Initial import

1 files changed, 2126 insertions, 0 deletions

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
new file mode 100644
index 000000000..2c61cf8c6
--- /dev/null
+++ b/drivers/block/xen-blkfront.c
@@ -0,0 +1,2126 @@
+/*
+ * blkfront.c
+ *
+ * XenLinux virtual block device driver.
+ *
+ * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
+ * Modifications by Mark A. Williamson are (c) Intel Research Cambridge
+ * Copyright (c) 2004, Christian Limpach
+ * Copyright (c) 2004, Andrew Warfield
+ * Copyright (c) 2005, Christopher Clark
+ * Copyright (c) 2005, XenSource Ltd
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/blkdev.h>
+#include <linux/hdreg.h>
+#include <linux/cdrom.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <linux/scatterlist.h>
+#include <linux/bitmap.h>
+#include <linux/list.h>
+
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/grant_table.h>
+#include <xen/events.h>
+#include <xen/page.h>
+#include <xen/platform_pci.h>
+
+#include <xen/interface/grant_table.h>
+#include <xen/interface/io/blkif.h>
+#include <xen/interface/io/protocols.h>
+
+#include <asm/xen/hypervisor.h>
+
+enum blkif_state {
+	BLKIF_STATE_DISCONNECTED,
+	BLKIF_STATE_CONNECTED,
+	BLKIF_STATE_SUSPENDED,
+};
+
+struct grant {
+	grant_ref_t gref;
+	unsigned long pfn;
+	struct list_head node;
+};
+
+struct blk_shadow {
+	struct blkif_request req;
+	struct request *request;
+	struct grant **grants_used;
+	struct grant **indirect_grants;
+	struct scatterlist *sg;
+};
+
+struct split_bio {
+	struct bio *bio;
+	atomic_t pending;
+	int err;
+};
+
+static DEFINE_MUTEX(blkfront_mutex);
+static const struct block_device_operations xlvbd_block_fops;
+
+/*
+ * Maximum number of segments in indirect requests, the actual value used by
+ * the frontend driver is the minimum of this value and the value provided
+ * by the backend driver.
+ */
+
+static unsigned int xen_blkif_max_segments = 32;
+module_param_named(max, xen_blkif_max_segments, int, S_IRUGO);
+MODULE_PARM_DESC(max, "Maximum amount of segments in indirect requests (default is 32)");
+
+#define BLK_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE)
+
+/*
+ * We have one of these per vbd, whether ide, scsi or 'other'.  They
+ * hang in private_data off the gendisk structure. We may end up
+ * putting all kinds of interesting stuff here :-)
+ */
+struct blkfront_info
+{
+	spinlock_t io_lock;
+	struct mutex mutex;
+	struct xenbus_device *xbdev;
+	struct gendisk *gd;
+	int vdevice;
+	blkif_vdev_t handle;
+	enum blkif_state connected;
+	int ring_ref;
+	struct blkif_front_ring ring;
+	unsigned int evtchn, irq;
+	struct request_queue *rq;
+	struct work_struct work;
+	struct gnttab_free_callback callback;
+	struct blk_shadow shadow[BLK_RING_SIZE];
+	struct list_head grants;
+	struct list_head indirect_pages;
+	unsigned int persistent_gnts_c;
+	unsigned long shadow_free;
+	unsigned int feature_flush;
+	unsigned int feature_discard:1;
+	unsigned int feature_secdiscard:1;
+	unsigned int discard_granularity;
+	unsigned int discard_alignment;
+	unsigned int feature_persistent:1;
+	unsigned int max_indirect_segments;
+	int is_ready;
+};
+
+static unsigned int nr_minors;
+static unsigned long *minors;
+static DEFINE_SPINLOCK(minor_lock);
+
+#define MAXIMUM_OUTSTANDING_BLOCK_REQS \
+	(BLKIF_MAX_SEGMENTS_PER_REQUEST * BLK_RING_SIZE)
+#define GRANT_INVALID_REF	0
+
+#define PARTS_PER_DISK		16
+#define PARTS_PER_EXT_DISK      256
+
+#define BLKIF_MAJOR(dev) ((dev)>>8)
+#define BLKIF_MINOR(dev) ((dev) & 0xff)
+
+#define EXT_SHIFT 28
+#define EXTENDED (1<<EXT_SHIFT)
+#define VDEV_IS_EXTENDED(dev) ((dev)&(EXTENDED))
+#define BLKIF_MINOR_EXT(dev) ((dev)&(~EXTENDED))
+#define EMULATED_HD_DISK_MINOR_OFFSET (0)
+#define EMULATED_HD_DISK_NAME_OFFSET (EMULATED_HD_DISK_MINOR_OFFSET / 256)
+#define EMULATED_SD_DISK_MINOR_OFFSET (0)
+#define EMULATED_SD_DISK_NAME_OFFSET (EMULATED_SD_DISK_MINOR_OFFSET / 256)
+
+#define DEV_NAME	"xvd"	/* name in /dev */
+
+#define SEGS_PER_INDIRECT_FRAME \
+	(PAGE_SIZE/sizeof(struct blkif_request_segment))
+#define INDIRECT_GREFS(_segs) \
+	((_segs + SEGS_PER_INDIRECT_FRAME - 1)/SEGS_PER_INDIRECT_FRAME)
+
+static int blkfront_setup_indirect(struct blkfront_info *info);
+
+static int get_id_from_freelist(struct blkfront_info *info)
+{
+	unsigned long free = info->shadow_free;
+	BUG_ON(free >= BLK_RING_SIZE);
+	info->shadow_free = info->shadow[free].req.u.rw.id;
+	info->shadow[free].req.u.rw.id = 0x0fffffee; /* debug */
+	return free;
+}
+
+static int add_id_to_freelist(struct blkfront_info *info,
+			       unsigned long id)
+{
+	if (info->shadow[id].req.u.rw.id != id)
+		return -EINVAL;
+	if (info->shadow[id].request == NULL)
+		return -EINVAL;
+	info->shadow[id].req.u.rw.id  = info->shadow_free;
+	info->shadow[id].request = NULL;
+	info->shadow_free = id;
+	return 0;
+}
+
+static int fill_grant_buffer(struct blkfront_info *info, int num)
+{
+	struct page *granted_page;
+	struct grant *gnt_list_entry, *n;
+	int i = 0;
+
+	while(i < num) {
+		gnt_list_entry = kzalloc(sizeof(struct grant), GFP_NOIO);
+		if (!gnt_list_entry)
+			goto out_of_memory;
+
+		if (info->feature_persistent) {
+			granted_page = alloc_page(GFP_NOIO);
+			if (!granted_page) {
+				kfree(gnt_list_entry);
+				goto out_of_memory;
+			}
+			gnt_list_entry->pfn = page_to_pfn(granted_page);
+		}
+
+		gnt_list_entry->gref = GRANT_INVALID_REF;
+		list_add(&gnt_list_entry->node, &info->grants);
+		i++;
+	}
+
+	return 0;
+
+out_of_memory:
+	list_for_each_entry_safe(gnt_list_entry, n,
+	                         &info->grants, node) {
+		list_del(&gnt_list_entry->node);
+		if (info->feature_persistent)
+			__free_page(pfn_to_page(gnt_list_entry->pfn));
+		kfree(gnt_list_entry);
+		i--;
+	}
+	BUG_ON(i != 0);
+	return -ENOMEM;
+}
+
+static struct grant *get_grant(grant_ref_t *gref_head,
+                               unsigned long pfn,
+                               struct blkfront_info *info)
+{
+	struct grant *gnt_list_entry;
+	unsigned long buffer_mfn;
+
+	BUG_ON(list_empty(&info->grants));
+	gnt_list_entry = list_first_entry(&info->grants, struct grant,
+	                                  node);
+	list_del(&gnt_list_entry->node);
+
+	if (gnt_list_entry->gref != GRANT_INVALID_REF) {
+		info->persistent_gnts_c--;
+		return gnt_list_entry;
+	}
+
+	/* Assign a gref to this page */
+	gnt_list_entry->gref = gnttab_claim_grant_reference(gref_head);
+	BUG_ON(gnt_list_entry->gref == -ENOSPC);
+	if (!info->feature_persistent) {
+		BUG_ON(!pfn);
+		gnt_list_entry->pfn = pfn;
+	}
+	buffer_mfn = pfn_to_mfn(gnt_list_entry->pfn);
+	gnttab_grant_foreign_access_ref(gnt_list_entry->gref,
+	                                info->xbdev->otherend_id,
+	                                buffer_mfn, 0);
+	return gnt_list_entry;
+}
+
+static const char *op_name(int op)
+{
+	static const char *const names[] = {
+		[BLKIF_OP_READ] = "read",
+		[BLKIF_OP_WRITE] = "write",
+		[BLKIF_OP_WRITE_BARRIER] = "barrier",
+		[BLKIF_OP_FLUSH_DISKCACHE] = "flush",
+		[BLKIF_OP_DISCARD] = "discard" };
+
+	if (op < 0 || op >= ARRAY_SIZE(names))
+		return "unknown";
+
+	if (!names[op])
+		return "reserved";
+
+	return names[op];
+}
+static int xlbd_reserve_minors(unsigned int minor, unsigned int nr)
+{
+	unsigned int end = minor + nr;
+	int rc;
+
+	if (end > nr_minors) {
+		unsigned long *bitmap, *old;
+
+		bitmap = kcalloc(BITS_TO_LONGS(end), sizeof(*bitmap),
+				 GFP_KERNEL);
+		if (bitmap == NULL)
+			return -ENOMEM;
+
+		spin_lock(&minor_lock);
+		if (end > nr_minors) {
+			old = minors;
+			memcpy(bitmap, minors,
