[PATCH] Btrfs-progs: let btrfs-image actually work on a balanced fs

[Josef Bacik <jbacik@fb.com>]

We use the read extent buffer infrastructure to read the super block when we are
creating a btrfs-image.  This works out fine most of the time except when the fs
has been balanced, then it fails to map the super block.  So we could fix
btrfs-image to read in the super in a special way, but thats more code.  So
instead just check in the eb reading code if we are reading the super and then
don't bother mapping the block, just read the actual offset.  This fixed some
poor guy who was trying to btrfs-image his fs that had been balanced.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 btrfs-image.c | 5 ++++-
 disk-io.c     | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/btrfs-image.c b/btrfs-image.c
index cb17f16..6643ad1 100644
--- a/btrfs-image.c
+++ b/btrfs-image.c
@@ -1020,6 +1020,9 @@ static int copy_tree_blocks(struct btrfs_root *root, struct extent_buffer *eb,
 	int i = 0;
 	int ret;
 
+	if (btrfs_header_bytenr(eb) == 65536)
+		printf("We have bytenr 65536, belongs to %llu, level %d\n",
+		       btrfs_header_owner(eb), btrfs_header_level(eb));
 	ret = add_extent(btrfs_header_bytenr(eb), root->leafsize, metadump, 0);
 	if (ret) {
 		fprintf(stderr, "Error adding metadata block\n");
@@ -1279,7 +1282,7 @@ static int create_metadump(const char *input, FILE *out, int num_threads,
 	}
 
 	ret = add_extent(BTRFS_SUPER_INFO_OFFSET, BTRFS_SUPER_INFO_SIZE,
-			&metadump, 0);
+			&metadump, 1);
 	if (ret) {
 		fprintf(stderr, "Error adding metadata %d\n", ret);
 		err = ret;
diff --git a/disk-io.c b/disk-io.c
index 26a532e..34c0a97 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -201,7 +201,8 @@ int read_whole_eb(struct btrfs_fs_info *info, struct extent_buffer *eb, int mirr
 		read_len = bytes_left;
 		device = NULL;
 
-		if (!info->on_restoring) {
+		if (!info->on_restoring &&
+		    eb->start != BTRFS_SUPER_INFO_OFFSET) {
 			ret = btrfs_map_block(&info->mapping_tree, READ,
 					      eb->start + offset, &read_len, &multi,
 					      mirror, NULL);
-- 
1.9.3