_sectors;
+
+	/* Now submit the read */
+	md_sync_acct(read_bio->bi_bdev, r10_bio->sectors);
+	atomic_inc(&r10_bio->remaining);
+	read_bio->bi_next = NULL;
+	generic_make_request(read_bio);
+	sector_nr += nr_sectors;
+	sectors_done += nr_sectors;
+	if (sector_nr <= last)
+		goto read_more;
+
+	/* Now that we have done the whole section we can
+	 * update reshape_progress
+	 */
+	if (mddev->reshape_backwards)
+		conf->reshape_progress -= sectors_done;
+	else
+		conf->reshape_progress += sectors_done;
+
+	return sectors_done;
+}
+
+static void end_reshape_request(struct r10bio *r10_bio);
+static int handle_reshape_read_error(struct mddev *mddev,
+				     struct r10bio *r10_bio);
+static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio)
+{
+	/* Reshape read completed.  Hopefully we have a block
+	 * to write out.
+	 * If we got a read error then we do sync 1-page reads from
+	 * elsewhere until we find the data - or give up.
+	 */
+	struct r10conf *conf = mddev->private;
+	int s;
+
+	if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
+		if (handle_reshape_read_error(mddev, r10_bio) < 0) {
+			/* Reshape has been aborted */
+			md_done_sync(mddev, r10_bio->sectors, 0);
+			return;
+		}
+
+	/* We definitely have the data in the pages, schedule the
+	 * writes.
+	 */
+	atomic_set(&r10_bio->remaining, 1);
+	for (s = 0; s < conf->copies*2; s++) {
+		struct bio *b;
+		int d = r10_bio->devs[s/2].devnum;
+		struct md_rdev *rdev;
+		if (s&1) {
+			rdev = conf->mirrors[d].replacement;
+			b = r10_bio->devs[s/2].repl_bio;
+		} else {
+			rdev = conf->mirrors[d].rdev;
+			b = r10_bio->devs[s/2].bio;
+		}
+		if (!rdev || test_bit(Faulty, &rdev->flags))
+			continue;
+		atomic_inc(&rdev->nr_pending);
+		md_sync_acct(b->bi_bdev, r10_bio->sectors);
+		atomic_inc(&r10_bio->remaining);
+		b->bi_next = NULL;
+		generic_make_request(b);
+	}
+	end_reshape_request(r10_bio);
+}
+
+static void end_reshape(struct r10conf *conf)
+{
+	if (test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery))
+		return;
+
+	spin_lock_irq(&conf->device_lock);
+	conf->prev = conf->geo;
+	md_finish_reshape(conf->mddev);
+	smp_wmb();
+	conf->reshape_progress = MaxSector;
+	spin_unlock_irq(&conf->device_lock);
+
+	/* read-ahead size must cover two whole stripes, which is
+	 * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
+	 */
+	if (conf->mddev->queue) {
+		int stripe = conf->geo.raid_disks *
+			((conf->mddev->chunk_sectors << 9) / PAGE_SIZE);
+		stripe /= conf->geo.near_copies;
+		if (conf->mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
+			conf->mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
+	}
+	conf->fullsync = 0;
+}
+
+static int handle_reshape_read_error(struct mddev *mddev,
+				     struct r10bio *r10_bio)
+{
+	/* Use sync reads to get the blocks from somewhere else */
+	int sectors = r10_bio->sectors;
+	struct r10conf *conf = mddev->private;
+	struct {
+		struct r10bio r10_bio;
+		struct r10dev devs[conf->copies];
+	} on_stack;
+	struct r10bio *r10b = &on_stack.r10_bio;
+	int slot = 0;
+	int idx = 0;
+	struct bio_vec *bvec = r10_bio->master_bio->bi_io_vec;
+
+	r10b->sector = r10_bio->sector;
+	__raid10_find_phys(&conf->prev, r10b);
+
+	while (sectors) {
+		int s = sectors;
+		int success = 0;
+		int first_slot = slot;
+
+		if (s > (PAGE_SIZE >> 9))
+			s = PAGE_SIZE >> 9;
+
+		while (!success) {
+			int d = r10b->devs[slot].devnum;
+			struct md_rdev *rdev = conf->mirrors[d].rdev;
+			sector_t addr;
+			if (rdev == NULL ||
+			    test_bit(Faulty, &rdev->flags) ||
+			    !test_bit(In_sync, &rdev->flags))
+				goto failed;
+
+			addr = r10b->devs[slot].addr + idx * PAGE_SIZE;
