[PATCH 3.12 72/82] md/raid1: restore ability for check and repair to fix read errors.

Greg Kroah-Hartman
2014-02-20T23:52:57Z

From: NeilBrown <neilb@suse.de>

commit 1877db75589a895bbdc4c4c3f23558e57b521141 upstream.

commit 30bc9b53878a9921b02e3b5bc4283ac1c6de102a
md/raid1: fix bio handling problems in process_checks()

Move the bio_reset() to a point before where BIO_UPTODATE is checked,
so that check now always report that the bio is uptodate, even if it is not.

This causes process_check() to sometimes treat read-errors as
successful matches so the good data isn't written out.

This patch preserves the flag until it is needed.

Bug was introduced in 3.11, but backported to 3.10-stable (as it fixed
an even worse bug). So suitable for any -stable since 3.10.

Reported-and-tested-by: Michael Tokarev <mjt@tls.msk.ru>
Fixed: 30bc9b53878a9921b02e3b5bc4283ac1c6de102a
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/raid1.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1855,11 +1855,15 @@ static int process_checks(struct r1bio *
for (i = 0; i < conf->raid_disks * 2; i++) {
int j;
int size;
+ int uptodate;
struct bio *b = r1_bio->bios[i];
if (b->bi_end_io != end_sync_read)
continue;
- /* fixup the bio for reuse */
+ /* fixup the bio for reuse, but preserve BIO_UPTODATE */
+ uptodate = test_bit(BIO_UPTODATE, &b->bi_flags);
bio_reset(b);
+ if (!uptodate)
+ clear_bit(BIO_UPTODATE, &b->bi_flags);
b->bi_vcnt = vcnt;
b->bi_size = r1_bio->sectors << 9;
b->bi_sector = r1_bio->sector +
@@ -1892,11 +1896,14 @@ static int process_checks(struct r1bio *
int j;
struct bio *pbio = r1_bio->bios[primary];
struct bio *sbio = r1_bio->bios[i];
+ int uptodate = test_bit(BIO_UPTODATE, &sbio->bi_flags);

if (sbio->bi_end_io != end_sync_read)
continue;
+ /* Now we can 'fixup' the BIO_UPTODATE flag */
+ set_bit(BIO_UPTODATE, &sbio->bi_flags);

- if (test_bit(BIO_UPTODATE, &sbio->bi_flags)) {
+ if (uptodate) {
for (j = vcnt; j-- ; ) {
struct page *p, *s;
p = pbio->bi_io_vec[j].bv_page;
@@ -1911,7 +1918,7 @@ static int process_checks(struct r1bio *
if (j >= 0)
atomic64_add(r1_bio->sectors, &mddev->resync_mismatches);
if (j < 0 || (test_bit(MD_RECOVERY_CHECK, &mddev->recovery)
- && test_bit(BIO_UPTODATE, &sbio->bi_flags))) {
+ && uptodate)) {
/* No need to write to this device. */
sbio->bi_end_io = NULL;
rdev_dec_pending(conf->mirrors[i].rdev, mddev);