dm thin metadata: stop tracking need for commit

Remove an optimisation that tracks whether or not a thin metadata commit
is needed.

If dm_pool_commit_metadata() is called and no changes have been made
to the metadata then this optimisation avoided writing to disk.

Removing because we're going to do something better later.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-thin-metadata.c

@@ -178,7 +178,6 @@ struct dm_pool_metadata {
 
 	struct rw_semaphore root_lock;
 	uint32_t time;
-	int need_commit;
 	dm_block_t root;
 	dm_block_t details_root;
 	struct list_head thin_devices;
@@ -479,7 +478,6 @@ static int init_pmd(struct dm_pool_metadata *pmd,
 
 	init_rwsem(&pmd->root_lock);
 	pmd->time = 0;
-	pmd->need_commit = 0;
 	pmd->details_root = 0;
 	pmd->trans_id = 0;
 	pmd->flags = 0;
@@ -503,11 +501,6 @@ static int __begin_transaction(struct dm_pool_metadata *pmd)
 	struct thin_disk_superblock *disk_super;
 	struct dm_block *sblock;
 
-	/*
-	 * __maybe_commit_transaction() resets these
-	 */
-	WARN_ON(pmd->need_commit);
-
 	/*
 	 * We re-read the superblock every time.  Shouldn't need to do this
 	 * really.
@@ -583,8 +576,6 @@ static int __write_changed_details(struct dm_pool_metadata *pmd)
 			list_del(&td->list);
 			kfree(td);
 		}
-
-		pmd->need_commit = 1;
 	}
 
 	return 0;
@@ -609,9 +600,6 @@ static int __commit_transaction(struct dm_pool_metadata *pmd)
 	if (r < 0)
 		return r;
 
-	if (!pmd->need_commit)
-		return r;
-
 	r = dm_sm_commit(pmd->data_sm);
 	if (r < 0)
 		return r;
@@ -650,11 +638,7 @@ static int __commit_transaction(struct dm_pool_metadata *pmd)
 	if (r < 0)
 		goto out_locked;
 
-	r = dm_tm_commit(pmd->tm, sblock);
-	if (!r)
-		pmd->need_commit = 0;
-
-	return r;
+	return dm_tm_commit(pmd->tm, sblock);
 
 out_locked:
 	dm_bm_unlock(sblock);
@@ -744,7 +728,6 @@ struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
 	}
 
 	pmd->flags = 0;
-	pmd->need_commit = 1;
 	r = dm_pool_commit_metadata(pmd);
 	if (r < 0) {
 		DMERR("%s: dm_pool_commit_metadata() failed, error = %d",
@@ -1042,8 +1025,6 @@ static int __delete_device(struct dm_pool_metadata *pmd, dm_thin_id dev)
 	if (r)
 		return r;
 
-	pmd->need_commit = 1;
-
 	return 0;
 }
 
@@ -1071,7 +1052,6 @@ int dm_pool_set_metadata_transaction_id(struct dm_pool_metadata *pmd,
 	}
 
 	pmd->trans_id = new_id;
-	pmd->need_commit = 1;
 	up_write(&pmd->root_lock);
 
 	return 0;
@@ -1113,8 +1093,6 @@ static int __reserve_metadata_snap(struct dm_pool_metadata *pmd)
 
 		dm_tm_dec(pmd->tm, held_root);
 		dm_tm_unlock(pmd->tm, copy);
-		pmd->need_commit = 1;
-
 		return -EBUSY;
 	}
 
@@ -1140,16 +1118,12 @@ static int __reserve_metadata_snap(struct dm_pool_metadata *pmd)
 			     &sb_validator, &sblock);
 	if (r) {
 		dm_tm_dec(pmd->tm, held_root);
-		pmd->need_commit = 1;
 		return r;
 	}
 
 	disk_super = dm_block_data(sblock);
 	disk_super->held_root = cpu_to_le64(held_root);
 	dm_bm_unlock(sblock);
-
-	pmd->need_commit = 1;
-
 	return 0;
 }
 
@@ -1179,7 +1153,6 @@ static int __release_metadata_snap(struct dm_pool_metadata *pmd)
 	disk_super = dm_block_data(sblock);
 	held_root = le64_to_cpu(disk_super->held_root);
 	disk_super->held_root = cpu_to_le64(0);
-	pmd->need_commit = 1;
 
 	dm_bm_unlock(sblock);
 
@@ -1317,7 +1290,6 @@ static int __insert(struct dm_thin_device *td, dm_block_t block,
 	struct dm_pool_metadata *pmd = td->pmd;
 	dm_block_t keys[2] = { td->id, block };
 
-	pmd->need_commit = 1;
 	value = cpu_to_le64(pack_block_time(data_block, pmd->time));
 	__dm_bless_for_disk(&value);
 
@@ -1358,7 +1330,6 @@ static int __remove(struct dm_thin_device *td, dm_block_t block)
 
 	td->mapped_blocks--;
 	td->changed = 1;
-	pmd->need_commit = 1;
 
 	return 0;
 }
@@ -1379,10 +1350,7 @@ int dm_pool_alloc_data_block(struct dm_pool_metadata *pmd, dm_block_t *result)
 	int r;
 
 	down_write(&pmd->root_lock);
-
 	r = dm_sm_new_block(pmd->data_sm, result);
-	pmd->need_commit = 1;
-
 	up_write(&pmd->root_lock);
 
 	return r;
@@ -1519,11 +1487,7 @@ static int __resize_data_dev(struct dm_pool_metadata *pmd, dm_block_t new_count)
 		return -EINVAL;
 	}
 
-	r = dm_sm_extend(pmd->data_sm, new_count - old_count);
-	if (!r)
-		pmd->need_commit = 1;
-
-	return r;
+	return dm_sm_extend(pmd->data_sm, new_count - old_count);
 }
 
 int dm_pool_resize_data_dev(struct dm_pool_metadata *pmd, dm_block_t new_count)