From: Dan Williams Date: Fri, 21 Dec 2018 19:35:53 +0000 (-0800) Subject: dax: Use non-exclusive wait in wait_entry_unlocked() X-Git-Tag: v5.0-rc1~83^2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d8a706414af4827fc0b4b1c0c631c607351938b9;p=thirdparty%2Flinux.git dax: Use non-exclusive wait in wait_entry_unlocked() 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 Cc: Matthew Wilcox Reported-by: Linus Torvalds Signed-off-by: Dan Williams --- diff --git a/fs/dax.c b/fs/dax.c index 48132eca3761d..042d3b31b413a 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)