md: When RAID5 is dirty, force reconstruct-write instead of read-modify-write.
Signed-off-by: Alex Lyakas <alex@zadarastorage.com>
Suggested-by: Yair Hershko <yair@zadarastorage.com>
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index d110126..9de8221 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2806,12 +2806,25 @@
int disks)
{
int rmw = 0, rcw = 0, i;
- if (conf->max_degraded == 2) {
- /* RAID6 requires 'rcw' in current implementation
- * Calculate the real rcw later - for now fake it
+ 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
* 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];