linux-kernel - Re: [PATCH] arch/cris: use get_user_pages

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Message-ID: <20180121233943.GO13338@ZenIV.linux.org.uk>
Date:   Sun, 21 Jan 2018 23:39:43 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     starvik@...s.com, jesper.nilsson@...s.com,
        akpm@...ux-foundation.org, linux-cris-kernel@...s.com,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH] arch/cris: use get_user_pages_fast()

On Sun, Jan 21, 2018 at 02:59:29PM -0800, Davidlohr Bueso wrote:
> Since we currently hold mmap_sem across both gup calls (and
> nothing more), we can substitute it with two _fast()
> alternatives and possibly avoid grabbing the lock.
> 
> This was found while adding mmap_sem wrappers, and was also
> previously reported by Al: https://lkml.org/lkml/2017/11/17/777

See commit 9a949e8ff92246c0753b2805c2a001cb991fffe5
Author: Al Viro <viro@...iv.linux.org.uk>
Date:   Sat Nov 18 14:37:46 2017 -0500

    cris: switch to get_user_pages_fast()
    
    no point holding ->mmap_sem over both calls.
    
    Signed-off-by: Al Viro <viro@...iv.linux.org.uk>


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