Btrfs: fix up read_tree_block to return proper error

The return value of read_tree_block() can confuse callers as it always
returns NULL for either -ENOMEM or -EIO, so it's likely that callers
parse it to a wrong error, for instance, in btrfs_read_tree_root().

This fixes the above issue.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 15 insertions, 13 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 2ef9a4b72d06..7f8377871283 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1149,12 +1149,12 @@ struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
 
 	buf = btrfs_find_create_tree_block(root, bytenr);
 	if (!buf)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	ret = btree_read_extent_buffer_pages(root, buf, 0, parent_transid);
 	if (ret) {
 		free_extent_buffer(buf);
-		return NULL;
+		return ERR_PTR(ret);
 	}
 	return buf;
 
@@ -1509,20 +1509,19 @@ static struct btrfs_root *btrfs_read_tree_root(struct btrfs_root *tree_root,
 	generation = btrfs_root_generation(&root->root_item);
 	root->node = read_tree_block(root, btrfs_root_bytenr(&root->root_item),
 				     generation);
-	if (!root->node) {
-		ret = -ENOMEM;
+	if (IS_ERR(root->node)) {
+		ret = PTR_ERR(root->node);
 		goto find_fail;
 	} else if (!btrfs_buffer_uptodate(root->node, generation, 0)) {
 		ret = -EIO;
-		goto read_fail;
+		free_extent_buffer(root->node);
+		goto find_fail;
 	}
 	root->commit_root = btrfs_root_node(root);
 out:
 	btrfs_free_path(path);
 	return root;
 
-read_fail:
-	free_extent_buffer(root->node);
 find_fail:
 	kfree(root);
 alloc_fail:
@@ -2320,8 +2319,11 @@ static int btrfs_replay_log(struct btrfs_fs_info *fs_info,
 
 	log_tree_root->node = read_tree_block(tree_root, bytenr,
 			fs_info->generation + 1);
-	if (!log_tree_root->node ||
-	    !extent_buffer_uptodate(log_tree_root->node)) {
+	if (IS_ERR(log_tree_root->node)) {
+		printk(KERN_ERR "BTRFS: failed to read log tree\n");
+		kfree(log_tree_root);
+		return PTR_ERR(log_tree_root->node);
+	} else if (!extent_buffer_uptodate(log_tree_root->node)) {
 		printk(KERN_ERR "BTRFS: failed to read log tree\n");
 		free_extent_buffer(log_tree_root->node);
 		kfree(log_tree_root);
@@ -2797,8 +2799,8 @@ int open_ctree(struct super_block *sb,
 	chunk_root->node = read_tree_block(chunk_root,
 					   btrfs_super_chunk_root(disk_super),
 					   generation);
-	if (!chunk_root->node ||
-	    !test_bit(EXTENT_BUFFER_UPTODATE, &chunk_root->node->bflags)) {
+	if (IS_ERR(chunk_root->node) ||
+	    !extent_buffer_uptodate(chunk_root->node)) {
 		printk(KERN_ERR "BTRFS: failed to read chunk root on %s\n",
 		       sb->s_id);
 		goto fail_tree_roots;
@@ -2834,8 +2836,8 @@ retry_root_backup:
 	tree_root->node = read_tree_block(tree_root,
 					  btrfs_super_root(disk_super),
 					  generation);
-	if (!tree_root->node ||
-	    !test_bit(EXTENT_BUFFER_UPTODATE, &tree_root->node->bflags)) {
+	if (IS_ERR(tree_root->node) ||
+	    !extent_buffer_uptodate(tree_root->node)) {
 		printk(KERN_WARNING "BTRFS: failed to read tree root on %s\n",
 		       sb->s_id);