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Commit 7bb23c49 authored by NeilBrown's avatar NeilBrown
Browse files

md/raid10: fix two problems with RAID10 resync. 



1/ When an different between blocks is found, data is copied from
   one bio to the other.  However bv_len is used as the length to
   copy and this could be zero.  So use r10_bio->sectors to calculate
   length instead.
   Using bv_len was probably always a bit dubious, but the introduction
   of bio_advance made it much more likely to be a problem.

2/ When preparing some blocks for sync, we don't set BIO_UPTODATE
   except on bios that we schedule for a read.  This ensures that
   missing/failed devices don't confuse the loop at the top of
   sync_request write.
   Commit 8be185f2 "raid10: Use bio_reset()"
   removed a loop which set BIO_UPTDATE on all appropriate bios.
   So we need to re-add that flag.

These bugs were introduced in 3.10, so this patch is suitable for
3.10-stable, and can remove a potential for data corruption.

Cc: stable@vger.kernel.org (3.10)
Reported-by: default avatarBrassow Jonathan <jbrassow@redhat.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 47188d39

drivers/md/raid10.c

+9 −2
Original line number Diff line number Diff line
@@ -2097,11 +2097,17 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio) 
			 * both 'first' and 'i', so we just compare them.

			 * All vec entries are PAGE_SIZE;

			 */

			for (j = 0; j < vcnt; j++)

			int sectors = r10_bio->sectors;

			for (j = 0; j < vcnt; j++) {

				int len = PAGE_SIZE;

				if (sectors < (len / 512))

					len = sectors * 512;

				if (memcmp(page_address(fbio->bi_io_vec[j].bv_page),

					   page_address(tbio->bi_io_vec[j].bv_page),

					   fbio->bi_io_vec[j].bv_len))

					   len))

					break;

				sectors -= len/512;

			}

			if (j == vcnt)

				continue;

			atomic64_add(r10_bio->sectors, &mddev->resync_mismatches);
@@ -3407,6 +3413,7 @@ static sector_t sync_request(struct mddev *mddev, sector_t sector_nr, 


		if (bio->bi_end_io == end_sync_read) {

			md_sync_acct(bio->bi_bdev, nr_sectors);

			set_bit(BIO_UPTODATE, &bio->bi_flags);

			generic_make_request(bio);

		}

	}