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authorDaniel Stodden <daniel.stodden@citrix.com>2010-08-07 18:36:53 +0200
committerJens Axboe <jaxboe@fusionio.com>2010-08-07 18:38:43 +0200
commit139617437aff1f0d3b57c2d7cc60e60efc8fe6c3 (patch)
tree2c903b3f6456ab4a7d70c16c864ceb63bc366a5e /drivers/block
parentb70f5fa043b318659c936d8c3c696250e6528944 (diff)
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>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/xen-blkfront.c31
1 files changed, 24 insertions, 7 deletions
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 1e406f0331e7..763a315712cc 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -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)