linux-kernel - Re: [patch 2/2] splice: dont readpage

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Message-ID: <20070315123829.GR15400@kernel.dk>
Date:	Thu, 15 Mar 2007 13:38:29 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [patch 2/2] splice: dont readpage

On Thu, Mar 15 2007, Nick Piggin wrote:
> On Thu, Mar 15, 2007 at 12:54:54PM +0100, Jens Axboe wrote:
> > On Wed, Mar 14 2007, Nick Piggin wrote:
> > > 
> > > Splice does not need to readpage to bring the page uptodate before writing
> > > to it, because prepare_write will take care of that for us.
> > 
> > Ah great, always good to get rid of some code.
> 
> Yeah, it should especially make block (but not page) sized and aligned
> writes into uncached files work much better, AFAIKS (won't require the
> synchronous read).

Yep, it's a nice improvement! Plus a cleanup.

> > > Splice is also wrong to SetPageUptodate before the page is actually uptodate.
> > > This results in the old uninitialised memory leak. This gets fixed as a
> > > matter of course when removing the readpage logic.
> > 
> > Leak, how? The page should still be locked all through to the copy.
> > Anyway, doesn't matter since you've killed it anyway. I have applied
> > this patch.
> 
> The read side doesn't need to lock the page if it is uptodate, and doesn't.

Oh, then there's definitely an issue.

-- 
Jens Axboe

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