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authorLinus Torvalds <torvalds@linux-foundation.org>2020-03-18 14:52:21 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-03-18 23:03:38 +0300
commitdcf23ac3e846ca0cf626c155a0e3fcbbcf4fae8a (patch)
treebcec3946a19e79751a97280bed14a633ad1a8ff8 /fs/cifs/file.c
parent5076190daded2197f62fe92cf69674488be44175 (diff)
downloadlinux-dcf23ac3e846ca0cf626c155a0e3fcbbcf4fae8a.tar.xz
locks: reinstate locks_delete_block optimization
There is measurable performance impact in some synthetic tests due to commit 6d390e4b5d48 (locks: fix a potential use-after-free problem when wakeup a waiter). Fix the race condition instead by clearing the fl_blocker pointer after the wake_up, using explicit acquire/release semantics. This does mean that we can no longer use the clearing of fl_blocker as the wait condition, so switch the waiters over to checking whether the fl_blocked_member list_head is empty. Reviewed-by: yangerkun <yangerkun@huawei.com> Reviewed-by: NeilBrown <neilb@suse.de> Fixes: 6d390e4b5d48 (locks: fix a potential use-after-free problem when wakeup a waiter) Signed-off-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/cifs/file.c')
-rw-r--r--fs/cifs/file.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 3b942ecdd4be..8f9d849a0012 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1169,7 +1169,8 @@ try_again:
rc = posix_lock_file(file, flock, NULL);
up_write(&cinode->lock_sem);
if (rc == FILE_LOCK_DEFERRED) {
- rc = wait_event_interruptible(flock->fl_wait, !flock->fl_blocker);
+ rc = wait_event_interruptible(flock->fl_wait,
+ list_empty(&flock->fl_blocked_member));
if (!rc)
goto try_again;
locks_delete_block(flock);