Initial import

1 files changed, 1885 insertions, 0 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
new file mode 100644
index 000000000..a5b343d20
--- /dev/null
+++ b/drivers/block/loop.c
@@ -0,0 +1,1885 @@
+/*
+ *  linux/drivers/block/loop.c
+ *
+ *  Written by Theodore Ts'o, 3/29/93
+ *
+ * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
+ * permitted under the GNU General Public License.
+ *
+ * DES encryption plus some minor changes by Werner Almesberger, 30-MAY-1993
+ * more DES encryption plus IDEA encryption by Nicholas J. Leon, June 20, 1996
+ *
+ * Modularized and updated for 1.1.16 kernel - Mitch Dsouza 28th May 1994
+ * Adapted for 1.3.59 kernel - Andries Brouwer, 1 Feb 1996
+ *
+ * Fixed do_loop_request() re-entrancy - Vincent.Renardias@waw.com Mar 20, 1997
+ *
+ * Added devfs support - Richard Gooch <rgooch@atnf.csiro.au> 16-Jan-1998
+ *
+ * Handle sparse backing files correctly - Kenn Humborg, Jun 28, 1998
+ *
+ * Loadable modules and other fixes by AK, 1998
+ *
+ * Make real block number available to downstream transfer functions, enables
+ * CBC (and relatives) mode encryption requiring unique IVs per data block.
+ * Reed H. Petty, rhp@draper.net
+ *
+ * Maximum number of loop devices now dynamic via max_loop module parameter.
+ * Russell Kroll <rkroll@exploits.org> 19990701
+ *
+ * Maximum number of loop devices when compiled-in now selectable by passing
+ * max_loop=<1-255> to the kernel on boot.
+ * Erik I. Bolsø, <eriki@himolde.no>, Oct 31, 1999
+ *
+ * Completely rewrite request handling to be make_request_fn style and
+ * non blocking, pushing work to a helper thread. Lots of fixes from
+ * Al Viro too.
+ * Jens Axboe <axboe@suse.de>, Nov 2000
+ *
+ * Support up to 256 loop devices
+ * Heinz Mauelshagen <mge@sistina.com>, Feb 2002
+ *
+ * Support for falling back on the write file operation when the address space
+ * operations write_begin is not available on the backing filesystem.
+ * Anton Altaparmakov, 16 Feb 2005
+ *
+ * Still To Fix:
+ * - Advisory locking is ignored here.
+ * - Should use an own CAP_* category instead of CAP_SYS_ADMIN
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/stat.h>
+#include <linux/errno.h>
+#include <linux/major.h>
+#include <linux/wait.h>
+#include <linux/blkdev.h>
+#include <linux/blkpg.h>
+#include <linux/init.h>
+#include <linux/swap.h>
+#include <linux/slab.h>
+#include <linux/compat.h>
+#include <linux/suspend.h>
+#include <linux/freezer.h>
+#include <linux/mutex.h>
+#include <linux/writeback.h>
+#include <linux/completion.h>
+#include <linux/highmem.h>
+#include <linux/kthread.h>
+#include <linux/splice.h>
+#include <linux/sysfs.h>
+#include <linux/miscdevice.h>
+#include <linux/falloc.h>
+#include <linux/uio.h>
+#include "loop.h"
+
+#include <asm/uaccess.h>
+
+static DEFINE_IDR(loop_index_idr);
+static DEFINE_MUTEX(loop_index_mutex);
+
+static int max_part;
+static int part_shift;
+
+static int transfer_xor(struct loop_device *lo, int cmd,
+			struct page *raw_page, unsigned raw_off,
+			struct page *loop_page, unsigned loop_off,
+			int size, sector_t real_block)
+{
+	char *raw_buf = kmap_atomic(raw_page) + raw_off;
+	char *loop_buf = kmap_atomic(loop_page) + loop_off;
+	char *in, *out, *key;
+	int i, keysize;
+
+	if (cmd == READ) {
+		in = raw_buf;
+		out = loop_buf;
+	} else {
+		in = loop_buf;
+		out = raw_buf;
+	}
+
+	key = lo->lo_encrypt_key;
+	keysize = lo->lo_encrypt_key_size;
+	for (i = 0; i < size; i++)
+		*out++ = *in++ ^ key[(i & 511) % keysize];
+
+	kunmap_atomic(loop_buf);
+	kunmap_atomic(raw_buf);
+	cond_resched();
+	return 0;
+}
+
+static int xor_init(struct loop_device *lo, const struct loop_info64 *info)
+{
+	if (unlikely(info->lo_encrypt_key_size <= 0))
+		return -EINVAL;
+	return 0;
+}
+
+static struct loop_func_table none_funcs = {
+	.number = LO_CRYPT_NONE,
+}; 
+
+static struct loop_func_table xor_funcs = {
+	.number = LO_CRYPT_XOR,
+	.transfer = transfer_xor,
+	.init = xor_init
+}; 
+
+/* xfer_funcs[0] is special - its release function is never called */
+static struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = {
+	&none_funcs,
+	&xor_funcs
+};
+
+static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file)
+{
+	loff_t loopsize;
+
+	/* Compute loopsize in bytes */
+	loopsize = i_size_read(file->f_mapping->host);
+	if (offset > 0)
+		loopsize -= offset;
+	/* offset is beyond i_size, weird but possible */
+	if (loopsize < 0)
+		return 0;
+
+	if (sizelimit > 0 && sizelimit < loopsize)
+		loopsize = sizelimit;
+	/*
+	 * Unfortunately, if we want to do I/O on the device,
+	 * the number of 512-byte sectors has to fit into a sector_t.
+	 */
+	return loopsize >> 9;
+}
+
+static loff_t get_loop_size(struct loop_device *lo, struct file *file)
+{
+	return get_size(lo->lo_offset, lo->lo_sizelimit, file);
+}
+
+static int
+figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
+{
+	loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
+	sector_t x = (sector_t)size;
+	struct block_device *bdev = lo->lo_device;
+
+	if (unlikely((loff_t)x != size))
+		return -EFBIG;
+	if (lo->lo_offset != offset)
+		lo->lo_offset = offset;
+	if (lo->lo_sizelimit != sizelimit)
+		lo->lo_sizelimit = sizelimit;
+	set_capacity(lo->lo_disk, x);
+	bd_set_size(bdev, (loff_t)get_capacity(bdev->bd_disk) << 9);
+	/* let user-space know about the new size */
+	kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
+	return 0;
+}
+
+static inline int
+lo_do_transfer(struct loop_device *lo, int cmd,
+	       struct page *rpage, unsigned roffs,
+	       struct page *lpage, unsigned loffs,
+	       int size, sector_t rblock)
+{
+	int ret;
+
+	ret = lo->transfer(lo, cmd, rpage, roffs, lpage, loffs, size, rblock);
+	if (likely(!ret))
+		return 0;
+
+	printk_ratelimited(KERN_ERR
+		"loop: Transfer error at byte offset %llu, length %i.\n",
+		(unsigned long long)rblock << 9, size);
+	return ret;
+}
+
+static int lo_write_bvec(struct file *file, struct bio_vec *bvec, loff_t *ppos)
+{
+	struct iov_iter i;
+	ssize_t bw;
+
+	iov_iter_bvec(&i, ITER_BVEC, bvec, 1, bvec->bv_len);
+
+	file_start_write(file);
+	bw = vfs_iter_write(file, &i, ppos);
+	file_end_write(file);
+
+	if (likely(bw ==  bvec->bv_len))
+		return 0;
+
+	printk_ratelimited(KERN_ERR
+		"loop: Write error at byte offset %llu, length %i.\n",
+		(unsigned long long)*ppos, bvec->bv_len);
+	if (bw >= 0)
+		bw = -EIO;
+	return bw;
+}
+
+static int lo_write_simple(struct loop_device *lo, struct request *rq,
+		loff_t pos)
+{
+	struct bio_vec bvec;
+	struct req_iterator iter;
+	int ret = 0;
+
+	rq_for_each_segment(bvec, rq, iter) {
+		ret = lo_write_bvec(lo->lo_backing_file, &bvec, &pos);
+		if (ret < 0)
+			break;
+		cond_resched();
+	}
+
+	return ret;
+}
+
+/*
+ * This is the slow, transforming version that needs to double buffer the
+ * data as it cannot do the transformations in place without having direct
+ * access to the destination pages of the backing file.
