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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20200901164827.GQ14765@casper.infradead.org> References: <20200901164827.GQ14765@casper.infradead.org> <159897769535.405783.17587409235571100774.stgit@warthog.procyon.org.uk> To: Matthew Wilcox Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/7] mm: Make more use of readahead_control MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <423538.1598989454.1@warthog.procyon.org.uk> Date: Tue, 01 Sep 2020 20:44:14 +0100 Message-ID: <423539.1598989454@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Rspamd-Queue-Id: 37E7C180AD806 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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: Matthew Wilcox wrote: > > Note that I've been > > passing the number of pages to read in rac->_nr_pages, and then saving it > > and changing it certain points, e.g. page_cache_readahead_unbounded(). > > I do not like this. You're essentially mutating the meaning of _nr_pages > as the ractl moves down the stack, and that's going to lead to bugs. > I'd keep it as a separate argument. The meaning isn't specified in linux/pagemap.h. Can you adjust the comments on the struct and on readahead_count() to make it more clear what the value represents? Thanks, David