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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20210321105309.GG3420@casper.infradead.org> References: <20210321105309.GG3420@casper.infradead.org> <161539526152.286939.8589700175877370401.stgit@warthog.procyon.org.uk> <161539528910.286939.1252328699383291173.stgit@warthog.procyon.org.uk> To: Matthew Wilcox Cc: dhowells@redhat.com, Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet , Linus Torvalds , Christoph Hellwig , 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 v4 02/28] mm: Add an unlock function for PG_private_2/PG_fscache MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <1885295.1616410586.1@warthog.procyon.org.uk> Date: Mon, 22 Mar 2021 10:56:26 +0000 Message-ID: <1885296.1616410586@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: A476A407F8F1 X-Stat-Signature: dnprmiesci4wdcnpacid1gktzbatdnez Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=63.128.21.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616410600-265165 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: > That also brings up that there is no set_page_private_2(). I think > that's OK -- you only set PageFsCache() immediately after reading the > page from the server. But I feel this "unlock_page_private_2" is actually > "clear_page_private_2" -- ie it's equivalent to writeback, not to lock. How about I do the following: (1) Add set_page_private_2() or mark_page_private_2() to set the PG_fscache_2 bit. It could take a ref on the page here. (2) Rename unlock_page_private_2() to end_page_private_2(). It could drop the ref on the page here, but that then means I can't use pagevec_release(). (3) Add wait_on_page_private_2() an analogue of wait_on_page_writeback() rather than wait_on_page_locked(). (4) Provide fscache synonyms of the above. David