Squashfs: add missing block release on error condition

squashfs_read_metadata forgets to release the cache block if
an error has occurred.
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>

fs/squashfs/cache.c

@@ -332,17 +332,20 @@ int squashfs_read_metadata(struct super_block *sb, void *buffer,
 		u64 *block, int *offset, int length)
 {
 	struct squashfs_sb_info *msblk = sb->s_fs_info;
-	int bytes, copied = length;
+	int bytes, res = length;
 	struct squashfs_cache_entry *entry;
 
 	TRACE("Entered squashfs_read_metadata [%llx:%x]\n", *block, *offset);
 
 	while (length) {
 		entry = squashfs_cache_get(sb, msblk->block_cache, *block, 0);
-		if (entry->error)
-			return entry->error;
-		else if (*offset >= entry->length)
-			return -EIO;
+		if (entry->error) {
+			res = entry->error;
+			goto error;
+		} else if (*offset >= entry->length) {
+			res = -EIO;
+			goto error;
+		}
 
 		bytes = squashfs_copy_data(buffer, entry, *offset, length);
 		if (buffer)
@@ -358,7 +361,11 @@ int squashfs_read_metadata(struct super_block *sb, void *buffer,
 		squashfs_cache_put(entry);
 	}
 
-	return copied;
+	return res;
+
+error:
+	squashfs_cache_put(entry);
+	return res;
 }