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xen: add virtual block device driver.

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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@xensource.com>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Greg KH <greg@kroah.com>
Cc: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jeremy Fitzhardinge 2007-07-17 18:37:06 -07:00 committed by Jeremy Fitzhardinge
parent 4bac07c993
commit 9f27ee5950
4 changed files with 1000 additions and 0 deletions
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9
drivers/block/Kconfig
View file

@ -427,4 +427,13 @@ config XILINX_SYSACE
help
Include support for the Xilinx SystemACE CompactFlash interface
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

1
drivers/block/Makefile
View file

@ -29,3 +29,4 @@ obj-$(CONFIG_VIODASD) += viodasd.o
obj-$(CONFIG_BLK_DEV_SX8) += sx8.o
obj-$(CONFIG_BLK_DEV_UB) += ub.o
obj-$(CONFIG_XEN_BLKDEV_FRONTEND) += xen-blkfront.o

988
drivers/block/xen-blkfront.c Normal file
View file

@ -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], &copy[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", &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;
}
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);

2
include/linux/major.h
View file

@ -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