linux/drivers/block/xen-blkfront.c
Ian Campbell a144ff09bc xen: Avoid allocations causing swap activity on the resume path
Avoid allocations causing swap activity on the resume path by
preventing the allocations from doing IO and allowing them
to access the emergency pools.

These paths are used when a frontend device is trying to connect
to its backend driver over Xenbus.  These reconnections are triggered
on demand by IO, so by definition there is already IO underway,
and further IO would naturally deadlock.  On resume, this path
is triggered when the running system tries to continue using its
devices.  If it cannot then the resume will fail; to try to avoid this
we let it dip into the emergency pools.

[ linux-2.6.18-xen changesets e8b49cfbdac, fdb998e79aba ]

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-07-03 13:21:13 +02:00

1060 lines
26 KiB
C

/*
* 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 <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 <xen/interface/io/protocols.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;
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;
int is_ready;
/**
* 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);
}
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;
}
int blkif_ioctl(struct inode *inode, struct file *filep,
unsigned command, unsigned long argument)
{
struct blkfront_info *info =
inode->i_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;
}
/*
* 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 req_iterator iter;
struct bio_vec *bvec;
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_segment(bvec, req, iter) {
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(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 = 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)
{
struct request_queue *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);
/* Make sure we don't use bounce buffers. */
blk_queue_bounce_limit(rq, BLK_BOUNCE_ANY);
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 error;
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);
error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO;
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);
error = -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 = __blk_end_request(req, error, blk_rq_bytes(req));
BUG_ON(ret);
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_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, 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_printf(xbt, dev->nodename, "protocol", "%s",
XEN_IO_PROTO_ABI_NATIVE);
if (err) {
message = "writing protocol";
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_NOIO | __GFP_REPEAT | __GFP_HIGH);
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);
info->is_ready = 1;
}
/**
* 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_disk(info->gd, 0);
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 blkfront_is_ready(struct xenbus_device *dev)
{
struct blkfront_info *info = dev->dev.driver_data;
return info->is_ready;
}
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 && info->is_ready)
blkfront_closing(dev);
}
return 0;
}
static struct block_device_operations xlvbd_block_fops =
{
.owner = THIS_MODULE,
.open = blkif_open,
.release = blkif_release,
.getgeo = blkif_getgeo,
.ioctl = blkif_ioctl,
};
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,
.is_ready = blkfront_is_ready,
};
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 __exit 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);
MODULE_ALIAS("xen:vbd");
MODULE_ALIAS("xenblk");