linux-kernel - Re: [PATCH] mm: mmap: Check all failures before set values

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Message-ID: <COL130-W527FEAA0BEC780957B6B18B9620@phx.gbl>
Date:	Mon, 24 Aug 2015 21:34:25 +0800
From:	Chen Gang <xili_gchen_5257@...mail.com>
To:	Michal Hocko <mhocko@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"riel@...hat.com" <riel@...hat.com>,
	"sasha.levin@...cle.com" <sasha.levin@...cle.com>,
	"gang.chen.5i5j@...il.com" <gang.chen.5i5j@...il.com>,
	Linux Memory <linux-mm@...ck.org>,
	kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: mmap: Check all failures before set values

On 8/24/15 19:32, Michal Hocko wrote:
> On Mon 24-08-15 00:59:39, gang.chen.5i5j@...com wrote:
>>> From: Chen Gang <gang.chen.5i5j@...il.com>
>>>
>>> When failure occurs and return, vma->vm_pgoff is already set, which is
>>> not a good idea.
> Why? The vma is not inserted anywhere and the failure path is supposed
> to simply free the vma.
>

It can save several insns when failure occurs.

It is always a little better to let the external function suppose fewer
callers' behalf.

It can save the code readers' (especially new readers') time resource
to avoid to analyze why set 'vma->vm_pgoff' before checking '-ENOMEM'
(may it cause issue? or is 'vm_pgoff' related with the next checking?).


Thanks.
--
Chen Gang

Open, share, and attitude like air, water, and life which God blessed