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Commit 9621ea6b authored by Dan Williams's avatar Dan Williams Committed by Greg Kroah-Hartman
Browse files

dax: Use non-exclusive wait in wait_entry_unlocked() 



commit d8a706414af4827fc0b4b1c0c631c607351938b9 upstream.

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: Matthew Wilcox <willy@infradead.org>
Reported-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent c555772c

fs/dax.c

+7 −9
Original line number Diff line number Diff line
@@ -275,18 +275,16 @@ static void wait_entry_unlocked(struct address_space *mapping, pgoff_t index, 
	ewait.wait.func = wake_exceptional_entry_func;



	wq = dax_entry_waitqueue(mapping, index, 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);

	xa_unlock_irq(&mapping->i_pages);

	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 unlock_mapping_entry(struct address_space *mapping, pgoff_t index)