[4/5] ceph: fix improper use of smp_mb__before_atomic()
diff mbox series

Message ID 1556568902-12464-5-git-send-email-andrea.parri@amarulasolutions.com
State New
Headers show
Series
  • Untitled series #111657
Related show

Commit Message

Andrea Parri April 29, 2019, 8:15 p.m. UTC
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().

Fixes: fdd4e15838e59 ("ceph: rework dcache readdir")
Cc: stable@vger.kernel.org
Reported-by: "Paul E. McKenney" <paulmck@linux.ibm.com>
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: "Yan, Zheng" <zyan@redhat.com>
Cc: Sage Weil <sage@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: ceph-devel@vger.kernel.org
---
 fs/ceph/super.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Peter Zijlstra April 30, 2019, 8:23 a.m. UTC | #1
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
>
Yan, Zheng April 30, 2019, 9:08 a.m. UTC | #2
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
> >
Andrea Parri May 9, 2019, 8:55 p.m. UTC | #3
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@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.

Thanks for the suggestion, Yan.

To be clear: would you like me to integrate your comment and resend?
any other suggestions?

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
> > >
Yan, Zheng May 13, 2019, 1:04 p.m. UTC | #4
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@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.
> 
> 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
>>>>
Andrea Parri May 13, 2019, 10:47 p.m. UTC | #5
> >>>         /*
> >>>          * 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

Will do: I'll let the merge window close and send v2 on top of -rc1.

Thanks,
  Andrea

Patch
diff mbox series

diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 16c03188578ea..b5c782e6d62f1 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -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();
+	smp_mb();
 	atomic64_set(&ci->i_complete_seq[0], release_count);
 	atomic64_set(&ci->i_complete_seq[1], ordered_count);
 }