1 files changed, 54 insertions, 15 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 2d2aaf6e98e2..2ae63c5b1c25 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -524,7 +524,11 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 			bi->bi_end_io = raid5_end_read_request;
 
 		rcu_read_lock();
-		rdev = rcu_dereference(conf->disks[i].rdev);
+		if (rw == READ &&
+		    test_bit(R5_ReadRepl, &sh->dev[i].flags))
+			rdev = rcu_dereference(conf->disks[i].replacement);
+		else
+			rdev = rcu_dereference(conf->disks[i].rdev);
 		if (rdev && test_bit(Faulty, &rdev->flags))
 			rdev = NULL;
 		if (rdev)
@@ -1605,11 +1609,18 @@ static void raid5_end_read_request(struct bio * bi, int error)
 		BUG();
 		return;
 	}
+	if (test_bit(R5_ReadRepl, &sh->dev[i].flags))
+		rdev = conf->disks[i].replacement;
+	else
+		rdev = conf->disks[i].rdev;
 
 	if (uptodate) {
 		set_bit(R5_UPTODATE, &sh->dev[i].flags);
 		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
-			rdev = conf->disks[i].rdev;
+			/* Note that this cannot happen on a
+			 * replacement device.  We just fail those on
+			 * any error
+			 */
 			printk_ratelimited(
 				KERN_INFO
 				"md/raid:%s: read error corrected"
@@ -1622,16 +1633,24 @@ static void raid5_end_read_request(struct bio * bi, int error)
 			clear_bit(R5_ReadError, &sh->dev[i].flags);
 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
 		}
-		if (atomic_read(&conf->disks[i].rdev->read_errors))
-			atomic_set(&conf->disks[i].rdev->read_errors, 0);
+		if (atomic_read(&rdev->read_errors))
+			atomic_set(&rdev->read_errors, 0);
 	} else {
-		const char *bdn = bdevname(conf->disks[i].rdev->bdev, b);
+		const char *bdn = bdevname(rdev->bdev, b);
 		int retry = 0;
-		rdev = conf->disks[i].rdev;
 
 		clear_bit(R5_UPTODATE, &sh->dev[i].flags);
 		atomic_inc(&rdev->read_errors);
-		if (conf->mddev->degraded >= conf->max_degraded)
+		if (test_bit(R5_ReadRepl, &sh->dev[i].flags))
+			printk_ratelimited(
+				KERN_WARNING
+				"md/raid:%s: read error on replacement device "
+				"(sector %llu on %s).\n",
+				mdname(conf->mddev),
+				(unsigned long long)(sh->sector
+						     + rdev->data_offset),
+				bdn);
+		else if (conf->mddev->degraded >= conf->max_degraded)
 			printk_ratelimited(
 				KERN_WARNING
 				"md/raid:%s: read error not correctable "
@@ -1665,7 +1684,7 @@ static void raid5_end_read_request(struct bio * bi, int error)
 			md_error(conf->mddev, rdev);
 		}
 	}
-	rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
+	rdev_dec_pending(rdev, conf->mddev);
 	clear_bit(R5_LOCKED, &sh->dev[i].flags);
 	set_bit(STRIPE_HANDLE, &sh->state);
 	release_stripe(sh);
@@ -3036,7 +3055,19 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
 		}
 		if (dev->written)
 			s->written++;
-		rdev = rcu_dereference(conf->disks[i].rdev);
+		/* Prefer to use the replacement for reads, but only
+		 * if it is recovered enough and has no bad blocks.
+		 */
+		rdev = rcu_dereference(conf->disks[i].replacement);
+		if (rdev && !test_bit(Faulty, &rdev->flags) &&
+		    rdev->recovery_offset >= sh->sector + STRIPE_SECTORS &&
+		    !is_badblock(rdev, sh->sector, STRIPE_SECTORS,
+				 &first_bad, &bad_sectors))
+			set_bit(R5_ReadRepl, &dev->flags);
+		else {
+			rdev = rcu_dereference(conf->disks[i].rdev);
+			clear_bit(R5_ReadRepl, &dev->flags);
+		}
 		if (rdev && test_bit(Faulty, &rdev->flags))
 			rdev = NULL;
 		if (rdev) {
@@ -3078,17 +3109,26 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
 			set_bit(R5_Insync, &dev->flags);
 
 		if (rdev && test_bit(R5_WriteError, &dev->flags)) {
-			clear_bit(R5_Insync, &dev->flags);
-			if (!test_bit(Faulty, &rdev->flags)) {
+			/* This flag does not apply to '.replacement'
+			 * only to .rdev, so make sure to check that*/
+			struct md_rdev *rdev2 = rcu_dereference(
+				conf->disks[i].rdev);
+			if (rdev2 == rdev)
+				clear_bit(R5_Insync, &dev->flags);
+			if (rdev2 && !test_bit(Faulty, &rdev2->flags)) {
 				s->handle_bad_blocks = 1;
-				atomic_inc(&rdev->nr_pending);
+				atomic_inc(&rdev2->nr_pending);
 			} else
 				clear_bit(R5_WriteError, &dev->flags);
 		}
 		if (rdev && test_bit(R5_MadeGood, &dev->flags)) {
-			if (!test_bit(Faulty, &rdev->flags)) {
+			/* This flag does not apply to '.replacement'
+			 * only to .rdev, so make sure to check that*/
+			struct md_rdev *rdev2 = rcu_dereference(
+				conf->disks[i].rdev);
+			if (rdev2 && !test_bit(Faulty, &rdev2->flags)) {
 				s->handle_bad_blocks = 1;
-				atomic_inc(&rdev->nr_pending);
+				atomic_inc(&rdev2->nr_pending);
 			} else
 				clear_bit(R5_MadeGood, &dev->flags);
 		}
@@ -4220,7 +4260,6 @@ static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
 			return handled;
 		}
 
-		set_bit(R5_ReadError, &sh->dev[dd_idx].flags);
 		if (!add_stripe_bio(sh, raid_bio, dd_idx, 0)) {
 			release_stripe(sh);
 			raid5_set_bi_hw_segments(raid_bio, scnt);