rbd: optimize barrier usage for Rmw atomic bitops
diff mbox series

Message ID 20200129181253.24999-1-dave@stgolabs.net
State New
Headers show
Series
  • rbd: optimize barrier usage for Rmw atomic bitops
Related show

Commit Message

Davidlohr Bueso Jan. 29, 2020, 6:12 p.m. UTC
For both set and clear_bit, we can avoid the unnecessary barrier
on non LL/SC architectures, such as x86. Instead, use the
smp_mb__{before,after}_atomic() calls.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 drivers/block/rbd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Ilya Dryomov Jan. 30, 2020, 12:52 p.m. UTC | #1
On Wed, Jan 29, 2020 at 7:23 PM Davidlohr Bueso <dave@stgolabs.net> wrote:
>
> For both set and clear_bit, we can avoid the unnecessary barrier
> on non LL/SC architectures, such as x86. Instead, use the
> smp_mb__{before,after}_atomic() calls.
>
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
> ---
>  drivers/block/rbd.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index 2b184563cd32..7bc79b2b8f65 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -1371,13 +1371,13 @@ static void rbd_osd_submit(struct ceph_osd_request *osd_req)
>  static void img_request_layered_set(struct rbd_img_request *img_request)
>  {
>         set_bit(IMG_REQ_LAYERED, &img_request->flags);
> -       smp_mb();
> +       smp_mb__after_atomic();
>  }
>
>  static void img_request_layered_clear(struct rbd_img_request *img_request)
>  {
>         clear_bit(IMG_REQ_LAYERED, &img_request->flags);
> -       smp_mb();
> +       smp_mb__after_atomic();
>  }
>
>  static bool img_request_layered_test(struct rbd_img_request *img_request)

Hi Davidlohr,

I don't think these barriers are needed at all.  I'll remove them.

Thanks,

                Ilya
Davidlohr Bueso Jan. 30, 2020, 3:02 p.m. UTC | #2
On Thu, 30 Jan 2020, Ilya Dryomov wrote:

>I don't think these barriers are needed at all.  I'll remove them.

Even better, thanks.

Patch
diff mbox series

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 2b184563cd32..7bc79b2b8f65 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1371,13 +1371,13 @@  static void rbd_osd_submit(struct ceph_osd_request *osd_req)
 static void img_request_layered_set(struct rbd_img_request *img_request)
 {
 	set_bit(IMG_REQ_LAYERED, &img_request->flags);
-	smp_mb();
+	smp_mb__after_atomic();
 }
 
 static void img_request_layered_clear(struct rbd_img_request *img_request)
 {
 	clear_bit(IMG_REQ_LAYERED, &img_request->flags);
-	smp_mb();
+	smp_mb__after_atomic();
 }
 
 static bool img_request_layered_test(struct rbd_img_request *img_request)