btrfs: simplify setting the full backref flag at update_ref_for_cow()

We keep a "new_flags" variable only to keep track if we need to update the
metadata extent's flags, and when we set BTRFS_BLOCK_FLAG_FULL_BACKREF in
the variable, we do it in an inner scope. Then check in an outer scope
if the variable is not 0 and if so call btrfs_set_disk_extent_flags().
The variable isn't used for anything else. This is somewhat confusing, so
to make it more straightforward update the extent's flags where we are
currently updating "new_flags" and remove the variable.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.c

@@ -417,7 +417,6 @@ static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
 	u64 refs;
 	u64 owner;
 	u64 flags;
-	u64 new_flags = 0;
 	int ret;
 
 	/*
@@ -481,7 +480,10 @@ static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
 				if (ret)
 					return ret;
 			}
-			new_flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
+			ret = btrfs_set_disk_extent_flags(trans, buf,
+						  BTRFS_BLOCK_FLAG_FULL_BACKREF);
+			if (ret)
+				return ret;
 		} else {
 
 			if (btrfs_root_id(root) == BTRFS_TREE_RELOC_OBJECTID)
@@ -491,11 +493,6 @@ static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
 			if (ret)
 				return ret;
 		}
-		if (new_flags != 0) {
-			ret = btrfs_set_disk_extent_flags(trans, buf, new_flags);
-			if (ret)
-				return ret;
-		}
 	} else {
 		if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
 			if (btrfs_root_id(root) == BTRFS_TREE_RELOC_OBJECTID)