The block device frontend driver allows the kernel to access block
devices exported exported by a virtual machine containing a physical
block device driver.
Signed-off-by: Ian Pratt <ian.pratt@xxxxxxxxxxxxx>
Signed-off-by: Christian Limpach <Christian.Limpach@xxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
---
drivers/block/Kconfig | 9
drivers/block/Makefile | 1
drivers/block/xen-blkfront.c | 988 ++++++++++++++++++++++++++++++++++++++++++
include/linux/major.h | 2
4 files changed, 1000 insertions(+)
===================================================================
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -425,4 +425,13 @@ config ATA_OVER_ETH
source "drivers/s390/block/Kconfig"
+config XEN_BLKDEV_FRONTEND
+ tristate "Xen virtual block device support"
+ depends on XEN
+ default y
+ help
+ This driver implements the front-end of the Xen virtual
+ block device driver. It communicates with a back-end driver
+ in another domain which drives the actual block device.
+
endif # BLK_DEV
===================================================================
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -28,3 +28,4 @@ obj-$(CONFIG_BLK_DEV_SX8) += sx8.o
obj-$(CONFIG_BLK_DEV_SX8) += sx8.o
obj-$(CONFIG_BLK_DEV_UB) += ub.o
+obj-$(CONFIG_XEN_BLKDEV_FRONTEND) += xen-blkfront.o
===================================================================
--- /dev/null
+++ b/drivers/block/xen-blkfront.c
@@ -0,0 +1,988 @@
+/*
+ * 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/module.h>
+
+#include <xen/xenbus.h>
+#include <xen/grant_table.h>
+#include <xen/events.h>
+#include <xen/page.h>
+
+#include <xen/interface/grant_table.h>
+#include <xen/interface/io/blkif.h>
+
+#include <asm/xen/hypervisor.h>
+
+enum blkif_state {
+ BLKIF_STATE_DISCONNECTED,
+ BLKIF_STATE_CONNECTED,
+ BLKIF_STATE_SUSPENDED,
+};
+
+struct blk_shadow {
+ struct blkif_request req;
+ unsigned long request;
+ unsigned long frame[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+};
+
+static struct block_device_operations xlvbd_block_fops;
+
+#define BLK_RING_SIZE __RING_SIZE((struct blkif_sring *)0, 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
+{
+ struct xenbus_device *xbdev;
+ dev_t dev;
+ 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];
+ unsigned long shadow_free;
+ int feature_barrier;
+
+ /**
+ * The number of people holding this device open. We won't allow a
+ * hot-unplug unless this is 0.
+ */
+ int users;
+};
+
+static DEFINE_SPINLOCK(blkif_io_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 BLKIF_MAJOR(dev) ((dev)>>8)
+#define BLKIF_MINOR(dev) ((dev) & 0xff)
+
+#define DEV_NAME "xvd" /* name in /dev */
+
+/* Information about our VBDs. */
+#define MAX_VBDS 64
+static LIST_HEAD(vbds_list);
+
+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.id;
+ info->shadow[free].req.id = 0x0fffffee; /* debug */
+ return free;
+}
+
+static void add_id_to_freelist(struct blkfront_info *info,
+ unsigned long id)
+{
+ info->shadow[id].req.id = info->shadow_free;
+ info->shadow[id].request = 0;
+ info->shadow_free = id;
+}
+
+static void blkif_restart_queue_callback(void *arg)
+{
+ struct blkfront_info *info = (struct blkfront_info *)arg;
+ schedule_work(&info->work);
+}
+
+/*
+ * blkif_queue_request
+ *
+ * request block io
+ *
+ * id: for guest use only.
+ * operation: BLKIF_OP_{READ,WRITE,PROBE}
+ * buffer: buffer to read/write into. this should be a
+ * virtual address in the guest os.
+ */
+static int blkif_queue_request(struct request *req)
+{
+ struct blkfront_info *info = req->rq_disk->private_data;
+ unsigned long buffer_mfn;
+ struct blkif_request *ring_req;
+ struct bio *bio;
+ struct bio_vec *bvec;
+ int idx;
+ unsigned long id;
+ unsigned int fsect, lsect;
+ int ref;
+ grant_ref_t gref_head;
+
+ if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
+ return 1;
+
+ if (gnttab_alloc_grant_references(
+ BLKIF_MAX_SEGMENTS_PER_REQUEST, &gref_head) < 0) {
+ gnttab_request_free_callback(
+ &info->callback,
+ blkif_restart_queue_callback,
+ info,
+ BLKIF_MAX_SEGMENTS_PER_REQUEST);
+ return 1;
+ }
+
+ /* 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 = (unsigned long)req;
+
+ ring_req->id = id;
+ ring_req->sector_number = (blkif_sector_t)req->sector;
+ ring_req->handle = info->handle;
+
+ ring_req->operation = rq_data_dir(req) ?
