linux-kernel - Re: [PATCH] mm/mmap.c: Remove useless statement "vma = NULL" in find

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Message-ID: <20150910181935.GB21456@redhat.com>
Date:	Thu, 10 Sep 2015 20:19:35 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Chen Gang <xili_gchen_5257@...mail.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"riel@...hat.com" <riel@...hat.com>, Michal Hocko <mhocko@...e.cz>,
	"sasha.levin@...cle.com" <sasha.levin@...cle.com>,
	"pfeiner@...gle.com" <pfeiner@...gle.com>,
	"aarcange@...hat.com" <aarcange@...hat.com>,
	"vishnu.ps@...sung.com" <vishnu.ps@...sung.com>,
	Linux Memory <linux-mm@...ck.org>,
	kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/mmap.c: Remove useless statement "vma = NULL" in
	find_vma()

On 09/10, Chen Gang wrote:
>
> On 9/10/15 00:26, Oleg Nesterov wrote:
> >
> > The implementation looks correct. Why do you think it can be not 1st vma?
> >
>
> It is in while (rb_node) {...}.
>
> - When we set "vma = tmp", it is alreay match "addr < vm_end".

Yes,

> - If "addr>= vm_start", we return this vma (else continue searching).

This is optimization, we can stop the search because in this case
vma == tmp is obviously the 1st vma with "addr < vm_end".

I simply can't understand your concerns. Perhaps you can make a
patch, then it will be more clear what me-or-you have missed.

Oleg.

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