From a7854487cd7128a30a7f4f5259de9f67d5efb95f Mon Sep 17 00:00:00 2001 From: Alexander Lyakas Date: Thu, 11 Oct 2012 13:50:12 +1100 Subject: [PATCH] md: When RAID5 is dirty, force reconstruct-write instead of read-modify-write. Signed-off-by: Alex Lyakas Suggested-by: Yair Hershko Signed-off-by: NeilBrown --- drivers/md/raid5.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index d11012604e28..9de8221f64ec 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -2806,12 +2806,25 @@ static void handle_stripe_dirtying(struct r5conf *conf, 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]; -- 2.20.1