Commit c337869d authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds

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: <stable@kernel.org>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a6d8113a
...@@ -2002,6 +2002,7 @@ static int __handle_issuing_new_read_requests5(struct stripe_head *sh, ...@@ -2002,6 +2002,7 @@ static int __handle_issuing_new_read_requests5(struct stripe_head *sh,
* have quiesced. * have quiesced.
*/ */
if ((s->uptodate == disks - 1) && if ((s->uptodate == disks - 1) &&
(s->failed && disk_idx == s->failed_num) &&
!test_bit(STRIPE_OP_CHECK, &sh->ops.pending)) { !test_bit(STRIPE_OP_CHECK, &sh->ops.pending)) {
set_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending); set_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending);
set_bit(R5_Wantcompute, &dev->flags); set_bit(R5_Wantcompute, &dev->flags);
...@@ -2087,7 +2088,9 @@ static void handle_issuing_new_read_requests6(struct stripe_head *sh, ...@@ -2087,7 +2088,9 @@ static void handle_issuing_new_read_requests6(struct stripe_head *sh,
/* we would like to get this block, possibly /* we would like to get this block, possibly
* by computing it, but we might not be able to * 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", pr_debug("Computing stripe %llu block %d\n",
(unsigned long long)sh->sector, i); (unsigned long long)sh->sector, i);
compute_block_1(sh, i, 0); compute_block_1(sh, i, 0);
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment