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From: Davidlohr Bueso <dave@stgolabs.net>
To: idryomov@gmail.com
Cc: ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org,
	dave@stgolabs.net, Davidlohr Bueso <dbueso@suse.de>
Subject: [PATCH] rbd: optimize barrier usage for Rmw atomic bitops
Date: Wed, 29 Jan 2020 10:12:53 -0800	[thread overview]
Message-ID: <20200129181253.24999-1-dave@stgolabs.net> (raw)

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)
-- 
2.16.4


             reply	other threads:[~2020-01-29 18:23 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-29 18:12 Davidlohr Bueso [this message]
2020-01-30 12:52 ` [PATCH] rbd: optimize barrier usage for Rmw atomic bitops Ilya Dryomov
2020-01-30 15:02   ` Davidlohr Bueso

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