+			       BITS_TO_LONGS(nr_minors) * sizeof(*bitmap));
+			minors = bitmap;
+			nr_minors = BITS_TO_LONGS(end) * BITS_PER_LONG;
+		} else
+			old = bitmap;
+		spin_unlock(&minor_lock);
+		kfree(old);
+	}
+
+	spin_lock(&minor_lock);
+	if (find_next_bit(minors, end, minor) >= end) {
+		bitmap_set(minors, minor, nr);
+		rc = 0;
+	} else
+		rc = -EBUSY;
+	spin_unlock(&minor_lock);
+
+	return rc;
+}
+
+static void xlbd_release_minors(unsigned int minor, unsigned int nr)
+{
+	unsigned int end = minor + nr;
+
+	BUG_ON(end > nr_minors);
+	spin_lock(&minor_lock);
+	bitmap_clear(minors,  minor, nr);
+	spin_unlock(&minor_lock);
+}
+
+static void blkif_restart_queue_callback(void *arg)
+{
+	struct blkfront_info *info = (struct blkfront_info *)arg;
+	schedule_work(&info->work);
+}
+
+static int blkif_getgeo(struct block_device *bd, struct hd_geometry *hg)
+{
+	/* We don't have real geometry info, but let's at least return
+	   values consistent with the size of the device */
+	sector_t nsect = get_capacity(bd->bd_disk);
+	sector_t cylinders = nsect;
+
+	hg->heads = 0xff;
+	hg->sectors = 0x3f;
+	sector_div(cylinders, hg->heads * hg->sectors);
+	hg->cylinders = cylinders;
+	if ((sector_t)(hg->cylinders + 1) * hg->heads * hg->sectors < nsect)
+		hg->cylinders = 0xffff;
+	return 0;
+}
+
+static int blkif_ioctl(struct block_device *bdev, fmode_t mode,
+		       unsigned command, unsigned long argument)
+{
+	struct blkfront_info *info = bdev->bd_disk->private_data;
+	int i;
+
+	dev_dbg(&info->xbdev->dev, "command: 0x%x, argument: 0x%lx\n",
+		command, (long)argument);
+
+	switch (command) {
+	case CDROMMULTISESSION:
+		dev_dbg(&info->xbdev->dev, "FIXME: support multisession CDs later\n");
+		for (i = 0; i < sizeof(struct cdrom_multisession); i++)
+			if (put_user(0, (char __user *)(argument + i)))
+				return -EFAULT;
+		return 0;
+
+	case CDROM_GET_CAPABILITY: {
+		struct gendisk *gd = info->gd;
+		if (gd->flags & GENHD_FL_CD)
+			return 0;
+		return -EINVAL;
+	}
+
+	default:
+		/*printk(KERN_ALERT "ioctl %08x not supported by Xen blkdev\n",
+		  command);*/
+		return -EINVAL; /* same return as native Linux */
+	}
+
+	return 0;
+}
+
+/*
+ * Generate a Xen blkfront IO request from a blk layer request.  Reads
+ * and writes are handled as expected.
+ *
+ * @req: a request struct
+ */
+static int blkif_queue_request(struct request *req)
+{
+	struct blkfront_info *info = req->rq_disk->private_data;
+	struct blkif_request *ring_req;
+	unsigned long id;
+	unsigned int fsect, lsect;
+	int i, ref, n;
+	struct blkif_request_segment *segments = NULL;
+
+	/*
+	 * Used to store if we are able to queue the request by just using
+	 * existing persistent grants, or if we have to get new grants,
+	 * as there are not sufficiently many free.
+	 */
+	bool new_persistent_gnts;
+	grant_ref_t gref_head;
+	struct grant *gnt_list_entry = NULL;
+	struct scatterlist *sg;
+	int nseg, max_grefs;
+
+	if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
+		return 1;
+
+	max_grefs = req->nr_phys_segments;
+	if (max_grefs > BLKIF_MAX_SEGMENTS_PER_REQUEST)
+		/*
+		 * If we are using indirect segments we need to account
+		 * for the indirect grefs used in the request.
+		 */
+		max_grefs += INDIRECT_GREFS(req->nr_phys_segments);
+
+	/* Check if we have enough grants to allocate a requests */
+	if (info->persistent_gnts_c < max_grefs) {
+		new_persistent_gnts = 1;
+		if (gnttab_alloc_grant_references(
+		    max_grefs - info->persistent_gnts_c,
+		    &gref_head) < 0) {
+			gnttab_request_free_callback(
+				&info->callback,
+				blkif_restart_queue_callback,
+				info,
+				max_grefs);
+			return 1;
+		}
+	} else
+		new_persistent_gnts = 0;
+
+	/* Fill out a communications ring structure. */
+	ring_req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);
+	id = get_id_from_freelist(info);
+	info->shadow[id].request = req;
+
+	if (unlikely(req->cmd_flags & (REQ_DISCARD | REQ_SECURE))) {
+		ring_req->operation = BLKIF_OP_DISCARD;
+		ring_req->u.discard.nr_sectors = blk_rq_sectors(req);
+		ring_req->u.discard.id = id;
+		ring_req->u.discard.sector_number = (blkif_sector_t)blk_rq_pos(req);
+		if ((req->cmd_flags & REQ_SECURE) && info->feature_secdiscard)
+			ring_req->u.discard.flag = BLKIF_DISCARD_SECURE;
+		else
+			ring_req->u.discard.flag = 0;
+	} else {
+		BUG_ON(info->max_indirect_segments == 0 &&
+		       req->nr_phys_segments > BLKIF_MAX_SEGMENTS_PER_REQUEST);
+		BUG_ON(info->max_indirect_segments &&
+		       req->nr_phys_segments > info->max_indirect_segments);
+		nseg = blk_rq_map_sg(req->q, req, info->shadow[id].sg);
+		ring_req->u.rw.id = id;
+		if (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST) {
+			/*
+			 * The indirect operation can only be a BLKIF_OP_READ or
+			 * BLKIF_OP_WRITE
+			 */
+			BUG_ON(req->cmd_flags & (REQ_FLUSH | REQ_FUA));
+			ring_req->operation = BLKIF_OP_INDIRECT;
+			ring_req->u.indirect.indirect_op = rq_data_dir(req) ?
+				BLKIF_OP_WRITE : BLKIF_OP_READ;
+			ring_req->u.indirect.sector_number = (blkif_sector_t)blk_rq_pos(req);
+			ring_req->u.indirect.handle = info->handle;
+			ring_req->u.indirect.nr_segments = nseg;
+		} else {
+			ring_req->u.rw.sector_number = (blkif_sector_t)blk_rq_pos(req);
+			ring_req->u.rw.handle = info->handle;
+			ring_req->operation = rq_data_dir(req) ?
+				BLKIF_OP_WRITE : BLKIF_OP_READ;
+			if (req->cmd_flags & (REQ_FLUSH | REQ_FUA)) {
+				/*
+				 * Ideally we can do an unordered flush-to-disk. In case the
+				 * backend onlysupports barriers, use that. A barrier request
+				 * a superset of FUA, so we can implement it the same
+				 * way.  (It's also a FLUSH+FUA, since it is
+				 * guaranteed ordered WRT previous writes.)
+				 */
+				switch (info->feature_flush &
+					((REQ_FLUSH|REQ_FUA))) {
+				case REQ_FLUSH|REQ_FUA:
+					ring_req->operation =
+						BLKIF_OP_WRITE_BARRIER;
+					break;
+				case REQ_FLUSH:
+					ring_req->operation =
+						BLKIF_OP_FLUSH_DISKCACHE;
+					break;
+				default:
+					ring_req->operation = 0;
+				}
+			}
+			ring_req->u.rw.nr_segments = nseg;
+		}
+		for_each_sg(info->shadow[id].sg, sg, nseg, i) {
+			fsect = sg->offset >> 9;
+			lsect = fsect + (sg->length >> 9) - 1;
+
+			if ((ring_req->operation == BLKIF_OP_INDIRECT) &&
+			    (i % SEGS_PER_INDIRECT_FRAME == 0)) {
+				unsigned long uninitialized_var(pfn);
+
+				if (segments)
+					kunmap_atomic(segments);
+
+				n = i / SEGS_PER_INDIRECT_FRAME;
+				if (!info->feature_persistent) {
+					struct page *indirect_page;
+
+					/* Fetch a pre-allocated page to use for indirect grefs */
+					BUG_ON(list_empty(&info->indirect_pages));
+					indirect_page = list_first_entry(&info->indirect_pages,
+					                                 struct page, lru);
+					list_del(&indirect_page->lru);
+					pfn = page_to_pfn(indirect_page);
+				}
+				gnt_list_entry = get_grant(&gref_head, pfn, info);
+				info->shadow[id].indirect_grants[n] = gnt_list_entry;
+				segments = kmap_atomic(pfn_to_page(gnt_list_entry->pfn));
+				ring_req->u.indirect.indirect_grefs[n] = gnt_list_entry->gref;
+			}
+
+			gnt_list_entry = get_grant(&gref_head, page_to_pfn(sg_page(sg)), info);
+			ref = gnt_list_entry->gref;
+
+			info->shadow[id].grants_used[i] = gnt_list_entry;
+
+			if (rq_data_dir(req) && info->feature_persistent) {
+				char *bvec_data;
+				void *shared_data;
+
+				BUG_ON(sg->offset + sg->length > PAGE_SIZE);
+
+				shared_data = kmap_atomic(pfn_to_page(gnt_list_entry->pfn));
+				bvec_data = kmap_atomic(sg_page(sg));
+
+				/*
+				 * this does not wipe data stored outside the
+				 * range sg->offset..sg->offset+sg->length.
