linux-kernel - Re: [PATCH] osd fs: __r4w_get_page rely on PageUptodate for uptodate

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Message-ID: <alpine.LSU.2.11.1511030734300.1856@eggly.anvils>
Date:	Tue, 3 Nov 2015 07:39:53 -0800 (PST)
From:	Hugh Dickins <hughd@...gle.com>
To:	Boaz Harrosh <boaz@...xistor.com>
cc:	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Christoph Lameter <cl@...ux.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-nfs@...r.kernel.org, linux-mm@...ck.org, osd-dev@...n-osd.org
Subject: Re: [PATCH] osd fs: __r4w_get_page rely on PageUptodate for
 uptodate

On Tue, 3 Nov 2015, Boaz Harrosh wrote:
> On 11/03/2015 04:49 AM, Hugh Dickins wrote:
> > On Mon, 2 Nov 2015, Boaz Harrosh wrote:
> >>
> >> Do you think the code is actually wrong as is?
> > 
> > Not that I know of: just a little too complicated and confusing.
> > 
> > But becomes slightly wrong if my simplification to page migration
> > goes through, since that introduces an instant when PageDirty is set
> > before the new page contains the correct data and is marked Uptodate.
> > Hence my patch.
> > 
> >>
> >> BTW: Very similar code is in fs/nfs/objlayout/objio_osd.c::__r4w_get_page
> > 
> > Indeed, the patch makes the same adjustment to that code too.
> > 
> 
> OK thanks. Let me setup and test your patch. On top of 4.3 is good?
> I'll send you a tested-by once I'm done.

Great, thanks Boaz, that will help a lot.  On top of 4.3 very good.

(Of course, that will not test the rare page migration race I shall
introduce later; but it will test that you're doing the right thing
with this change at your end, when you will be safe against the race.)

Hugh
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