get_unlocked_entry() uses an exclusive wait because it is guaranteed to eventually obtain the lock and follow on with an unlock+wakeup cycle. The wait_entry_unlocked() path does not have the same guarantee. Rather than open-code an extra wakeup, just switch to a non-exclusive wait. Cc: Jan Kara <jack@xxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> --- fs/dax.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 48132eca3761..042d3b31b413 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)