+				 * Therefore, blkback *could* see data from
+				 * previous requests. This is OK as long as
+				 * persistent grants are shared with just one
+				 * domain. It may need refactoring if this
+				 * changes
+				 */
+				memcpy(shared_data + sg->offset,
+				       bvec_data   + sg->offset,
+				       sg->length);
+
+				kunmap_atomic(bvec_data);
+				kunmap_atomic(shared_data);
+			}
+			if (ring_req->operation != BLKIF_OP_INDIRECT) {
+				ring_req->u.rw.seg[i] =
+						(struct blkif_request_segment) {
+							.gref       = ref,
+							.first_sect = fsect,
+							.last_sect  = lsect };
+			} else {
+				n = i % SEGS_PER_INDIRECT_FRAME;
+				segments[n] =
+					(struct blkif_request_segment) {
+							.gref       = ref,
+							.first_sect = fsect,
+							.last_sect  = lsect };
+			}
+		}
+		if (segments)
+			kunmap_atomic(segments);
+	}
+
+	info->ring.req_prod_pvt++;
+
+	/* Keep a private copy so we can reissue requests when recovering. */
+	info->shadow[id].req = *ring_req;
+
+	if (new_persistent_gnts)
+		gnttab_free_grant_references(gref_head);
+
+	return 0;
+}
+
+
+static inline void flush_requests(struct blkfront_info *info)
+{
+	int notify;
+
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&info->ring, notify);
+
+	if (notify)
+		notify_remote_via_irq(info->irq);
+}
+
+static inline bool blkif_request_flush_invalid(struct request *req,
+					       struct blkfront_info *info)
+{
+	return ((req->cmd_type != REQ_TYPE_FS) ||
+		((req->cmd_flags & REQ_FLUSH) &&
+		 !(info->feature_flush & REQ_FLUSH)) ||
+		((req->cmd_flags & REQ_FUA) &&
+		 !(info->feature_flush & REQ_FUA)));
+}
+
+/*
+ * do_blkif_request
+ *  read a block; request is in a request queue
+ */
+static void do_blkif_request(struct request_queue *rq)
+{
+	struct blkfront_info *info = NULL;
+	struct request *req;
+	int queued;
+
+	pr_debug("Entered do_blkif_request\n");
+
+	queued = 0;
+
+	while ((req = blk_peek_request(rq)) != NULL) {
+		info = req->rq_disk->private_data;
+
+		if (RING_FULL(&info->ring))
+			goto wait;
+
+		blk_start_request(req);
+
+		if (blkif_request_flush_invalid(req, info)) {
+			__blk_end_request_all(req, -EOPNOTSUPP);
+			continue;
+		}
+
+		pr_debug("do_blk_req %p: cmd %p, sec %lx, "
+			 "(%u/%u) [%s]\n",
+			 req, req->cmd, (unsigned long)blk_rq_pos(req),
+			 blk_rq_cur_sectors(req), blk_rq_sectors(req),
+			 rq_data_dir(req) ? "write" : "read");
+
+		if (blkif_queue_request(req)) {
+			blk_requeue_request(rq, req);
+wait:
+			/* Avoid pointless unplugs. */
+			blk_stop_queue(rq);
+			break;
+		}
+
+		queued++;
+	}
+
+	if (queued != 0)
+		flush_requests(info);
+}
+
+static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
+				unsigned int physical_sector_size,
+				unsigned int segments)
+{
+	struct request_queue *rq;
+	struct blkfront_info *info = gd->private_data;
+
+	rq = blk_init_queue(do_blkif_request, &info->io_lock);
+	if (rq == NULL)
+		return -1;
+
+	queue_flag_set_unlocked(QUEUE_FLAG_VIRT, rq);
+
+	if (info->feature_discard) {
+		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, rq);
+		blk_queue_max_discard_sectors(rq, get_capacity(gd));
+		rq->limits.discard_granularity = info->discard_granularity;
+		rq->limits.discard_alignment = info->discard_alignment;
+		if (info->feature_secdiscard)
+			queue_flag_set_unlocked(QUEUE_FLAG_SECDISCARD, rq);
+	}
+
+	/* Hard sector size and max sectors impersonate the equiv. hardware. */
+	blk_queue_logical_block_size(rq, sector_size);
+	blk_queue_physical_block_size(rq, physical_sector_size);
+	blk_queue_max_hw_sectors(rq, (segments * PAGE_SIZE) / 512);
+
+	/* Each segment in a request is up to an aligned page in size. */
+	blk_queue_segment_boundary(rq, PAGE_SIZE - 1);
+	blk_queue_max_segment_size(rq, PAGE_SIZE);
+
+	/* Ensure a merged request will fit in a single I/O ring slot. */
+	blk_queue_max_segments(rq, segments);
+
+	/* Make sure buffer addresses are sector-aligned. */
+	blk_queue_dma_alignment(rq, 511);
+
+	/* Make sure we don't use bounce buffers. */
+	blk_queue_bounce_limit(rq, BLK_BOUNCE_ANY);
+
+	gd->queue = rq;
+
+	return 0;
+}
+
+static const char *flush_info(unsigned int feature_flush)
+{
+	switch (feature_flush & ((REQ_FLUSH | REQ_FUA))) {
+	case REQ_FLUSH|REQ_FUA:
+		return "barrier: enabled;";
+	case REQ_FLUSH:
+		return "flush diskcache: enabled;";
+	default:
+		return "barrier or flush: disabled;";
+	}
+}
+
+static void xlvbd_flush(struct blkfront_info *info)
+{
+	blk_queue_flush(info->rq, info->feature_flush);
+	pr_info("blkfront: %s: %s %s %s %s %s\n",
+		info->gd->disk_name, flush_info(info->feature_flush),
+		"persistent grants:", info->feature_persistent ?
