diff options
| author | Jan Kara <jack@suse.cz> | 2019-07-30 13:10:14 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-08-06 19:08:18 +0200 |
| commit | 4c825540af16197d84e6cf943972eccf6ea54ff6 (patch) | |
| tree | 2c264c18b205db9fdd574339068bc720f5f8bd67 /include/linux/fs.h | |
| parent | 4461f834098f88df90abaefbfe283d60a117feea (diff) | |
loop: Fix mount(2) failure due to race with LOOP_SET_FD
commit 89e524c04fa966330e2e80ab2bc50b9944c5847a upstream.
Commit 33ec3e53e7b1 ("loop: Don't change loop device under exclusive
opener") made LOOP_SET_FD ioctl acquire exclusive block device reference
while it updates loop device binding. However this can make perfectly
valid mount(2) fail with EBUSY due to racing LOOP_SET_FD holding
temporarily the exclusive bdev reference in cases like this:
for i in {a..z}{a..z}; do
dd if=/dev/zero of=$i.image bs=1k count=0 seek=1024
mkfs.ext2 $i.image
mkdir mnt$i
done
echo "Run"
for i in {a..z}{a..z}; do
mount -o loop -t ext2 $i.image mnt$i &
done
Fix the problem by not getting full exclusive bdev reference in
LOOP_SET_FD but instead just mark the bdev as being claimed while we
update the binding information. This just blocks new exclusive openers
instead of failing them with EBUSY thus fixing the problem.
Fixes: 33ec3e53e7b1 ("loop: Don't change loop device under exclusive opener")
Cc: stable@vger.kernel.org
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/fs.h')
| -rw-r--r-- | include/linux/fs.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index 79fec8a8413f..5186ac5b2a29 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2615,6 +2615,12 @@ extern struct block_device *blkdev_get_by_path(const char *path, fmode_t mode, void *holder); extern struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder); +extern struct block_device *bd_start_claiming(struct block_device *bdev, + void *holder); +extern void bd_finish_claiming(struct block_device *bdev, + struct block_device *whole, void *holder); +extern void bd_abort_claiming(struct block_device *bdev, + struct block_device *whole, void *holder); extern void blkdev_put(struct block_device *bdev, fmode_t mode); extern int __blkdev_reread_part(struct block_device *bdev); extern int blkdev_reread_part(struct block_device *bdev); |