linux-kernel - Re: [PATCH v2 2/8] block,fs,mm: IO cgroup tracking for buffered write

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Message-ID: <AANLkTinnDTa8_rVorBsacm-uHqJSA=JbYM9RKXswd8Sr@mail.gmail.com>
Date:	Wed, 23 Mar 2011 10:21:01 -0700
From:	Justin TerAvest <teravest@...gle.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	vgoyal@...hat.com, jaxboe@...ionio.com, m-ikeda@...jp.nec.com,
	ryov@...inux.co.jp, taka@...inux.co.jp, righi.andrea@...il.com,
	guijianfeng@...fujitsu.com, balbir@...ux.vnet.ibm.com,
	ctalbott@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/8] block,fs,mm: IO cgroup tracking for buffered write

On Tue, Mar 22, 2011 at 9:52 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
> On Tue, 22 Mar 2011 16:08:49 -0700
> Justin TerAvest <teravest@...gle.com> wrote:
>
>> +static inline void page_cgroup_set_blkio_id(struct page_cgroup *pc,
>> +                             unsigned long id)
>> +{
>> +     unsigned long old, new, prev;
>> +
>> +     /* pc->flags isn't lock protected, so we must cmpxchg. */
>> +     WARN_ON(id >= (1UL << PAGE_TRACKING_ID_BITS));
>> +     do {
>> +             new = old = pc->flags;
>> +             new &= (1UL << PAGE_TRACKING_ID_SHIFT) - 1;
>> +             new |= (unsigned long)(id << PAGE_TRACKING_ID_SHIFT);
>> +             prev = cmpxchg(&pc->flags, old, new);
>> +     } while (prev != old);
>
> How to support archs which doesn't have cmpxchg ?
> At least, you need take care of compile error.

Hi Kame,

Is there really no generic cmpxchg()? I thought that was what
include/asm-generic/cmpxchg-local.h was for.

Thanks,
Justin

>
> Thanks,
> -Kame
>
>
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