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b=uzIfzPbqeWDSXjHiBgkEJnEtvR/x00pI80yfMOPspsqu8FySfDHUqzDYaUa33dMPa 9VuWj+8Sla/wxa6LgFUP4mUw5Uqld7oPO/Rc7VTvnZTkP4QUsX0WNIBJRfMKEbOm5E 0O3SbfpH6tCZjpWaiiD1fNODTiZvR3ChGvm1WdEivsVrn36vxh5q5dSLX0Bq7q6TW/ ZIfiaLlaRb/QTv1p8yRpvlyNCDsCx+PAndbRntFM/P58FfzqAwLyMhP9mXUnvR6Pti auvyf2mCECPYJDUbbakovkI3Q9PN8/kFR339yvIkgqaDOFi20gDtMTllo/pWmelP5F gBuJs50KKDLcA== Date: Fri, 2 Aug 2024 15:44:05 +0100 From: Simon Horman To: David Howells Cc: 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 Message-ID: <20240802144405.GD2504122@kernel.org> References: <20240731190742.GS1967603@kernel.org> <20240729162002.3436763-1-dhowells@redhat.com> <20240729162002.3436763-19-dhowells@redhat.com> <117846.1722608282@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <117846.1722608282@warthog.procyon.org.uk> X-Rspamd-Queue-Id: ECC8DC0002 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: rbg5xmpymianuixyzpgt6yqgsfee1hq6 X-HE-Tag: 1722609856-261544 X-HE-Meta: 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 W2Ez1tM8 wyYHs4EhUM8NeXgPGYP/ZGl9tzgNyknT7nGzzPSa1Ejh5dx3c0ygEzsaOjlNgapaXNWWl3RkUjNInrgk0PebVsP4/PM+YEaeY60O4bCqeXY7p06qO7Lw/etsIyajtlVNpmdAq5Veh+DC7/rbkPAmBGD1r/qCNV/vN0vI+oET+xY45+nfw7miKy6hyjcDzyy/si/31zNPcYbAXnxOwjzl1DMFeNQMP7arsRGGgsli32dbQDwnBPJPzdZq1w7VuHOu8lacG5zNFhdDLAms9RBbJGt5TsQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Aug 02, 2024 at 03:18:02PM +0100, David Howells wrote: > 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. Thanks, I think that should make the compiler happy without significantly altering the flow or readability of the code.