linux-kernel - Re: [PATCH 1/4] mm: add new mmgrab() helper

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Date:   Fri, 16 Dec 2016 10:56:24 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vegard Nossum <vegard.nossum@...cle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Rik van Riel <riel@...hat.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Ingo Molnar <mingo@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 1/4] mm: add new mmgrab() helper

On Fri, Dec 16, 2016 at 09:21:59AM +0100, Vegard Nossum wrote:
> Apart from adding the helper function itself, the rest of the kernel is
> converted mechanically using:
> 
>   git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)->mm_count);/mmgrab\(\1\);/'
>   git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)\.mm_count);/mmgrab\(\&\1\);/'
> 
> This is needed for a later patch that hooks into the helper, but might be
> a worthwhile cleanup on its own.

Given the desire to replace all refcounting with a specific refcount
type, this seems to make sense.

FYI: http://www.openwall.com/lists/kernel-hardening/2016/12/07/8

But I must say mmget() vs mmgrab() is a wee bit confusing.