linux-kernel - Re: [PATCH] aio: Cleanup unnecessary test for nr

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Message-ID: <20160620141739.GK14480@ZenIV.linux.org.uk>
Date:	Mon, 20 Jun 2016 15:17:39 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Minfei Huang <mnghuan@...il.com>
Cc:	bcrl@...ck.org, linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
	linux-kernel@...r.kernel.org, minfei.hmf@...baba-inc.com
Subject: Re: [PATCH] aio: Cleanup unnecessary test for nr_pages

On Mon, Jun 20, 2016 at 10:05:45PM +0800, Minfei Huang wrote:
> Ping. Any comment is appreciate.
> 
> Thanks
> Minfei
> 
> On 06/13/16 at 12:33P, Minfei Huang wrote:
> > The variable nr_pages is always more than 1, because the size of
> > structure aio_ring is bigger than 0. So remove unnecessary test for
> > nr_page.

What this test really checks is that the value we'd put into nr_pages
(PFN_UP(size)) is not greater than 2^31.  Whether it's redundant or not
is a separate question - it very well might be, due to the code in
ioctx_alloc() that caps nr_events, but that needs a proof.  In any case,
the reasons you are offering in commit message are wrong - it's about
size being too _large_, not too small.