diff options
| author | Eric Sandeen <sandeen@redhat.com> | 2013-03-09 15:18:39 +0000 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-03-20 15:03:41 +0000 |
| commit | 2d8db10e98fca5bb13e70c3f35d7c0ff79df638c (patch) | |
| tree | b43325de487055ee2c36d0281471f3760718245e /fs/btrfs | |
| parent | 3a6356e64de5d426feaa812fe4af37b13a756a3f (diff) | |
btrfs: use rcu_barrier() to wait for bdev puts at unmount
commit bc178622d40d87e75abc131007342429c9b03351 upstream.
Doing this would reliably fail with -EBUSY for me:
# mount /dev/sdb2 /mnt/scratch; umount /mnt/scratch; mkfs.btrfs -f /dev/sdb2
...
unable to open /dev/sdb2: Device or resource busy
because mkfs.btrfs tries to open the device O_EXCL, and somebody still has it.
Using systemtap to track bdev gets & puts shows a kworker thread doing a
blkdev put after mkfs attempts a get; this is left over from the unmount
path:
btrfs_close_devices
__btrfs_close_devices
call_rcu(&device->rcu, free_device);
free_device
INIT_WORK(&device->rcu_work, __free_device);
schedule_work(&device->rcu_work);
so unmount might complete before __free_device fires & does its blkdev_put.
Adding an rcu_barrier() to btrfs_close_devices() causes unmount to wait
until all blkdev_put()s are done, and the device is truly free once
unmount completes.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'fs/btrfs')
| -rw-r--r-- | fs/btrfs/volumes.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index d544035f696..9899205bc43 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -577,6 +577,12 @@ int btrfs_close_devices(struct btrfs_fs_devices *fs_devices) __btrfs_close_devices(fs_devices); free_fs_devices(fs_devices); } + /* + * Wait for rcu kworkers under __btrfs_close_devices + * to finish all blkdev_puts so device is really + * free when umount is done. + */ + rcu_barrier(); return ret; } |