Re: [PATCH 0/4] Fix filesystem freezing

Dave Chinner
2012-01-12T02:48:47Z

On Thu, Jan 12, 2012 at 02:20:49AM +0100, Jan Kara wrote:
>
> Hello,
>
> filesystem freezing is currently racy and thus we can end up with dirty data
> on frozen filesystem (see changelog of the first patch for detailed race
> description and proposed fix). This patch series aims at fixing this.

It only fixes the dirty data race (i.e. SB_FREEZE_WRITE). The same
race conditions exist for SB_FREEZE_TRANS on XFS, and so need the
same fix. That race has had one previous attempt at fixing it in
XFS but that's not possible:

b2ce397 Revert "xfs: fix filesystsem freeze race in xfs_trans_alloc"
7a249cf xfs: fix filesystsem freeze race in xfs_trans_alloc

It was looking at that problem earlier today that lead to the
solution Eric proposed. Essentially the method in these patches
needs to replace the xfs specifc m_active_trans counter and delay
during ->fs_freeze to prevent that race condition....

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com