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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pEAly-000dbw-DB; Sat, 07 Jan 2023 15:06:14 +0000 Date: Sat, 7 Jan 2023 15:06:14 +0000 From: Matthew Wilcox To: Christoph Hellwig Cc: David Howells , Linus Torvalds , Steve French , Shyam Prasad N , Rohith Surabattula , Dave Wysochanski , Dominique Martinet , Ilya Dryomov , linux-cachefs@redhat.com, linux-cifs@vger.kernel.org, linux-afs@lists.infradead.org, v9fs-developer@lists.sourceforge.net, ceph-devel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Jeff Layton , linux-erofs@lists.ozlabs.org, linux-ext4@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 3/3] mm: Make filemap_release_folio() better inform shrink_folio_list() Message-ID: References: <167172131368.2334525.8569808925687731937.stgit@warthog.procyon.org.uk> <167172134962.2334525.570622889806603086.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 24AF520002 X-Rspam-User: X-Stat-Signature: cgcnqr8x9fqemrj8fcyu5hoyk7d43958 X-HE-Tag: 1673104005-53553 X-HE-Meta: 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 cp1elqxQ BfgzQ 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: On Fri, Dec 23, 2022 at 07:31:14AM -0800, Christoph Hellwig wrote: > On Thu, Dec 22, 2022 at 03:02:29PM +0000, David Howells wrote: > > Make filemap_release_folio() return one of three values: > > > > (0) FILEMAP_CANT_RELEASE_FOLIO > > > > Couldn't release the folio's private data, so the folio can't itself > > be released. > > > > (1) FILEMAP_RELEASED_FOLIO > > > > The private data on the folio was released and the folio can be > > released. > > > > (2) FILEMAP_FOLIO_HAD_NO_PRIVATE > > These names read really odd, due to the different placementments > of FOLIO, the present vs past tense and the fact that 2 also released > the folio, and the reliance of callers that one value of an enum > must be 0, while no unprecedented, is a bit ugly. Agreed. The thing is that it's not the filemap that's being released, it's the folio. So these should be: FOLIO_RELEASE_SUCCESS FOLIO_RELEASE_FAILED FOLIO_RELEASE_NO_PRIVATE ... but of course, NO_PRIVATE is also a success. So it's a really weird thing to be reporting. I'm with you on the latter half of this email: > But do we even need them? What abut just open coding > filemap_release_folio (which is a mostly trivial function) in > shrink_folio_list, which is the only place that cares? > > if (folio_has_private(folio) && folio_needs_release(folio)) { > if (folio_test_writeback(folio)) > goto activate_locked; > > if (mapping && mapping->a_ops->release_folio) { > if (!mapping->a_ops->release_folio(folio, gfp)) > goto activate_locked; > } else { > if (!try_to_free_buffers(folio)) > goto activate_locked; > } > > if (!mapping && folio_ref_count(folio) == 1) { > ... > > alternatively just keep using filemap_release_folio and just add the > folio_needs_release in the first branch. That duplicates the test, > but makes the change a one-liner. Or just drop patch 3 entirely?