Merge branch 'md-next' of git://github.com/goldwynr/linux into for-next

md-cluster: A better way for METADATA_UPDATED processing

The processing of METADATA_UPDATED message is too simple and prone to
errors. Besides, it would not update the internal data structures as
required.

This set of patches reads the superblock from one of the device of the MD
and checks for changes in the in-memory data structures. If there is a change,
it performs the necessary actions to keep the internal data structures
as it would be in the primary node.

An example is if a devices turns faulty. The algorithm is:

1. The initiator node marks the device as faulty and updates the superblock
2. The initiator node sends METADATA_UPDATED with an advisory  device number to the rest of the nodes.
3. The receiving node on receiving the METADATA_UPDATED message
  3.1 Reads the superblock
  3.2 Detects a device has failed by comparing with memory structure
  3.3 Calls the necessary functions to record the failure and get the device out of the active array.
  3.4 Acknowledges the message.

The patch series also fixes adding the disk which was impacted because of
the changes.

Patches can also be found at
https://github.com/goldwynr/linux branch md-next

Changes since V2:
 - Fix status synchrnoization after --add and --re-add operations
 - Included Guoqing's patches on endian correctness, zeroing cmsg etc
 - Restructure add_new_disk() and cancel()

1 files changed, 248 insertions, 111 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index c702de18207a..a71b36f0acb0 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1735,6 +1735,9 @@ static void super_1_sync(struct mddev *mddev, struct md_rdev *rdev)
 		}
 	}
 
+	if (mddev_is_clustered(mddev))
+		sb->feature_map |= cpu_to_le32(MD_FEATURE_CLUSTERED);
+
 	if (rdev->badblocks.count == 0)
 		/* Nothing to do for bad blocks*/ ;
 	else if (sb->bblog_offset == 0)
@@ -2196,18 +2199,72 @@ static void sync_sbs(struct mddev *mddev, int nospares)
 	}
 }
 
+static bool does_sb_need_changing(struct mddev *mddev)
+{
+	struct md_rdev *rdev;
+	struct mdp_superblock_1 *sb;
+	int role;
+
+	/* Find a good rdev */
+	rdev_for_each(rdev, mddev)
+		if ((rdev->raid_disk >= 0) && !test_bit(Faulty, &rdev->flags))
+			break;
+
+	/* No good device found. */
+	if (!rdev)
+		return false;
+
+	sb = page_address(rdev->sb_page);
+	/* Check if a device has become faulty or a spare become active */
+	rdev_for_each(rdev, mddev) {
+		role = le16_to_cpu(sb->dev_roles[rdev->desc_nr]);
+		/* Device activated? */
+		if (role == 0xffff && rdev->raid_disk >=0 &&
+		    !test_bit(Faulty, &rdev->flags))
+			return true;
+		/* Device turned faulty? */
+		if (test_bit(Faulty, &rdev->flags) && (role < 0xfffd))
+			return true;
+	}
+
+	/* Check if any mddev parameters have changed */
+	if ((mddev->dev_sectors != le64_to_cpu(sb->size)) ||
+	    (mddev->reshape_position != le64_to_cpu(sb->reshape_position)) ||
+	    (mddev->recovery_cp != le64_to_cpu(sb->resync_offset)) ||
+	    (mddev->layout != le64_to_cpu(sb->layout)) ||
+	    (mddev->raid_disks != le32_to_cpu(sb->raid_disks)) ||
+	    (mddev->chunk_sectors != le32_to_cpu(sb->chunksize)))
+		return true;
+
+	return false;
+}
+
 void md_update_sb(struct mddev *mddev, int force_change)
 {
 	struct md_rdev *rdev;
 	int sync_req;
 	int nospares = 0;
 	int any_badblocks_changed = 0;
+	int ret = -1;
 
