md/raid5: preferentially read from replacement device if possible.

[deliverable/linux.git] / drivers / md / raid5.c

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 2d2aaf6e98e2608c302cbcc025a5c6a8427699ab..2ae63c5b1c2591f7a174a9b11f3f7638ba97ff66 100644 (file)
--- 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);