linux-kernel - Re: [PATCH 02/18] mm: make vm

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Date:	Fri, 11 Mar 2016 13:43:41 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Alex Deucher <alexander.deucher@....com>,
	Alex Thorlton <athorlton@....com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Christian König <christian.koenig@....com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Davidlohr Bueso <dave@...olabs.net>,
	David Rientjes <rientjes@...gle.com>,
	"H . Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>,
	Ingo Molnar <mingo@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	linux-arch@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Petr Cermak <petrcermak@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 02/18] mm: make vm_mmap killable

On 03/11/2016 01:12 PM, Michal Hocko wrote:
> On Fri 11-03-16 10:59:30, Vlastimil Babka wrote:
>> On 02/29/2016 02:26 PM, Michal Hocko wrote:
>> >From: Michal Hocko <mhocko@...e.com>
>> >
>> >All the callers of vm_mmap seem to check for the failure already
>> >and bail out in one way or another on the error which means that
>>
>> Hmm I'm not that sure about this one:
>>   17   1071  fs/binfmt_elf.c <<load_elf_binary>>
>>
>> Assigns result of vm_mmap() to "error" variable which is never checked.
>
> Yes it is not checked but not used either. If the current got killed
> then it wouldn't return to the userspace so my understanding is that not
> checking this value is not a problem. At least that is my understanding.

Hmm, that's true. So,

Acked-by: Vlastimil Babka <vbabka@...e.cz>

>> Shouldn't __must_check trigger here?
>
> well, __must_check is a misleading name. It doesn't actually enforce the
> value is checked. It just has to be used and an assignment is
> sufficient. I was discussing this without our gcc guy and he promissed
> to look and try to come up with a different attribute which would
> actually work like __must_check.

OK!