Re: [PATCH 2/4] Btrfs-progs: fsck: disallow partial opening if critical roots corrupted

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

-------- Original Message --------
Subject: [PATCH 2/4] Btrfs-progs: fsck: disallow partial opening if 
critical roots corrupted
From: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
To: linux-btrfs@vger.kernel.org
Date: 2014年05月28日 19:20
> If btrfs tree root is corrupted, fsck will hit the following segmentation.
>
> enabling repair mode
> Check tree block failed, want=29376512, have=0
> Check tree block failed, want=29376512, have=0
> Check tree block failed, want=29376512, have=0
> Check tree block failed, want=29376512, have=0
> Check tree block failed, want=29376512, have=0
> read block failed check_tree_block
> Couldn't read tree root
> Checking filesystem on /dev/sda9
> UUID: 0e1a754d-04a5-4256-ae79-0f769751803e
> Critical roots corrupted, unable to fsck the FS
> Segmentation fault (core dumped)
>
> In btrfs_setup_all_roots(), we could tolerate some trees(extent tree, csum tree)
> corrupted, and we have did careful check inside that function, it will
> return NULL if critial roots corrupt(for example tree root).
>
> The problem is that we check @OPEN_CTREE_PARTIAL flag again after
> calling btrfs_setup_all_roots() which will successfully return
> @fs_info though critial roots corrupted.
>
> Fix this problem by removing @OPEN_CTREE_PARTIAL flag check outsize
> btrfs_setup_all_roots().
>
> Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
> ---
>   disk-io.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/disk-io.c b/disk-io.c
> index 58f3f07..63e153d 100644
> --- a/disk-io.c
> +++ b/disk-io.c
> @@ -1134,13 +1134,10 @@ static struct btrfs_fs_info *__open_ctree_fd(int fp, const char *path,
>   
>   	ret = btrfs_setup_all_roots(fs_info, root_tree_bytenr, flags);
>   	if (ret)
> -		goto out_failed;
> +		goto out_chunk;
>   
>   	return fs_info;
>   
> -out_failed:
> -	if (flags & OPEN_CTREE_PARTIAL)
> -		return fs_info;
>   out_chunk:
>   	btrfs_release_all_roots(fs_info);
>   	btrfs_cleanup_all_caches(fs_info);
Tested-by: Qu Wenruo <quwenruo@cn.fujitsu.com>

This patch fixed a lot of segfault when checking fsfuzzed btrfs image.

Thanks,
Qu