+ BLKIF_OP_WRITE : BLKIF_OP_READ;
+ if (blk_barrier_rq(req))
+ ring_req->operation = BLKIF_OP_WRITE_BARRIER;
+
+ ring_req->nr_segments = 0;
+ rq_for_each_bio (bio, req) {
+ bio_for_each_segment (bvec, bio, idx) {
+ BUG_ON(ring_req->nr_segments
+ == BLKIF_MAX_SEGMENTS_PER_REQUEST);
+ buffer_mfn = pfn_to_mfn(page_to_pfn(bvec->bv_page));
+ fsect = bvec->bv_offset >> 9;
+ lsect = fsect + (bvec->bv_len >> 9) - 1;
+ /* install a grant reference. */
+ ref = gnttab_claim_grant_reference(&gref_head);
+ BUG_ON(ref == -ENOSPC);
+
+ gnttab_grant_foreign_access_ref(
+ ref,
+ info->xbdev->otherend_id,
+ buffer_mfn,
+ rq_data_dir(req) );
+
+ info->shadow[id].frame[ring_req->nr_segments] =
+ mfn_to_pfn(buffer_mfn);
+
+ ring_req->seg[ring_req->nr_segments] =
+ (struct blkif_request_segment) {
+ .gref = ref,
+ .first_sect = fsect,
+ .last_sect = lsect };
+
+ ring_req->nr_segments++;
+ }
+ }
+
+ info->ring.req_prod_pvt++;
+
+ /* Keep a private copy so we can reissue requests when recovering. */
+ info->shadow[id].req = *ring_req;
+
+ 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);
+}
+
+/*
+ * do_blkif_request
+ * read a block; request is in a request queue
+ */
+static void do_blkif_request(request_queue_t *rq)
+{
+ struct blkfront_info *info = NULL;
+ struct request *req;
+ int queued;
+
+ pr_debug("Entered do_blkif_request\n");
+
+ queued = 0;
+
+ while ((req = elv_next_request(rq)) != NULL) {
+ info = req->rq_disk->private_data;
+ if (!blk_fs_request(req)) {
+ end_request(req, 0);
+ continue;
+ }
+
+ if (RING_FULL(&info->ring))
+ goto wait;
+
+ pr_debug("do_blk_req %p: cmd %p, sec %lx, "
+ "(%u/%li) buffer:%p [%s]\n",
+ req, req->cmd, (unsigned long)req->sector,
+ req->current_nr_sectors,
+ req->nr_sectors, req->buffer,
+ rq_data_dir(req) ? "write" : "read");
+
+
+ blkdev_dequeue_request(req);
+ 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)
+{
+ request_queue_t *rq;
+
+ rq = blk_init_queue(do_blkif_request, &blkif_io_lock);
+ if (rq == NULL)
+ return -1;
+
+ elevator_init(rq, "noop");
+
+ /* Hard sector size and max sectors impersonate the equiv. hardware. */
+ blk_queue_hardsect_size(rq, sector_size);
+ blk_queue_max_sectors(rq, 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_phys_segments(rq, BLKIF_MAX_SEGMENTS_PER_REQUEST);
+ blk_queue_max_hw_segments(rq, BLKIF_MAX_SEGMENTS_PER_REQUEST);
+
+ /* Make sure buffer addresses are sector-aligned. */
+ blk_queue_dma_alignment(rq, 511);
+
+ gd->queue = rq;
+
+ return 0;
+}
+
+
+static int xlvbd_barrier(struct blkfront_info *info)
+{
+ int err;
+
+ err = blk_queue_ordered(info->rq,
+ info->feature_barrier ? QUEUE_ORDERED_DRAIN :
QUEUE_ORDERED_NONE,
+ NULL);
+
+ if (err)
+ return err;
+
+ printk(KERN_INFO "blkfront: %s: barriers %s\n",
+ info->gd->disk_name,
+ info->feature_barrier ? "enabled" : "disabled");
+ return 0;
+}
+
+
+static int xlvbd_alloc_gendisk(int minor, blkif_sector_t capacity,
+ int vdevice, u16 vdisk_info, u16 sector_size,
+ struct blkfront_info *info)
+{
+ struct gendisk *gd;
+ int nr_minors = 1;
+ int err = -ENODEV;
+
+ BUG_ON(info->gd != NULL);
+ BUG_ON(info->rq != NULL);
+
+ if ((minor % PARTS_PER_DISK) == 0)
+ nr_minors = PARTS_PER_DISK;
+
+ gd = alloc_disk(nr_minors);
+ if (gd == NULL)
+ goto out;
+
+ if (nr_minors > 1)
+ sprintf(gd->disk_name, "%s%c", DEV_NAME,
+ 'a' + minor / PARTS_PER_DISK);
+ else
+ sprintf(gd->disk_name, "%s%c%d", DEV_NAME,
+ 'a' + minor / PARTS_PER_DISK,
+ minor % PARTS_PER_DISK);
+
+ 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)) {
+ del_gendisk(gd);
