btrfs: remove trivial wrapper btrfs_read_buffer()

The function btrfs_read_buffer() is useless, it just calls
btree_read_extent_buffer_pages() with exactly the same arguments.

So remove it and rename btree_read_extent_buffer_pages() to
btrfs_read_extent_buffer(), which is a shorter name, has the "btrfs_"
prefix (since it's used outside disk-io.c) and the name is clear enough
about what it does.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 31c3f59..3ad84fe 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -374,9 +374,9 @@ int btrfs_verify_level_key(struct extent_buffer *eb, int level,
  * @level:		expected level, mandatory check
  * @first_key:		expected key of first slot, skip check if NULL
  */
-static int btree_read_extent_buffer_pages(struct extent_buffer *eb,
-					  u64 parent_transid, int level,
-					  struct btrfs_key *first_key)
+int btrfs_read_extent_buffer(struct extent_buffer *eb,
+			     u64 parent_transid, int level,
+			     struct btrfs_key *first_key)
 {
 	struct btrfs_fs_info *fs_info = eb->fs_info;
 	struct extent_io_tree *io_tree;
@@ -1118,8 +1118,7 @@ struct extent_buffer *read_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr,
 	if (IS_ERR(buf))
 		return buf;
 
-	ret = btree_read_extent_buffer_pages(buf, parent_transid,
-					     level, first_key);
+	ret = btrfs_read_extent_buffer(buf, parent_transid, level, first_key);
 	if (ret) {
 		free_extent_buffer_stale(buf);
 		return ERR_PTR(ret);
@@ -4862,13 +4861,6 @@ void btrfs_btree_balance_dirty_nodelay(struct btrfs_fs_info *fs_info)
 	__btrfs_btree_balance_dirty(fs_info, 0);
 }
 
-int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid, int level,
-		      struct btrfs_key *first_key)
-{
-	return btree_read_extent_buffer_pages(buf, parent_transid,
-					      level, first_key);
-}
-
 static void btrfs_error_commit_super(struct btrfs_fs_info *fs_info)
 {
 	/* cleanup FS via transaction */