md: fix bug in error handling during raid1 repair

If raid1/repair (which reads all block and fixes any differences it finds)
hits a read error, it doesn't reset the bio for writing before writing
correct data back, so the read error isn't fixed, and the device probably
gets a zero-length write which it might complain about.

Signed-off-by: Neil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 7 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 3a95cc5e029c..46677d7d9980 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1240,17 +1240,24 @@ static void sync_request_write(mddev_t *mddev, r1bio_t *r1_bio)
                         }
                 r1_bio->read_disk = primary;
                 for (i=0; i<mddev->raid_disks; i++)
-                        if (r1_bio->bios[i]->bi_end_io == end_sync_read &&
-                            test_bit(BIO_UPTODATE, &r1_bio->bios[i]->bi_flags)) {
+                        if (r1_bio->bios[i]->bi_end_io == end_sync_read) {
                                 int j;
                                 int vcnt = r1_bio->sectors >> (PAGE_SHIFT- 9);
                                 struct bio *pbio = r1_bio->bios[primary];
                                 struct bio *sbio = r1_bio->bios[i];
-                                for (j = vcnt; j-- ; )
-                                        if (memcmp(page_address(pbio->bi_io_vec[j].bv_page),
-                                                   page_address(sbio->bi_io_vec[j].bv_page),
-                                                   PAGE_SIZE))
-                                                break;
+
+                                if (test_bit(BIO_UPTODATE, &sbio->bi_flags)) {
+                                        for (j = vcnt; j-- ; ) {
+                                                struct page *p, *s;
+                                                p = pbio->bi_io_vec[j].bv_page;
+                                                s = sbio->bi_io_vec[j].bv_page;
+                                                if (memcmp(page_address(p),
+                                                           page_address(s),
+                                                           PAGE_SIZE))
+                                                        break;
+                                        }
+                                } else
+                                        j = 0;
                                 if (j >= 0)
                                         mddev->resync_mismatches += r1_bio->sectors;
                                 if (j < 0 || test_bit(MD_RECOVERY_CHECK, &mddev->recovery)) {