 	if (mddev->ro) {
 		if (force_change)
 			set_bit(MD_CHANGE_DEVS, &mddev->flags);
 		return;
 	}
+
+	if (mddev_is_clustered(mddev)) {
+		if (test_and_clear_bit(MD_CHANGE_DEVS, &mddev->flags))
+			force_change = 1;
+		ret = md_cluster_ops->metadata_update_start(mddev);
+		/* Has someone else has updated the sb */
+		if (!does_sb_need_changing(mddev)) {
+			if (ret == 0)
+				md_cluster_ops->metadata_update_cancel(mddev);
+			clear_bit(MD_CHANGE_PENDING, &mddev->flags);
+			return;
+		}
+	}
 repeat:
 	/* First make sure individual recovery_offsets are correct */
 	rdev_for_each(rdev, mddev) {
@@ -2356,6 +2413,9 @@ repeat:
 		clear_bit(BlockedBadBlocks, &rdev->flags);
 		wake_up(&rdev->blocked_wait);
 	}
+
+	if (mddev_is_clustered(mddev) && ret == 0)
+		md_cluster_ops->metadata_update_finish(mddev);
 }
 EXPORT_SYMBOL(md_update_sb);
 
@@ -2490,17 +2550,16 @@ state_store(struct md_rdev *rdev, const char *buf, size_t len)
 			err = -EBUSY;
 		else {
 			struct mddev *mddev = rdev->mddev;
-			if (mddev_is_clustered(mddev))
-				md_cluster_ops->remove_disk(mddev, rdev);
-			md_kick_rdev_from_array(rdev);
-			if (mddev_is_clustered(mddev))
-				md_cluster_ops->metadata_update_start(mddev);
-			if (mddev->pers)
-				md_update_sb(mddev, 1);
-			md_new_event(mddev);
-			if (mddev_is_clustered(mddev))
-				md_cluster_ops->metadata_update_finish(mddev);
 			err = 0;
+			if (mddev_is_clustered(mddev))
+				err = md_cluster_ops->remove_disk(mddev, rdev);
+
+			if (err == 0) {
+				md_kick_rdev_from_array(rdev);
+				if (mddev->pers)
+					md_update_sb(mddev, 1);
+				md_new_event(mddev);
+			}
 		}
 	} else if (cmd_match(buf, "writemostly")) {
 		set_bit(WriteMostly, &rdev->flags);
@@ -2688,15 +2747,9 @@ slot_store(struct md_rdev *rdev, const char *buf, size_t len)
 			rdev->saved_raid_disk = -1;
 		clear_bit(In_sync, &rdev->flags);
 		clear_bit(Bitmap_sync, &rdev->flags);
-		err = rdev->mddev->pers->
-			hot_add_disk(rdev->mddev, rdev);
-		if (err) {
-			rdev->raid_disk = -1;
-			return err;
-		} else
-			sysfs_notify_dirent_safe(rdev->sysfs_state);
-		if (sysfs_link_rdev(rdev->mddev, rdev))
-			/* failure here is OK */;
+		remove_and_add_spares(rdev->mddev, rdev);
+		if (rdev->raid_disk == -1)
+			return -EBUSY;
 		/* don't wakeup anyone, leave that to userspace. */
 	} else {
 		if (slot >= rdev->mddev->raid_disks &&
@@ -3198,14 +3251,6 @@ static void analyze_sbs(struct mddev *mddev)
 				md_kick_rdev_from_array(rdev);
 				continue;
 			}
-			/* No device should have a Candidate flag
-			 * when reading devices
-			 */
-			if (test_bit(Candidate, &rdev->flags)) {
-				pr_info("md: kicking Cluster Candidate %s from array!\n",
-					bdevname(rdev->bdev, b));
-				md_kick_rdev_from_array(rdev);
-			}
 		}
 		if (mddev->level == LEVEL_MULTIPATH) {
 			rdev->desc_nr = i++;
@@ -4066,12 +4111,8 @@ size_store(struct mddev *mddev, const char *buf, size_t len)
 	if (err)
 		return err;
 	if (mddev->pers) {
-		if (mddev_is_clustered(mddev))
-			md_cluster_ops->metadata_update_start(mddev);
 		err = update_size(mddev, sectors);
 		md_update_sb(mddev, 1);
-		if (mddev_is_clustered(mddev))
-			md_cluster_ops->metadata_update_finish(mddev);
 	} else {
 		if (mddev->dev_sectors == 0 ||
 		    mddev->dev_sectors > sectors)
@@ -5309,8 +5350,6 @@ static void md_clean(struct mddev *mddev)
 