+			success = sync_page_io(rdev,
+					       addr,
+					       s << 9,
+					       bvec[idx].bv_page,
+					       READ, false);
+			if (success)
+				break;
+		failed:
+			slot++;
+			if (slot >= conf->copies)
+				slot = 0;
+			if (slot == first_slot)
+				break;
+		}
+		if (!success) {
+			/* couldn't read this block, must give up */
+			set_bit(MD_RECOVERY_INTR,
+				&mddev->recovery);
+			return -EIO;
+		}
+		sectors -= s;
+		idx++;
+	}
+	return 0;
+}
+
+static void end_reshape_write(struct bio *bio, int error)
+{
+	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct r10bio *r10_bio = bio->bi_private;
+	struct mddev *mddev = r10_bio->mddev;
+	struct r10conf *conf = mddev->private;
+	int d;
+	int slot;
+	int repl;
+	struct md_rdev *rdev = NULL;
+
+	d = find_bio_disk(conf, r10_bio, bio, &slot, &repl);
+	if (repl)
+		rdev = conf->mirrors[d].replacement;
+	if (!rdev) {
+		smp_mb();
+		rdev = conf->mirrors[d].rdev;
+	}
+
+	if (!uptodate) {
+		/* FIXME should record badblock */
+		md_error(mddev, rdev);
+	}
+
+	rdev_dec_pending(rdev, mddev);
+	end_reshape_request(r10_bio);
+}
+
+static void end_reshape_request(struct r10bio *r10_bio)
+{
+	if (!atomic_dec_and_test(&r10_bio->remaining))
+		return;
+	md_done_sync(r10_bio->mddev, r10_bio->sectors, 1);
+	bio_put(r10_bio->master_bio);
+	put_buf(r10_bio);
+}
+
+static void raid10_finish_reshape(struct mddev *mddev)
+{
+	struct r10conf *conf = mddev->private;
+
+	if (test_bit(MD_RECOVERY_INTR, &mddev->recovery))
+		return;
+
+	if (mddev->delta_disks > 0) {
+		sector_t size = raid10_size(mddev, 0, 0);
+		md_set_array_sectors(mddev, size);
+		if (mddev->recovery_cp > mddev->resync_max_sectors) {
+			mddev->recovery_cp = mddev->resync_max_sectors;
+			set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+		}
+		mddev->resync_max_sectors = size;
+		set_capacity(mddev->gendisk, mddev->array_sectors);
+		revalidate_disk(mddev->gendisk);
+	} else {
+		int d;
+		for (d = conf->geo.raid_disks ;
+		     d < conf->geo.raid_disks - mddev->delta_disks;
+		     d++) {
+			struct md_rdev *rdev = conf->mirrors[d].rdev;
+			if (rdev)
+				clear_bit(In_sync, &rdev->flags);
+			rdev = conf->mirrors[d].replacement;
+			if (rdev)
+				clear_bit(In_sync, &rdev->flags);
+		}
+	}
+	mddev->layout = mddev->new_layout;
+	mddev->chunk_sectors = 1 << conf->geo.chunk_shift;
+	mddev->reshape_position = MaxSector;
+	mddev->delta_disks = 0;
+	mddev->reshape_backwards = 0;
+}
+
+static struct md_personality raid10_personality =
+{
+	.name		= "raid10",
+	.level		= 10,
+	.owner		= THIS_MODULE,
+	.make_request	= make_request,
+	.run		= run,
+	.free		= raid10_free,
+	.status		= status,
+	.error_handler	= error,
+	.hot_add_disk	= raid10_add_disk,
+	.hot_remove_disk= raid10_remove_disk,
+	.spare_active	= raid10_spare_active,
+	.sync_request	= sync_request,
+	.quiesce	= raid10_quiesce,
+	.size		= raid10_size,
+	.resize		= raid10_resize,
+	.takeover	= raid10_takeover,
+	.check_reshape	= raid10_check_reshape,
+	.start_reshape	= raid10_start_reshape,
+	.finish_reshape	= raid10_finish_reshape,
+	.congested	= raid10_congested,
+	.mergeable_bvec	= raid10_mergeable_bvec,
+};
+
+static int __init raid_init(void)
+{
+	return register_md_personality(&raid10_personality);
+}
+
+static void raid_exit(void)
+{
+	unregister_md_personality(&raid10_personality);
+}
+
+module_init(raid_init);
+module_exit(raid_exit);
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("RAID10 (striped mirror) personality for MD");
+MODULE_ALIAS("md-personality-9"); /* RAID10 */
+MODULE_ALIAS("md-raid10");
+MODULE_ALIAS("md-level-10");
+
+module_param(max_queued_requests, int, S_IRUGO|S_IWUSR);