[PATCH] Revert "md: When RAID5 is dirty, force reconstruct-write instead of read-modify-write."

[Jes.Sorensen@redhat.com]

From: Jes Sorensen <Jes.Sorensen@redhat.com>

This reverts commit a7854487cd7128a30a7f4f5259de9f67d5efb95f.

The above patch would cause lockups of RAID4/5 arrays if a drive is
going faulty during reconstruction.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
---
 drivers/md/raid5.c | 19 +++----------------
 1 file changed, 3 insertions(+), 16 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index aa76865..bc3a085 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3159,25 +3159,12 @@ static void handle_stripe_dirtying(struct r5conf *conf,
 				   int disks)
 {
 	int rmw = 0, rcw = 0, i;
-	sector_t recovery_cp = conf->mddev->recovery_cp;
-
-	/* RAID6 requires 'rcw' in current implementation.
-	 * Otherwise, check whether resync is now happening or should start.
-	 * If yes, then the array is dirty (after unclean shutdown or
-	 * initial creation), so parity in some stripes might be inconsistent.
-	 * In this case, we need to always do reconstruct-write, to ensure
-	 * that in case of drive failure or read-error correction, we
-	 * generate correct data from the parity.
-	 */
-	if (conf->max_degraded == 2 ||
-	    (recovery_cp < MaxSector && sh->sector >= recovery_cp)) {
-		/* Calculate the real rcw later - for now make it
+	if (conf->max_degraded == 2) {
+		/* RAID6 requires 'rcw' in current implementation
+		 * Calculate the real rcw later - for now fake it
 		 * look like rcw is cheaper
 		 */
 		rcw = 1; rmw = 2;
-		pr_debug("force RCW max_degraded=%u, recovery_cp=%llu sh->sector=%llu\n",
-			 conf->max_degraded, (unsigned long long)recovery_cp,
-			 (unsigned long long)sh->sector);
 	} else for (i = disks; i--; ) {
 		/* would I have to read this buffer for read_modify_write */
 		struct r5dev *dev = &sh->dev[i];
-- 
1.8.3.1