File 2104-btrfs-progs-Check-metadata-mirrors-in-find-root.patch of Package btrfsprogs.356

From 4469ed43b26b6e7d5ad5cfea45e99708e39de4a6 Mon Sep 17 00:00:00 2001
From: David Marcin <djmarcin@google.com>
Date: Wed, 16 Nov 2011 12:18:08 -0800
Subject: [PATCH 169/170] btrfs-progs: Check metadata mirrors in find-root.

Signed-off-by: David Marcin <djmarcin@google.com>
---
 btrfs-find-root.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

Index: btrfs-progs-v3.14/btrfs-find-root.c
===================================================================
--- btrfs-progs-v3.14.orig/btrfs-find-root.c
+++ btrfs-progs-v3.14/btrfs-find-root.c
@@ -230,6 +230,8 @@ static int find_root(struct btrfs_root *
 	while (1) {
 		u64 map_length = 4096;
 		u64 type;
+		int mirror_num;
+		int num_copies;
 
 		if (offset >
 		    btrfs_super_total_bytes(root->fs_info->super_copy)) {
@@ -246,9 +248,11 @@ static int find_root(struct btrfs_root *
 			}
 			offset = metadata_offset;
 		}
+		mirror_num = 1;
+	again:
 		err = __btrfs_map_block(&root->fs_info->mapping_tree, READ,
 				      offset, &map_length, &type,
-				      &multi, 0, NULL);
+				      &multi, mirror_num, NULL);
 		if (err) {
 			offset += map_length;
 			continue;
@@ -267,9 +271,16 @@ static int find_root(struct btrfs_root *
 
 		err = read_physical(root, fd, offset, bytenr, map_length);
 		if (!err) {
+			/* Found the root. */
 			ret = 0;
 			break;
 		} else if (err < 0) {
+			num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
+						      offset, map_length);
+			mirror_num++;
+			if (mirror_num <= num_copies)
+				goto again;
+			/* Unrecoverable error in read. */
 			ret = err;
 			break;
 		}