+ */
+static int lo_write_transfer(struct loop_device *lo, struct request *rq,
+		loff_t pos)
+{
+	struct bio_vec bvec, b;
+	struct req_iterator iter;
+	struct page *page;
+	int ret = 0;
+
+	page = alloc_page(GFP_NOIO);
+	if (unlikely(!page))
+		return -ENOMEM;
+
+	rq_for_each_segment(bvec, rq, iter) {
+		ret = lo_do_transfer(lo, WRITE, page, 0, bvec.bv_page,
+			bvec.bv_offset, bvec.bv_len, pos >> 9);
+		if (unlikely(ret))
+			break;
+
+		b.bv_page = page;
+		b.bv_offset = 0;
+		b.bv_len = bvec.bv_len;
+		ret = lo_write_bvec(lo->lo_backing_file, &b, &pos);
+		if (ret < 0)
+			break;
+	}
+
+	__free_page(page);
+	return ret;
+}
+
+static int lo_read_simple(struct loop_device *lo, struct request *rq,
+		loff_t pos)
+{
+	struct bio_vec bvec;
+	struct req_iterator iter;
+	struct iov_iter i;
+	ssize_t len;
+
+	rq_for_each_segment(bvec, rq, iter) {
+		iov_iter_bvec(&i, ITER_BVEC, &bvec, 1, bvec.bv_len);
+		len = vfs_iter_read(lo->lo_backing_file, &i, &pos);
+		if (len < 0)
+			return len;
+
+		flush_dcache_page(bvec.bv_page);
+
+		if (len != bvec.bv_len) {
+			struct bio *bio;
+
+			__rq_for_each_bio(bio, rq)
+				zero_fill_bio(bio);
+			break;
+		}
+		cond_resched();
+	}
+
+	return 0;
+}
+
+static int lo_read_transfer(struct loop_device *lo, struct request *rq,
+		loff_t pos)
+{
+	struct bio_vec bvec, b;
+	struct req_iterator iter;
+	struct iov_iter i;
+	struct page *page;
+	ssize_t len;
+	int ret = 0;
+
+	page = alloc_page(GFP_NOIO);
+	if (unlikely(!page))
+		return -ENOMEM;
+
+	rq_for_each_segment(bvec, rq, iter) {
+		loff_t offset = pos;
+
+		b.bv_page = page;
+		b.bv_offset = 0;
+		b.bv_len = bvec.bv_len;
+
+		iov_iter_bvec(&i, ITER_BVEC, &b, 1, b.bv_len);
+		len = vfs_iter_read(lo->lo_backing_file, &i, &pos);
+		if (len < 0) {
+			ret = len;
+			goto out_free_page;
+		}
+
+		ret = lo_do_transfer(lo, READ, page, 0, bvec.bv_page,
+			bvec.bv_offset, len, offset >> 9);
+		if (ret)
+			goto out_free_page;
+
+		flush_dcache_page(bvec.bv_page);
+
+		if (len != bvec.bv_len) {
+			struct bio *bio;
+
+			__rq_for_each_bio(bio, rq)
+				zero_fill_bio(bio);
+			break;
+		}
+	}
+
+	ret = 0;
+out_free_page:
+	__free_page(page);
+	return ret;
+}
+
+static int lo_discard(struct loop_device *lo, struct request *rq, loff_t pos)
+{
+	/*
+	 * We use punch hole to reclaim the free space used by the
+	 * image a.k.a. discard. However we do not support discard if
+	 * encryption is enabled, because it may give an attacker
+	 * useful information.
+	 */
+	struct file *file = lo->lo_backing_file;
+	int mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE;
+	int ret;
+
+	if ((!file->f_op->fallocate) || lo->lo_encrypt_key_size) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	ret = file->f_op->fallocate(file, mode, pos, blk_rq_bytes(rq));
+	if (unlikely(ret && ret != -EINVAL && ret != -EOPNOTSUPP))
+		ret = -EIO;
+ out:
+	return ret;
+}
+
+static int lo_req_flush(struct loop_device *lo, struct request *rq)
+{
+	struct file *file = lo->lo_backing_file;
+	int ret = vfs_fsync(file, 0);
+	if (unlikely(ret && ret != -EINVAL))
+		ret = -EIO;
+
+	return ret;
+}
+
+static int do_req_filebacked(struct loop_device *lo, struct request *rq)
+{
+	loff_t pos;
+	int ret;
+
+	pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset;
+
+	if (rq->cmd_flags & REQ_WRITE) {
+		if (rq->cmd_flags & REQ_FLUSH)
+			ret = lo_req_flush(lo, rq);
+		else if (rq->cmd_flags & REQ_DISCARD)
+			ret = lo_discard(lo, rq, pos);
+		else if (lo->transfer)
+			ret = lo_write_transfer(lo, rq, pos);
+		else
+			ret = lo_write_simple(lo, rq, pos);
+
+	} else {
+		if (lo->transfer)
+			ret = lo_read_transfer(lo, rq, pos);
+		else
+			ret = lo_read_simple(lo, rq, pos);
+	}
+
+	return ret;
+}
+
+struct switch_request {
+	struct file *file;
+	struct completion wait;
+};
+
+/*
+ * Do the actual switch; called from the BIO completion routine
+ */
+static void do_loop_switch(struct loop_device *lo, struct switch_request *p)
+{
+	struct file *file = p->file;
+	struct file *old_file = lo->lo_backing_file;
+	struct address_space *mapping;
+
+	/* if no new file, only flush of queued bios requested */
+	if (!file)
+		return;
+
+	mapping = file->f_mapping;
+	mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
+	lo->lo_backing_file = file;
+	lo->lo_blocksize = S_ISBLK(mapping->host->i_mode) ?
+		mapping->host->i_bdev->bd_block_size : PAGE_SIZE;
+	lo->old_gfp_mask = mapping_gfp_mask(mapping);
+	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
+}
+
+/*
+ * loop_switch performs the hard work of switching a backing store.
+ * First it needs to flush existing IO, it does this by sending a magic
+ * BIO down the pipe. The completion of this BIO does the actual switch.
+ */
+static int loop_switch(struct loop_device *lo, struct file *file)
+{
+	struct switch_request w;
+
+	w.file = file;
+
+	/* freeze queue and wait for completion of scheduled requests */
+	blk_mq_freeze_queue(lo->lo_queue);
+
+	/* do the switch action */
+	do_loop_switch(lo, &w);
+
+	/* unfreeze */
+	blk_mq_unfreeze_queue(lo->lo_queue);
+
+	return 0;
+}
+
+/*
+ * Helper to flush the IOs in loop, but keeping loop thread running
+ */
+static int loop_flush(struct loop_device *lo)
+{
+	return loop_switch(lo, NULL);
+}
+
+/*
+ * loop_change_fd switched the backing store of a loopback device to
+ * a new file. This is useful for operating system installers to free up
+ * the original file and in High Availability environments to switch to
+ * an alternative location for the content in case of server meltdown.
