btrfs-progs: Allow open_ctree to return fs_info even chunk tree is corrupted

Current open_ctree_fs_info() won't return anything if chunk tree root is
corrupted.
This makes some function, like btrfs-find-root, unable to find any older
chunk tree root, even it is possible to use system_chunk_array in super
block.

And at least two users in mail list has reported such heavily chunk
corruption.
Although we have 'btrfs rescue chunk-recovery' but it's too time
consuming and sometimes not able to cope with a specific filesystem
corruption.

This patch adds a new open ctree flag,
OPEN_CTREE_IGNORE_CHUNK_TREE_ERROR, allowing fs_info to be returned from
open_ctree_fs_info() even there is no valid tree root in it.

Also adds a new close_ctree() variant, close_ctree_fs_info() to handle
possible fs_info without any root.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
[ adjusted error messages ]
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/ctree.h b/ctree.h
index 21b04458..5ab0f4a4 100644
--- a/ctree.h
+++ b/ctree.h
@@ -1029,6 +1029,7 @@ struct btrfs_fs_info {
 	unsigned int quota_enabled:1;
 	unsigned int suppress_check_block_errors:1;
 	unsigned int ignore_fsid_mismatch:1;
+	unsigned int ignore_chunk_tree_error:1;
 
 	int (*free_extent_hook)(struct btrfs_trans_handle *trans,
 				struct btrfs_root *root,