Btrfs: kill the orphan space calculation for snapshots

This patch kills off the calculation for the amount of space needed for the
orphan operations during a snapshot.  The thing is we only do snapshots on
commit, so any space that is in the block_rsv->freed[] isn't going to be in the
new snapshot anyway, so there isn't any reason to require that space to be
reserved for the snapshot to occur.  Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>

fs/btrfs/ctree.h

@@ -2577,11 +2577,6 @@ int btrfs_update_inode(struct btrfs_trans_handle *trans,
 int btrfs_orphan_add(struct btrfs_trans_handle *trans, struct inode *inode);
 int btrfs_orphan_del(struct btrfs_trans_handle *trans, struct inode *inode);
 int btrfs_orphan_cleanup(struct btrfs_root *root);
-void btrfs_orphan_pre_snapshot(struct btrfs_trans_handle *trans,
-				struct btrfs_pending_snapshot *pending,
-				u64 *bytes_to_reserve);
-void btrfs_orphan_post_snapshot(struct btrfs_trans_handle *trans,
-				struct btrfs_pending_snapshot *pending);
 void btrfs_orphan_commit_root(struct btrfs_trans_handle *trans,
 			      struct btrfs_root *root);
 int btrfs_cont_expand(struct inode *inode, loff_t oldsize, loff_t size);

fs/btrfs/inode.c

@@ -2079,89 +2079,6 @@ void btrfs_run_delayed_iputs(struct btrfs_root *root)
 	up_read(&root->fs_info->cleanup_work_sem);
 }
 
-/*
- * calculate extra metadata reservation when snapshotting a subvolume
- * contains orphan files.
- */
-void btrfs_orphan_pre_snapshot(struct btrfs_trans_handle *trans,
-				struct btrfs_pending_snapshot *pending,
-				u64 *bytes_to_reserve)
-{
-	struct btrfs_root *root;
-	struct btrfs_block_rsv *block_rsv;
-	u64 num_bytes;
-	int index;
-
-	root = pending->root;
-	if (!root->orphan_block_rsv || list_empty(&root->orphan_list))
-		return;
-
-	block_rsv = root->orphan_block_rsv;
-
-	/* orphan block reservation for the snapshot */
-	num_bytes = block_rsv->size;
-
-	/*
-	 * after the snapshot is created, COWing tree blocks may use more
-	 * space than it frees. So we should make sure there is enough
-	 * reserved space.
-	 */
-	index = trans->transid & 0x1;
-	if (block_rsv->reserved + block_rsv->freed[index] < block_rsv->size) {
-		num_bytes += block_rsv->size -
-			     (block_rsv->reserved + block_rsv->freed[index]);
-	}
-
-	*bytes_to_reserve += num_bytes;
-}
-
-void btrfs_orphan_post_snapshot(struct btrfs_trans_handle *trans,
-				struct btrfs_pending_snapshot *pending)
-{
-	struct btrfs_root *root = pending->root;
-	struct btrfs_root *snap = pending->snap;
-	struct btrfs_block_rsv *block_rsv;
-	u64 num_bytes;
-	int index;
-	int ret;
-
-	if (!root->orphan_block_rsv || list_empty(&root->orphan_list))
-		return;
-
-	/* refill source subvolume's orphan block reservation */
-	block_rsv = root->orphan_block_rsv;
-	index = trans->transid & 0x1;
-	if (block_rsv->reserved + block_rsv->freed[index] < block_rsv->size) {
-		num_bytes = block_rsv->size -
-			    (block_rsv->reserved + block_rsv->freed[index]);
-		ret = btrfs_block_rsv_migrate(&pending->block_rsv,
-					      root->orphan_block_rsv,
-					      num_bytes);
-		BUG_ON(ret);
-	}
-
-	/* setup orphan block reservation for the snapshot */
-	block_rsv = btrfs_alloc_block_rsv(snap);
-	BUG_ON(!block_rsv);
-
-	btrfs_add_durable_block_rsv(root->fs_info, block_rsv);
-	snap->orphan_block_rsv = block_rsv;
-
-	num_bytes = root->orphan_block_rsv->size;
-	ret = btrfs_block_rsv_migrate(&pending->block_rsv,
-				      block_rsv, num_bytes);
-	BUG_ON(ret);
-
-#if 0
-	/* insert orphan item for the snapshot */
-	WARN_ON(!root->orphan_item_inserted);
-	ret = btrfs_insert_orphan_item(trans, root->fs_info->tree_root,
-				       snap->root_key.objectid);
-	BUG_ON(ret);
-	snap->orphan_item_inserted = 1;
-#endif
-}
-
 enum btrfs_orphan_cleanup_state {
 	ORPHAN_CLEANUP_STARTED	= 1,
 	ORPHAN_CLEANUP_DONE	= 2,

fs/btrfs/transaction.c

@@ -911,7 +911,6 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	}
 
 	btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
-	btrfs_orphan_pre_snapshot(trans, pending, &to_reserve);
 
 	if (to_reserve > 0) {
 		ret = btrfs_block_rsv_add(trans, root, &pending->block_rsv,
@@ -1002,7 +1001,6 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	BUG_ON(IS_ERR(pending->snap));
 
 	btrfs_reloc_post_snapshot(trans, pending);
-	btrfs_orphan_post_snapshot(trans, pending);
 fail:
 	kfree(new_root_item);
 	trans->block_rsv = rsv;