linux-kernel - [PATCH 06/10] netfs: Remove redundant use of smp

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Message-ID: <20241213135013.2964079-7-dhowells@redhat.com>
Date: Fri, 13 Dec 2024 13:50:06 +0000
From: David Howells <dhowells@...hat.com>
To: Christian Brauner <christian@...uner.io>
Cc: David Howells <dhowells@...hat.com>,
	Max Kellermann <max.kellermann@...os.com>,
	Ilya Dryomov <idryomov@...il.com>,
	Xiubo Li <xiubli@...hat.com>,
	Trond Myklebust <trondmy@...nel.org>,
	Jeff Layton <jlayton@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	netfs@...ts.linux.dev,
	linux-afs@...ts.infradead.org,
	linux-cifs@...r.kernel.org,
	linux-nfs@...r.kernel.org,
	ceph-devel@...r.kernel.org,
	v9fs@...ts.linux.dev,
	linux-erofs@...ts.ozlabs.org,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Zilin Guan <zilin@....edu.cn>,
	Akira Yokosawa <akiyks@...il.com>
Subject: [PATCH 06/10] netfs: Remove redundant use of smp_rmb()

From: Zilin Guan <zilin@....edu.cn>

The function netfs_unbuffered_write_iter_locked() in
fs/netfs/direct_write.c contains an unnecessary smp_rmb() call after
wait_on_bit(). Since wait_on_bit() already incorporates a memory barrier
that ensures the flag update is visible before the function returns, the
smp_rmb() provides no additional benefit and incurs unnecessary overhead.

This patch removes the redundant barrier to simplify and optimize the code.

Signed-off-by: Zilin Guan <zilin@....edu.cn>
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Akira Yokosawa <akiyks@...il.com>
cc: Jeff Layton <jlayton@...nel.org>
cc: netfs@...ts.linux.dev
cc: linux-fsdevel@...r.kernel.org
Link: https://lore.kernel.org/r/20241207021952.2978530-1-zilin@seu.edu.cn/
---
 fs/netfs/direct_write.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c
index 88f2adfab75e..173e8b5e6a93 100644
--- a/fs/netfs/direct_write.c
+++ b/fs/netfs/direct_write.c
@@ -104,7 +104,6 @@ ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *
 		trace_netfs_rreq(wreq, netfs_rreq_trace_wait_ip);
 		wait_on_bit(&wreq->flags, NETFS_RREQ_IN_PROGRESS,
 			    TASK_UNINTERRUPTIBLE);
-		smp_rmb(); /* Read error/transferred after RIP flag */
 		ret = wreq->error;
 		if (ret == 0) {
 			ret = wreq->transferred;