kernfs: fix locking around kernfs_ops->release() callback

The release callback may be called from two places - file release
operation and kernfs open file draining.  kernfs_open_file->mutex is
used to synchronize the two callsites.  This unfortunately leads to
possible circular locking because of->mutex is used to protect the
usual kernfs operations which may use locking constructs which are
held while removing and thus draining kernfs files.

@of->mutex is for synchronizing concurrent kernfs access operations
and all we need here is synchronization between the releaes and drain
paths.  As the drain path has to grab kernfs_open_file_mutex anyway,
let's use the mutex to synchronize the release operation instead.

Signed-off-by: Tejun Heo <[email protected]>
Reported-and-tested-by: Tony Lindgren <[email protected]>
Fixes: 0e67db2f9fe9 ("kernfs: add kernfs_ops->open/release() callbacks")
Acked-by: Greg Kroah-Hartman <[email protected]>

0 files changed, 0 insertions, 0 deletions