 static void __md_stop_writes(struct mddev *mddev)
 {
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_start(mddev);
 	set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 	flush_workqueue(md_misc_wq);
 	if (mddev->sync_thread) {
@@ -5329,8 +5368,6 @@ static void __md_stop_writes(struct mddev *mddev)
 		mddev->in_sync = 1;
 		md_update_sb(mddev, 1);
 	}
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_finish(mddev);
 }
 
 void md_stop_writes(struct mddev *mddev)
@@ -5910,19 +5947,12 @@ static int add_new_disk(struct mddev *mddev, mdu_disk_info_t *info)
 		 * check whether the device shows up in other nodes
 		 */
 		if (mddev_is_clustered(mddev)) {
-			if (info->state & (1 << MD_DISK_CANDIDATE)) {
-				/* Through --cluster-confirm */
+			if (info->state & (1 << MD_DISK_CANDIDATE))
 				set_bit(Candidate, &rdev->flags);
-				err = md_cluster_ops->new_disk_ack(mddev, true);
-				if (err) {
-					export_rdev(rdev);
-					return err;
-				}
-			} else if (info->state & (1 << MD_DISK_CLUSTER_ADD)) {
+			else if (info->state & (1 << MD_DISK_CLUSTER_ADD)) {
 				/* --add initiated by this node */
-				err = md_cluster_ops->add_new_disk_start(mddev, rdev);
+				err = md_cluster_ops->add_new_disk(mddev, rdev);
 				if (err) {
-					md_cluster_ops->add_new_disk_finish(mddev);
 					export_rdev(rdev);
 					return err;
 				}
@@ -5931,13 +5961,23 @@ static int add_new_disk(struct mddev *mddev, mdu_disk_info_t *info)
 
 		rdev->raid_disk = -1;
 		err = bind_rdev_to_array(rdev, mddev);
+
 		if (err)
 			export_rdev(rdev);
-		else
+
+		if (mddev_is_clustered(mddev)) {
+			if (info->state & (1 << MD_DISK_CANDIDATE))
+				md_cluster_ops->new_disk_ack(mddev, (err == 0));
+			else {
+				if (err)
+					md_cluster_ops->add_new_disk_cancel(mddev);
+				else
+					err = add_bound_rdev(rdev);
+			}
+
+		} else if (!err)
 			err = add_bound_rdev(rdev);
-		if (mddev_is_clustered(mddev) &&
-				(info->state & (1 << MD_DISK_CLUSTER_ADD)))
-			md_cluster_ops->add_new_disk_finish(mddev);
+
 		return err;
 	}
 
@@ -5993,13 +6033,17 @@ static int hot_remove_disk(struct mddev *mddev, dev_t dev)
 {
 	char b[BDEVNAME_SIZE];
 	struct md_rdev *rdev;
+	int ret = -1;
 
 	rdev = find_rdev(mddev, dev);
 	if (!rdev)
 		return -ENXIO;
 
 	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_start(mddev);
+		ret = md_cluster_ops->metadata_update_start(mddev);
+
+	if (rdev->raid_disk < 0)
+		goto kick_rdev;
 
 	clear_bit(Blocked, &rdev->flags);
 	remove_and_add_spares(mddev, rdev);
@@ -6007,20 +6051,19 @@ static int hot_remove_disk(struct mddev *mddev, dev_t dev)
 	if (rdev->raid_disk >= 0)
 		goto busy;
 
-	if (mddev_is_clustered(mddev))
+kick_rdev:
+	if (mddev_is_clustered(mddev) && ret == 0)
 		md_cluster_ops->remove_disk(mddev, rdev);
 
 	md_kick_rdev_from_array(rdev);
 	md_update_sb(mddev, 1);
 	md_new_event(mddev);
 
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_finish(mddev);
-
 	return 0;
 busy:
-	if (mddev_is_clustered(mddev))
+	if (mddev_is_clustered(mddev) && ret == 0)
 		md_cluster_ops->metadata_update_cancel(mddev);
+
 	printk(KERN_WARNING "md: cannot remove active disk %s from %s ...\n",
 		bdevname(rdev->bdev,b), mdname(mddev));
 	return -EBUSY;
@@ -6071,14 +6114,12 @@ static int hot_add_disk(struct mddev *mddev, dev_t dev)
 		goto abort_export;
 	}
 
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_start(mddev);
 	clear_bit(In_sync, &rdev->flags);
 	rdev->desc_nr = -1;
 	rdev->saved_raid_disk = -1;
 	err = bind_rdev_to_array(rdev, mddev);
 	if (err)
-		goto abort_clustered;
+		goto abort_export;
 
