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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20210216103215.GB27714@lst.de> References: <20210216103215.GB27714@lst.de> <161340385320.1303470.2392622971006879777.stgit@warthog.procyon.org.uk> <161340389201.1303470.14353807284546854878.stgit@warthog.procyon.org.uk> To: Christoph Hellwig , "Matthew Wilcox (Oracle)" Cc: dhowells@redhat.com, Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet , Alexander Viro , linux-mm@kvack.org, linux-cachefs@redhat.com, linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, Jeff Layton , David Wysochanski , linux-kernel@vger.kernel.org Subject: Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <1429174.1613476104.1@warthog.procyon.org.uk> Date: Tue, 16 Feb 2021 11:48:24 +0000 Message-ID: <1429175.1613476104@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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: Christoph Hellwig wrote: > On Mon, Feb 15, 2021 at 03:44:52PM +0000, David Howells wrote: > > Provide a function, readahead_expand(), that expands the set of pages > > specified by a readahead_control object to encompass a revised area with a > > proposed size and length. > ... > So looking at linux-next this seems to have a user, but that user is > dead wood given that nothing implements ->expand_readahead. Interesting question. Code on my fscache-iter branch does implement this, but I was asked to split the patchset up, so that's not in this subset. > Looking at the code structure I think netfs_readahead and > netfs_rreq_expand is a complete mess and needs to be turned upside > down, that is instead of calling back from netfs_readahead to the > calling file system, split it into a few helpers called by the > caller. > > But even after this can't we just expose the cache granule boundary > to the VM so that the read-ahead request gets setup correctly from > the very beginning? You need to argue this one with Willy. In my opinion, the VM should ask the filesystem and the expansion be done before ->readahead() is called. Willy disagrees, however. David