linux-kernel - Re: [GIT PULL] Btrfs

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Message-ID: <CA+5PVA4NAmFnc3s6CaaDow9P3xLXOiEngHjQ_P5+TEG--LZ9ZQ@mail.gmail.com>
Date:	Fri, 13 Sep 2013 11:38:15 -0400
From:	Josh Boyer <jwboyer@...oraproject.org>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Chris Mason <chris.mason@...ionio.com>,
	Mark Fasheh <mfasheh@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	Russell King <rmk@....linux.org.uk>
Subject: Re: [GIT PULL] Btrfs

On Fri, Sep 13, 2013 at 11:06 AM, Josh Boyer <jwboyer@...il.com> wrote:
> On Fri, Sep 13, 2013 at 8:15 AM, Russell King <rmk@....linux.org.uk> wrote:
>> On Fri, Sep 13, 2013 at 07:53:21AM -0400, Josh Boyer wrote:
>>> I'm not an ARM expert, so I don't know if ARM should use the
>>> asm-generic implementations, or just use __get_user/__put_user in all
>>> cases.  I've CC'd rmk.
>>
>> Why do we have uaccess-unaligned.h ?  Normally, these kinds of things
>> are spawned by architectures which have problems with unaligned accesses,
>> ARM being one of them, but afaik we've never need this.
>>
>> With the kernel-side trapping of unaligned accesses on older hardware,
>> we've always dealt with the normal accessor faulting.
>>
>> From what I can tell in the git history, these unaligned put_user and
>> get_user have existed all the way back to the dawn of git use.
>>
>> Can someone enlighten me why we have them?

I somehow fail at email and dropped Russell from CC on accident.  Sigh.

> So while that gets sorted out, would it be safe to just do as Geert
> did on m68k and put:
>
> #define __put_user_unaligned(x, ptr) __put_user((x), (ptr))
>
> in arch/arm/include/asm/uaccess.h, and let the normal accessors and
> kernel-side trapping deal with things?  I'm thinking that's a local
> fix until something gets sorted upstream, but I don't want to do it if
> it's going to break things.
>
> josh
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