Merge tag 'dax-fix-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

Pull dax fix from Dan Williams:
 "Clean up unnecessary usage of prepare_to_wait_exclusive().

  While I feel a bit silly sending a single-commit pull-request there is
  nothing else queued up for dax this cycle. This change has shipped in
  -next for multiple releases"

* tag 'dax-fix-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  dax: Use non-exclusive wait in wait_entry_unlocked()

1 files changed, 7 insertions, 9 deletions

diff --git a/fs/dax.c b/fs/dax.c
index 262e14f29933..6959837cc465 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -246,18 +246,16 @@ static void wait_entry_unlocked(struct xa_state *xas, void *entry)
 	ewait.wait.func = wake_exceptional_entry_func;
 
 	wq = dax_entry_waitqueue(xas, entry, &ewait.key);
-	prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);
+	/*
+	 * Unlike get_unlocked_entry() there is no guarantee that this
+	 * path ever successfully retrieves an unlocked entry before an
+	 * inode dies. Perform a non-exclusive wait in case this path
+	 * never successfully performs its own wake up.
+	 */
+	prepare_to_wait(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);
 	xas_unlock_irq(xas);
 	schedule();
 	finish_wait(wq, &ewait.wait);
-
-	/*
-	 * Entry lock waits are exclusive. Wake up the next waiter since
-	 * we aren't sure we will acquire the entry lock and thus wake
-	 * the next waiter up on unlock.
-	 */
-	if (waitqueue_active(wq))
-		__wake_up(wq, TASK_NORMAL, 1, &ewait.key);
 }
 
 static void put_unlocked_entry(struct xa_state *xas, void *entry)