dax: Use non-exclusive wait in wait_entry_unlocked() (d8a70641) · Commits · 戴 / test

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@suse.cz> Cc: Matthew Wilcox <willy@infradead.org> Reported-by:

Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by:

Dan Williams <dan.j.williams@intel.com>

fs/dax.c

+7 −9

Original line number	Diff line number	Diff line
		@@ -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)

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