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From: Rik van Riel <riel@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Tao Ma <tm@tao.ma>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH] mlock: operate on any regions with protection != PROT_NONE
Date: Tue, 01 Feb 2011 12:57:07 -0500	[thread overview]
Message-ID: <4D484973.6080603@redhat.com> (raw)
In-Reply-To: <AANLkTinG7eHR1_kfEyvJYw52ngyvqv5UzigEOddsi9ye@mail.gmail.com>

On 02/01/2011 12:59 AM, Linus Torvalds wrote:
> On Tue, Feb 1, 2011 at 11:03 AM, Michel Lespinasse<walken@google.com>  wrote:
>>
>> I am proposing to let mlock ignore vma protection in all cases except
>> PROT_NONE.
>
> What's so special about PROT_NONE? If you want to mlock something
> without actually being able to then fault that in, why not?
>
> IOW, why wouldn't it be right to just make FOLL_FORCE be unconditional in mlock?

I could think of a combination of reasons.

Specifically, some libc/linker magic will set up PROT_NONE
areas for programs automatically.

Some programs use mlockall to lock themselves into memory,
with no idea that PROT_NONE areas were set up behind its
back.

Faulting in the PROT_NONE memory will result is wasted
memory, without the application even realizing it.

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  parent reply	other threads:[~2011-02-01 17:57 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-01  1:03 [PATCH] mlock: operate on any regions with protection != PROT_NONE Michel Lespinasse
2011-02-01  1:08 ` Michel Lespinasse
2011-02-01  5:59 ` Linus Torvalds
2011-02-01  6:36   ` Michel Lespinasse
2011-02-01 17:57   ` Rik van Riel [this message]
2011-02-01 17:57 ` Rik van Riel
2011-02-03  0:57   ` KOSAKI Motohiro

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