f2fs: fix error path of ->symlink

Now, in ->symlink of f2fs, we kept the fixed invoking order between
f2fs_add_link and page_symlink since we should init node info firstly
in f2fs_add_link, then such node info can be used in page_symlink.

But we didn't fix to release meta info which was done before page_symlink
in our error path, so this will leave us corrupt symlink entry in its
parent's dentry page. Fix this issue by adding f2fs_unlink in the error
path for removing such linking.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/namei.c

@@ -410,11 +410,14 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
 	 * If the symlink path is stored into inline_data, there is no
 	 * performance regression.
 	 */
-	if (!err)
+	if (!err) {
 		filemap_write_and_wait_range(inode->i_mapping, 0, p_len - 1);
 
-	if (IS_DIRSYNC(dir))
-		f2fs_sync_fs(sbi->sb, 1);
+		if (IS_DIRSYNC(dir))
+			f2fs_sync_fs(sbi->sb, 1);
+	} else {
+		f2fs_unlink(dir, dentry);
+	}
 
 	kfree(sd);
 	f2fs_fname_crypto_free_buffer(&disk_link);