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

From: Eric Sandeen
Date: Fri Feb 03 2012 - 21:42:59 EST

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

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