Re: [Bisect] ext4_validate_inode_bitmap:98: comm stress-ng: Corrupt inode bitmap

[dann frazier <dann.frazier@canonical.com>]

On Thu, Jul 12, 2018 at 5:08 PM Theodore Y. Ts'o <tytso@mit.edu> wrote:
>
> >
> > Review console log and on each run I have filesystem rebuild. The problem
> > is that mke2fs I am using is 1.44.3-rc2. I am now reseting the environment
> > and re-test.
> >
>
> Could it be that you saw the error in ext4_validate_block_bitmap()?

Looks like it. From Ike's report:

# grep EXT4 d05-4-ipmi.log
[ 26.215587] EXT4-fs (sdb2): mounted filesystem with ordered data
mode. Opts: (null)
[ 29.844105] EXT4-fs (sdb2): re-mounted. Opts: errors=remount-ro
[ 3586.211348] EXT4-fs error (device sda2):
ext4_validate_block_bitmap:383: comm stress-ng: bg 4705: bad block
bitmap checksum
[ 8254.776992] EXT4-fs error (device sda2):
ext4_validate_block_bitmap:383: comm stress-ng: bg 4193: bad block
bitmap checksum

I've ran my test case for several days w/ just the inode bitmap fix
and haven't been able to reproduce it - but perhaps that's just the
nature of the chdir test.

> The patch which I sent Dann only fixed the problem for inode bitmaps;
> I noticed today that we need to fix it for block allocation bitmaps as
> well.

I've also now ran several iterations w/ the block bitmap fix as well,
and still no problems, so:

Tested-by: dann frazier <dann.frazier@canonical.com>

> commit 8d5a803c6a6ce4ec258e31f76059ea5153ba46ef
> Author: Theodore Ts'o <tytso@mit.edu>
> Date:   Thu Jul 12 19:08:05 2018 -0400
>
>     ext4: check for allocation block validity with block group locked
>
>     With commit 044e6e3d74a3: "ext4: don't update checksum of new
>     initialized bitmaps" the buffer valid bit will get set without
>     actually setting up the checksum for the allocation bitmap, since the
>     checksum will get calculated once we actually allocate an inode or
>     block.
>
>     If we are doing this, then we need to (re-)check the verified bit
>     after we take the block group lock.  Otherwise, we could race with
>     another process reading and verifying the bitmap, which would then
>     complain about the checksum being invalid.
>
>     https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1780137
>
>     Signed-off-by: Theodore Ts'o <tytso@mit.edu>
>     Cc: stable@kernel.org

Would it also make sense to add the following?

Fixes: 044e6e3d74a3 ("ext4: don't update checksum of new initialized bitmaps")

  -dann

> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
> index e68cefe08261..aa52d87985aa 100644
> --- a/fs/ext4/balloc.c
> +++ b/fs/ext4/balloc.c
> @@ -368,6 +368,8 @@ static int ext4_validate_block_bitmap(struct super_block *sb,
>                 return -EFSCORRUPTED;
>
>         ext4_lock_group(sb, block_group);
> +       if (buffer_verified(bh))
> +               goto verified;
>         if (unlikely(!ext4_block_bitmap_csum_verify(sb, block_group,
>                         desc, bh))) {
>                 ext4_unlock_group(sb, block_group);
> @@ -386,6 +388,7 @@ static int ext4_validate_block_bitmap(struct super_block *sb,
>                 return -EFSCORRUPTED;
>         }
>         set_buffer_verified(bh);
> +verified:
>         ext4_unlock_group(sb, block_group);
>         return 0;
>  }
> diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> index fb83750c1a14..e9d8e2667ab5 100644
> --- a/fs/ext4/ialloc.c
> +++ b/fs/ext4/ialloc.c
> @@ -90,6 +90,8 @@ static int ext4_validate_inode_bitmap(struct super_block *sb,
>                 return -EFSCORRUPTED;
>
>         ext4_lock_group(sb, block_group);
> +       if (buffer_verified(bh))
> +               goto verified;
>         blk = ext4_inode_bitmap(sb, desc);
>         if (!ext4_inode_bitmap_csum_verify(sb, block_group, desc, bh,
>                                            EXT4_INODES_PER_GROUP(sb) / 8)) {
> @@ -101,6 +103,7 @@ static int ext4_validate_inode_bitmap(struct super_block *sb,
>                 return -EFSBADCRC;
>         }
>         set_buffer_verified(bh);
> +verified:
>         ext4_unlock_group(sb, block_group);
>         return 0;
>  }