 	/*
 	 * The rest should better be atomic, we can have disk failures
@@ -6088,9 +6129,6 @@ static int hot_add_disk(struct mddev *mddev, dev_t dev)
 	rdev->raid_disk = -1;
 
 	md_update_sb(mddev, 1);
-
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_finish(mddev);
 	/*
 	 * Kick recovery, maybe this spare has to be added to the
 	 * array immediately.
@@ -6100,9 +6138,6 @@ static int hot_add_disk(struct mddev *mddev, dev_t dev)
 	md_new_event(mddev);
 	return 0;
 
-abort_clustered:
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_cancel(mddev);
 abort_export:
 	export_rdev(rdev);
 	return err;
@@ -6420,8 +6455,6 @@ static int update_array_info(struct mddev *mddev, mdu_array_info_t *info)
 			return rv;
 		}
 	}
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_start(mddev);
 	if (info->size >= 0 && mddev->dev_sectors / 2 != info->size)
 		rv = update_size(mddev, (sector_t)info->size * 2);
 
@@ -6479,12 +6512,8 @@ static int update_array_info(struct mddev *mddev, mdu_array_info_t *info)
 		}
 	}
 	md_update_sb(mddev, 1);
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_finish(mddev);
 	return rv;
 err:
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_cancel(mddev);
 	return rv;
 }
 
@@ -7597,11 +7626,7 @@ int md_allow_write(struct mddev *mddev)
 		    mddev->safemode == 0)
 			mddev->safemode = 1;
 		spin_unlock(&mddev->lock);
-		if (mddev_is_clustered(mddev))
-			md_cluster_ops->metadata_update_start(mddev);
 		md_update_sb(mddev, 0);
-		if (mddev_is_clustered(mddev))
-			md_cluster_ops->metadata_update_finish(mddev);
 		sysfs_notify_dirent_safe(mddev->sysfs_state);
 	} else
 		spin_unlock(&mddev->lock);
@@ -7633,6 +7658,7 @@ void md_do_sync(struct md_thread *thread)
 	struct md_rdev *rdev;
 	char *desc, *action = NULL;
 	struct blk_plug plug;
+	bool cluster_resync_finished = false;
 
 	/* just incase thread restarts... */
 	if (test_bit(MD_RECOVERY_DONE, &mddev->recovery))
@@ -7802,9 +7828,6 @@ void md_do_sync(struct md_thread *thread)
 	md_new_event(mddev);
 	update_time = jiffies;
 
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->resync_start(mddev, j, max_sectors);
-
 	blk_start_plug(&plug);
 	while (j < max_sectors) {
 		sector_t sectors;
@@ -7868,8 +7891,6 @@ void md_do_sync(struct md_thread *thread)
 			j = max_sectors;
 		if (j > 2)
 			mddev->curr_resync = j;
-		if (mddev_is_clustered(mddev))
-			md_cluster_ops->resync_info_update(mddev, j, max_sectors);
 		mddev->curr_mark_cnt = io_sectors;
 		if (last_check == 0)
 			/* this is the earliest that rebuild will be
@@ -7940,7 +7961,11 @@ void md_do_sync(struct md_thread *thread)
 		mddev->curr_resync_completed = mddev->curr_resync;
 		sysfs_notify(&mddev->kobj, NULL, "sync_completed");
 	}
-	/* tell personality that we are finished */
+	/* tell personality and other nodes that we are finished */
+	if (mddev_is_clustered(mddev)) {
+		md_cluster_ops->resync_finish(mddev);
+		cluster_resync_finished = true;
+	}
 	mddev->pers->sync_request(mddev, max_sectors, &skipped);
 
 	if (!test_bit(MD_RECOVERY_CHECK, &mddev->recovery) &&
@@ -7976,11 +8001,13 @@ void md_do_sync(struct md_thread *thread)
 		}
 	}
  skip:
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->resync_finish(mddev);
-
 	set_bit(MD_CHANGE_DEVS, &mddev->flags);
 
