Re: [PATCH 6/8] xfs: Use generic writers counter instead of m_active_trans counter

[Eric Sandeen <sandeen@xxxxxxxxxxx>]

On 1/20/12 2:34 PM, Jan Kara wrote:
> m_active_trans counter is racy wrt filesystem freezing. The patch replaces it
> with generic counter of running transactions which is properly synchronized
> with filesystem freezing. Things are a bit more complex because we need to log
> a dummy transaction and free block counters after the filesystem is frozen so
> we need to pass information to _xfs_trans_alloc() whether the transaction is
> part of filesystem freezing or not.
> 
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---

...

>  xfs_trans_t *
>  _xfs_trans_alloc(
>       xfs_mount_t     *mp,
>       uint            type,
> -     uint            memflags)
> +     uint            memflags,
> +     bool            freezing)
>  {
>       xfs_trans_t     *tp;
>  
> -     atomic_inc(&mp->m_active_trans);
> -
> +     if (!freezing)
> +             sb_start_write(mp->m_super, SB_FREEZE_TRANS);
> +     else
> +             WARN_ON(xfs_test_for_freeze(mp) != SB_FREEZE_TRANS);

Hm this could be an issue because for both the umount path and the 
freeze / xfs_quiesce_attr path, we call xfs_log_sbcount which sends
"true" for freezing and we'll trip up here because we won't be
in SB_FREEZE_TRANS during umount.

I think we have to push the flag all the way up to xfs_log_sbcount
callers?

-Eric