+ * This can only work if the loop device is used read-only, and if the
+ * new backing store is the same size and type as the old backing store.
+ */
+static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
+			  unsigned int arg)
+{
+	struct file	*file, *old_file;
+	struct inode	*inode;
+	int		error;
+
+	error = -ENXIO;
+	if (lo->lo_state != Lo_bound)
+		goto out;
+
+	/* the loop device has to be read-only */
+	error = -EINVAL;
+	if (!(lo->lo_flags & LO_FLAGS_READ_ONLY))
+		goto out;
+
+	error = -EBADF;
+	file = fget(arg);
+	if (!file)
+		goto out;
+
+	inode = file->f_mapping->host;
+	old_file = lo->lo_backing_file;
+
+	error = -EINVAL;
+
+	if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
+		goto out_putf;
+
+	/* size of the new backing store needs to be the same */
+	if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
+		goto out_putf;
+
+	/* and ... switch */
+	error = loop_switch(lo, file);
+	if (error)
+		goto out_putf;
+
+	fput(old_file);
+	if (lo->lo_flags & LO_FLAGS_PARTSCAN)
+		ioctl_by_bdev(bdev, BLKRRPART, 0);
+	return 0;
+
+ out_putf:
+	fput(file);
+ out:
+	return error;
+}
+
+static inline int is_loop_device(struct file *file)
+{
+	struct inode *i = file->f_mapping->host;
+
+	return i && S_ISBLK(i->i_mode) && MAJOR(i->i_rdev) == LOOP_MAJOR;
+}
+
+/*
+ * for AUFS
+ * no get/put for file.
+ */
+struct file *loop_backing_file(struct super_block *sb)
+{
+	struct file *ret;
+	struct loop_device *l;
+
+	ret = NULL;
+	if (MAJOR(sb->s_dev) == LOOP_MAJOR) {
+		l = sb->s_bdev->bd_disk->private_data;
+		ret = l->lo_backing_file;
+	}
+	return ret;
+}
+EXPORT_SYMBOL(loop_backing_file);
+
+/* loop sysfs attributes */
+
+static ssize_t loop_attr_show(struct device *dev, char *page,
+			      ssize_t (*callback)(struct loop_device *, char *))
+{
+	struct gendisk *disk = dev_to_disk(dev);
+	struct loop_device *lo = disk->private_data;
+
+	return callback(lo, page);
+}
+
+#define LOOP_ATTR_RO(_name)						\
+static ssize_t loop_attr_##_name##_show(struct loop_device *, char *);	\
+static ssize_t loop_attr_do_show_##_name(struct device *d,		\
+				struct device_attribute *attr, char *b)	\
+{									\
+	return loop_attr_show(d, b, loop_attr_##_name##_show);		\
+}									\
+static struct device_attribute loop_attr_##_name =			\
+	__ATTR(_name, S_IRUGO, loop_attr_do_show_##_name, NULL);
+
+static ssize_t loop_attr_backing_file_show(struct loop_device *lo, char *buf)
+{
+	ssize_t ret;
+	char *p = NULL;
+
+	spin_lock_irq(&lo->lo_lock);
+	if (lo->lo_backing_file)
+		p = d_path(&lo->lo_backing_file->f_path, buf, PAGE_SIZE - 1);
+	spin_unlock_irq(&lo->lo_lock);
+
+	if (IS_ERR_OR_NULL(p))
+		ret = PTR_ERR(p);
+	else {
+		ret = strlen(p);
+		memmove(buf, p, ret);
+		buf[ret++] = '\n';
+		buf[ret] = 0;
+	}
+
+	return ret;
+}
+
+static ssize_t loop_attr_offset_show(struct loop_device *lo, char *buf)
+{
+	return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_offset);
+}
+
+static ssize_t loop_attr_sizelimit_show(struct loop_device *lo, char *buf)
+{
+	return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_sizelimit);
+}
+
+static ssize_t loop_attr_autoclear_show(struct loop_device *lo, char *buf)
+{
+	int autoclear = (lo->lo_flags & LO_FLAGS_AUTOCLEAR);
+
+	return sprintf(buf, "%s\n", autoclear ? "1" : "0");
+}
+
+static ssize_t loop_attr_partscan_show(struct loop_device *lo, char *buf)
+{
+	int partscan = (lo->lo_flags & LO_FLAGS_PARTSCAN);
+
+	return sprintf(buf, "%s\n", partscan ? "1" : "0");
+}
+
+LOOP_ATTR_RO(backing_file);
+LOOP_ATTR_RO(offset);
+LOOP_ATTR_RO(sizelimit);
+LOOP_ATTR_RO(autoclear);
+LOOP_ATTR_RO(partscan);
+
+static struct attribute *loop_attrs[] = {
+	&loop_attr_backing_file.attr,
+	&loop_attr_offset.attr,
+	&loop_attr_sizelimit.attr,
+	&loop_attr_autoclear.attr,
+	&loop_attr_partscan.attr,
+	NULL,
+};
+
+static struct attribute_group loop_attribute_group = {
+	.name = "loop",
+	.attrs= loop_attrs,
+};
+
+static int loop_sysfs_init(struct loop_device *lo)
+{
+	return sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
+				  &loop_attribute_group);
+}
+
+static void loop_sysfs_exit(struct loop_device *lo)
+{
+	sysfs_remove_group(&disk_to_dev(lo->lo_disk)->kobj,
+			   &loop_attribute_group);
+}
+
+static void loop_config_discard(struct loop_device *lo)
+{
+	struct file *file = lo->lo_backing_file;
+	struct inode *inode = file->f_mapping->host;
+	struct request_queue *q = lo->lo_queue;
+
+	/*
+	 * We use punch hole to reclaim the free space used by the
+	 * image a.k.a. discard. However we do not support discard if
+	 * encryption is enabled, because it may give an attacker
+	 * useful information.
+	 */
+	if ((!file->f_op->fallocate) ||
+	    lo->lo_encrypt_key_size) {
+		q->limits.discard_granularity = 0;
+		q->limits.discard_alignment = 0;
+		q->limits.max_discard_sectors = 0;
+		q->limits.discard_zeroes_data = 0;
+		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
+		return;
+	}
+
+	q->limits.discard_granularity = inode->i_sb->s_blocksize;
+	q->limits.discard_alignment = 0;
+	q->limits.max_discard_sectors = UINT_MAX >> 9;
+	q->limits.discard_zeroes_data = 1;
+	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
+}
+
+static int loop_set_fd(struct loop_device *lo, fmode_t mode,
+		       struct block_device *bdev, unsigned int arg)
+{
+	struct file	*file, *f;
+	struct inode	*inode;
+	struct address_space *mapping;
+	unsigned lo_blocksize;
+	int		lo_flags = 0;
+	int		error;
+	loff_t		size;
+
+	/* This is safe, since we have a reference from open(). */
+	__module_get(THIS_MODULE);
+
+	error = -EBADF;
+	file = fget(arg);
+	if (!file)
+		goto out;
+
+	error = -EBUSY;
+	if (lo->lo_state != Lo_unbound)
+		goto out_putf;
+
+	/* Avoid recursion */
+	f = file;
+	while (is_loop_device(f)) {
+		struct loop_device *l;
+
+		if (f->f_mapping->host->i_bdev == bdev)
+			goto out_putf;
+
+		l = f->f_mapping->host->i_bdev->bd_disk->private_data;
+		if (l->lo_state == Lo_unbound) {
+			error = -EINVAL;
+			goto out_putf;
+		}
+		f = l->lo_backing_file;
+	}
+
+	mapping = file->f_mapping;
+	inode = mapping->host;
+
+	error = -EINVAL;
+	if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
+		goto out_putf;
+
+	if (!(file->f_mode & FMODE_WRITE) || !(mode & FMODE_WRITE) ||
+	    !file->f_op->write_iter)
+		lo_flags |= LO_FLAGS_READ_ONLY;
+
+	lo_blocksize = S_ISBLK(inode->i_mode) ?
