From c337869d95011495fa181536786e74aa2d7ff031 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 5 Jun 2008 22:45:54 -0700 Subject: [PATCH] md: do not compute parity unless it is on a failed drive If a block is computed (rather than read) then a check/repair operation may be lead to believe that the data on disk is correct, when infact it isn't. So only compute blocks for failed devices. This issue has been around since at least 2.6.12, but has become harder to hit in recent kernels since most reads bypass the cache. echo repair > /sys/block/mdN/md/sync_action will set the parity blocks to the correct state. Cc: Signed-off-by: Dan Williams Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/md/raid5.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index f0f0585c10..c37e256b11 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -2002,6 +2002,7 @@ static int __handle_issuing_new_read_requests5(struct stripe_head *sh, * have quiesced. */ if ((s->uptodate == disks - 1) && + (s->failed && disk_idx == s->failed_num) && !test_bit(STRIPE_OP_CHECK, &sh->ops.pending)) { set_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending); set_bit(R5_Wantcompute, &dev->flags); @@ -2087,7 +2088,9 @@ static void handle_issuing_new_read_requests6(struct stripe_head *sh, /* we would like to get this block, possibly * by computing it, but we might not be able to */ - if (s->uptodate == disks-1) { + if ((s->uptodate == disks - 1) && + (s->failed && (i == r6s->failed_num[0] || + i == r6s->failed_num[1]))) { pr_debug("Computing stripe %llu block %d\n", (unsigned long long)sh->sector, i); compute_block_1(sh, i, 0); -- 2.39.5