linux-kernel - Re: [patch 1/2] mm: dont clear PG_uptodate in invalidate_complete

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Message-Id: <E1KBXSF-00076u-7Y@pomaz-ex.szeredi.hu>
Date:	Wed, 25 Jun 2008 18:02:43 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	johnpol@....mipt.ru
CC:	miklos@...redi.hu, jens.axboe@...cle.com,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, hugh@...itas.com,
	nickpiggin@...oo.com.au
Subject: Re: [patch 1/2] mm: dont clear PG_uptodate in invalidate_complete_page2()

> > > Is this nfs/fuse problem you described:
> > > http://marc.info/?l=linux-fsdevel&m=121396920822693&w=2
> > 
> > Yes.
> 
> I do not know fuse good enough, but it looks like if your patch only
> fixes issue for pages which are in splice buffer during invalidation,
> any subsequent call for splice() will get correct new data (at least
> invoke readpage(s)), but in the description of error there was a
> long timeout between reading and writing, so it was a fresh splice()
> call, which suddenly started to return errors.
> 
> Is it possible that by having uptodate bit in place, but page was
> actually freed but not removed from all trees and so on, so it
> masked read errors? This may be not the right conclusion though :)

No, the mechanics of the problem are well understood.  Only the
solution is problematic :)

Miklos
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