+		"enabled;" : "disabled;", "indirect descriptors:",
+		info->max_indirect_segments ? "enabled;" : "disabled;");
+}
+
+static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
+{
+	int major;
+	major = BLKIF_MAJOR(vdevice);
+	*minor = BLKIF_MINOR(vdevice);
+	switch (major) {
+		case XEN_IDE0_MAJOR:
+			*offset = (*minor / 64) + EMULATED_HD_DISK_NAME_OFFSET;
+			*minor = ((*minor / 64) * PARTS_PER_DISK) +
+				EMULATED_HD_DISK_MINOR_OFFSET;
+			break;
+		case XEN_IDE1_MAJOR:
+			*offset = (*minor / 64) + 2 + EMULATED_HD_DISK_NAME_OFFSET;
+			*minor = (((*minor / 64) + 2) * PARTS_PER_DISK) +
+				EMULATED_HD_DISK_MINOR_OFFSET;
+			break;
+		case XEN_SCSI_DISK0_MAJOR:
+			*offset = (*minor / PARTS_PER_DISK) + EMULATED_SD_DISK_NAME_OFFSET;
+			*minor = *minor + EMULATED_SD_DISK_MINOR_OFFSET;
+			break;
+		case XEN_SCSI_DISK1_MAJOR:
+		case XEN_SCSI_DISK2_MAJOR:
+		case XEN_SCSI_DISK3_MAJOR:
+		case XEN_SCSI_DISK4_MAJOR:
+		case XEN_SCSI_DISK5_MAJOR:
+		case XEN_SCSI_DISK6_MAJOR:
+		case XEN_SCSI_DISK7_MAJOR:
+			*offset = (*minor / PARTS_PER_DISK) + 
+				((major - XEN_SCSI_DISK1_MAJOR + 1) * 16) +
+				EMULATED_SD_DISK_NAME_OFFSET;
+			*minor = *minor +
+				((major - XEN_SCSI_DISK1_MAJOR + 1) * 16 * PARTS_PER_DISK) +
+				EMULATED_SD_DISK_MINOR_OFFSET;
+			break;
+		case XEN_SCSI_DISK8_MAJOR:
+		case XEN_SCSI_DISK9_MAJOR:
+		case XEN_SCSI_DISK10_MAJOR:
+		case XEN_SCSI_DISK11_MAJOR:
+		case XEN_SCSI_DISK12_MAJOR:
+		case XEN_SCSI_DISK13_MAJOR:
+		case XEN_SCSI_DISK14_MAJOR:
+		case XEN_SCSI_DISK15_MAJOR:
+			*offset = (*minor / PARTS_PER_DISK) + 
+				((major - XEN_SCSI_DISK8_MAJOR + 8) * 16) +
+				EMULATED_SD_DISK_NAME_OFFSET;
+			*minor = *minor +
+				((major - XEN_SCSI_DISK8_MAJOR + 8) * 16 * PARTS_PER_DISK) +
+				EMULATED_SD_DISK_MINOR_OFFSET;
+			break;
+		case XENVBD_MAJOR:
+			*offset = *minor / PARTS_PER_DISK;
+			break;
+		default:
+			printk(KERN_WARNING "blkfront: your disk configuration is "
+					"incorrect, please use an xvd device instead\n");
+			return -ENODEV;
+	}
+	return 0;
+}
+
+static char *encode_disk_name(char *ptr, unsigned int n)
+{
+	if (n >= 26)
+		ptr = encode_disk_name(ptr, n / 26 - 1);
+	*ptr = 'a' + n % 26;
+	return ptr + 1;
+}
+
+static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
+			       struct blkfront_info *info,
+			       u16 vdisk_info, u16 sector_size,
+			       unsigned int physical_sector_size)
+{
+	struct gendisk *gd;
+	int nr_minors = 1;
+	int err;
+	unsigned int offset;
+	int minor;
+	int nr_parts;
+	char *ptr;
+
+	BUG_ON(info->gd != NULL);
+	BUG_ON(info->rq != NULL);
+
+	if ((info->vdevice>>EXT_SHIFT) > 1) {
+		/* this is above the extended range; something is wrong */
+		printk(KERN_WARNING "blkfront: vdevice 0x%x is above the extended range; ignoring\n", info->vdevice);
+		return -ENODEV;
+	}
+
+	if (!VDEV_IS_EXTENDED(info->vdevice)) {
+		err = xen_translate_vdev(info->vdevice, &minor, &offset);
+		if (err)
+			return err;		
+ 		nr_parts = PARTS_PER_DISK;
+	} else {
+		minor = BLKIF_MINOR_EXT(info->vdevice);
+		nr_parts = PARTS_PER_EXT_DISK;
+		offset = minor / nr_parts;
+		if (xen_hvm_domain() && offset < EMULATED_HD_DISK_NAME_OFFSET + 4)
+			printk(KERN_WARNING "blkfront: vdevice 0x%x might conflict with "
+					"emulated IDE disks,\n\t choose an xvd device name"
+					"from xvde on\n", info->vdevice);
+	}
+	if (minor >> MINORBITS) {
+		pr_warn("blkfront: %#x's minor (%#x) out of range; ignoring\n",
+			info->vdevice, minor);
+		return -ENODEV;
+	}
+
+	if ((minor % nr_parts) == 0)
+		nr_minors = nr_parts;
+
+	err = xlbd_reserve_minors(minor, nr_minors);
+	if (err)
+		goto out;
+	err = -ENODEV;
+
+	gd = alloc_disk(nr_minors);
+	if (gd == NULL)
+		goto release;
+
+	strcpy(gd->disk_name, DEV_NAME);
+	ptr = encode_disk_name(gd->disk_name + sizeof(DEV_NAME) - 1, offset);
+	BUG_ON(ptr >= gd->disk_name + DISK_NAME_LEN);
+	if (nr_minors > 1)
+		*ptr = 0;
+	else
+		snprintf(ptr, gd->disk_name + DISK_NAME_LEN - ptr,
+			 "%d", minor & (nr_parts - 1));
+
+	gd->major = XENVBD_MAJOR;
+	gd->first_minor = minor;
+	gd->fops = &xlvbd_block_fops;
+	gd->private_data = info;
+	gd->driverfs_dev = &(info->xbdev->dev);
+	set_capacity(gd, capacity);
+
+	if (xlvbd_init_blk_queue(gd, sector_size, physical_sector_size,
+				 info->max_indirect_segments ? :
+				 BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
+		del_gendisk(gd);
+		goto release;
+	}
+
+	info->rq = gd->queue;
+	info->gd = gd;
+
+	xlvbd_flush(info);
+
+	if (vdisk_info & VDISK_READONLY)
+		set_disk_ro(gd, 1);
+
+	if (vdisk_info & VDISK_REMOVABLE)
+		gd->flags |= GENHD_FL_REMOVABLE;
+
+	if (vdisk_info & VDISK_CDROM)
+		gd->flags |= GENHD_FL_CD;
+
+	return 0;
+
+ release:
+	xlbd_release_minors(minor, nr_minors);
+ out:
+	return err;
+}
+
+static void xlvbd_release_gendisk(struct blkfront_info *info)
+{
+	unsigned int minor, nr_minors;
+	unsigned long flags;
+
+	if (info->rq == NULL)
+		return;
+
+	spin_lock_irqsave(&info->io_lock, flags);
+
+	/* No more blkif_request(). */
+	blk_stop_queue(info->rq);
+
+	/* No more gnttab callback work. */
+	gnttab_cancel_free_callback(&info->callback);
+	spin_unlock_irqrestore(&info->io_lock, flags);
+
+	/* Flush gnttab callback work. Must be done with no locks held. */
+	flush_work(&info->work);
+
+	del_gendisk(info->gd);
+
+	minor = info->gd->first_minor;
+	nr_minors = info->gd->minors;
+	xlbd_release_minors(minor, nr_minors);
+
+	blk_cleanup_queue(info->rq);
+	info->rq = NULL;
+
+	put_disk(info->gd);
+	info->gd = NULL;
+}
+
+static void kick_pending_request_queues(struct blkfront_info *info)
+{
+	if (!RING_FULL(&info->ring)) {
+		/* Re-enable calldowns. */
+		blk_start_queue(info->rq);
+		/* Kick things off immediately. */
+		do_blkif_request(info->rq);
+	}
+}
+
+static void blkif_restart_queue(struct work_struct *work)
+{
+	struct blkfront_info *info = container_of(work, struct blkfront_info, work);
+
+	spin_lock_irq(&info->io_lock);
+	if (info->connected == BLKIF_STATE_CONNECTED)
+		kick_pending_request_queues(info);
+	spin_unlock_irq(&info->io_lock);
+}
+
+static void blkif_free(struct blkfront_info *info, int suspend)
+{
+	struct grant *persistent_gnt;
+	struct grant *n;
+	int i, j, segs;
+
+	/* Prevent new requests being issued until we fix things up. */
+	spin_lock_irq(&info->io_lock);
+	info->connected = suspend ?
+		BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
+	/* No more blkif_request(). */
+	if (info->rq)
+		blk_stop_queue(info->rq);
+
+	/* Remove all persistent grants */
+	if (!list_empty(&info->grants)) {
+		list_for_each_entry_safe(persistent_gnt, n,
+		                         &info->grants, node) {
+			list_del(&persistent_gnt->node);
+			if (persistent_gnt->gref != GRANT_INVALID_REF) {
+				gnttab_end_foreign_access(persistent_gnt->gref,
+				                          0, 0UL);
+				info->persistent_gnts_c--;
+			}
+			if (info->feature_persistent)
+				__free_page(pfn_to_page(persistent_gnt->pfn));
+			kfree(persistent_gnt);
+		}
+	}
+	BUG_ON(info->persistent_gnts_c != 0);
+
+	/*
+	 * Remove indirect pages, this only happens when using indirect
+	 * descriptors but not persistent grants
+	 */
+	if (!list_empty(&info->indirect_pages)) {
+		struct page *indirect_page, *n;
+
+		BUG_ON(info->feature_persistent);
+		list_for_each_entry_safe(indirect_page, n, &info->indirect_pages, lru) {
+			list_del(&indirect_page->lru);
+			__free_page(indirect_page);
+		}
+	}
+
+	for (i = 0; i < BLK_RING_SIZE; i++) {
+		/*
+		 * Clear persistent grants present in requests already
+		 * on the shared ring
+		 */
+		if (!info->shadow[i].request)
+			goto free_shadow;
+
+		segs = info->shadow[i].req.operation == BLKIF_OP_INDIRECT ?
