1 files changed, 21 insertions, 46 deletions

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index b6a2d2081a24..e60e1326376a 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -186,6 +186,7 @@ struct dm_pool_metadata {
 	uint32_t time;
 	dm_block_t root;
 	dm_block_t details_root;
+	dm_block_t held_root;
 	struct list_head thin_devices;
 	uint64_t trans_id;
 	unsigned long flags;
@@ -748,6 +749,7 @@ static int __open_metadata(struct dm_pool_metadata *pmd)
 	 */
 	pmd->root = le64_to_cpu(disk_super->data_mapping_root);
 	pmd->details_root = le64_to_cpu(disk_super->device_details_root);
+	pmd->held_root = le64_to_cpu(disk_super->held_root);
 
 	__setup_btree_details(pmd);
 	dm_bm_unlock(sblock);
@@ -838,6 +840,7 @@ static int __begin_transaction(struct dm_pool_metadata *pmd)
 	pmd->time = le32_to_cpu(disk_super->time);
 	pmd->root = le64_to_cpu(disk_super->data_mapping_root);
 	pmd->details_root = le64_to_cpu(disk_super->device_details_root);
+	pmd->held_root = le64_to_cpu(disk_super->held_root);
 	pmd->trans_id = le64_to_cpu(disk_super->trans_id);
 	pmd->flags = le32_to_cpu(disk_super->flags);
 	pmd->data_block_size = le32_to_cpu(disk_super->data_block_size);
@@ -928,6 +931,7 @@ static int __commit_transaction(struct dm_pool_metadata *pmd)
 	disk_super->time = cpu_to_le32(pmd->time);
 	disk_super->data_mapping_root = cpu_to_le64(pmd->root);
 	disk_super->device_details_root = cpu_to_le64(pmd->details_root);
+	disk_super->held_root = cpu_to_le64(pmd->held_root);
 	disk_super->trans_id = cpu_to_le64(pmd->trans_id);
 	disk_super->flags = cpu_to_le32(pmd->flags);
 
@@ -1333,9 +1337,14 @@ static int __reserve_metadata_snap(struct dm_pool_metadata *pmd)
 {
 	int r, inc;
 	struct thin_disk_superblock *disk_super;
-	struct dm_block *copy, *sblock;
+	struct dm_block *copy;
 	dm_block_t held_root;
 
+	if (pmd->held_root) {
+		DMWARN("Pool metadata snapshot already exists: release this before taking another.");
+		return -EBUSY;
+	}
+
 	/*
 	 * We commit to ensure the btree roots which we increment in a
 	 * moment are up to date.
@@ -1353,22 +1362,16 @@ static int __reserve_metadata_snap(struct dm_pool_metadata *pmd)
 	dm_sm_inc_block(pmd->metadata_sm, THIN_SUPERBLOCK_LOCATION);
 	r = dm_tm_shadow_block(pmd->tm, THIN_SUPERBLOCK_LOCATION,
 			       &sb_validator, &copy, &inc);
-	if (r)
+	if (r) {
+		dm_sm_dec_block(pmd->metadata_sm, THIN_SUPERBLOCK_LOCATION);
 		return r;
+	}
 
 	BUG_ON(!inc);
 
 	held_root = dm_block_location(copy);
 	disk_super = dm_block_data(copy);
 
-	if (le64_to_cpu(disk_super->held_root)) {
-		DMWARN("Pool metadata snapshot already exists: release this before taking another.");
-
-		dm_tm_dec(pmd->tm, held_root);
-		dm_tm_unlock(pmd->tm, copy);
-		return -EBUSY;
-	}
-
 	/*
 	 * Wipe the spacemap since we're not publishing this.
 	 */
@@ -1384,18 +1387,8 @@ static int __reserve_metadata_snap(struct dm_pool_metadata *pmd)
 	dm_tm_inc(pmd->tm, le64_to_cpu(disk_super->device_details_root));
 	dm_tm_unlock(pmd->tm, copy);
 
-	/*
-	 * Write the held root into the superblock.
-	 */
-	r = superblock_lock(pmd, &sblock);
-	if (r) {
-		dm_tm_dec(pmd->tm, held_root);
-		return r;
-	}
+	pmd->held_root = held_root;
 
-	disk_super = dm_block_data(sblock);
-	disk_super->held_root = cpu_to_le64(held_root);
-	dm_bm_unlock(sblock);
 	return 0;
 }
 
@@ -1415,18 +1408,10 @@ static int __release_metadata_snap(struct dm_pool_metadata *pmd)
 {
 	int r;
 	struct thin_disk_superblock *disk_super;
-	struct dm_block *sblock, *copy;
+	struct dm_block *copy;
 	dm_block_t held_root;
 
-	r = superblock_lock(pmd, &sblock);
-	if (r)
-		return r;
-
-	disk_super = dm_block_data(sblock);
-	held_root = le64_to_cpu(disk_super->held_root);
-	disk_super->held_root = cpu_to_le64(0);
-
-	dm_bm_unlock(sblock);
+	held_root = pmd->held_root;
 
 	if (!held_root) {
 		DMWARN("No pool metadata snapshot found: nothing to release.");
@@ -1437,13 +1422,15 @@ static int __release_metadata_snap(struct dm_pool_metadata *pmd)
 	if (r)
 		return r;
 
+	pmd->held_root = 0;
+
 	disk_super = dm_block_data(copy);
 	dm_btree_del(&pmd->info, le64_to_cpu(disk_super->data_mapping_root));
 	dm_btree_del(&pmd->details_info, le64_to_cpu(disk_super->device_details_root));
-	dm_sm_dec_block(pmd->metadata_sm, held_root);
-
 	dm_tm_unlock(pmd->tm, copy);
 
+	dm_sm_dec_block(pmd->metadata_sm, held_root);
+
 	return 0;
 }
 
@@ -1462,19 +1449,7 @@ int dm_pool_release_metadata_snap(struct dm_pool_metadata *pmd)
 static int __get_metadata_snap(struct dm_pool_metadata *pmd,
 			       dm_block_t *result)
 {
-	int r;
-	struct thin_disk_superblock *disk_super;
-	struct dm_block *sblock;
-
-	r = dm_bm_read_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
-			    &sb_validator, &sblock);
-	if (r)
-		return r;
-
-	disk_super = dm_block_data(sblock);
-	*result = le64_to_cpu(disk_super->held_root);
-
-	dm_bm_unlock(sblock);
+	*result = pmd->held_root;
 
 	return 0;
 }