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