+		       info->shadow[i].req.u.indirect.nr_segments :
+		       info->shadow[i].req.u.rw.nr_segments;
+		for (j = 0; j < segs; j++) {
+			persistent_gnt = info->shadow[i].grants_used[j];
+			gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
+			if (info->feature_persistent)
+				__free_page(pfn_to_page(persistent_gnt->pfn));
+			kfree(persistent_gnt);
+		}
+
+		if (info->shadow[i].req.operation != BLKIF_OP_INDIRECT)
+			/*
+			 * If this is not an indirect operation don't try to
+			 * free indirect segments
+			 */
+			goto free_shadow;
+
+		for (j = 0; j < INDIRECT_GREFS(segs); j++) {
+			persistent_gnt = info->shadow[i].indirect_grants[j];
+			gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
+			__free_page(pfn_to_page(persistent_gnt->pfn));
+			kfree(persistent_gnt);
+		}
+
+free_shadow:
+		kfree(info->shadow[i].grants_used);
+		info->shadow[i].grants_used = NULL;
+		kfree(info->shadow[i].indirect_grants);
+		info->shadow[i].indirect_grants = NULL;
+		kfree(info->shadow[i].sg);
+		info->shadow[i].sg = NULL;
+	}
+
+	/* No more gnttab callback work. */
+	gnttab_cancel_free_callback(&info->callback);
+	spin_unlock_irq(&info->io_lock);
+
+	/* Flush gnttab callback work. Must be done with no locks held. */
+	flush_work(&info->work);
+
+	/* Free resources associated with old device channel. */
+	if (info->ring_ref != GRANT_INVALID_REF) {
+		gnttab_end_foreign_access(info->ring_ref, 0,
+					  (unsigned long)info->ring.sring);
+		info->ring_ref = GRANT_INVALID_REF;
+		info->ring.sring = NULL;
+	}
+	if (info->irq)
+		unbind_from_irqhandler(info->irq, info);
+	info->evtchn = info->irq = 0;
+
+}
+
+static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
+			     struct blkif_response *bret)
+{
+	int i = 0;
+	struct scatterlist *sg;
+	char *bvec_data;
+	void *shared_data;
+	int nseg;
+
+	nseg = s->req.operation == BLKIF_OP_INDIRECT ?
+		s->req.u.indirect.nr_segments : s->req.u.rw.nr_segments;
+
+	if (bret->operation == BLKIF_OP_READ && info->feature_persistent) {
+		/*
+		 * Copy the data received from the backend into the bvec.
+		 * Since bv_offset can be different than 0, and bv_len different
+		 * than PAGE_SIZE, we have to keep track of the current offset,
+		 * to be sure we are copying the data from the right shared page.
+		 */
+		for_each_sg(s->sg, sg, nseg, i) {
+			BUG_ON(sg->offset + sg->length > PAGE_SIZE);
+			shared_data = kmap_atomic(
+				pfn_to_page(s->grants_used[i]->pfn));
+			bvec_data = kmap_atomic(sg_page(sg));
+			memcpy(bvec_data   + sg->offset,
+			       shared_data + sg->offset,
+			       sg->length);
+			kunmap_atomic(bvec_data);
+			kunmap_atomic(shared_data);
+		}
+	}
+	/* Add the persistent grant into the list of free grants */
+	for (i = 0; i < nseg; i++) {
+		if (gnttab_query_foreign_access(s->grants_used[i]->gref)) {
+			/*
+			 * If the grant is still mapped by the backend (the
+			 * backend has chosen to make this grant persistent)
+			 * we add it at the head of the list, so it will be
+			 * reused first.
+			 */
+			if (!info->feature_persistent)
+				pr_alert_ratelimited("backed has not unmapped grant: %u\n",
+						     s->grants_used[i]->gref);
+			list_add(&s->grants_used[i]->node, &info->grants);
+			info->persistent_gnts_c++;
+		} else {
+			/*
+			 * If the grant is not mapped by the backend we end the
+			 * foreign access and add it to the tail of the list,
+			 * so it will not be picked again unless we run out of
+			 * persistent grants.
+			 */
+			gnttab_end_foreign_access(s->grants_used[i]->gref, 0, 0UL);
+			s->grants_used[i]->gref = GRANT_INVALID_REF;
+			list_add_tail(&s->grants_used[i]->node, &info->grants);
+		}
+	}
+	if (s->req.operation == BLKIF_OP_INDIRECT) {
+		for (i = 0; i < INDIRECT_GREFS(nseg); i++) {
+			if (gnttab_query_foreign_access(s->indirect_grants[i]->gref)) {
+				if (!info->feature_persistent)
+					pr_alert_ratelimited("backed has not unmapped grant: %u\n",
+							     s->indirect_grants[i]->gref);
+				list_add(&s->indirect_grants[i]->node, &info->grants);
+				info->persistent_gnts_c++;
+			} else {
+				struct page *indirect_page;
+
+				gnttab_end_foreign_access(s->indirect_grants[i]->gref, 0, 0UL);
+				/*
+				 * Add the used indirect page back to the list of
+				 * available pages for indirect grefs.
+				 */
+				indirect_page = pfn_to_page(s->indirect_grants[i]->pfn);
+				list_add(&indirect_page->lru, &info->indirect_pages);
+				s->indirect_grants[i]->gref = GRANT_INVALID_REF;
+				list_add_tail(&s->indirect_grants[i]->node, &info->grants);
+			}
+		}
+	}
+}
+
+static irqreturn_t blkif_interrupt(int irq, void *dev_id)
+{
+	struct request *req;
+	struct blkif_response *bret;
+	RING_IDX i, rp;
+	unsigned long flags;
+	struct blkfront_info *info = (struct blkfront_info *)dev_id;
+	int error;
+
+	spin_lock_irqsave(&info->io_lock, flags);
+
+	if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) {
+		spin_unlock_irqrestore(&info->io_lock, flags);
+		return IRQ_HANDLED;
+	}
+
+ again:
+	rp = info->ring.sring->rsp_prod;
+	rmb(); /* Ensure we see queued responses up to 'rp'. */
+
+	for (i = info->ring.rsp_cons; i != rp; i++) {
+		unsigned long id;
+
+		bret = RING_GET_RESPONSE(&info->ring, i);
+		id   = bret->id;
+		/*
+		 * The backend has messed up and given us an id that we would
+		 * never have given to it (we stamp it up to BLK_RING_SIZE -
+		 * look in get_id_from_freelist.
+		 */
+		if (id >= BLK_RING_SIZE) {
+			WARN(1, "%s: response to %s has incorrect id (%ld)\n",
+			     info->gd->disk_name, op_name(bret->operation), id);
+			/* We can't safely get the 'struct request' as
+			 * the id is busted. */
+			continue;
+		}
+		req  = info->shadow[id].request;
+
+		if (bret->operation != BLKIF_OP_DISCARD)
+			blkif_completion(&info->shadow[id], info, bret);
+
+		if (add_id_to_freelist(info, id)) {
+			WARN(1, "%s: response to %s (id %ld) couldn't be recycled!\n",
+			     info->gd->disk_name, op_name(bret->operation), id);
+			continue;
+		}
+
+		error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO;
+		switch (bret->operation) {
+		case BLKIF_OP_DISCARD:
+			if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
+				struct request_queue *rq = info->rq;
+				printk(KERN_WARNING "blkfront: %s: %s op failed\n",
+					   info->gd->disk_name, op_name(bret->operation));
+				error = -EOPNOTSUPP;
+				info->feature_discard = 0;
+				info->feature_secdiscard = 0;
+				queue_flag_clear(QUEUE_FLAG_DISCARD, rq);
+				queue_flag_clear(QUEUE_FLAG_SECDISCARD, rq);
+			}
+			__blk_end_request_all(req, error);
+			break;
+		case BLKIF_OP_FLUSH_DISKCACHE:
+		case BLKIF_OP_WRITE_BARRIER:
+			if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
+				printk(KERN_WARNING "blkfront: %s: %s op failed\n",
+				       info->gd->disk_name, op_name(bret->operation));
+				error = -EOPNOTSUPP;
+			}
+			if (unlikely(bret->status == BLKIF_RSP_ERROR &&
+				     info->shadow[id].req.u.rw.nr_segments == 0)) {
+				printk(KERN_WARNING "blkfront: %s: empty %s op failed\n",
+				       info->gd->disk_name, op_name(bret->operation));
+				error = -EOPNOTSUPP;
+			}
+			if (unlikely(error)) {
+				if (error == -EOPNOTSUPP)
+					error = 0;
+				info->feature_flush = 0;
+				xlvbd_flush(info);
+			}
+			/* fall through */
+		case BLKIF_OP_READ:
+		case BLKIF_OP_WRITE:
+			if (unlikely(bret->status != BLKIF_RSP_OKAY))
+				dev_dbg(&info->xbdev->dev, "Bad return from blkdev data "
+					"request: %x\n", bret->status);
+
+			__blk_end_request_all(req, error);
+			break;
+		default:
+			BUG();
+		}
+	}
+
+	info->ring.rsp_cons = i;
+