+		inode->i_bdev->bd_block_size : PAGE_SIZE;
+
+	error = -EFBIG;
+	size = get_loop_size(lo, file);
+	if ((loff_t)(sector_t)size != size)
+		goto out_putf;
+	error = -ENOMEM;
+	lo->wq = alloc_workqueue("kloopd%d",
+			WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 16,
+			lo->lo_number);
+	if (!lo->wq)
+		goto out_putf;
+
+	error = 0;
+
+	set_device_ro(bdev, (lo_flags & LO_FLAGS_READ_ONLY) != 0);
+
+	lo->lo_blocksize = lo_blocksize;
+	lo->lo_device = bdev;
+	lo->lo_flags = lo_flags;
+	lo->lo_backing_file = file;
+	lo->transfer = NULL;
+	lo->ioctl = NULL;
+	lo->lo_sizelimit = 0;
+	lo->old_gfp_mask = mapping_gfp_mask(mapping);
+	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
+
+	if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
+		blk_queue_flush(lo->lo_queue, REQ_FLUSH);
+
+	set_capacity(lo->lo_disk, size);
+	bd_set_size(bdev, size << 9);
+	loop_sysfs_init(lo);
+	/* let user-space know about the new size */
+	kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
+
+	set_blocksize(bdev, lo_blocksize);
+
+	lo->lo_state = Lo_bound;
+	if (part_shift)
+		lo->lo_flags |= LO_FLAGS_PARTSCAN;
+	if (lo->lo_flags & LO_FLAGS_PARTSCAN)
+		ioctl_by_bdev(bdev, BLKRRPART, 0);
+
+	/* Grab the block_device to prevent its destruction after we
+	 * put /dev/loopXX inode. Later in loop_clr_fd() we bdput(bdev).
+	 */
+	bdgrab(bdev);
+	return 0;
+
+ out_putf:
+	fput(file);
+ out:
+	/* This is safe: open() is still holding a reference. */
+	module_put(THIS_MODULE);
+	return error;
+}
+
+static int
+loop_release_xfer(struct loop_device *lo)
+{
+	int err = 0;
+	struct loop_func_table *xfer = lo->lo_encryption;
+
+	if (xfer) {
+		if (xfer->release)
+			err = xfer->release(lo);
+		lo->transfer = NULL;
+		lo->lo_encryption = NULL;
+		module_put(xfer->owner);
+	}
+	return err;
+}
+
+static int
+loop_init_xfer(struct loop_device *lo, struct loop_func_table *xfer,
+	       const struct loop_info64 *i)
+{
+	int err = 0;
+
+	if (xfer) {
+		struct module *owner = xfer->owner;
+
+		if (!try_module_get(owner))
+			return -EINVAL;
+		if (xfer->init)
+			err = xfer->init(lo, i);
+		if (err)
+			module_put(owner);
+		else
+			lo->lo_encryption = xfer;
+	}
+	return err;
+}
+
+static int loop_clr_fd(struct loop_device *lo)
+{
+	struct file *filp = lo->lo_backing_file;
+	gfp_t gfp = lo->old_gfp_mask;
+	struct block_device *bdev = lo->lo_device;
+
+	if (lo->lo_state != Lo_bound)
+		return -ENXIO;
+
+	/*
+	 * If we've explicitly asked to tear down the loop device,
+	 * and it has an elevated reference count, set it for auto-teardown when
+	 * the last reference goes away. This stops $!~#$@ udev from
+	 * preventing teardown because it decided that it needs to run blkid on
+	 * the loopback device whenever they appear. xfstests is notorious for
+	 * failing tests because blkid via udev races with a losetup
+	 * <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
+	 * command to fail with EBUSY.
+	 */
+	if (lo->lo_refcnt > 1) {
+		lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
+		mutex_unlock(&lo->lo_ctl_mutex);
+		return 0;
+	}
+
+	if (filp == NULL)
+		return -EINVAL;
+
+	spin_lock_irq(&lo->lo_lock);
+	lo->lo_state = Lo_rundown;
+	lo->lo_backing_file = NULL;
+	spin_unlock_irq(&lo->lo_lock);
+
+	loop_release_xfer(lo);
+	lo->transfer = NULL;
+	lo->ioctl = NULL;
+	lo->lo_device = NULL;
+	lo->lo_encryption = NULL;
+	lo->lo_offset = 0;
+	lo->lo_sizelimit = 0;
+	lo->lo_encrypt_key_size = 0;
+	memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
+	memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
+	memset(lo->lo_file_name, 0, LO_NAME_SIZE);
+	if (bdev) {
+		bdput(bdev);
+		invalidate_bdev(bdev);
+	}
+	set_capacity(lo->lo_disk, 0);
+	loop_sysfs_exit(lo);
+	if (bdev) {
+		bd_set_size(bdev, 0);
+		/* let user-space know about this change */
+		kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
+	}
+	mapping_set_gfp_mask(filp->f_mapping, gfp);
+	lo->lo_state = Lo_unbound;
+	/* This is safe: open() is still holding a reference. */
+	module_put(THIS_MODULE);
+	if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev)
+		ioctl_by_bdev(bdev, BLKRRPART, 0);
+	lo->lo_flags = 0;
+	if (!part_shift)
+		lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
+	destroy_workqueue(lo->wq);
+	lo->wq = NULL;
+	mutex_unlock(&lo->lo_ctl_mutex);
+	/*
+	 * Need not hold lo_ctl_mutex to fput backing file.
+	 * Calling fput holding lo_ctl_mutex triggers a circular
+	 * lock dependency possibility warning as fput can take
+	 * bd_mutex which is usually taken before lo_ctl_mutex.
