Subject: [PATCH] md:change resync_mismatches to atomic64_t to avoid races

Now that multiple threads can handle stripes, it is safer to
use an atomic64_t for resync_mismatches, to avoid update races.
Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/md.c

@@ -4269,7 +4269,8 @@ static ssize_t
 mismatch_cnt_show(struct mddev *mddev, char *page)
 {
 	return sprintf(page, "%llu\n",
-		       (unsigned long long) mddev->resync_mismatches);
+		       (unsigned long long)
+		       atomic64_read(&mddev->resync_mismatches));
 }
 
 static struct md_sysfs_entry md_scan_mode =
@@ -5235,7 +5236,7 @@ static void md_clean(struct mddev *mddev)
 	mddev->new_layout = 0;
 	mddev->new_chunk_sectors = 0;
 	mddev->curr_resync = 0;
-	mddev->resync_mismatches = 0;
+	atomic64_set(&mddev->resync_mismatches, 0);
 	mddev->suspend_lo = mddev->suspend_hi = 0;
 	mddev->sync_speed_min = mddev->sync_speed_max = 0;
 	mddev->recovery = 0;
@@ -7357,7 +7358,7 @@ void md_do_sync(struct md_thread *thread)
 		 * which defaults to physical size, but can be virtual size
 		 */
 		max_sectors = mddev->resync_max_sectors;
-		mddev->resync_mismatches = 0;
+		atomic64_set(&mddev->resync_mismatches, 0);
 		/* we don't use the checkpoint if there's a bitmap */
 		if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
 			j = mddev->resync_min;

drivers/md/md.h

@@ -282,7 +282,7 @@ struct mddev {
 
 	sector_t			resync_max_sectors; /* may be set by personality */
 
-	sector_t			resync_mismatches; /* count of sectors where
+	atomic64_t			resync_mismatches; /* count of sectors where
 							    * parity/replica mismatch found
 							    */
 

drivers/md/raid1.c

@@ -1876,7 +1876,7 @@ static int process_checks(struct r1bio *r1_bio)
 		} else
 			j = 0;
 		if (j >= 0)
-			mddev->resync_mismatches += r1_bio->sectors;
+			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))) {
 			/* No need to write to this device. */

drivers/md/raid10.c

@@ -2011,7 +2011,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
 					break;
 			if (j == vcnt)
 				continue;
-			mddev->resync_mismatches += r10_bio->sectors;
+			atomic64_add(r10_bio->sectors, &mddev->resync_mismatches);
 			if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
 				/* Don't fix anything. */
 				continue;

drivers/md/raid5.c

@@ -2973,7 +2973,7 @@ static void handle_parity_checks5(struct r5conf *conf, struct stripe_head *sh,
 			 */
 			set_bit(STRIPE_INSYNC, &sh->state);
 		else {
-			conf->mddev->resync_mismatches += STRIPE_SECTORS;
+			atomic64_add(STRIPE_SECTORS, &conf->mddev->resync_mismatches);
 			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
 				/* don't try to repair!! */
 				set_bit(STRIPE_INSYNC, &sh->state);
@@ -3125,7 +3125,7 @@ static void handle_parity_checks6(struct r5conf *conf, struct stripe_head *sh,
 				 */
 			}
 		} else {
-			conf->mddev->resync_mismatches += STRIPE_SECTORS;
+			atomic64_add(STRIPE_SECTORS, &conf->mddev->resync_mismatches);
 			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
 				/* don't try to repair!! */
 				set_bit(STRIPE_INSYNC, &sh->state);