[PATCH] md: Checkpoint and allow restart of raid5 reshape

We allow the superblock to record an 'old' and a 'new' geometry, and a
position where any conversion is up to.  The geometry allows for changing
chunksize, layout and level as well as number of devices.

When using verion-0.90 superblock, we convert the version to 0.91 while the
conversion is happening so that an old kernel will refuse the assemble the
array.  For version-1, we use a feature bit for the same effect.

When starting an array we check for an incomplete reshape and restart the
reshape process if needed.  If the reshape stopped at an awkward time (like
when updating the first stripe) we refuse to assemble the array, and let
user-space worry about it.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/md.c

@@ -662,7 +662,8 @@ static int super_90_load(mdk_rdev_t *rdev, mdk_rdev_t *refdev, int minor_version
 	}
 
 	if (sb->major_version != 0 ||
-	    sb->minor_version != 90) {
+	    sb->minor_version < 90 ||
+	    sb->minor_version > 91) {
 		printk(KERN_WARNING "Bad version number %d.%d on %s\n",
 			sb->major_version, sb->minor_version,
 			b);
@@ -747,6 +748,20 @@ static int super_90_validate(mddev_t *mddev, mdk_rdev_t *rdev)
 		mddev->bitmap_offset = 0;
 		mddev->default_bitmap_offset = MD_SB_BYTES >> 9;
 
+		if (mddev->minor_version >= 91) {
+			mddev->reshape_position = sb->reshape_position;
+			mddev->delta_disks = sb->delta_disks;
+			mddev->new_level = sb->new_level;
+			mddev->new_layout = sb->new_layout;
+			mddev->new_chunk = sb->new_chunk;
+		} else {
+			mddev->reshape_position = MaxSector;
+			mddev->delta_disks = 0;
+			mddev->new_level = mddev->level;
+			mddev->new_layout = mddev->layout;
+			mddev->new_chunk = mddev->chunk_size;
+		}
+
 		if (sb->state & (1<<MD_SB_CLEAN))
 			mddev->recovery_cp = MaxSector;
 		else {
@@ -841,7 +856,6 @@ static void super_90_sync(mddev_t *mddev, mdk_rdev_t *rdev)
 
 	sb->md_magic = MD_SB_MAGIC;
 	sb->major_version = mddev->major_version;
-	sb->minor_version = mddev->minor_version;
 	sb->patch_version = mddev->patch_version;
 	sb->gvalid_words  = 0; /* ignored */
 	memcpy(&sb->set_uuid0, mddev->uuid+0, 4);
@@ -860,6 +874,17 @@ static void super_90_sync(mddev_t *mddev, mdk_rdev_t *rdev)
 	sb->events_hi = (mddev->events>>32);
 	sb->events_lo = (u32)mddev->events;
 
