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

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Message-ID: <20190430082332.GB2677@hirez.programming.kicks-ass.net>
Date:   Tue, 30 Apr 2019 10:23:32 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andrea Parri <andrea.parri@...rulasolutions.com>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        "Yan, Zheng" <zyan@...hat.com>, Sage Weil <sage@...hat.com>,
        Ilya Dryomov <idryomov@...il.com>, ceph-devel@...r.kernel.org
Subject: Re: [PATCH 4/5] ceph: fix improper use of smp_mb__before_atomic()

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.
	 */

> +	smp_mb();

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