ext2: ext2_find_entry() return -ENOENT if no entry found

Almost all callers of ext2_find_entry() transform NULL return value to
-ENOENT, so just let ext2_find_entry() retuen -ENOENT instead of NULL
if no valid entry found, and also switch to check the return value of
ext2_inode_by_name() in ext2_lookup() and ext2_get_parent().

Link: https://lore.kernel.org/r/20200608034043.10451-2-yi.zhang@huawei.comSigned-off-by: zhangyi (F) <yi.zhang@huawei.com>
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext2/dir.c

@@ -393,7 +393,7 @@ struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
 		}
 	} while (n != start);
 out:
-	return NULL;
+	return ERR_PTR(-ENOENT);
 
 found:
 	*res_page = page;
@@ -419,7 +419,7 @@ int ext2_inode_by_name(struct inode *dir, const struct qstr *child, ino_t *ino)
 	struct page *page;
 	
 	de = ext2_find_entry(dir, child, &page);
-	if (IS_ERR_OR_NULL(de))
+	if (IS_ERR(de))
 		return PTR_ERR(de);
 
 	*ino = le32_to_cpu(de->inode);

fs/ext2/namei.c

@@ -56,17 +56,18 @@ static inline int ext2_add_nondir(struct dentry *dentry, struct inode *inode)
 static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, unsigned int flags)
 {
 	struct inode * inode;
-	ino_t ino = 0;
+	ino_t ino;
 	int res;
 	
 	if (dentry->d_name.len > EXT2_NAME_LEN)
 		return ERR_PTR(-ENAMETOOLONG);
 
 	res = ext2_inode_by_name(dir, &dentry->d_name, &ino);
-	if (res)
+	if (res) {
+		if (res != -ENOENT)
 			return ERR_PTR(res);
 		inode = NULL;
-	if (ino) {
+	} else {
 		inode = ext2_iget(dir->i_sb, ino);
 		if (inode == ERR_PTR(-ESTALE)) {
 			ext2_error(dir->i_sb, __func__,
@@ -81,14 +82,13 @@ static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, uns
 struct dentry *ext2_get_parent(struct dentry *child)
 {
 	struct qstr dotdot = QSTR_INIT("..", 2);
-	ino_t ino = 0;
+	ino_t ino;
 	int res;
 
 	res = ext2_inode_by_name(d_inode(child), &dotdot, &ino);
 	if (res)
 		return ERR_PTR(res);
-	if (!ino)
-		return ERR_PTR(-ENOENT);
+
 	return d_obtain_alias(ext2_iget(child->d_sb, ino));
 } 
 
@@ -287,10 +287,6 @@ static int ext2_unlink(struct inode * dir, struct dentry *dentry)
 		err = PTR_ERR(de);
 		goto out;
 	}
-	if (!de) {
-		err = -ENOENT;
-		goto out;
-	}
 
 	err = ext2_delete_entry (de, page);
 	if (err)
@@ -347,10 +343,6 @@ static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
 		err = PTR_ERR(old_de);
 		goto out;
 	}
-	if (!old_de) {
-		err = -ENOENT;
-		goto out;
-	}
 
 	if (S_ISDIR(old_inode->i_mode)) {
 		err = -EIO;
@@ -367,14 +359,11 @@ static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
 		if (dir_de && !ext2_empty_dir (new_inode))
 			goto out_dir;
 
-		err = -ENOENT;
 		new_de = ext2_find_entry(new_dir, &new_dentry->d_name, &new_page);
 		if (IS_ERR(new_de)) {
 			err = PTR_ERR(new_de);
 			goto out_dir;
 		}
-		if (!new_de)
-			goto out_dir;
 		ext2_set_link(new_dir, new_de, new_page, old_inode, 1);
 		new_inode->i_ctime = current_time(new_inode);
 		if (dir_de)