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);