raid5-cache: check stripe finish out of order

stripes could finish out of order. Hence r5l_move_io_unit_list() of
__r5l_stripe_write_finished might not move any entry and leave
stripe_end_ios list empty.

This applies on top of http://marc.info/?l=linux-raid&m=144122700510667

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index ea1480392ebac3c0cbad7119a5955823b58a5b46..30c7e5e79a02ef1575d9124089adb82c4f8137a0 100644 (file)
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -550,8 +550,13 @@ static void __r5l_stripe_write_finished(struct r5l_io_unit *io)
 
        spin_lock_irqsave(&log->io_list_lock, flags);
        __r5l_set_io_unit_state(io, IO_UNIT_STRIPE_END);
+       /* might move 0 entry */
        r5l_move_io_unit_list(&log->flushed_ios, &log->stripe_end_ios,
                              IO_UNIT_STRIPE_END);
+       if (list_empty(&log->stripe_end_ios)) {
+               spin_unlock_irqrestore(&log->io_list_lock, flags);
+               return;
+       }
 
        last = list_last_entry(&log->stripe_end_ios,
                               struct r5l_io_unit, log_sibling);