Re: [PATCH 4/5] ceph: fix improper use of smp_mb__before_atomic()

Yan, Zheng
2019-04-30T09:08:59Z

On Tue, Apr 30, 2019 at 4:26 PM Peter Zijlstra <peterz@infradead.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.

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