md/raid5: add some missing locking in handle_failed_stripe.

We really should hold the stripe_lock while accessing
'toread' else we could race with add_stripe_bio and corrupt
a list.

Reported-by: "Jianpeng Ma" <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 758b77296404..36c0a158730b 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2552,8 +2552,10 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
                 if (!test_bit(R5_Wantfill, &sh->dev[i].flags) &&
                     (!test_bit(R5_Insync, &sh->dev[i].flags) ||
                       test_bit(R5_ReadError, &sh->dev[i].flags))) {
+                        spin_lock_irq(&sh->stripe_lock);
                         bi = sh->dev[i].toread;
                         sh->dev[i].toread = NULL;
+                        spin_unlock_irq(&sh->stripe_lock);
                         if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
                                 wake_up(&conf->wait_for_overlap);
                         if (bi) s->to_read--;