+	if (mddev_is_clustered(mddev) &&
+	    test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
+	    !cluster_resync_finished)
+		md_cluster_ops->resync_finish(mddev);
+
 	spin_lock(&mddev->lock);
 	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
 		/* We completed so min/max setting can be forgotten if used. */
@@ -8023,10 +8050,14 @@ static int remove_and_add_spares(struct mddev *mddev,
 	if (removed && mddev->kobj.sd)
 		sysfs_notify(&mddev->kobj, NULL, "degraded");
 
-	if (this)
+	if (this && removed)
 		goto no_add;
 
 	rdev_for_each(rdev, mddev) {
+		if (this && this != rdev)
+			continue;
+		if (test_bit(Candidate, &rdev->flags))
+			continue;
 		if (rdev->raid_disk >= 0 &&
 		    !test_bit(In_sync, &rdev->flags) &&
 		    !test_bit(Faulty, &rdev->flags))
@@ -8060,14 +8091,25 @@ no_add:
 static void md_start_sync(struct work_struct *ws)
 {
 	struct mddev *mddev = container_of(ws, struct mddev, del_work);
+	int ret = 0;
+
+	if (mddev_is_clustered(mddev)) {
+		ret = md_cluster_ops->resync_start(mddev);
+		if (ret) {
+			mddev->sync_thread = NULL;
+			goto out;
+		}
+	}
 
 	mddev->sync_thread = md_register_thread(md_do_sync,
 						mddev,
 						"resync");
+out:
 	if (!mddev->sync_thread) {
-		printk(KERN_ERR "%s: could not start resync"
-		       " thread...\n",
-		       mdname(mddev));
+		if (!(mddev_is_clustered(mddev) && ret == -EAGAIN))
+			printk(KERN_ERR "%s: could not start resync"
+			       " thread...\n",
+			       mdname(mddev));
 		/* leave the spares where they are, it shouldn't hurt */
 		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
 		clear_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
@@ -8186,13 +8228,8 @@ void md_check_recovery(struct mddev *mddev)
 				sysfs_notify_dirent_safe(mddev->sysfs_state);
 		}
 
-		if (mddev->flags & MD_UPDATE_SB_FLAGS) {
-			if (mddev_is_clustered(mddev))
-				md_cluster_ops->metadata_update_start(mddev);
+		if (mddev->flags & MD_UPDATE_SB_FLAGS)
 			md_update_sb(mddev, 0);
-			if (mddev_is_clustered(mddev))
-				md_cluster_ops->metadata_update_finish(mddev);
-		}
 
 		if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) &&
 		    !test_bit(MD_RECOVERY_DONE, &mddev->recovery)) {
@@ -8290,8 +8327,6 @@ void md_reap_sync_thread(struct mddev *mddev)
 			set_bit(MD_CHANGE_DEVS, &mddev->flags);
 		}
 	}
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_start(mddev);
 	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
 	    mddev->pers->finish_reshape)
 		mddev->pers->finish_reshape(mddev);
@@ -8304,8 +8339,6 @@ void md_reap_sync_thread(struct mddev *mddev)
 			rdev->saved_raid_disk = -1;
 
 	md_update_sb(mddev, 1);
-	if (mddev_is_clustered(mddev))
-		md_cluster_ops->metadata_update_finish(mddev);
 	clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
 	clear_bit(MD_RECOVERY_DONE, &mddev->recovery);
 	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
@@ -8928,25 +8961,129 @@ err_wq:
 	return ret;
 }
 
-void md_reload_sb(struct mddev *mddev)
+static void check_sb_changes(struct mddev *mddev, struct md_rdev *rdev)
 {
-	struct md_rdev *rdev, *tmp;
+	struct mdp_superblock_1 *sb = page_address(rdev->sb_page);
+	struct md_rdev *rdev2;
+	int role, ret;
+	char b[BDEVNAME_SIZE];
 