+	 */
+	fput(filp);
+	return 0;
+}
+
+static int
+loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
+{
+	int err;
+	struct loop_func_table *xfer;
+	kuid_t uid = current_uid();
+
+	if (lo->lo_encrypt_key_size &&
+	    !uid_eq(lo->lo_key_owner, uid) &&
+	    !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (lo->lo_state != Lo_bound)
+		return -ENXIO;
+	if ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE)
+		return -EINVAL;
+
+	err = loop_release_xfer(lo);
+	if (err)
+		return err;
+
+	if (info->lo_encrypt_type) {
+		unsigned int type = info->lo_encrypt_type;
+
+		if (type >= MAX_LO_CRYPT)
+			return -EINVAL;
+		xfer = xfer_funcs[type];
+		if (xfer == NULL)
+			return -EINVAL;
+	} else
+		xfer = NULL;
+
+	err = loop_init_xfer(lo, xfer, info);
+	if (err)
+		return err;
+
+	if (lo->lo_offset != info->lo_offset ||
+	    lo->lo_sizelimit != info->lo_sizelimit)
+		if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit))
+			return -EFBIG;
+
+	loop_config_discard(lo);
+
+	memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
+	memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
+	lo->lo_file_name[LO_NAME_SIZE-1] = 0;
+	lo->lo_crypt_name[LO_NAME_SIZE-1] = 0;
+
+	if (!xfer)
+		xfer = &none_funcs;
+	lo->transfer = xfer->transfer;
+	lo->ioctl = xfer->ioctl;
+
+	if ((lo->lo_flags & LO_FLAGS_AUTOCLEAR) !=
+	     (info->lo_flags & LO_FLAGS_AUTOCLEAR))
+		lo->lo_flags ^= LO_FLAGS_AUTOCLEAR;
+
+	if ((info->lo_flags & LO_FLAGS_PARTSCAN) &&
+	     !(lo->lo_flags & LO_FLAGS_PARTSCAN)) {
+		lo->lo_flags |= LO_FLAGS_PARTSCAN;
+		lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;
+		ioctl_by_bdev(lo->lo_device, BLKRRPART, 0);
+	}
+
+	lo->lo_encrypt_key_size = info->lo_encrypt_key_size;
+	lo->lo_init[0] = info->lo_init[0];
+	lo->lo_init[1] = info->lo_init[1];
+	if (info->lo_encrypt_key_size) {
+		memcpy(lo->lo_encrypt_key, info->lo_encrypt_key,
+		       info->lo_encrypt_key_size);
+		lo->lo_key_owner = uid;
+	}
+
+	return 0;
+}
+
+static int
+loop_get_status(struct loop_device *lo, struct loop_info64 *info)
+{
+	struct file *file = lo->lo_backing_file;
+	struct kstat stat;
+	int error;
+
+	if (lo->lo_state != Lo_bound)
+		return -ENXIO;
+	error = vfs_getattr(&file->f_path, &stat);
+	if (error)
+		return error;
+	memset(info, 0, sizeof(*info));
+	info->lo_number = lo->lo_number;
+	info->lo_device = huge_encode_dev(stat.dev);
+	info->lo_inode = stat.ino;
+	info->lo_rdevice = huge_encode_dev(lo->lo_device ? stat.rdev : stat.dev);
+	info->lo_offset = lo->lo_offset;
+	info->lo_sizelimit = lo->lo_sizelimit;
+	info->lo_flags = lo->lo_flags;
+	memcpy(info->lo_file_name, lo->lo_file_name, LO_NAME_SIZE);
+	memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);
+	info->lo_encrypt_type =
+		lo->lo_encryption ? lo->lo_encryption->number : 0;
+	if (lo->lo_encrypt_key_size && capable(CAP_SYS_ADMIN)) {
+		info->lo_encrypt_key_size = lo->lo_encrypt_key_size;
+		memcpy(info->lo_encrypt_key, lo->lo_encrypt_key,
+		       lo->lo_encrypt_key_size);
+	}
+	return 0;
+}
+
+static void
+loop_info64_from_old(const struct loop_info *info, struct loop_info64 *info64)
+{
+	memset(info64, 0, sizeof(*info64));
+	info64->lo_number = info->lo_number;
+	info64->lo_device = info->lo_device;
+	info64->lo_inode = info->lo_inode;
+	info64->lo_rdevice = info->lo_rdevice;
+	info64->lo_offset = info->lo_offset;
+	info64->lo_sizelimit = 0;
+	info64->lo_encrypt_type = info->lo_encrypt_type;
+	info64->lo_encrypt_key_size = info->lo_encrypt_key_size;
+	info64->lo_flags = info->lo_flags;
+	info64->lo_init[0] = info->lo_init[0];
+	info64->lo_init[1] = info->lo_init[1];
+	if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
+		memcpy(info64->lo_crypt_name, info->lo_name, LO_NAME_SIZE);
+	else
+		memcpy(info64->lo_file_name, info->lo_name, LO_NAME_SIZE);
+	memcpy(info64->lo_encrypt_key, info->lo_encrypt_key, LO_KEY_SIZE);
+}
+
+static int
+loop_info64_to_old(const struct loop_info64 *info64, struct loop_info *info)
+{
+	memset(info, 0, sizeof(*info));
+	info->lo_number = info64->lo_number;
+	info->lo_device = info64->lo_device;
+	info->lo_inode = info64->lo_inode;
+	info->lo_rdevice = info64->lo_rdevice;
+	info->lo_offset = info64->lo_offset;
+	info->lo_encrypt_type = info64->lo_encrypt_type;
+	info->lo_encrypt_key_size = info64->lo_encrypt_key_size;
+	info->lo_flags = info64->lo_flags;
+	info->lo_init[0] = info64->lo_init[0];
+	info->lo_init[1] = info64->lo_init[1];
+	if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
+		memcpy(info->lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
+	else
+		memcpy(info->lo_name, info64->lo_file_name, LO_NAME_SIZE);
+	memcpy(info->lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
+
+	/* error in case values were truncated */
+	if (info->lo_device != info64->lo_device ||
+	    info->lo_rdevice != info64->lo_rdevice ||
+	    info->lo_inode != info64->lo_inode ||
+	    info->lo_offset != info64->lo_offset)
+		return -EOVERFLOW;
+
+	return 0;
+}
+
+static int
+loop_set_status_old(struct loop_device *lo, const struct loop_info __user *arg)
+{
+	struct loop_info info;
+	struct loop_info64 info64;
+
+	if (copy_from_user(&info, arg, sizeof (struct loop_info)))
+		return -EFAULT;
+	loop_info64_from_old(&info, &info64);
+	return loop_set_status(lo, &info64);
+}
+
+static int
+loop_set_status64(struct loop_device *lo, const struct loop_info64 __user *arg)
+{
+	struct loop_info64 info64;
+
+	if (copy_from_user(&info64, arg, sizeof (struct loop_info64)))
+		return -EFAULT;
+	return loop_set_status(lo, &info64);
+}
+
+static int
+loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) {
+	struct loop_info info;
+	struct loop_info64 info64;
+	int err = 0;
+
+	if (!arg)
+		err = -EINVAL;
+	if (!err)
+		err = loop_get_status(lo, &info64);
+	if (!err)
+		err = loop_info64_to_old(&info64, &info);
+	if (!err && copy_to_user(arg, &info, sizeof(info)))
+		err = -EFAULT;
+
+	return err;
+}
+
+static int
+loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
+	struct loop_info64 info64;
+	int err = 0;
+
+	if (!arg)
+		err = -EINVAL;
+	if (!err)
+		err = loop_get_status(lo, &info64);
+	if (!err && copy_to_user(arg, &info64, sizeof(info64)))
+		err = -EFAULT;
+
+	return err;
+}
+
+static int loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
+{
+	if (unlikely(lo->lo_state != Lo_bound))
+		return -ENXIO;
+
+	return figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit);
+}
+
+static int lo_ioctl(struct block_device *bdev, fmode_t mode,
+	unsigned int cmd, unsigned long arg)
+{
+	struct loop_device *lo = bdev->bd_disk->private_data;
+	int err;
+
+	mutex_lock_nested(&lo->lo_ctl_mutex, 1);
+	switch (cmd) {
+	case LOOP_SET_FD:
+		err = loop_set_fd(lo, mode, bdev, arg);
+		break;
+	case LOOP_CHANGE_FD:
+		err = loop_change_fd(lo, bdev, arg);
+		break;
+	case LOOP_CLR_FD:
+		/* loop_clr_fd would have unlocked lo_ctl_mutex on success */