+	if (i != info->ring.req_prod_pvt) {
+		int more_to_do;
+		RING_FINAL_CHECK_FOR_RESPONSES(&info->ring, more_to_do);
+		if (more_to_do)
+			goto again;
+	} else
+		info->ring.sring->rsp_event = i + 1;
+
+	kick_pending_request_queues(info);
+
+	spin_unlock_irqrestore(&info->io_lock, flags);
+
+	return IRQ_HANDLED;
+}
+
+
+static int setup_blkring(struct xenbus_device *dev,
+			 struct blkfront_info *info)
+{
+	struct blkif_sring *sring;
+	grant_ref_t gref;
+	int err;
+
+	info->ring_ref = GRANT_INVALID_REF;
+
+	sring = (struct blkif_sring *)__get_free_page(GFP_NOIO | __GFP_HIGH);
+	if (!sring) {
+		xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
+		return -ENOMEM;
+	}
+	SHARED_RING_INIT(sring);
+	FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
+
+	err = xenbus_grant_ring(dev, info->ring.sring, 1, &gref);
+	if (err < 0) {
+		free_page((unsigned long)sring);
+		info->ring.sring = NULL;
+		goto fail;
+	}
+	info->ring_ref = gref;
+
+	err = xenbus_alloc_evtchn(dev, &info->evtchn);
+	if (err)
+		goto fail;
+
+	err = bind_evtchn_to_irqhandler(info->evtchn, blkif_interrupt, 0,
+					"blkif", info);
+	if (err <= 0) {
+		xenbus_dev_fatal(dev, err,
+				 "bind_evtchn_to_irqhandler failed");
+		goto fail;
+	}
+	info->irq = err;
+
+	return 0;
+fail:
+	blkif_free(info, 0);
+	return err;
+}
+
+
+/* Common code used when first setting up, and when resuming. */
+static int talk_to_blkback(struct xenbus_device *dev,
+			   struct blkfront_info *info)
+{
+	const char *message = NULL;
+	struct xenbus_transaction xbt;
+	int err;
+
+	/* Create shared ring, alloc event channel. */
+	err = setup_blkring(dev, info);
+	if (err)
+		goto out;
+
+again:
+	err = xenbus_transaction_start(&xbt);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "starting transaction");
+		goto destroy_blkring;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename,
+			    "ring-ref", "%u", info->ring_ref);
+	if (err) {
+		message = "writing ring-ref";
+		goto abort_transaction;
+	}
+	err = xenbus_printf(xbt, dev->nodename,
+			    "event-channel", "%u", info->evtchn);
+	if (err) {
+		message = "writing event-channel";
+		goto abort_transaction;
+	}
+	err = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
+			    XEN_IO_PROTO_ABI_NATIVE);
+	if (err) {
+		message = "writing protocol";
+		goto abort_transaction;
+	}
+	err = xenbus_printf(xbt, dev->nodename,
+			    "feature-persistent", "%u", 1);
+	if (err)
+		dev_warn(&dev->dev,
+			 "writing persistent grants feature to xenbus");
+
+	err = xenbus_transaction_end(xbt, 0);
+	if (err) {
+		if (err == -EAGAIN)
+			goto again;
+		xenbus_dev_fatal(dev, err, "completing transaction");
+		goto destroy_blkring;
+	}
+
+	xenbus_switch_state(dev, XenbusStateInitialised);
+
+	return 0;
+
+ abort_transaction:
+	xenbus_transaction_end(xbt, 1);
+	if (message)
+		xenbus_dev_fatal(dev, err, "%s", message);
+ destroy_blkring:
+	blkif_free(info, 0);
+ out:
+	return err;
+}
+
+/**
+ * Entry point to this code when a new device is created.  Allocate the basic
+ * structures and the ring buffer for communication with the backend, and
+ * inform the backend of the appropriate details for those.  Switch to
+ * Initialised state.
+ */
+static int blkfront_probe(struct xenbus_device *dev,
+			  const struct xenbus_device_id *id)
+{
+	int err, vdevice, i;
+	struct blkfront_info *info;
+
+	/* FIXME: Use dynamic device id if this is not set. */
+	err = xenbus_scanf(XBT_NIL, dev->nodename,
+			   "virtual-device", "%i", &vdevice);
+	if (err != 1) {
+		/* go looking in the extended area instead */
+		err = xenbus_scanf(XBT_NIL, dev->nodename, "virtual-device-ext",
+				   "%i", &vdevice);
+		if (err != 1) {
+			xenbus_dev_fatal(dev, err, "reading virtual-device");
+			return err;
+		}
+	}
+
+	if (xen_hvm_domain()) {
+		char *type;
+		int len;
+		/* no unplug has been done: do not hook devices != xen vbds */
+		if (xen_has_pv_and_legacy_disk_devices()) {
+			int major;
+
+			if (!VDEV_IS_EXTENDED(vdevice))
+				major = BLKIF_MAJOR(vdevice);
+			else
+				major = XENVBD_MAJOR;
+
+			if (major != XENVBD_MAJOR) {
+				printk(KERN_INFO
+						"%s: HVM does not support vbd %d as xen block device\n",
+						__func__, vdevice);
+				return -ENODEV;
+			}
+		}
+		/* do not create a PV cdrom device if we are an HVM guest */
+		type = xenbus_read(XBT_NIL, dev->nodename, "device-type", &len);
+		if (IS_ERR(type))
+			return -ENODEV;
+		if (strncmp(type, "cdrom", 5) == 0) {
+			kfree(type);
+			return -ENODEV;
+		}
+		kfree(type);
+	}
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info) {
+		xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
+		return -ENOMEM;
+	}
+
+	mutex_init(&info->mutex);
+	spin_lock_init(&info->io_lock);
+	info->xbdev = dev;
+	info->vdevice = vdevice;
+	INIT_LIST_HEAD(&info->grants);
+	INIT_LIST_HEAD(&info->indirect_pages);
+	info->persistent_gnts_c = 0;
+	info->connected = BLKIF_STATE_DISCONNECTED;
+	INIT_WORK(&info->work, blkif_restart_queue);
+
+	for (i = 0; i < BLK_RING_SIZE; i++)
+		info->shadow[i].req.u.rw.id = i+1;
+	info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
+
+	/* Front end dir is a number, which is used as the id. */
+	info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0);
+	dev_set_drvdata(&dev->dev, info);
+
+	err = talk_to_blkback(dev, info);
+	if (err) {
+		kfree(info);
+		dev_set_drvdata(&dev->dev, NULL);
+		return err;
+	}
+
+	return 0;
+}
+
+static void split_bio_end(struct bio *bio, int error)
+{
+	struct split_bio *split_bio = bio->bi_private;
+
+	if (error)
+		split_bio->err = error;
+
+	if (atomic_dec_and_test(&split_bio->pending)) {
+		split_bio->bio->bi_phys_segments = 0;
+		bio_endio(split_bio->bio, split_bio->err);
+		kfree(split_bio);
+	}
+	bio_put(bio);
+}
+
+static int blkif_recover(struct blkfront_info *info)
+{
+	int i;
+	struct request *req, *n;
+	struct blk_shadow *copy;
+	int rc;
+	struct bio *bio, *cloned_bio;
+	struct bio_list bio_list, merge_bio;
+	unsigned int segs, offset;
+	int pending, size;
+	struct split_bio *split_bio;
+	struct list_head requests;
+
+	/* Stage 1: Make a safe copy of the shadow state. */
+	copy = kmemdup(info->shadow, sizeof(info->shadow),
+		       GFP_NOIO | __GFP_REPEAT | __GFP_HIGH);
+	if (!copy)
+		return -ENOMEM;
+
+	/* Stage 2: Set up free list. */
+	memset(&info->shadow, 0, sizeof(info->shadow));
+	for (i = 0; i < BLK_RING_SIZE; i++)
+		info->shadow[i].req.u.rw.id = i+1;
+	info->shadow_free = info->ring.req_prod_pvt;
+	info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
+
+	rc = blkfront_setup_indirect(info);
+	if (rc) {
+		kfree(copy);
+		return rc;
+	}
+
+	segs = info->max_indirect_segments ? : BLKIF_MAX_SEGMENTS_PER_REQUEST;
+	blk_queue_max_segments(info->rq, segs);
+	bio_list_init(&bio_list);
+	INIT_LIST_HEAD(&requests);
+	for (i = 0; i < BLK_RING_SIZE; i++) {
+		/* Not in use? */
+		if (!copy[i].request)
+			continue;
+
+		/*
+		 * Get the bios in the request so we can re-queue them.
+		 */
+		if (copy[i].request->cmd_flags &
+		    (REQ_FLUSH | REQ_FUA | REQ_DISCARD | REQ_SECURE)) {
+			/*
+			 * Flush operations don't contain bios, so
+			 * we need to requeue the whole request
+			 */
+			list_add(&copy[i].request->queuelist, &requests);
+			continue;
+		}
+		merge_bio.head = copy[i].request->bio;
+		merge_bio.tail = copy[i].request->biotail;
+		bio_list_merge(&bio_list, &merge_bio);
+		copy[i].request->bio = NULL;
+		blk_end_request_all(copy[i].request, 0);
+	}
+
+	kfree(copy);
+
+	/*
+	 * Empty the queue, this is important because we might have
+	 * requests in the queue with more segments than what we
+	 * can handle now.