+ goto out;
+ }
+
+ info->rq = gd->queue;
+ info->gd = gd;
+
+ if (info->feature_barrier)
+ xlvbd_barrier(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;
+
+ out:
+ return err;
+}
+
+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(&blkif_io_lock);
+ if (info->connected == BLKIF_STATE_CONNECTED)
+ kick_pending_request_queues(info);
+ spin_unlock_irq(&blkif_io_lock);
+}
+
+static void blkif_free(struct blkfront_info *info, int suspend)
+{
+ /* Prevent new requests being issued until we fix things up. */
+ spin_lock_irq(&blkif_io_lock);
+ info->connected = suspend ?
+ BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
+ /* No more blkif_request(). */
+ if (info->rq)
+ blk_stop_queue(info->rq);
+ /* No more gnttab callback work. */
+ gnttab_cancel_free_callback(&info->callback);
+ spin_unlock_irq(&blkif_io_lock);
+
+ /* Flush gnttab callback work. Must be done with no locks held. */
+ flush_scheduled_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)
+{
+ int i;
+ for (i = 0; i < s->req.nr_segments; i++)
+ gnttab_end_foreign_access(s->req.seg[i].gref, 0, 0UL);
+}
+
+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 uptodate;
+
+ spin_lock_irqsave(&blkif_io_lock, flags);
+
+ if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) {
+ spin_unlock_irqrestore(&blkif_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;
+ int ret;
+
+ bret = RING_GET_RESPONSE(&info->ring, i);
+ id = bret->id;
+ req = (struct request *)info->shadow[id].request;
+
+ blkif_completion(&info->shadow[id]);
+
+ add_id_to_freelist(info, id);
+
+ uptodate = (bret->status == BLKIF_RSP_OKAY);
+ switch (bret->operation) {
+ case BLKIF_OP_WRITE_BARRIER:
+ if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
+ printk(KERN_WARNING "blkfront: %s: write
barrier op failed\n",
+ info->gd->disk_name);
+ uptodate = -EOPNOTSUPP;
+ info->feature_barrier = 0;
+ xlvbd_barrier(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);
+
+ ret = end_that_request_first(req, uptodate,
+ req->hard_nr_sectors);
+ BUG_ON(ret);
+ end_that_request_last(req, uptodate);
+ 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(&blkif_io_lock, flags);
+
+ return IRQ_HANDLED;
+}
+
+
+static int setup_blkring(struct xenbus_device *dev,
+ struct blkfront_info *info)
+{
+ struct blkif_sring *sring;
+ int err;
+
+ info->ring_ref = GRANT_INVALID_REF;
+
+ sring = (struct blkif_sring *)__get_free_page(GFP_KERNEL);
+ 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, virt_to_mfn(info->ring.sring));
+ if (err < 0) {
+ free_page((unsigned long)sring);
+ info->ring.sring = NULL;
+ goto fail;
+ }
+ info->ring_ref = err;
+
+ err = xenbus_alloc_evtchn(dev, &info->evtchn);
+ if (err)
+ goto fail;
+
+ err = bind_evtchn_to_irqhandler(info->evtchn,
+ blkif_interrupt,
+ IRQF_SAMPLE_RANDOM, "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_backend(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_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) {
+ xenbus_dev_fatal(dev, err, "reading virtual-device");
+ return err;
+ }
+
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info) {
+ xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
+ return -ENOMEM;
+ }
+
+ info->xbdev = dev;
+ info->vdevice = vdevice;
+ info->connected = BLKIF_STATE_DISCONNECTED;
+ INIT_WORK(&info->work, blkif_restart_queue);
+
+ for (i = 0; i < BLK_RING_SIZE; i++)
+ info->shadow[i].req.id = i+1;
+ info->shadow[BLK_RING_SIZE-1].req.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->dev.driver_data = info;
+