+		err = loop_clr_fd(lo);
+		if (!err)
+			goto out_unlocked;
+		break;
+	case LOOP_SET_STATUS:
+		err = -EPERM;
+		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
+			err = loop_set_status_old(lo,
+					(struct loop_info __user *)arg);
+		break;
+	case LOOP_GET_STATUS:
+		err = loop_get_status_old(lo, (struct loop_info __user *) arg);
+		break;
+	case LOOP_SET_STATUS64:
+		err = -EPERM;
+		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
+			err = loop_set_status64(lo,
+					(struct loop_info64 __user *) arg);
+		break;
+	case LOOP_GET_STATUS64:
+		err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
+		break;
+	case LOOP_SET_CAPACITY:
+		err = -EPERM;
+		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
+			err = loop_set_capacity(lo, bdev);
+		break;
+	default:
+		err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
+	}
+	mutex_unlock(&lo->lo_ctl_mutex);
+
+out_unlocked:
+	return err;
+}
+
+#ifdef CONFIG_COMPAT
+struct compat_loop_info {
+	compat_int_t	lo_number;      /* ioctl r/o */
+	compat_dev_t	lo_device;      /* ioctl r/o */
+	compat_ulong_t	lo_inode;       /* ioctl r/o */
+	compat_dev_t	lo_rdevice;     /* ioctl r/o */
+	compat_int_t	lo_offset;
+	compat_int_t	lo_encrypt_type;
+	compat_int_t	lo_encrypt_key_size;    /* ioctl w/o */
+	compat_int_t	lo_flags;       /* ioctl r/o */
+	char		lo_name[LO_NAME_SIZE];
+	unsigned char	lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
+	compat_ulong_t	lo_init[2];
+	char		reserved[4];
+};
+
+/*
+ * Transfer 32-bit compatibility structure in userspace to 64-bit loop info
+ * - noinlined to reduce stack space usage in main part of driver
+ */
+static noinline int
+loop_info64_from_compat(const struct compat_loop_info __user *arg,
+			struct loop_info64 *info64)
+{
+	struct compat_loop_info info;
+
+	if (copy_from_user(&info, arg, sizeof(info)))
+		return -EFAULT;
+
+	memset(info64, 0, sizeof(*info64));
+	info64->lo_number = info.lo_number;
+	info64->lo_device = info.lo_device;
+	info64->lo_inode = info.lo_inode;
+	info64->lo_rdevice = info.lo_rdevice;
+	info64->lo_offset = info.lo_offset;
+	info64->lo_sizelimit = 0;
+	info64->lo_encrypt_type = info.lo_encrypt_type;
+	info64->lo_encrypt_key_size = info.lo_encrypt_key_size;
+	info64->lo_flags = info.lo_flags;
+	info64->lo_init[0] = info.lo_init[0];
+	info64->lo_init[1] = info.lo_init[1];
+	if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
+		memcpy(info64->lo_crypt_name, info.lo_name, LO_NAME_SIZE);
+	else
+		memcpy(info64->lo_file_name, info.lo_name, LO_NAME_SIZE);
+	memcpy(info64->lo_encrypt_key, info.lo_encrypt_key, LO_KEY_SIZE);
+	return 0;
+}
+
+/*
+ * Transfer 64-bit loop info to 32-bit compatibility structure in userspace
+ * - noinlined to reduce stack space usage in main part of driver
+ */
+static noinline int
+loop_info64_to_compat(const struct loop_info64 *info64,
+		      struct compat_loop_info __user *arg)
+{
+	struct compat_loop_info info;
+
+	memset(&info, 0, sizeof(info));
+	info.lo_number = info64->lo_number;
+	info.lo_device = info64->lo_device;
+	info.lo_inode = info64->lo_inode;
+	info.lo_rdevice = info64->lo_rdevice;
+	info.lo_offset = info64->lo_offset;
+	info.lo_encrypt_type = info64->lo_encrypt_type;
+	info.lo_encrypt_key_size = info64->lo_encrypt_key_size;
+	info.lo_flags = info64->lo_flags;
+	info.lo_init[0] = info64->lo_init[0];
+	info.lo_init[1] = info64->lo_init[1];
+	if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
+		memcpy(info.lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
+	else
+		memcpy(info.lo_name, info64->lo_file_name, LO_NAME_SIZE);
+	memcpy(info.lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
+
+	/* error in case values were truncated */
+	if (info.lo_device != info64->lo_device ||
+	    info.lo_rdevice != info64->lo_rdevice ||
+	    info.lo_inode != info64->lo_inode ||
+	    info.lo_offset != info64->lo_offset ||
+	    info.lo_init[0] != info64->lo_init[0] ||
+	    info.lo_init[1] != info64->lo_init[1])
+		return -EOVERFLOW;
+
+	if (copy_to_user(arg, &info, sizeof(info)))
+		return -EFAULT;
+	return 0;
+}
+
+static int
+loop_set_status_compat(struct loop_device *lo,
+		       const struct compat_loop_info __user *arg)
+{
+	struct loop_info64 info64;
+	int ret;
+
+	ret = loop_info64_from_compat(arg, &info64);
+	if (ret < 0)
+		return ret;
+	return loop_set_status(lo, &info64);
+}
+
+static int
+loop_get_status_compat(struct loop_device *lo,
+		       struct compat_loop_info __user *arg)
+{
+	struct loop_info64 info64;
+	int err = 0;
+
+	if (!arg)
+		err = -EINVAL;
+	if (!err)
+		err = loop_get_status(lo, &info64);
+	if (!err)
+		err = loop_info64_to_compat(&info64, arg);
+	return err;
+}
+
+static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
+			   unsigned int cmd, unsigned long arg)
+{
+	struct loop_device *lo = bdev->bd_disk->private_data;
+	int err;
+
+	switch(cmd) {
+	case LOOP_SET_STATUS:
+		mutex_lock(&lo->lo_ctl_mutex);
+		err = loop_set_status_compat(
+			lo, (const struct compat_loop_info __user *) arg);
+		mutex_unlock(&lo->lo_ctl_mutex);
+		break;
+	case LOOP_GET_STATUS:
+		mutex_lock(&lo->lo_ctl_mutex);
+		err = loop_get_status_compat(
+			lo, (struct compat_loop_info __user *) arg);
+		mutex_unlock(&lo->lo_ctl_mutex);
+		break;
+	case LOOP_SET_CAPACITY:
+	case LOOP_CLR_FD:
+	case LOOP_GET_STATUS64:
+	case LOOP_SET_STATUS64:
+		arg = (unsigned long) compat_ptr(arg);
+	case LOOP_SET_FD:
+	case LOOP_CHANGE_FD:
+		err = lo_ioctl(bdev, mode, cmd, arg);
+		break;
+	default:
+		err = -ENOIOCTLCMD;
+		break;
+	}
+	return err;
+}
+#endif
+
+static int lo_open(struct block_device *bdev, fmode_t mode)
+{
+	struct loop_device *lo;
+	int err = 0;
+
+	mutex_lock(&loop_index_mutex);
+	lo = bdev->bd_disk->private_data;
+	if (!lo) {
+		err = -ENXIO;
+		goto out;
+	}
+
+	mutex_lock(&lo->lo_ctl_mutex);
+	lo->lo_refcnt++;
+	mutex_unlock(&lo->lo_ctl_mutex);
+out:
+	mutex_unlock(&loop_index_mutex);
+	return err;
+}
+
+static void lo_release(struct gendisk *disk, fmode_t mode)
+{
+	struct loop_device *lo = disk->private_data;
+	int err;
+
+	mutex_lock(&lo->lo_ctl_mutex);
+
+	if (--lo->lo_refcnt)
+		goto out;
+
+	if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
+		/*
+		 * In autoclear mode, stop the loop thread
+		 * and remove configuration after last close.
+		 */
+		err = loop_clr_fd(lo);
+		if (!err)
+			return;
+	} else {
+		/*
+		 * Otherwise keep thread (if running) and config,
+		 * but flush possible ongoing bios in thread.
+		 */
+		loop_flush(lo);
+	}
+
+out:
+	mutex_unlock(&lo->lo_ctl_mutex);
+}
+
+static const struct block_device_operations lo_fops = {
+	.owner =	THIS_MODULE,
+	.open =		lo_open,
+	.release =	lo_release,
+	.ioctl =	lo_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl =	lo_compat_ioctl,
+#endif
+};
+
+/*
+ * And now the modules code and kernel interface.
