linux-kernel - Re: msync(2) bug(?), returns AOP_WRITEPAGE

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Message-ID: <84144f020710221340n6586b6d6web28cea481809b93@mail.gmail.com>
Date:	Mon, 22 Oct 2007 23:40:14 +0300
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	"Hugh Dickins" <hugh@...itas.com>
Cc:	"Erez Zadok" <ezk@...sunysb.edu>, "Ryan Finnie" <ryan@...nie.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	cjwatson@...ntu.com, linux-mm@...ck.org
Subject: Re: msync(2) bug(?), returns AOP_WRITEPAGE_ACTIVATE to userland

Hi Hugh,

On 10/22/07, Hugh Dickins <hugh@...itas.com> wrote:
> I don't disagree with your unionfs_writepages patch, Pekka, but I think
> it should be viewed as an optimization (don't waste time trying to write
> a group of pages when we know that nothing will be done) rather than as
> essential.

Ok, so tmpfs needs your fix still.

On 10/22/07, Hugh Dickins <hugh@...itas.com> wrote:
> > So now I wonder if we still need the patch to prevent AOP_WRITEPAGE_ACTIVATE
> > from being returned to userland.  I guess we still need it, b/c even with
> > your patch, generic_writepages() can return AOP_WRITEPAGE_ACTIVATE back to
> > the VFS and we need to ensure that doesn't "leak" outside the kernel.
>
> Can it now?  Current git has a patch from Andrew which bears a striking
> resemblance to that from Pekka, stopping the leak from write_cache_pages.

I don't think it can, it looks ok now.

                             Pekka
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