Btrfs: cleanup to make the function btrfs_delalloc_reserve_metadata more logic

The original code is a little confusing and not clear, The right
way to deal with the kernel code like this:
		[...]
		if (ret)
			goto out;
		[...]

So i move the common clean_up code to the place labeled with
out_fail, this will be easier to maintain.
Signed-off-by: NWang Shilong <wangsl-fnst@cn.fujitsu.com>
Signed-off-by: NJosef Bacik <jbacik@fusionio.com>

fs/btrfs/extent-tree.c

@@ -4721,6 +4721,8 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
 	enum btrfs_reserve_flush_enum flush = BTRFS_RESERVE_FLUSH_ALL;
 	int ret = 0;
 	bool delalloc_lock = true;
+	u64 to_free = 0;
+	unsigned dropped;
 
 	/* If we are a free space inode we need to not flush since we will be in
 	 * the middle of a transaction commit.  We also don't need the delalloc
@@ -4764,27 +4766,41 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
 	csum_bytes = BTRFS_I(inode)->csum_bytes;
 	spin_unlock(&BTRFS_I(inode)->lock);
 
-	if (root->fs_info->quota_enabled)
+	if (root->fs_info->quota_enabled) {
 		ret = btrfs_qgroup_reserve(root, num_bytes +
 					   nr_extents * root->leafsize);
+		if (ret)
+			goto out_fail;
+	}
 
-	/*
-	 * ret != 0 here means the qgroup reservation failed, we go straight to
-	 * the shared error handling then.
-	 */
-	if (ret == 0) {
-		ret = reserve_metadata_bytes(root, block_rsv,
-					     to_reserve, flush);
-		if (ret && root->fs_info->quota_enabled) {
+	ret = reserve_metadata_bytes(root, block_rsv, to_reserve, flush);
+	if (unlikely(ret)) {
+		if (root->fs_info->quota_enabled)
 			btrfs_qgroup_free(root, num_bytes +
 						nr_extents * root->leafsize);
+		goto out_fail;
 	}
+
+	spin_lock(&BTRFS_I(inode)->lock);
+	if (extra_reserve) {
+		set_bit(BTRFS_INODE_DELALLOC_META_RESERVED,
+			&BTRFS_I(inode)->runtime_flags);
+		nr_extents--;
 	}
+	BTRFS_I(inode)->reserved_extents += nr_extents;
+	spin_unlock(&BTRFS_I(inode)->lock);
 
-	if (ret) {
-		u64 to_free = 0;
-		unsigned dropped;
+	if (delalloc_lock)
+		mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
 
+	if (to_reserve)
+		trace_btrfs_space_reservation(root->fs_info,"delalloc",
+					      btrfs_ino(inode), to_reserve, 1);
+	block_rsv_add_bytes(block_rsv, to_reserve, 1);
+
+	return 0;
+
+out_fail:
 	spin_lock(&BTRFS_I(inode)->lock);
 	dropped = drop_outstanding_extent(inode);
 	/*
@@ -4805,34 +4821,12 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
 
 	if (to_free) {
 		btrfs_block_rsv_release(root, block_rsv, to_free);
-			trace_btrfs_space_reservation(root->fs_info,
-						      "delalloc",
-						      btrfs_ino(inode),
-						      to_free, 0);
+		trace_btrfs_space_reservation(root->fs_info, "delalloc",
+					      btrfs_ino(inode), to_free, 0);
 	}
 	if (delalloc_lock)
 		mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
 	return ret;
-	}
-
-	spin_lock(&BTRFS_I(inode)->lock);
-	if (extra_reserve) {
-		set_bit(BTRFS_INODE_DELALLOC_META_RESERVED,
-			&BTRFS_I(inode)->runtime_flags);
-		nr_extents--;
-	}
-	BTRFS_I(inode)->reserved_extents += nr_extents;
-	spin_unlock(&BTRFS_I(inode)->lock);
-
-	if (delalloc_lock)
-		mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
-
-	if (to_reserve)
-		trace_btrfs_space_reservation(root->fs_info,"delalloc",
-					      btrfs_ino(inode), to_reserve, 1);
-	block_rsv_add_bytes(block_rsv, to_reserve, 1);
-
-	return 0;
 }
 
 /**