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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20240731190742.GS1967603@kernel.org> References: <20240731190742.GS1967603@kernel.org> <20240729162002.3436763-1-dhowells@redhat.com> <20240729162002.3436763-19-dhowells@redhat.com> To: Simon Horman Cc: dhowells@redhat.com, Christian Brauner , Steve French , Matthew Wilcox , Jeff Layton , Gao Xiang , Dominique Martinet , Marc Dionne , Paulo Alcantara , Shyam Prasad N , Tom Talpey , Eric Van Hensbergen , Ilya Dryomov , 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, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 18/24] netfs: Speed up buffered reading Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <117845.1722608282.1@warthog.procyon.org.uk> Date: Fri, 02 Aug 2024 15:18:02 +0100 Message-ID: <117846.1722608282@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Simon Horman wrote: > If the code ever reaches this line, then slice will be used > uninitialised below. It can't actually happen (or, at least, it shouldn't). There are only three ways of obtaining data: downloading from the server (NETFS_DOWNLOAD_FROM_SERVER), reading from the cache (NETFS_READ_FROM_CACHE) and just clearing space (NETFS_FILL_WITH_ZEROES); each of those has its own if-statement that will set 'slice' or will switch the source to a different type that will set 'slice'. The problem is that the compiler doesn't know this. The check for NETFS_INVALID_READ is there just in case. Possibly: if (source == NETFS_INVALID_READ) break; could be replaced with a WARN_ON_ONCE() and an unconditional break. David