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blkfront: Fix blkfront backend switch race (bdev open) 

We need not mind if users grab a late handle on a closing disk. We
probably even should not. But we have to make sure it's not a dead
one already

Let the bdev deal with a gendisk deleted under its feet. Takes the
info mutex to decide a race against backend closing.

Signed-off-by: Daniel Stodden <daniel.stodden@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Daniel Stodden 2010-08-07 18:36:53 +02:00 committed by Jens Axboe
parent b70f5fa043
commit 139617437a
1 changed files with 24 additions and 7 deletions
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31
drivers/block/xen-blkfront.c
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@ -1118,16 +1118,33 @@ static int blkfront_is_ready(struct xenbus_device *dev)
static int blkif_open(struct block_device *bdev, fmode_t mode)
{
struct blkfront_info *info = bdev->bd_disk->private_data;
if (!info->xbdev)
return -ENODEV;
struct gendisk *disk = bdev->bd_disk;
struct blkfront_info *info;
int err = 0;
lock_kernel();
info->users++;
unlock_kernel();
return 0;
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);
if (!err)
++info->users;
unlock_kernel();
out:
return err;
}
static int blkif_release(struct gendisk *disk, fmode_t mode)