tree 4d4c72ede037788ddc62d5dab7227bb6f4a3b24b
parent bc56e2cafa3f80954a278d74bd18349ac3cb8fa5
author Omar Sandoval <osandov@fb.com> 1522125551 -0700
committer Jens Axboe <axboe@kernel.dk> 1522182071 -0600

loop: don't call into filesystem while holding lo_ctl_mutex

We hit an issue where a loop device on NFS was stuck in
loop_get_status() doing vfs_getattr() after the NFS server died, which
caused a pile-up of uninterruptible processes waiting on lo_ctl_mutex.
There's no reason to hold this lock while we wait on the filesystem;
let's drop it so that other processes can do their thing. We need to
grab a reference on lo_backing_file while we use it, and we can get rid
of the check on lo_device, which has been unnecessary since commit
a34c0ae9ebd6 ("[PATCH] loop: remove the bio remapping capability") in
the linux-history tree.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>