+	 */
+	spin_lock_irq(&info->io_lock);
+	while ((req = blk_fetch_request(info->rq)) != NULL) {
+		if (req->cmd_flags &
+		    (REQ_FLUSH | REQ_FUA | REQ_DISCARD | REQ_SECURE)) {
+			list_add(&req->queuelist, &requests);
+			continue;
+		}
+		merge_bio.head = req->bio;
+		merge_bio.tail = req->biotail;
+		bio_list_merge(&bio_list, &merge_bio);
+		req->bio = NULL;
+		if (req->cmd_flags & (REQ_FLUSH | REQ_FUA))
+			pr_alert("diskcache flush request found!\n");
+		__blk_end_request_all(req, 0);
+	}
+	spin_unlock_irq(&info->io_lock);
+
+	xenbus_switch_state(info->xbdev, XenbusStateConnected);
+
+	spin_lock_irq(&info->io_lock);
+
+	/* Now safe for us to use the shared ring */
+	info->connected = BLKIF_STATE_CONNECTED;
+
+	/* Kick any other new requests queued since we resumed */
+	kick_pending_request_queues(info);
+
+	list_for_each_entry_safe(req, n, &requests, queuelist) {
+		/* Requeue pending requests (flush or discard) */
+		list_del_init(&req->queuelist);
+		BUG_ON(req->nr_phys_segments > segs);
+		blk_requeue_request(info->rq, req);
+	}
+	spin_unlock_irq(&info->io_lock);
+
+	while ((bio = bio_list_pop(&bio_list)) != NULL) {
+		/* Traverse the list of pending bios and re-queue them */
+		if (bio_segments(bio) > segs) {
+			/*
+			 * This bio has more segments than what we can
+			 * handle, we have to split it.
+			 */
+			pending = (bio_segments(bio) + segs - 1) / segs;
+			split_bio = kzalloc(sizeof(*split_bio), GFP_NOIO);
+			BUG_ON(split_bio == NULL);
+			atomic_set(&split_bio->pending, pending);
+			split_bio->bio = bio;
+			for (i = 0; i < pending; i++) {
+				offset = (i * segs * PAGE_SIZE) >> 9;
+				size = min((unsigned int)(segs * PAGE_SIZE) >> 9,
+					   (unsigned int)bio_sectors(bio) - offset);
+				cloned_bio = bio_clone(bio, GFP_NOIO);
+				BUG_ON(cloned_bio == NULL);
+				bio_trim(cloned_bio, offset, size);
+				cloned_bio->bi_private = split_bio;
+				cloned_bio->bi_end_io = split_bio_end;
+				submit_bio(cloned_bio->bi_rw, cloned_bio);
+			}
+			/*
+			 * Now we have to wait for all those smaller bios to
+			 * end, so we can also end the "parent" bio.
+			 */
+			continue;
+		}
+		/* We don't need to split this bio */
+		submit_bio(bio->bi_rw, bio);
+	}
+
+	return 0;
+}
+
+/**
+ * We are reconnecting to the backend, due to a suspend/resume, or a backend
+ * driver restart.  We tear down our blkif structure and recreate it, but
+ * leave the device-layer structures intact so that this is transparent to the
+ * rest of the kernel.
+ */
+static int blkfront_resume(struct xenbus_device *dev)
+{
+	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
+	int err;
+
+	dev_dbg(&dev->dev, "blkfront_resume: %s\n", dev->nodename);
+
+	blkif_free(info, info->connected == BLKIF_STATE_CONNECTED);
+
+	err = talk_to_blkback(dev, info);
+
+	/*
+	 * We have to wait for the backend to switch to
+	 * connected state, since we want to read which
+	 * features it supports.
+	 */
+
+	return err;
+}
+
+static void
+blkfront_closing(struct blkfront_info *info)
+{
+	struct xenbus_device *xbdev = info->xbdev;
+	struct block_device *bdev = NULL;
+
+	mutex_lock(&info->mutex);
+
+	if (xbdev->state == XenbusStateClosing) {
+		mutex_unlock(&info->mutex);
+		return;
+	}
+
+	if (info->gd)
+		bdev = bdget_disk(info->gd, 0);
+
+	mutex_unlock(&info->mutex);
+
+	if (!bdev) {
+		xenbus_frontend_closed(xbdev);
+		return;
+	}
+
+	mutex_lock(&bdev->bd_mutex);
+
+	if (bdev->bd_openers) {
+		xenbus_dev_error(xbdev, -EBUSY,
+				 "Device in use; refusing to close");
+		xenbus_switch_state(xbdev, XenbusStateClosing);
+	} else {
+		xlvbd_release_gendisk(info);
+		xenbus_frontend_closed(xbdev);
+	}
+
+	mutex_unlock(&bdev->bd_mutex);
+	bdput(bdev);
+}
+
+static void blkfront_setup_discard(struct blkfront_info *info)
+{
+	int err;
+	unsigned int discard_granularity;
+	unsigned int discard_alignment;
+	unsigned int discard_secure;
+
+	info->feature_discard = 1;
+	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+		"discard-granularity", "%u", &discard_granularity,
+		"discard-alignment", "%u", &discard_alignment,
+		NULL);
+	if (!err) {
+		info->discard_granularity = discard_granularity;
+		info->discard_alignment = discard_alignment;
+	}
+	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+		    "discard-secure", "%d", &discard_secure,
+		    NULL);
+	if (!err)
+		info->feature_secdiscard = !!discard_secure;
+}
+
+static int blkfront_setup_indirect(struct blkfront_info *info)
+{
+	unsigned int indirect_segments, segs;
+	int err, i;
+
+	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+			    "feature-max-indirect-segments", "%u", &indirect_segments,
+			    NULL);
+	if (err) {
+		info->max_indirect_segments = 0;
+		segs = BLKIF_MAX_SEGMENTS_PER_REQUEST;
+	} else {
+		info->max_indirect_segments = min(indirect_segments,
+						  xen_blkif_max_segments);
+		segs = info->max_indirect_segments;
+	}
+
+	err = fill_grant_buffer(info, (segs + INDIRECT_GREFS(segs)) * BLK_RING_SIZE);
+	if (err)
+		goto out_of_memory;
+
+	if (!info->feature_persistent && info->max_indirect_segments) {
+		/*
+		 * We are using indirect descriptors but not persistent
+		 * grants, we need to allocate a set of pages that can be
+		 * used for mapping indirect grefs
+		 */
+		int num = INDIRECT_GREFS(segs) * BLK_RING_SIZE;
+
+		BUG_ON(!list_empty(&info->indirect_pages));
+		for (i = 0; i < num; i++) {
+			struct page *indirect_page = alloc_page(GFP_NOIO);
+			if (!indirect_page)
+				goto out_of_memory;
+			list_add(&indirect_page->lru, &info->indirect_pages);
+		}
+	}
+
+	for (i = 0; i < BLK_RING_SIZE; i++) {
+		info->shadow[i].grants_used = kzalloc(
+			sizeof(info->shadow[i].grants_used[0]) * segs,
+			GFP_NOIO);
+		info->shadow[i].sg = kzalloc(sizeof(info->shadow[i].sg[0]) * segs, GFP_NOIO);
+		if (info->max_indirect_segments)
+			info->shadow[i].indirect_grants = kzalloc(
+				sizeof(info->shadow[i].indirect_grants[0]) *
+				INDIRECT_GREFS(segs),
+				GFP_NOIO);
+		if ((info->shadow[i].grants_used == NULL) ||
+			(info->shadow[i].sg == NULL) ||
+		     (info->max_indirect_segments &&
+		     (info->shadow[i].indirect_grants == NULL)))
+			goto out_of_memory;
+		sg_init_table(info->shadow[i].sg, segs);
+	}
+
+
+	return 0;
+
+out_of_memory:
+	for (i = 0; i < BLK_RING_SIZE; i++) {
+		kfree(info->shadow[i].grants_used);
+		info->shadow[i].grants_used = NULL;
+		kfree(info->shadow[i].sg);
+		info->shadow[i].sg = NULL;
+		kfree(info->shadow[i].indirect_grants);
+		info->shadow[i].indirect_grants = NULL;
+	}
+	if (!list_empty(&info->indirect_pages)) {
+		struct page *indirect_page, *n;
+		list_for_each_entry_safe(indirect_page, n, &info->indirect_pages, lru) {
+			list_del(&indirect_page->lru);
+			__free_page(indirect_page);
+		}
+	}
+	return -ENOMEM;
+}
+
+/*
+ * Invoked when the backend is finally 'ready' (and has told produced
+ * the details about the physical device - #sectors, size, etc).
+ */
+static void blkfront_connect(struct blkfront_info *info)
+{
+	unsigned long long sectors;
+	unsigned long sector_size;
+	unsigned int physical_sector_size;
+	unsigned int binfo;
+	int err;
+	int barrier, flush, discard, persistent;
+
+	switch (info->connected) {
+	case BLKIF_STATE_CONNECTED:
+		/*
+		 * Potentially, the back-end may be signalling
+		 * a capacity change; update the capacity.
+		 */
+		err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+				   "sectors", "%Lu", &sectors);
+		if (XENBUS_EXIST_ERR(err))
+			return;
+		printk(KERN_INFO "Setting capacity to %Lu\n",
+		       sectors);
+		set_capacity(info->gd, sectors);
+		revalidate_disk(info->gd);
+
+		return;
+	case BLKIF_STATE_SUSPENDED:
+		/*
+		 * If we are recovering from suspension, we need to wait
+		 * for the backend to announce it's features before
+		 * reconnecting, at least we need to know if the backend
+		 * supports indirect descriptors, and how many.
