btrfs: unify the error handling pattern for read_tree_block()

We had an error handling pattern for read_tree_block() like this:

	eb = read_tree_block();
	if (IS_ERR(eb)) {
		/*
		 * Handling error here
		 * Normally ended up with return or goto out.
		 */
	} else if (!extent_buffer_uptodate(eb)) {
		/*
		 * Different error handling here
		 * Normally also ended up with return or goto out;
		 */
	}

This is fine, but if we want to add extra check for each
read_tree_block(), the existing if-else-if is not that expandable and
will take reader some seconds to figure out there is no extra branch.

Here we change it to a more common way, without the extra else:

	eb = read_tree_block();
	if (IS_ERR(eb)) {
		/*
		 * Handling error here
		 */
		return eb or goto out;
	}
	if (!extent_buffer_uptodate(eb)) {
		/*
		 * Different error handling here
		 */
		return eb or goto out;
	}

This also removes some oddball call sites which uses some creative way
to check error.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/backref.c

@@ -789,11 +789,13 @@ static int add_missing_keys(struct btrfs_fs_info *fs_info,
 		if (IS_ERR(eb)) {
 			free_pref(ref);
 			return PTR_ERR(eb);
-		} else if (!extent_buffer_uptodate(eb)) {
+		}
+		if (!extent_buffer_uptodate(eb)) {
 			free_pref(ref);
 			free_extent_buffer(eb);
 			return -EIO;
 		}
+
 		if (lock)
 			btrfs_tree_read_lock(eb);
 		if (btrfs_header_level(eb) == 0)
@@ -1335,7 +1337,8 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
 				if (IS_ERR(eb)) {
 					ret = PTR_ERR(eb);
 					goto out;
-				} else if (!extent_buffer_uptodate(eb)) {
+				}
+				if (!extent_buffer_uptodate(eb)) {
 					free_extent_buffer(eb);
 					ret = -EIO;
 					goto out;

fs/btrfs/ctree.c

@@ -846,9 +846,11 @@ struct extent_buffer *btrfs_read_node_slot(struct extent_buffer *parent,
 			     btrfs_header_owner(parent),
 			     btrfs_node_ptr_generation(parent, slot),
 			     level - 1, &first_key);
-	if (!IS_ERR(eb) && !extent_buffer_uptodate(eb)) {
+	if (IS_ERR(eb))
+		return eb;
+	if (!extent_buffer_uptodate(eb)) {
 		free_extent_buffer(eb);
-		eb = ERR_PTR(-EIO);
+		return ERR_PTR(-EIO);
 	}
 
 	return eb;
@@ -1460,19 +1462,19 @@ read_block_for_search(struct btrfs_root *root, struct btrfs_path *p,
 	ret = -EAGAIN;
 	tmp = read_tree_block(fs_info, blocknr, root->root_key.objectid,
 			      gen, parent_level - 1, &first_key);
-	if (!IS_ERR(tmp)) {
-		/*
-		 * If the read above didn't mark this buffer up to date,
-		 * it will never end up being up to date.  Set ret to EIO now
-		 * and give up so that our caller doesn't loop forever
-		 * on our EAGAINs.
-		 */
-		if (!extent_buffer_uptodate(tmp))
-			ret = -EIO;
-		free_extent_buffer(tmp);
-	} else {
-		ret = PTR_ERR(tmp);
+	if (IS_ERR(tmp)) {
+		btrfs_release_path(p);
+		return PTR_ERR(tmp);
 	}
+	/*
+	 * If the read above didn't mark this buffer up to date,
+	 * it will never end up being up to date.  Set ret to EIO now
+	 * and give up so that our caller doesn't loop forever
+	 * on our EAGAINs.
+	 */
+	if (!extent_buffer_uptodate(tmp))
+		ret = -EIO;
+	free_extent_buffer(tmp);
 
 	btrfs_release_path(p);
 	return ret;

fs/btrfs/disk-io.c

@@ -1543,7 +1543,8 @@ static struct btrfs_root *read_tree_root_path(struct btrfs_root *tree_root,
 		ret = PTR_ERR(root->node);
 		root->node = NULL;
 		goto fail;
-	} else if (!btrfs_buffer_uptodate(root->node, generation, 0)) {
+	}
+	if (!btrfs_buffer_uptodate(root->node, generation, 0)) {
 		ret = -EIO;
 		goto fail;
 	}
@@ -2537,11 +2538,13 @@ static int btrfs_replay_log(struct btrfs_fs_info *fs_info,
 		log_tree_root->node = NULL;
 		btrfs_put_root(log_tree_root);
 		return ret;
-	} else if (!extent_buffer_uptodate(log_tree_root->node)) {
+	}
+	if (!extent_buffer_uptodate(log_tree_root->node)) {
 		btrfs_err(fs_info, "failed to read log tree");
 		btrfs_put_root(log_tree_root);
 		return -EIO;
 	}
+
 	/* returns with log_tree_root freed on success */
 	ret = btrfs_recover_log_trees(log_tree_root);
 	if (ret) {
@@ -2983,15 +2986,14 @@ static int load_super_root(struct btrfs_root *root, u64 bytenr, u64 gen, int lev
 	if (IS_ERR(root->node)) {
 		ret = PTR_ERR(root->node);
 		root->node = NULL;
-	} else if (!extent_buffer_uptodate(root->node)) {
+		return ret;
+	}
+	if (!extent_buffer_uptodate(root->node)) {
 		free_extent_buffer(root->node);
 		root->node = NULL;
-		ret = -EIO;
+		return -EIO;
 	}
 
-	if (ret)
-		return ret;
-
 	btrfs_set_root_node(&root->root_item, root->node);
 	root->commit_root = btrfs_root_node(root);
 	btrfs_set_root_refs(&root->root_item, 1);

fs/btrfs/print-tree.c

@@ -392,9 +392,9 @@ void btrfs_print_tree(struct extent_buffer *c, bool follow)
 				       btrfs_header_owner(c),
 				       btrfs_node_ptr_generation(c, i),
 				       level - 1, &first_key);
-		if (IS_ERR(next)) {
+		if (IS_ERR(next))
 			continue;
-		} else if (!extent_buffer_uptodate(next)) {
+		if (!extent_buffer_uptodate(next)) {
 			free_extent_buffer(next);
 			continue;
 		}

fs/btrfs/relocation.c

@@ -2599,9 +2599,9 @@ static int get_tree_block_key(struct btrfs_fs_info *fs_info,
 
 	eb = read_tree_block(fs_info, block->bytenr, block->owner,
 			     block->key.offset, block->level, NULL);
-	if (IS_ERR(eb)) {
+	if (IS_ERR(eb))
 		return PTR_ERR(eb);
-	} else if (!extent_buffer_uptodate(eb)) {
+	if (!extent_buffer_uptodate(eb)) {
 		free_extent_buffer(eb);
 		return -EIO;
 	}