md/raid1: restore ability for check and repair to fix read errors.

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>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index afaa5d425e9a..e73740b55aea 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1854,11 +1854,15 @@ static int process_checks(struct r1bio *r1_bio)
         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 +
@@ -1891,11 +1895,14 @@ static int process_checks(struct r1bio *r1_bio)
                 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;
@@ -1910,7 +1917,7 @@ static int process_checks(struct r1bio *r1_bio)
                 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);