linux-kernel - Re: [PATCH] slab : allow SLAB_RED_ZONE and SLAB_STORE

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Message-ID: <51DE554F.8020107@kernel.org>
Date:	Thu, 11 Jul 2013 09:48:47 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Matthieu CASTET <matthieu.castet@...rot.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	Matthieu CASTET <castet.matthieu@...e.fr>,
	Russell King <rmk@....linux.org.uk>,
	Shiyong Li <shi-yong.li@...orola.com>,
	Christoph Lameter <cl@...ux.com>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] slab : allow SLAB_RED_ZONE and SLAB_STORE_USER to work
 on arm

(nine months later...)

On 10/31/2012 12:01 PM, Matthieu CASTET wrote:
>> This piece of code tends to break in peculiar ways every time someone
>> touches it. I could use some more convincing in the changelog this
>> time it won't...
>
> Ok, is the following changelog is ok ?
>
> The current slab code only allow to put redzone( and user store) info if "buffer
> alignment(ralign) <= __alignof__(unsigned long long)". This was done because we
> want to keep the buffer aligned for user even after adding redzone at the
> beginning of the buffer (the user store is stored after user buffer) [1]
>
> But instead of disabling this feature when "ralign > __alignof__(unsigned long
> long)", we can force the alignment by allocating ralign before user buffer.
>
> This is done by setting ralign in obj_offset when "ralign > __alignof__(unsigned
> long long)" and keeping the old behavior when  "ralign <= __alignof__(unsigned
> long long)" (we set sizeof(unsigned long long)).
>
> The 5c5e3b33b7cb959a401f823707bee006caadd76e commit wasn't handling "ralign <=
> __alignof__(unsigned long long)", that's why it broked some configuration.
>
> This was tested on omap3 (ralign is 64 and __alignof__(unsigned long long) is 8)

Care to resend this patch with the above changelog? I'll see
if I can find someone to ACK it for v3.12.

			Pekka
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