+ */
+static int max_loop;
+module_param(max_loop, int, S_IRUGO);
+MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
+module_param(max_part, int, S_IRUGO);
+MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
+
+int loop_register_transfer(struct loop_func_table *funcs)
+{
+	unsigned int n = funcs->number;
+
+	if (n >= MAX_LO_CRYPT || xfer_funcs[n])
+		return -EINVAL;
+	xfer_funcs[n] = funcs;
+	return 0;
+}
+
+static int unregister_transfer_cb(int id, void *ptr, void *data)
+{
+	struct loop_device *lo = ptr;
+	struct loop_func_table *xfer = data;
+
+	mutex_lock(&lo->lo_ctl_mutex);
+	if (lo->lo_encryption == xfer)
+		loop_release_xfer(lo);
+	mutex_unlock(&lo->lo_ctl_mutex);
+	return 0;
+}
+
+int loop_unregister_transfer(int number)
+{
+	unsigned int n = number;
+	struct loop_func_table *xfer;
+
+	if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
+		return -EINVAL;
+
+	xfer_funcs[n] = NULL;
+	idr_for_each(&loop_index_idr, &unregister_transfer_cb, xfer);
+	return 0;
+}
+
+EXPORT_SYMBOL(loop_register_transfer);
+EXPORT_SYMBOL(loop_unregister_transfer);
+
+static int loop_queue_rq(struct blk_mq_hw_ctx *hctx,
+		const struct blk_mq_queue_data *bd)
+{
+	struct loop_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);
+	struct loop_device *lo = cmd->rq->q->queuedata;
+
+	blk_mq_start_request(bd->rq);
+
+	if (lo->lo_state != Lo_bound)
+		return -EIO;
+
+	if (cmd->rq->cmd_flags & REQ_WRITE) {
+		struct loop_device *lo = cmd->rq->q->queuedata;
+		bool need_sched = true;
+
+		spin_lock_irq(&lo->lo_lock);
+		if (lo->write_started)
+			need_sched = false;
+		else
+			lo->write_started = true;
+		list_add_tail(&cmd->list, &lo->write_cmd_head);
+		spin_unlock_irq(&lo->lo_lock);
+
+		if (need_sched)
+			queue_work(lo->wq, &lo->write_work);
+	} else {
+		queue_work(lo->wq, &cmd->read_work);
+	}
+
+	return BLK_MQ_RQ_QUEUE_OK;
+}
+
+static void loop_handle_cmd(struct loop_cmd *cmd)
+{
+	const bool write = cmd->rq->cmd_flags & REQ_WRITE;
+	struct loop_device *lo = cmd->rq->q->queuedata;
+	int ret = -EIO;
+
+	if (write && (lo->lo_flags & LO_FLAGS_READ_ONLY))
+		goto failed;
+
+	ret = do_req_filebacked(lo, cmd->rq);
+
+ failed:
+	if (ret)
+		cmd->rq->errors = -EIO;
+	blk_mq_complete_request(cmd->rq);
+}
+
+static void loop_queue_write_work(struct work_struct *work)
+{
+	struct loop_device *lo =
+		container_of(work, struct loop_device, write_work);
+	LIST_HEAD(cmd_list);
+
+	spin_lock_irq(&lo->lo_lock);
+ repeat:
+	list_splice_init(&lo->write_cmd_head, &cmd_list);
+	spin_unlock_irq(&lo->lo_lock);
+
+	while (!list_empty(&cmd_list)) {
+		struct loop_cmd *cmd = list_first_entry(&cmd_list,
+				struct loop_cmd, list);
+		list_del_init(&cmd->list);
+		loop_handle_cmd(cmd);
+	}
+
+	spin_lock_irq(&lo->lo_lock);
+	if (!list_empty(&lo->write_cmd_head))
+		goto repeat;
+	lo->write_started = false;
+	spin_unlock_irq(&lo->lo_lock);
+}
+
+static void loop_queue_read_work(struct work_struct *work)
+{
+	struct loop_cmd *cmd =
+		container_of(work, struct loop_cmd, read_work);
+
+	loop_handle_cmd(cmd);
+}
+
+static int loop_init_request(void *data, struct request *rq,
+		unsigned int hctx_idx, unsigned int request_idx,
+		unsigned int numa_node)
+{
+	struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
+
+	cmd->rq = rq;
+	INIT_WORK(&cmd->read_work, loop_queue_read_work);
+
+	return 0;
+}
+
+static struct blk_mq_ops loop_mq_ops = {
+	.queue_rq       = loop_queue_rq,
+	.map_queue      = blk_mq_map_queue,
+	.init_request	= loop_init_request,
+};
+
+static int loop_add(struct loop_device **l, int i)
+{
+	struct loop_device *lo;
+	struct gendisk *disk;
+	int err;
+
+	err = -ENOMEM;
+	lo = kzalloc(sizeof(*lo), GFP_KERNEL);
+	if (!lo)
+		goto out;
+
+	lo->lo_state = Lo_unbound;
+
+	/* allocate id, if @id >= 0, we're requesting that specific id */
+	if (i >= 0) {
+		err = idr_alloc(&loop_index_idr, lo, i, i + 1, GFP_KERNEL);
+		if (err == -ENOSPC)
+			err = -EEXIST;
+	} else {
+		err = idr_alloc(&loop_index_idr, lo, 0, 0, GFP_KERNEL);
+	}
+	if (err < 0)
+		goto out_free_dev;
+	i = err;
+
+	err = -ENOMEM;
+	lo->tag_set.ops = &loop_mq_ops;
+	lo->tag_set.nr_hw_queues = 1;
+	lo->tag_set.queue_depth = 128;
+	lo->tag_set.numa_node = NUMA_NO_NODE;
+	lo->tag_set.cmd_size = sizeof(struct loop_cmd);
+	lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE;
+	lo->tag_set.driver_data = lo;
+
+	err = blk_mq_alloc_tag_set(&lo->tag_set);
+	if (err)
+		goto out_free_idr;
+
+	lo->lo_queue = blk_mq_init_queue(&lo->tag_set);
+	if (IS_ERR_OR_NULL(lo->lo_queue)) {
+		err = PTR_ERR(lo->lo_queue);
+		goto out_cleanup_tags;
+	}
+	lo->lo_queue->queuedata = lo;
+
+	INIT_LIST_HEAD(&lo->write_cmd_head);
+	INIT_WORK(&lo->write_work, loop_queue_write_work);
+
+	disk = lo->lo_disk = alloc_disk(1 << part_shift);
+	if (!disk)
+		goto out_free_queue;
+
+	/*
+	 * Disable partition scanning by default. The in-kernel partition
+	 * scanning can be requested individually per-device during its
+	 * setup. Userspace can always add and remove partitions from all
+	 * devices. The needed partition minors are allocated from the
+	 * extended minor space, the main loop device numbers will continue
+	 * to match the loop minors, regardless of the number of partitions
+	 * used.
+	 *
+	 * If max_part is given, partition scanning is globally enabled for
+	 * all loop devices. The minors for the main loop devices will be
+	 * multiples of max_part.
+	 *
+	 * Note: Global-for-all-devices, set-only-at-init, read-only module
+	 * parameteters like 'max_loop' and 'max_part' make things needlessly
+	 * complicated, are too static, inflexible and may surprise
+	 * userspace tools. Parameters like this in general should be avoided.
