From: NeilBrown <neilb@suse.de>
Date: Fri, 8 May 2015 08:19:33 +0000 (+1000)
Subject: md/raid5: avoid reading parity blocks for full-stripe write to degraded array
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=10d82c5f0d167ef75a2d8d7d4eed9ee43d3369c9;p=openwrt%2Fstaging%2Fblogic.git

md/raid5: avoid reading parity blocks for full-stripe write to degraded array

When performing a reconstruct write, we need to read all blocks
that are not being over-written .. except the parity (P and Q) blocks.

The code currently reads these (as they are not being over-written!)
unnecessarily.

Signed-off-by: NeilBrown <neilb@suse.de>
Fixes: ea664c8245f3 ("md/raid5: need_this_block: tidy/fix last condition.")
---

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 415cac6d89bd..85dc0e67fb88 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3282,7 +3282,9 @@ static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
 		/* reconstruct-write isn't being forced */
 		return 0;
 	for (i = 0; i < s->failed; i++) {
-		if (!test_bit(R5_UPTODATE, &fdev[i]->flags) &&
+		if (s->failed_num[i] != sh->pd_idx &&
+		    s->failed_num[i] != sh->qd_idx &&
+		    !test_bit(R5_UPTODATE, &fdev[i]->flags) &&
 		    !test_bit(R5_OVERWRITE, &fdev[i]->flags))
 			return 1;
 	}