From: Andreas Gruenbacher agruenba@redhat.com
[ Upstream commit 486408d690e130c3adacf816754b97558d715f46 ]
In gfs2_inode_lookup and gfs2_create_inode, we're calling gfs2_cancel_delete_work which currently cancels any remote delete work (delete_work_func) synchronously. This means that if the work is currently running, it will wait for it to finish. We're doing this to pevent a previous instance of an inode from having any influence on the next instance.
However, delete_work_func uses gfs2_inode_lookup internally, and we can end up in a deadlock when delete_work_func gets interrupted at the wrong time. For example,
(1) An inode's iopen glock has delete work queued, but the inode itself has been evicted from the inode cache.
(2) The delete work is preempted before reaching gfs2_inode_lookup.
(3) Another process recreates the inode (gfs2_create_inode). It tries to cancel any outstanding delete work, which blocks waiting for the ongoing delete work to finish.
(4) The delete work calls gfs2_inode_lookup, which blocks waiting for gfs2_create_inode to instantiate and unlock the new inode => deadlock.
It turns out that when the delete work notices that its inode has been re-instantiated, it will do nothing. This means that it's safe to cancel the delete work asynchronously. This prevents the kind of deadlock described above.
Signed-off-by: Andreas Gruenbacher agruenba@redhat.com Signed-off-by: Bob Peterson rpeterso@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/gfs2/glock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index e0eaa9cf9fb6f..8ca89adf31a86 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -1919,7 +1919,7 @@ bool gfs2_queue_delete_work(struct gfs2_glock *gl, unsigned long delay)
void gfs2_cancel_delete_work(struct gfs2_glock *gl) { - if (cancel_delayed_work_sync(&gl->gl_delete)) { + if (cancel_delayed_work(&gl->gl_delete)) { clear_bit(GLF_PENDING_DELETE, &gl->gl_flags); gfs2_glock_put(gl); }