md: support blocking writes to an array on device failure

Allows a userspace metadata handler to take action upon detecting a device
failure.

Based on an original patch by Neil Brown.

Changes:
-added blocked_wait waitqueue to rdev
-don't qualify Blocked with Faulty always let userspace block writes
-added md_wait_for_blocked_rdev to wait for the block device to be clear, if
 userspace misses the notification another one is sent every 5 seconds
-set MD_RECOVERY_NEEDED after clearing "blocked"
-kill DoBlock flag, just test mddev->external

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 968dacaced6d..087eee0cb809 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2607,6 +2607,7 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
         }
 }
 
+
 /*
  * handle_stripe - do things to a stripe.
  *
@@ -2632,6 +2633,7 @@ static void handle_stripe5(struct stripe_head *sh)
         struct stripe_head_state s;
         struct r5dev *dev;
         unsigned long pending = 0;
+        mdk_rdev_t *blocked_rdev = NULL;
 
         memset(&s, 0, sizeof(s));
         pr_debug("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d "
@@ -2691,6 +2693,11 @@ static void handle_stripe5(struct stripe_head *sh)
                 if (dev->written)
                         s.written++;
                 rdev = rcu_dereference(conf->disks[i].rdev);
+                if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+                        blocked_rdev = rdev;
+                        atomic_inc(&rdev->nr_pending);
+                        break;
+                }
                 if (!rdev || !test_bit(In_sync, &rdev->flags)) {
                         /* The ReadError flag will just be confusing now */
                         clear_bit(R5_ReadError, &dev->flags);
@@ -2705,6 +2712,11 @@ static void handle_stripe5(struct stripe_head *sh)
         }
         rcu_read_unlock();
 
+        if (unlikely(blocked_rdev)) {
+                set_bit(STRIPE_HANDLE, &sh->state);
+                goto unlock;
+        }
+
         if (s.to_fill && !test_and_set_bit(STRIPE_OP_BIOFILL, &sh->ops.pending))
                 sh->ops.count++;
 
@@ -2894,8 +2906,13 @@ static void handle_stripe5(struct stripe_head *sh)
         if (sh->ops.count)
                 pending = get_stripe_work(sh);
 
+ unlock:
         spin_unlock(&sh->lock);
 
+        /* wait for this device to become unblocked */
+        if (unlikely(blocked_rdev))
+                md_wait_for_blocked_rdev(blocked_rdev, conf->mddev);
+
         if (pending)
                 raid5_run_ops(sh, pending);
 
@@ -2912,6 +2929,7 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
         struct stripe_head_state s;
         struct r6_state r6s;
         struct r5dev *dev, *pdev, *qdev;
+        mdk_rdev_t *blocked_rdev = NULL;
 
         r6s.qd_idx = raid6_next_disk(pd_idx, disks);
         pr_debug("handling stripe %llu, state=%#lx cnt=%d, "
@@ -2975,6 +2993,11 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                 if (dev->written)
                         s.written++;
                 rdev = rcu_dereference(conf->disks[i].rdev);
+                if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+                        blocked_rdev = rdev;
+                        atomic_inc(&rdev->nr_pending);
+                        break;
+                }
                 if (!rdev || !test_bit(In_sync, &rdev->flags)) {
                         /* The ReadError flag will just be confusing now */
                         clear_bit(R5_ReadError, &dev->flags);
@@ -2989,6 +3012,11 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                         set_bit(R5_Insync, &dev->flags);
         }
         rcu_read_unlock();
+
+        if (unlikely(blocked_rdev)) {
+                set_bit(STRIPE_HANDLE, &sh->state);
+                goto unlock;
+        }
         pr_debug("locked=%d uptodate=%d to_read=%d"
                " to_write=%d failed=%d failed_num=%d,%d\n",
                s.locked, s.uptodate, s.to_read, s.to_write, s.failed,
@@ -3094,8 +3122,13 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
             !test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending))
                 handle_stripe_expansion(conf, sh, &r6s);
 
+ unlock:
         spin_unlock(&sh->lock);
 
+        /* wait for this device to become unblocked */
+        if (unlikely(blocked_rdev))
+                md_wait_for_blocked_rdev(blocked_rdev, conf->mddev);
+
         return_io(return_bi);
 
         for (i=disks; i-- ;) {