Re: [PATCH] slab : allow SLAB_RED_ZONE and SLAB_STORE_USER to workon arm

From: Pekka Enberg
Date: Thu Jul 11 2013 - 02:48:54 EST


(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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