-	rdev_for_each_safe(rdev, tmp, mddev) {
-		rdev->sb_loaded = 0;
-		ClearPageUptodate(rdev->sb_page);
+	/* Check for change of roles in the active devices */
+	rdev_for_each(rdev2, mddev) {
+		if (test_bit(Faulty, &rdev2->flags))
+			continue;
+
+		/* Check if the roles changed */
+		role = le16_to_cpu(sb->dev_roles[rdev2->desc_nr]);
+
+		if (test_bit(Candidate, &rdev2->flags)) {
+			if (role == 0xfffe) {
+				pr_info("md: Removing Candidate device %s because add failed\n", bdevname(rdev2->bdev,b));
+				md_kick_rdev_from_array(rdev2);
+				continue;
+			}
+			else
+				clear_bit(Candidate, &rdev2->flags);
+		}
+
+		if (role != rdev2->raid_disk) {
+			/* got activated */
+			if (rdev2->raid_disk == -1 && role != 0xffff) {
+				rdev2->saved_raid_disk = role;
+				ret = remove_and_add_spares(mddev, rdev2);
+				pr_info("Activated spare: %s\n",
+						bdevname(rdev2->bdev,b));
+				continue;
+			}
+			/* device faulty
+			 * We just want to do the minimum to mark the disk
+			 * as faulty. The recovery is performed by the
+			 * one who initiated the error.
+			 */
+			if ((role == 0xfffe) || (role == 0xfffd)) {
+				md_error(mddev, rdev2);
+				clear_bit(Blocked, &rdev2->flags);
+			}
+		}
 	}
-	mddev->raid_disks = 0;
-	analyze_sbs(mddev);
-	rdev_for_each_safe(rdev, tmp, mddev) {
-		struct mdp_superblock_1 *sb = page_address(rdev->sb_page);
-		/* since we don't write to faulty devices, we figure out if the
-		 *  disk is faulty by comparing events
-		 */
-		if (mddev->events > sb->events)
-			set_bit(Faulty, &rdev->flags);
+
+	/* recovery_cp changed */
+	if (le64_to_cpu(sb->resync_offset) != mddev->recovery_cp)
+		mddev->recovery_cp = le64_to_cpu(sb->resync_offset);
+
+	/* Finally set the event to be up to date */
+	mddev->events = le64_to_cpu(sb->events);
+}
+
+static int read_rdev(struct mddev *mddev, struct md_rdev *rdev)
+{
+	int err;
+	struct page *swapout = rdev->sb_page;
+	struct mdp_superblock_1 *sb;
+
+	/* Store the sb page of the rdev in the swapout temporary
+	 * variable in case we err in the future
+	 */
+	rdev->sb_page = NULL;
+	alloc_disk_sb(rdev);
+	ClearPageUptodate(rdev->sb_page);
+	rdev->sb_loaded = 0;
+	err = super_types[mddev->major_version].load_super(rdev, NULL, mddev->minor_version);
+
+	if (err < 0) {
+		pr_warn("%s: %d Could not reload rdev(%d) err: %d. Restoring old values\n",
+				__func__, __LINE__, rdev->desc_nr, err);
+		put_page(rdev->sb_page);
+		rdev->sb_page = swapout;
+		rdev->sb_loaded = 1;
+		return err;
+	}
+
+	sb = page_address(rdev->sb_page);
+	/* Read the offset unconditionally, even if MD_FEATURE_RECOVERY_OFFSET
+	 * is not set
+	 */
+
+	if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_RECOVERY_OFFSET))
+		rdev->recovery_offset = le64_to_cpu(sb->recovery_offset);
+
+	/* The other node finished recovery, call spare_active to set
+	 * device In_sync and mddev->degraded
+	 */
+	if (rdev->recovery_offset == MaxSector &&
+	    !test_bit(In_sync, &rdev->flags) &&
+	    mddev->pers->spare_active(mddev))
+		sysfs_notify(&mddev->kobj, NULL, "degraded");
+
+	put_page(swapout);
+	return 0;
+}
+
+void md_reload_sb(struct mddev *mddev, int nr)
+{
+	struct md_rdev *rdev;
+	int err;
+
+	/* Find the rdev */
+	rdev_for_each_rcu(rdev, mddev) {
+		if (rdev->desc_nr == nr)
+			break;
+	}
+
+	if (!rdev || rdev->desc_nr != nr) {
+		pr_warn("%s: %d Could not find rdev with nr %d\n", __func__, __LINE__, nr);
+		return;
 	}
 
+	err = read_rdev(mddev, rdev);
+	if (err < 0)
+		return;
+
+	check_sb_changes(mddev, rdev);
+
+	/* Read all rdev's to update recovery_offset */
+	rdev_for_each_rcu(rdev, mddev)
+		read_rdev(mddev, rdev);
 }
 EXPORT_SYMBOL(md_reload_sb);