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[106.167.137.155]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-218a1e50455sm10069475ad.159.2024.12.14.02.16.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 14 Dec 2024 02:16:22 -0800 (PST) Message-ID: <27fff669-bec4-4255-ba2f-4b154b474d97@gmail.com> Date: Sat, 14 Dec 2024 19:16:18 +0900 Precedence: bulk X-Mailing-List: v9fs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 07/10] netfs: Fix missing barriers by using clear_and_wake_up_bit() To: David Howells , Christian Brauner Cc: Max Kellermann , Ilya Dryomov , Xiubo Li , Trond Myklebust , Jeff Layton , Matthew Wilcox , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs@lists.linux.dev, linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zilin Guan , Akira Yokosawa References: <20241213135013.2964079-1-dhowells@redhat.com> <20241213135013.2964079-8-dhowells@redhat.com> Content-Language: en-US From: Akira Yokosawa In-Reply-To: <20241213135013.2964079-8-dhowells@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi David, David Howells wrote: > Use clear_and_wake_up_bit() rather than something like: > > clear_bit_unlock(NETFS_RREQ_IN_PROGRESS, &rreq->flags); > wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS); > > as there needs to be a barrier inserted between which is present in > clear_and_wake_up_bit(). If I am reading the kernel-doc comment of clear_bit_unlock() [1, 2]: This operation is atomic and provides release barrier semantics. correctly, there already seems to be a barrier which should be good enough. [1]: https://www.kernel.org/doc/html/latest/core-api/kernel-api.html#c.clear_bit_unlock [2]: include/asm-generic/bitops/instrumented-lock.h > > Fixes: 288ace2f57c9 ("netfs: New writeback implementation") > Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading") So I'm not sure this fixes anything. What am I missing? Thanks, Akira > Signed-off-by: David Howells > cc: Zilin Guan > cc: Akira Yokosawa > cc: Jeff Layton > cc: netfs@lists.linux.dev > cc: linux-fsdevel@vger.kernel.org > --- > fs/netfs/read_collect.c | 3 +-- > fs/netfs/write_collect.c | 9 +++------ > 2 files changed, 4 insertions(+), 8 deletions(-) > [...]