+	 */
+	if (!part_shift)
+		disk->flags |= GENHD_FL_NO_PART_SCAN;
+	disk->flags |= GENHD_FL_EXT_DEVT;
+	mutex_init(&lo->lo_ctl_mutex);
+	lo->lo_number		= i;
+	spin_lock_init(&lo->lo_lock);
+	disk->major		= LOOP_MAJOR;
+	disk->first_minor	= i << part_shift;
+	disk->fops		= &lo_fops;
+	disk->private_data	= lo;
+	disk->queue		= lo->lo_queue;
+	sprintf(disk->disk_name, "loop%d", i);
+	add_disk(disk);
+	*l = lo;
+	return lo->lo_number;
+
+out_free_queue:
+	blk_cleanup_queue(lo->lo_queue);
+out_cleanup_tags:
+	blk_mq_free_tag_set(&lo->tag_set);
+out_free_idr:
+	idr_remove(&loop_index_idr, i);
+out_free_dev:
+	kfree(lo);
+out:
+	return err;
+}
+
+static void loop_remove(struct loop_device *lo)
+{
+	blk_cleanup_queue(lo->lo_queue);
+	del_gendisk(lo->lo_disk);
+	blk_mq_free_tag_set(&lo->tag_set);
+	put_disk(lo->lo_disk);
+	kfree(lo);
+}
+
+static int find_free_cb(int id, void *ptr, void *data)
+{
+	struct loop_device *lo = ptr;
+	struct loop_device **l = data;
+
+	if (lo->lo_state == Lo_unbound) {
+		*l = lo;
+		return 1;
+	}
+	return 0;
+}
+
+static int loop_lookup(struct loop_device **l, int i)
+{
+	struct loop_device *lo;
+	int ret = -ENODEV;
+
+	if (i < 0) {
+		int err;
+
+		err = idr_for_each(&loop_index_idr, &find_free_cb, &lo);
+		if (err == 1) {
+			*l = lo;
+			ret = lo->lo_number;
+		}
+		goto out;
+	}
+
+	/* lookup and return a specific i */
+	lo = idr_find(&loop_index_idr, i);
+	if (lo) {
+		*l = lo;
+		ret = lo->lo_number;
+	}
+out:
+	return ret;
+}
+
+static struct kobject *loop_probe(dev_t dev, int *part, void *data)
+{
+	struct loop_device *lo;
+	struct kobject *kobj;
+	int err;
+
+	mutex_lock(&loop_index_mutex);
+	err = loop_lookup(&lo, MINOR(dev) >> part_shift);
+	if (err < 0)
+		err = loop_add(&lo, MINOR(dev) >> part_shift);
+	if (err < 0)
+		kobj = NULL;
+	else
+		kobj = get_disk(lo->lo_disk);
+	mutex_unlock(&loop_index_mutex);
+
+	*part = 0;
+	return kobj;
+}
+
+static long loop_control_ioctl(struct file *file, unsigned int cmd,
+			       unsigned long parm)
+{
+	struct loop_device *lo;
+	int ret = -ENOSYS;
+
+	mutex_lock(&loop_index_mutex);
+	switch (cmd) {
+	case LOOP_CTL_ADD:
+		ret = loop_lookup(&lo, parm);
+		if (ret >= 0) {
+			ret = -EEXIST;
+			break;
+		}
+		ret = loop_add(&lo, parm);
+		break;
+	case LOOP_CTL_REMOVE:
+		ret = loop_lookup(&lo, parm);
+		if (ret < 0)
+			break;
+		mutex_lock(&lo->lo_ctl_mutex);
+		if (lo->lo_state != Lo_unbound) {
+			ret = -EBUSY;
+			mutex_unlock(&lo->lo_ctl_mutex);
+			break;
+		}
+		if (lo->lo_refcnt > 0) {
+			ret = -EBUSY;
+			mutex_unlock(&lo->lo_ctl_mutex);
+			break;
+		}
+		lo->lo_disk->private_data = NULL;
+		mutex_unlock(&lo->lo_ctl_mutex);
+		idr_remove(&loop_index_idr, lo->lo_number);
+		loop_remove(lo);
+		break;
+	case LOOP_CTL_GET_FREE:
+		ret = loop_lookup(&lo, -1);
+		if (ret >= 0)
+			break;
+		ret = loop_add(&lo, -1);
+	}
+	mutex_unlock(&loop_index_mutex);
+
+	return ret;
+}
+
+static const struct file_operations loop_ctl_fops = {
+	.open		= nonseekable_open,
+	.unlocked_ioctl	= loop_control_ioctl,
+	.compat_ioctl	= loop_control_ioctl,
+	.owner		= THIS_MODULE,
+	.llseek		= noop_llseek,
+};
+
+static struct miscdevice loop_misc = {
+	.minor		= LOOP_CTRL_MINOR,
+	.name		= "loop-control",
+	.fops		= &loop_ctl_fops,
+};
+
+MODULE_ALIAS_MISCDEV(LOOP_CTRL_MINOR);
+MODULE_ALIAS("devname:loop-control");
+
+static int __init loop_init(void)
+{
+	int i, nr;
+	unsigned long range;
+	struct loop_device *lo;
+	int err;
+
+	err = misc_register(&loop_misc);
+	if (err < 0)
+		return err;
+
+	part_shift = 0;
+	if (max_part > 0) {
+		part_shift = fls(max_part);
+
+		/*
+		 * Adjust max_part according to part_shift as it is exported
+		 * to user space so that user can decide correct minor number
+		 * if [s]he want to create more devices.
+		 *
+		 * Note that -1 is required because partition 0 is reserved
+		 * for the whole disk.
+		 */
+		max_part = (1UL << part_shift) - 1;
+	}
+
+	if ((1UL << part_shift) > DISK_MAX_PARTS) {
+		err = -EINVAL;
+		goto misc_out;
+	}
+
+	if (max_loop > 1UL << (MINORBITS - part_shift)) {
+		err = -EINVAL;
+		goto misc_out;
+	}
+
+	/*
+	 * If max_loop is specified, create that many devices upfront.
+	 * This also becomes a hard limit. If max_loop is not specified,
+	 * create CONFIG_BLK_DEV_LOOP_MIN_COUNT loop devices at module
+	 * init time. Loop devices can be requested on-demand with the
+	 * /dev/loop-control interface, or be instantiated by accessing
+	 * a 'dead' device node.
+	 */
+	if (max_loop) {
+		nr = max_loop;
+		range = max_loop << part_shift;
+	} else {
+		nr = CONFIG_BLK_DEV_LOOP_MIN_COUNT;
+		range = 1UL << MINORBITS;
+	}
+
+	if (register_blkdev(LOOP_MAJOR, "loop")) {
+		err = -EIO;
+		goto misc_out;
+	}
+
+	blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
+				  THIS_MODULE, loop_probe, NULL, NULL);
+
+	/* pre-create number of devices given by config or max_loop */
+	mutex_lock(&loop_index_mutex);
+	for (i = 0; i < nr; i++)
+		loop_add(&lo, i);
+	mutex_unlock(&loop_index_mutex);
+
+	printk(KERN_INFO "loop: module loaded\n");
+	return 0;
+
+misc_out:
+	misc_deregister(&loop_misc);
+	return err;
+}
+
+static int loop_exit_cb(int id, void *ptr, void *data)
+{
+	struct loop_device *lo = ptr;
+
+	loop_remove(lo);
+	return 0;
+}
+
+static void __exit loop_exit(void)
+{
+	unsigned long range;
+
+	range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;
+
+	idr_for_each(&loop_index_idr, &loop_exit_cb, NULL);
+	idr_destroy(&loop_index_idr);
+
+	blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
+	unregister_blkdev(LOOP_MAJOR, "loop");
+
+	misc_deregister(&loop_misc);
+}
+
+module_init(loop_init);
+module_exit(loop_exit);
+
+#ifndef MODULE
+static int __init max_loop_setup(char *str)
+{
+	max_loop = simple_strtol(str, NULL, 0);
+	return 1;
+}
+
+__setup("max_loop=", max_loop_setup);
+#endif