Date: Fri, 1 Jun 2007 03:53:49 +0200
From: Nick Piggin <npiggin@suse.de>
To: Mark Fasheh <mark.fasheh@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org
Subject: Re: 2.6.22-rc3-mm1 - page_mkwrite() breakage
Message-ID: <20070601015349.GC28585@wotan.suse.de>
References: <20070530235823.793f00d9.akpm@linux-foundation.org> <20070531231354.GR20632@ca-server1.us.oracle.com> <20070601010129.GA15878@wotan.suse.de> <20070601012440.GS20632@ca-server1.us.oracle.com> <20070601013402.GB28585@wotan.suse.de> <20070601014517.GT20632@ca-server1.us.oracle.com>
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On Thu, May 31, 2007 at 06:45:17PM -0700, Mark Fasheh wrote:
> On Fri, Jun 01, 2007 at 03:34:02AM +0200, Nick Piggin wrote:
> > > Here's a nasty idea... Would it be valid for ->page_mkwrite to unlock the
> > > page, so long as it's returned in a locked state? Though, do we even need
> > > the page lock that early? It seemed to me that you were adding it for
> > > consistency reasons (I could be wrong though).
> > 
> > You could do that, but you'd have to probably check that it is
> > within i_size after you relock it, I think... yeah, that might
> > be the best thing for ocfs to do for now.
> 
> Well, ocfs2 already does i_size checks in page_mkwrite, so we're covered
> with respect to truncate races.
> 
> I'm still not clear though - what was the reason for adding the page locking
> there in the 1st place?

Yeah, its to cover page invalidation races. There is a description in
an earlier patch's changelog.

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