+		 */
+		blkif_recover(info);
+		return;
+
+	default:
+		break;
+	}
+
+	dev_dbg(&info->xbdev->dev, "%s:%s.\n",
+		__func__, info->xbdev->otherend);
+
+	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+			    "sectors", "%llu", &sectors,
+			    "info", "%u", &binfo,
+			    "sector-size", "%lu", &sector_size,
+			    NULL);
+	if (err) {
+		xenbus_dev_fatal(info->xbdev, err,
+				 "reading backend fields at %s",
+				 info->xbdev->otherend);
+		return;
+	}
+
+	/*
+	 * physcial-sector-size is a newer field, so old backends may not
+	 * provide this. Assume physical sector size to be the same as
+	 * sector_size in that case.
+	 */
+	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+			   "physical-sector-size", "%u", &physical_sector_size);
+	if (err != 1)
+		physical_sector_size = sector_size;
+
+	info->feature_flush = 0;
+
+	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+			    "feature-barrier", "%d", &barrier,
+			    NULL);
+
+	/*
+	 * If there's no "feature-barrier" defined, then it means
+	 * we're dealing with a very old backend which writes
+	 * synchronously; nothing to do.
+	 *
+	 * If there are barriers, then we use flush.
+	 */
+	if (!err && barrier)
+		info->feature_flush = REQ_FLUSH | REQ_FUA;
+	/*
+	 * And if there is "feature-flush-cache" use that above
+	 * barriers.
+	 */
+	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+			    "feature-flush-cache", "%d", &flush,
+			    NULL);
+
+	if (!err && flush)
+		info->feature_flush = REQ_FLUSH;
+
+	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+			    "feature-discard", "%d", &discard,
+			    NULL);
+
+	if (!err && discard)
+		blkfront_setup_discard(info);
+
+	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+			    "feature-persistent", "%u", &persistent,
+			    NULL);
+	if (err)
+		info->feature_persistent = 0;
+	else
+		info->feature_persistent = persistent;
+
+	err = blkfront_setup_indirect(info);
+	if (err) {
+		xenbus_dev_fatal(info->xbdev, err, "setup_indirect at %s",
+				 info->xbdev->otherend);
+		return;
+	}
+
+	err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size,
+				  physical_sector_size);
+	if (err) {
+		xenbus_dev_fatal(info->xbdev, err, "xlvbd_add at %s",
+				 info->xbdev->otherend);
+		return;
+	}
+
+	xenbus_switch_state(info->xbdev, XenbusStateConnected);
+
+	/* Kick pending requests. */
+	spin_lock_irq(&info->io_lock);
+	info->connected = BLKIF_STATE_CONNECTED;
+	kick_pending_request_queues(info);
+	spin_unlock_irq(&info->io_lock);
+
+	add_disk(info->gd);
+
+	info->is_ready = 1;
+}
+
+/**
+ * Callback received when the backend's state changes.
+ */
+static void blkback_changed(struct xenbus_device *dev,
+			    enum xenbus_state backend_state)
+{
+	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
+
+	dev_dbg(&dev->dev, "blkfront:blkback_changed to state %d.\n", backend_state);
+
+	switch (backend_state) {
+	case XenbusStateInitialising:
+	case XenbusStateInitWait:
+	case XenbusStateInitialised:
+	case XenbusStateReconfiguring:
+	case XenbusStateReconfigured:
+	case XenbusStateUnknown:
+		break;
+
+	case XenbusStateConnected:
+		blkfront_connect(info);
+		break;
+
+	case XenbusStateClosed:
+		if (dev->state == XenbusStateClosed)
+			break;
+		/* Missed the backend's Closing state -- fallthrough */
+	case XenbusStateClosing:
+		blkfront_closing(info);
+		break;
+	}
+}
+
+static int blkfront_remove(struct xenbus_device *xbdev)
+{
+	struct blkfront_info *info = dev_get_drvdata(&xbdev->dev);
+	struct block_device *bdev = NULL;
+	struct gendisk *disk;
+
+	dev_dbg(&xbdev->dev, "%s removed", xbdev->nodename);
+
+	blkif_free(info, 0);
+
+	mutex_lock(&info->mutex);
+
+	disk = info->gd;
+	if (disk)
+		bdev = bdget_disk(disk, 0);
+
+	info->xbdev = NULL;
+	mutex_unlock(&info->mutex);
+
+	if (!bdev) {
+		kfree(info);
+		return 0;
+	}
+
+	/*
+	 * The xbdev was removed before we reached the Closed
+	 * state. See if it's safe to remove the disk. If the bdev
+	 * isn't closed yet, we let release take care of it.
+	 */
+
+	mutex_lock(&bdev->bd_mutex);
+	info = disk->private_data;
+
+	dev_warn(disk_to_dev(disk),
+		 "%s was hot-unplugged, %d stale handles\n",
+		 xbdev->nodename, bdev->bd_openers);
+
+	if (info && !bdev->bd_openers) {
+		xlvbd_release_gendisk(info);
+		disk->private_data = NULL;
+		kfree(info);
+	}
+
+	mutex_unlock(&bdev->bd_mutex);
+	bdput(bdev);
+
+	return 0;
+}
+
+static int blkfront_is_ready(struct xenbus_device *dev)
+{
+	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
+
+	return info->is_ready && info->xbdev;
+}
+
+static int blkif_open(struct block_device *bdev, fmode_t mode)
+{
+	struct gendisk *disk = bdev->bd_disk;
+	struct blkfront_info *info;
+	int err = 0;
+
+	mutex_lock(&blkfront_mutex);
+
+	info = disk->private_data;
+	if (!info) {
+		/* xbdev gone */
+		err = -ERESTARTSYS;
+		goto out;
+	}
+
+	mutex_lock(&info->mutex);
+
+	if (!info->gd)
+		/* xbdev is closed */
+		err = -ERESTARTSYS;
+
+	mutex_unlock(&info->mutex);
+
+out:
+	mutex_unlock(&blkfront_mutex);
+	return err;
+}
+
+static void blkif_release(struct gendisk *disk, fmode_t mode)
+{
+	struct blkfront_info *info = disk->private_data;
+	struct block_device *bdev;
+	struct xenbus_device *xbdev;
+
+	mutex_lock(&blkfront_mutex);
+
+	bdev = bdget_disk(disk, 0);
+
+	if (!bdev) {
+		WARN(1, "Block device %s yanked out from us!\n", disk->disk_name);
+		goto out_mutex;
+	}
+	if (bdev->bd_openers)
+		goto out;
+
+	/*
+	 * Check if we have been instructed to close. We will have
+	 * deferred this request, because the bdev was still open.
+	 */
+
+	mutex_lock(&info->mutex);
+	xbdev = info->xbdev;
+
+	if (xbdev && xbdev->state == XenbusStateClosing) {
+		/* pending switch to state closed */
+		dev_info(disk_to_dev(bdev->bd_disk), "releasing disk\n");
+		xlvbd_release_gendisk(info);
+		xenbus_frontend_closed(info->xbdev);
+ 	}
+
+	mutex_unlock(&info->mutex);
+
+	if (!xbdev) {
+		/* sudden device removal */
+		dev_info(disk_to_dev(bdev->bd_disk), "releasing disk\n");
+		xlvbd_release_gendisk(info);
+		disk->private_data = NULL;
+		kfree(info);
+	}
+
+out:
+	bdput(bdev);
+out_mutex:
+	mutex_unlock(&blkfront_mutex);
+}
+
+static const struct block_device_operations xlvbd_block_fops =
+{
+	.owner = THIS_MODULE,
+	.open = blkif_open,
+	.release = blkif_release,
+	.getgeo = blkif_getgeo,
+	.ioctl = blkif_ioctl,
+};
+
+
+static const struct xenbus_device_id blkfront_ids[] = {
+	{ "vbd" },
+	{ "" }
+};
+
+static struct xenbus_driver blkfront_driver = {
+	.ids  = blkfront_ids,
+	.probe = blkfront_probe,
+	.remove = blkfront_remove,
+	.resume = blkfront_resume,
+	.otherend_changed = blkback_changed,
+	.is_ready = blkfront_is_ready,
+};
+
+static int __init xlblk_init(void)
+{
+	int ret;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	if (!xen_has_pv_disk_devices())
+		return -ENODEV;
+
+	if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) {
+		printk(KERN_WARNING "xen_blk: can't get major %d with name %s\n",
+		       XENVBD_MAJOR, DEV_NAME);
+		return -ENODEV;
+	}
+
+	ret = xenbus_register_frontend(&blkfront_driver);
+	if (ret) {
+		unregister_blkdev(XENVBD_MAJOR, DEV_NAME);
+		return ret;
+	}
+
+	return 0;
+}
+module_init(xlblk_init);
+
+
+static void __exit xlblk_exit(void)
+{
+	xenbus_unregister_driver(&blkfront_driver);
+	unregister_blkdev(XENVBD_MAJOR, DEV_NAME);
+	kfree(minors);
+}
+module_exit(xlblk_exit);
+
+MODULE_DESCRIPTION("Xen virtual block device frontend");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_BLOCKDEV_MAJOR(XENVBD_MAJOR);
+MODULE_ALIAS("xen:vbd");
+MODULE_ALIAS("xenblk");