+	if (mddev->reshape_position == MaxSector)
+		sb->minor_version = 90;
+	else {
+		sb->minor_version = 91;
+		sb->reshape_position = mddev->reshape_position;
+		sb->new_level = mddev->new_level;
+		sb->delta_disks = mddev->delta_disks;
+		sb->new_layout = mddev->new_layout;
+		sb->new_chunk = mddev->new_chunk;
+	}
+	mddev->minor_version = sb->minor_version;
 	if (mddev->in_sync)
 	{
 		sb->recovery_cp = mddev->recovery_cp;
@@ -1104,6 +1129,20 @@ static int super_1_validate(mddev_t *mddev, mdk_rdev_t *rdev)
 			}
 			mddev->bitmap_offset = (__s32)le32_to_cpu(sb->bitmap_offset);
 		}
+		if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_RESHAPE_ACTIVE)) {
+			mddev->reshape_position = le64_to_cpu(sb->reshape_position);
+			mddev->delta_disks = le32_to_cpu(sb->delta_disks);
+			mddev->new_level = le32_to_cpu(sb->new_level);
+			mddev->new_layout = le32_to_cpu(sb->new_layout);
+			mddev->new_chunk = le32_to_cpu(sb->new_chunk)<<9;
+		} else {
+			mddev->reshape_position = MaxSector;
+			mddev->delta_disks = 0;
+			mddev->new_level = mddev->level;
+			mddev->new_layout = mddev->layout;
+			mddev->new_chunk = mddev->chunk_size;
+		}
+
 	} else if (mddev->pers == NULL) {
 		/* Insist of good event counter while assembling */
 		__u64 ev1 = le64_to_cpu(sb->events);
@@ -1175,6 +1214,14 @@ static void super_1_sync(mddev_t *mddev, mdk_rdev_t *rdev)
 		sb->bitmap_offset = cpu_to_le32((__u32)mddev->bitmap_offset);
 		sb->feature_map = cpu_to_le32(MD_FEATURE_BITMAP_OFFSET);
 	}
+	if (mddev->reshape_position != MaxSector) {
+		sb->feature_map |= cpu_to_le32(MD_FEATURE_RESHAPE_ACTIVE);
+		sb->reshape_position = cpu_to_le64(mddev->reshape_position);
+		sb->new_layout = cpu_to_le32(mddev->new_layout);
+		sb->delta_disks = cpu_to_le32(mddev->delta_disks);
+		sb->new_level = cpu_to_le32(mddev->new_level);
+		sb->new_chunk = cpu_to_le32(mddev->new_chunk>>9);
+	}
 
 	max_dev = 0;
 	ITERATE_RDEV(mddev,rdev2,tmp)
@@ -1497,7 +1544,7 @@ static void sync_sbs(mddev_t * mddev)
 	}
 }
 
-static void md_update_sb(mddev_t * mddev)
+void md_update_sb(mddev_t * mddev)
 {
 	int err;
 	struct list_head *tmp;
@@ -1574,6 +1621,7 @@ static void md_update_sb(mddev_t * mddev)
 	wake_up(&mddev->sb_wait);
 
 }
+EXPORT_SYMBOL_GPL(md_update_sb);
 
 /* words written to sysfs files may, or my not, be \n terminated.
  * We want to accept with case. For this we use cmd_match.
@@ -2545,6 +2593,14 @@ static int do_md_run(mddev_t * mddev)
 	mddev->level = pers->level;
 	strlcpy(mddev->clevel, pers->name, sizeof(mddev->clevel));
 
+	if (mddev->reshape_position != MaxSector &&
+	    pers->reshape == NULL) {
+		/* This personality cannot handle reshaping... */
+		mddev->pers = NULL;
+		module_put(pers->owner);
+		return -EINVAL;
+	}
+
 	mddev->recovery = 0;
 	mddev->resync_max_sectors = mddev->size << 1; /* may be over-ridden by personality */
 	mddev->barriers_work = 1;
@@ -3433,11 +3489,18 @@ static int set_array_info(mddev_t * mddev, mdu_array_info_t *info)
 	mddev->default_bitmap_offset = MD_SB_BYTES >> 9;
 	mddev->bitmap_offset = 0;
 
+	mddev->reshape_position = MaxSector;
+
 	/*
 	 * Generate a 128 bit UUID
 	 */
 	get_random_bytes(mddev->uuid, 16);
 
+	mddev->new_level = mddev->level;
+	mddev->new_chunk = mddev->chunk_size;
+	mddev->new_layout = mddev->layout;
+	mddev->delta_disks = 0;
+
 	return 0;
 }
 

drivers/md/raid1.c

@@ -1789,6 +1789,11 @@ static int run(mddev_t *mddev)
 		       mdname(mddev), mddev->level);
 		goto out;
 	}
+	if (mddev->reshape_position != MaxSector) {
+		printk("raid1: %s: reshape_position set but not supported\n",
+		       mdname(mddev));
+		goto out;
+	}
 	/*
 	 * copy the already verified devices into our private RAID1
 	 * bookkeeping area. [whatever we allocate in run(),