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 <1300835335-2777-3-git-send-email-teravest@google.com> <20110323135241.4ada8334.kamezawa.hiroyu@jp.fujitsu.com>
From: Justin TerAvest <teravest@google.com>
Date: Wed, 23 Mar 2011 10:21:01 -0700
Message-ID: <AANLkTinnDTa8_rVorBsacm-uHqJSA=JbYM9RKXswd8Sr@mail.gmail.com>
Subject: Re: [PATCH v2 2/8] block,fs,mm: IO cgroup tracking for buffered write
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: vgoyal@redhat.com, jaxboe@fusionio.com, m-ikeda@ds.jp.nec.com,
        ryov@valinux.co.jp, taka@valinux.co.jp, righi.andrea@gmail.com,
        guijianfeng@cn.fujitsu.com, balbir@linux.vnet.ibm.com,
        ctalbott@google.com, linux-kernel@vger.kernel.org
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On Tue, Mar 22, 2011 at 9:52 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
> On Tue, 22 Mar 2011 16:08:49 -0700
> Justin TerAvest <teravest@google.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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