+ err = talk_to_backend(dev, info);
+ if (err) {
+ kfree(info);
+ dev->dev.driver_data = NULL;
+ return err;
+ }
+
+ return 0;
+}
+
+
+static int blkif_recover(struct blkfront_info *info)
+{
+ int i;
+ struct blkif_request *req;
+ struct blk_shadow *copy;
+ int j;
+
+ /* Stage 1: Make a safe copy of the shadow state. */
+ copy = kmalloc(sizeof(info->shadow), GFP_KERNEL);
+ if (!copy)
+ return -ENOMEM;
+ memcpy(copy, info->shadow, sizeof(info->shadow));
+
+ /* 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.id = i+1;
+ info->shadow_free = info->ring.req_prod_pvt;
+ info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
+
+ /* Stage 3: Find pending requests and requeue them. */
+ for (i = 0; i < BLK_RING_SIZE; i++) {
+ /* Not in use? */
+ if (copy[i].request == 0)
+ continue;
+
+ /* Grab a request slot and copy shadow state into it. */
+ req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);
+ *req = copy[i].req;
+
+ /* We get a new request id, and must reset the shadow state. */
+ req->id = get_id_from_freelist(info);
+ memcpy(&info->shadow[req->id], ©[i], sizeof(copy[i]));
+
+ /* Rewrite any grant references invalidated by susp/resume. */
+ for (j = 0; j < req->nr_segments; j++)
+ gnttab_grant_foreign_access_ref(
+ req->seg[j].gref,
+ info->xbdev->otherend_id,
+ pfn_to_mfn(info->shadow[req->id].frame[j]),
+ rq_data_dir(
+ (struct request *)
+ info->shadow[req->id].request));
+ info->shadow[req->id].req = *req;
+
+ info->ring.req_prod_pvt++;
+ }
+
+ kfree(copy);
+
+ xenbus_switch_state(info->xbdev, XenbusStateConnected);
+
+ spin_lock_irq(&blkif_io_lock);
+
+ /* Now safe for us to use the shared ring */
+ info->connected = BLKIF_STATE_CONNECTED;
+
+ /* Send off requeued requests */
+ flush_requests(info);
+
+ /* Kick any other new requests queued since we resumed */
+ kick_pending_request_queues(info);
+
+ spin_unlock_irq(&blkif_io_lock);
+
+ 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->dev.driver_data;
+ int err;
+
+ dev_dbg(&dev->dev, "blkfront_resume: %s\n", dev->nodename);
+
+ blkif_free(info, info->connected == BLKIF_STATE_CONNECTED);
+
+ err = talk_to_backend(dev, info);
+ if (info->connected == BLKIF_STATE_SUSPENDED && !err)
+ err = blkif_recover(info);
+
+ return err;
+}
+
+
+/*
+ * 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 binfo;
+ int err;
+
+ if ((info->connected == BLKIF_STATE_CONNECTED) ||
+ (info->connected == BLKIF_STATE_SUSPENDED) )
+ return;
+
+ dev_dbg(&info->xbdev->dev, "%s:%s.\n",
+ __func__, info->xbdev->otherend);
+
+ err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+ "sectors", "%llu", §ors,
+ "info", "%u", &binfo,
+ "sector-size", "%lu", §or_size,
+ NULL);
+ if (err) {
+ xenbus_dev_fatal(info->xbdev, err,
+ "reading backend fields at %s",
+ info->xbdev->otherend);
+ return;
+ }
+
+ err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+ "feature-barrier", "%lu", &info->feature_barrier,
+ NULL);
+ if (err)
+ info->feature_barrier = 0;
+
+ err = xlvbd_alloc_gendisk(BLKIF_MINOR(info->vdevice),
+ sectors, info->vdevice,
+ binfo, sector_size, info);
+ 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(&blkif_io_lock);
+ info->connected = BLKIF_STATE_CONNECTED;
+ kick_pending_request_queues(info);
+ spin_unlock_irq(&blkif_io_lock);
+
+ add_disk(info->gd);
+}
+
+/**
+ * Handle the change of state of the backend to Closing. We must delete our
+ * device-layer structures now, to ensure that writes are flushed through to
+ * the backend. Once is this done, we can switch to Closed in
+ * acknowledgement.
