md: raid1: Fix restoration of bio between failed read and write.

When performing a "recovery" or "check" pass on a RAID1 array, we read
from each device and possible, if there is a difference or a read error,
write back to some devices.

We use the same 'bio' for both read and write, resetting various fields
between the two operations.

We forgot to reset bv_offset and bv_len however.  These are often left
unchanged, but in the case where there is an IO error one or two sectors
into a page, they are changed.

This results in correctable errors not being corrected properly.  It does
not result in any data corruption.

Cc: "Fairbanks, David" <David.Fairbanks@stratus.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 2 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 21629ae46682..d0f4021bbc2e 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1284,6 +1284,7 @@ static void sync_request_write(mddev_t *mddev, r1bio_t *r1_bio)
                                         rdev_dec_pending(conf->mirrors[i].rdev, mddev);
                                 } else {
                                         /* fixup the bio for reuse */
+                                        int size;
                                         sbio->bi_vcnt = vcnt;
                                         sbio->bi_size = r1_bio->sectors << 9;
                                         sbio->bi_idx = 0;
@@ -1297,10 +1298,20 @@ static void sync_request_write(mddev_t *mddev, r1bio_t *r1_bio)
                                         sbio->bi_sector = r1_bio->sector +
                                                 conf->mirrors[i].rdev->data_offset;
                                         sbio->bi_bdev = conf->mirrors[i].rdev->bdev;
-                                        for (j = 0; j < vcnt ; j++)
-                                                memcpy(page_address(sbio->bi_io_vec[j].bv_page),
+                                        size = sbio->bi_size;
+                                        for (j = 0; j < vcnt ; j++) {
+                                                struct bio_vec *bi;
+                                                bi = &sbio->bi_io_vec[j];
+                                                bi->bv_offset = 0;
+                                                if (size > PAGE_SIZE)
+                                                        bi->bv_len = PAGE_SIZE;
+                                                else
+                                                        bi->bv_len = size;
+                                                size -= PAGE_SIZE;
+                                                memcpy(page_address(bi->bv_page),
                                                        page_address(pbio->bi_io_vec[j].bv_page),
                                                        PAGE_SIZE);
+                                        }
 
                                 }
                         }