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)