linux-kernel - Re: [patch v3] splice: fix race with page invalidation

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Message-ID: <20080730175406.GN20055@kernel.dk>
Date:	Wed, 30 Jul 2008 19:54:07 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	nickpiggin@...oo.com.au, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch v3] splice: fix race with page invalidation

On Wed, Jul 30 2008, Miklos Szeredi wrote:
> On Wed, 30 Jul 2008, Linus Torvalds wrote:
> > On Wed, 30 Jul 2008, Miklos Szeredi wrote:
> > > 
> > > There are no real disadvantages: splice() from a file was
> > > originally meant to be asynchronous, but in reality it only did
> > > that for non-readahead pages, which happen rarely.
> > 
> > I still don't like this. I still don't see the point, and I still
> > think there is something fundamentally wrong elsewhere.

You snipped the part where Linus objected to dismissing the async
nature, I fully agree with that part.

> We discussed the possible solutions with Nick, and came to the
> conclusion, that short term (i.e. 2.6.27) this is probably the best
> solution.

Ehm where? Nick also said that he didn't like removing the ->confirm()
bits as they are completely related to the async nature of splice. You
already submitted this exact patch earlier and it was nak'ed.

> Long term sure, I have no problem with implementing async splice.
> 
> In fact, I may even have personal interest in looking at splice,
> because people are asking for a zero-copy interface for fuse.
> 
> But that is definitely not 2.6.27, so I think you should reconsider
> taking this patch, which is obviously correct due to its simplicity,
> and won't cause any performance regressions either.

Then please just fix the issue, instead of removing the bits that make
this possible.

-- 
Jens Axboe

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