+ */
+static void blkfront_closing(struct xenbus_device *dev)
+{
+ struct blkfront_info *info = dev->dev.driver_data;
+ unsigned long flags;
+
+ dev_dbg(&dev->dev, "blkfront_closing: %s removed\n", dev->nodename);
+
+ if (info->rq == NULL)
+ goto out;
+
+ spin_lock_irqsave(&blkif_io_lock, flags);
+
+ del_gendisk(info->gd);
+
+ /* No more blkif_request(). */
+ blk_stop_queue(info->rq);
+
+ /* No more gnttab callback work. */
+ gnttab_cancel_free_callback(&info->callback);
+ spin_unlock_irqrestore(&blkif_io_lock, flags);
+
+ /* Flush gnttab callback work. Must be done with no locks held. */
+ flush_scheduled_work();
+
+ blk_cleanup_queue(info->rq);
+ info->rq = NULL;
+
+ out:
+ xenbus_frontend_closed(dev);
+}
+
+/**
+ * Callback received when the backend's state changes.
+ */
+static void backend_changed(struct xenbus_device *dev,
+ enum xenbus_state backend_state)
+{
+ struct blkfront_info *info = dev->dev.driver_data;
+ struct block_device *bd;
+
+ dev_dbg(&dev->dev, "blkfront:backend_changed.\n");
+
+ switch (backend_state) {
+ case XenbusStateInitialising:
+ case XenbusStateInitWait:
+ case XenbusStateInitialised:
+ case XenbusStateUnknown:
+ case XenbusStateClosed:
+ break;
+
+ case XenbusStateConnected:
+ blkfront_connect(info);
+ break;
+
+ case XenbusStateClosing:
+ bd = bdget(info->dev);
+ if (bd == NULL)
+ xenbus_dev_fatal(dev, -ENODEV, "bdget failed");
+
+ mutex_lock(&bd->bd_mutex);
+ if (info->users > 0)
+ xenbus_dev_error(dev, -EBUSY,
+ "Device in use; refusing to close");
+ else
+ blkfront_closing(dev);
+ mutex_unlock(&bd->bd_mutex);
+ bdput(bd);
+ break;
+ }
+}
+
+static int blkfront_remove(struct xenbus_device *dev)
+{
+ struct blkfront_info *info = dev->dev.driver_data;
+
+ dev_dbg(&dev->dev, "blkfront_remove: %s removed\n", dev->nodename);
+
+ blkif_free(info, 0);
+
+ kfree(info);
+
+ return 0;
+}
+
+static int blkif_open(struct inode *inode, struct file *filep)
+{
+ struct blkfront_info *info = inode->i_bdev->bd_disk->private_data;
+ info->users++;
+ return 0;
+}
+
+static int blkif_release(struct inode *inode, struct file *filep)
+{
+ struct blkfront_info *info = inode->i_bdev->bd_disk->private_data;
+ info->users--;
+ if (info->users == 0) {
+ /* Check whether we have been instructed to close. We will
+ have ignored this request initially, as the device was
+ still mounted. */
+ struct xenbus_device *dev = info->xbdev;
+ enum xenbus_state state =
xenbus_read_driver_state(dev->otherend);
+
+ if (state == XenbusStateClosing)
+ blkfront_closing(dev);
+ }
+ return 0;
+}
+
+static struct block_device_operations xlvbd_block_fops =
+{
+ .owner = THIS_MODULE,
+ .open = blkif_open,
+ .release = blkif_release,
+};
+
+
+static struct xenbus_device_id blkfront_ids[] = {
+ { "vbd" },
+ { "" }
+};
+
+static struct xenbus_driver blkfront = {
+ .name = "vbd",
+ .owner = THIS_MODULE,
+ .ids = blkfront_ids,
+ .probe = blkfront_probe,
+ .remove = blkfront_remove,
+ .resume = blkfront_resume,
+ .otherend_changed = backend_changed,
+};
+
+static int __init xlblk_init(void)
+{
+ if (!is_running_on_xen())
+ 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;
+ }
+
+ return xenbus_register_frontend(&blkfront);
+}
+module_init(xlblk_init);
+
+
+static void xlblk_exit(void)
+{
+ return xenbus_unregister_driver(&blkfront);
+}
+module_exit(xlblk_exit);
+
+MODULE_DESCRIPTION("Xen virtual block device frontend");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_BLOCKDEV_MAJOR(XENVBD_MAJOR);
===================================================================
--- a/include/linux/major.h
+++ b/include/linux/major.h
@@ -158,6 +158,8 @@
#define VXSPEC_MAJOR 200 /* VERITAS volume config driver */
#define VXDMP_MAJOR 201 /* VERITAS volume multipath driver */
+#define XENVBD_MAJOR 202 /* Xen virtual block device */
+
#define MSR_MAJOR 202
#define CPUID_MAJOR 203
--
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