[PATCH V2 1/2] Btrfs: fix error path in create_pending_snapshot()

[Miao Xie <miaox@cn.fujitsu.com>]

This patch fixes the following problem:
- If we failed to deal with the delayed dir items, we should abort transaction,
  just as its comment said. Fix it.
- If root reference or root back reference insertion failed, we should
  abort transaction. Fix it.
- Do not restore the trans->rsv if we doesn't change it.
- make the error path more clearly.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
Changelog v1 -> v2:
- fix double dput() when aborting transaction. In the previous version of the patches,
  this problem was fixed in the second patch, it is not good because this problem is
  the bug of the patch in fact. 
---
 fs/btrfs/transaction.c |   37 ++++++++++++++++---------------------
 1 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index b72b068..4d579fe 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -932,18 +932,16 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	u64 objectid;
 	u64 root_flags;
 
-	rsv = trans->block_rsv;
-
 	new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
 	if (!new_root_item) {
 		ret = pending->error = -ENOMEM;
-		goto fail;
+		goto root_item_alloc_fail;
 	}
 
 	ret = btrfs_find_free_objectid(tree_root, &objectid);
 	if (ret) {
 		pending->error = ret;
-		goto fail;
+		goto no_free_objectid;
 	}
 
 	btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
@@ -953,7 +951,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 						  to_reserve);
 		if (ret) {
 			pending->error = ret;
-			goto fail;
+			goto no_free_objectid;
 		}
 	}
 
@@ -961,6 +959,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	key.offset = (u64)-1;
 	key.type = BTRFS_ROOT_ITEM_KEY;
 
+	rsv = trans->block_rsv;
 	trans->block_rsv = &pending->block_rsv;
 
 	dentry = pending->dentry;
@@ -980,17 +979,16 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 				BTRFS_FT_DIR, index);
 	if (ret == -EEXIST) {
 		pending->error = -EEXIST;
-		dput(parent);
 		goto fail;
 	} else if (ret) {
-		goto abort_trans_dput;
+		goto abort_trans;
 	}
 
 	btrfs_i_size_write(parent_inode, parent_inode->i_size +
 					 dentry->d_name.len * 2);
 	ret = btrfs_update_inode(trans, parent_root, parent_inode);
 	if (ret)
-		goto abort_trans_dput;
+		goto abort_trans;
 
 	/*
 	 * pull in the delayed directory update
@@ -999,10 +997,8 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	 * snapshot
 	 */
 	ret = btrfs_run_delayed_items(trans, root);
-	if (ret) { /* Transaction aborted */
-		dput(parent);
-		goto fail;
-	}
+	if (ret)	/* Transaction aborted */
+		goto abort_trans;
 
 	record_root_in_trans(trans, root);
 	btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
@@ -1021,7 +1017,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	if (ret) {
 		btrfs_tree_unlock(old);
 		free_extent_buffer(old);
-		goto abort_trans_dput;
+		goto abort_trans;
 	}
 
 	btrfs_set_lock_blocking(old);
@@ -1031,7 +1027,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	btrfs_tree_unlock(old);
 	free_extent_buffer(old);
 	if (ret)
-		goto abort_trans_dput;
+		goto abort_trans;
 
 	/* see comments in should_cow_block() */
 	root->force_cow = 1;
@@ -1044,7 +1040,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	btrfs_tree_unlock(tmp);
 	free_extent_buffer(tmp);
 	if (ret)
-		goto abort_trans_dput;
+		goto abort_trans;
 
 	/*
 	 * insert root back/forward references
@@ -1053,9 +1049,8 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 				 parent_root->root_key.objectid,
 				 btrfs_ino(parent_inode), index,
 				 dentry->d_name.name, dentry->d_name.len);
-	dput(parent);
 	if (ret)
-		goto fail;
+		goto abort_trans;
 
 	key.offset = (u64)-1;
 	pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);
@@ -1067,15 +1062,15 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	ret = btrfs_reloc_post_snapshot(trans, pending);
 	if (ret)
 		goto abort_trans;
-	ret = 0;
 fail:
-	kfree(new_root_item);
+	dput(parent);
 	trans->block_rsv = rsv;
+no_free_objectid:
+	kfree(new_root_item);
+root_item_alloc_fail:
 	btrfs_block_rsv_release(root, &pending->block_rsv, (u64)-1);
 	return ret;
 
-abort_trans_dput:
-	dput(parent);
 abort_trans:
 	btrfs_abort_transaction(trans, root, ret);
 	goto fail;
-- 
1.7.6.5