From: NeilBrown <neilb@suse.de>
Date: Fri, 22 May 2015 05:20:04 +0000 (+1000)
Subject: md/raid5: Ensure a batch member is not handled prematurely.
X-Git-Tag: firefly_0821_release~176^2~1716^2~7
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=b15a9dbdbfe72848b7ed4cd3f97fe80daaf99c89;p=firefly-linux-kernel-4.4.55.git

md/raid5: Ensure a batch member is not handled prematurely.

If a stripe is a member of a batch, but not the head, it must
not be handled separately from the rest of the batch.

'clear_batch_ready()' handles this requirement to some
extent but not completely.  If a member is passed to handle_stripe()
a second time it returns '0' indicating the stripe can be handled,
which is wrong.
So add an extra test.

Signed-off-by: NeilBrown <neilb@suse.de>
---

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 42d0ea6c8597..e58736740bac 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4200,9 +4200,13 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
 
 static int clear_batch_ready(struct stripe_head *sh)
 {
+	/* Return '1' if this is a member of batch, or
+	 * '0' if it is a lone stripe or a head which can now be
+	 * handled.
+	 */
 	struct stripe_head *tmp;
 	if (!test_and_clear_bit(STRIPE_BATCH_READY, &sh->state))
-		return 0;
+		return (sh->batch_head && sh->batch_head != sh);
 	spin_lock(&sh->stripe_lock);
 	if (!sh->batch_head) {
 		spin_unlock(&sh->stripe_lock);