From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Subject: Re: possible regression by the barrier patch in
	2.6.30-rc2
Date: Mon, 20 Apr 2009 13:27:00 +0900
Message-ID: <49EBF994.90801@ct.jp.nec.com>
References: <49E80C1E.1040905@ct.jp.nec.com>
	<20090417132252.GA7843@agk.fab.redhat.com>
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To: Mikulas Patocka <mpatocka@redhat.com>, Alasdair G Kergon <agk@redhat.com>
Cc: device-mapper development <dm-devel@redhat.com>
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Hi Alasdair, Mikulas,

On 2009/04/17 22:22 +0900, Alasdair G Kergon wrote:
> On Fri, Apr 17, 2009 at 01:57:02PM +0900, Kiyoshi Ueda wrote:
>> 1. The semantics of flush suspend has been changed.
> 
> We absolutely must complete any I/O issued as a result of the lock_fs()
> call in dm_suspend().

I think that lock_fs() waits for I/O to complete, so no semantics change
in case of LOCKFS && FLUSH. (All I/O issued from lock_fs() are flushed.)

But in case of NO_LOCKFS && FLUSH, the semantics is changed:
  from: I/Os submitted before the suspend invocation are flushed
  to:   I/Os submitted even before the suspend invocation may not be flushed

I have no idea whether someone gets real damage by this semantics change.

> Alasdair

Thanks,
Kiyoshi Ueda