linux-kernel - Re: [PATCH 4/5] ceph: fix improper use of smp_mb__before

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Message-ID: <6956e700-ef56-7f20-4e6c-3ad86c9fd89e@redhat.com>
Date:   Mon, 13 May 2019 21:04:10 +0800
From:   "Yan, Zheng" <zyan@...hat.com>
To:     Andrea Parri <andrea.parri@...rulasolutions.com>,
        "Yan, Zheng" <ukernel@...il.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sage Weil <sage@...hat.com>, Ilya Dryomov <idryomov@...il.com>,
        ceph-devel <ceph-devel@...r.kernel.org>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 4/5] ceph: fix improper use of smp_mb__before_atomic()

On 5/10/19 4:55 AM, Andrea Parri wrote:
> On Tue, Apr 30, 2019 at 05:08:43PM +0800, Yan, Zheng wrote:
>> On Tue, Apr 30, 2019 at 4:26 PM Peter Zijlstra <peterz@...radead.org> wrote:
>>>
>>> On Mon, Apr 29, 2019 at 10:15:00PM +0200, Andrea Parri wrote:
>>>> This barrier only applies to the read-modify-write operations; in
>>>> particular, it does not apply to the atomic64_set() primitive.
>>>>
>>>> Replace the barrier with an smp_mb().
>>>>
>>>
>>>> @@ -541,7 +541,7 @@ static inline void __ceph_dir_set_complete(struct ceph_inode_info *ci,
>>>>                                           long long release_count,
>>>>                                           long long ordered_count)
>>>>   {
>>>> -     smp_mb__before_atomic();
>>>
>>> same
>>>          /*
>>>           * XXX: the comment that explain this barrier goes here.
>>>           */
>>>
>>
>> makes sure operations that setup readdir cache (update page cache and
>> i_size) are strongly ordered with following atomic64_set.
> 
> Thanks for the suggestion, Yan.
> 
> To be clear: would you like me to integrate your comment and resend?
> any other suggestions?
> 

Yes, please

Regards
Yan, Zheng

> Thanx,
>    Andrea
> 
> 
>>
>>>> +     smp_mb();
>>>
>>>>        atomic64_set(&ci->i_complete_seq[0], release_count);
>>>>        atomic64_set(&ci->i_complete_seq[1], ordered_count);
>>>>   }
>>>> --
>>>> 2.7.4
>>>>