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Received: from willy by casper.infradead.org with local (Exim 4.98.1 #2 (Red Hat Linux)) id 1txqSX-0000000DYhZ-1mPH; Thu, 27 Mar 2025 16:52:01 +0000 Date: Thu, 27 Mar 2025 16:52:01 +0000 From: Matthew Wilcox To: Zi Yan Cc: linux-fsdevel@vger.kernel.org, David Hildenbrand , Joanne Koong , linux-mm@kvack.org, intel-gfx@lists.freedesktop.org Subject: Re: [PATCH 06/11] migrate: Remove call to ->writepage Message-ID: References: <20250307135414.2987755-1-willy@infradead.org> <20250307135414.2987755-7-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 9F558100012 X-Stat-Signature: bzrxj155w3r9q4bbdfk68hnhzqgc6jzg X-Rspam-User: X-HE-Tag: 1743094324-390547 X-HE-Meta: U2FsdGVkX1+71ALjZhIpXu+eEd0NOpfNECMadWhLyeNvH8nedXKbsq3iQ+nO/MSdkDN8eQ7hhv3B5fK//v/n57n5iM8O1xxr7vdIHwFxCWX3N0sFO//6g5kPXFZWphoEm6Tcai+AYYXlYDK6oq1wnN7pJJ/6Yg2KmUOCQSVQStWl5CQ+mwMzWOtKZtt4MFrR8Ke/rI8pVjupW+Nb9ukEry2Z/HSaBtmmuzwYVlLmjL4mK2lynxzyT/2NXqdqR2Gb/bSkOg2zsjB5sXs37pFflHskb7M26mwQB8yTH6VcrpX2KCD/6x91Zp5HVXCluzzmyXTNqHZ+yr1Joxmubs9SniRfiFbES40JSoSeDNF/p2Lo+cBgKLljyPSgiPt1d54HI4qf26PAGpHmWEyQ/fW/HH2JaHLQAK7n3Rx2SxE6B0WTUbbN5TWci2lYb4YuSr+y4NzG8CfNxJUyYzOd0+mK/t9vLTiGxT+6AMn0W5Kv0Gv9bxbBeJmj5QYh5ELwT/9eUqZyJqFdIZU5uZzQhZUCYr/hUBolIM4sKdiXlzRfttkVc6Ix2WSHnz27ggC+S+pxIhECTdaZxwqbZ2WunDK5hXgD+wcPdzfpWU84UcoxpRGb3wDcXI1EXmH5QZjJmtRa5WTuWP1Enx1hYBTAP4RKPpz8bVEw1DUichGMosNVMFFFgQdPm7HJRnPf49ODUv+Yb9PcViKwRSlMbjhERagN48jH+VbSWvStL4wpLE7IcpfQqqpuOfNJebFwXPgjJWFwUbX09BzRZ6ol6OxBdx8Xbu3LNbMlUGXhyqhnqISpoLDX1920sM3PZiJ4AOmYeindtknBjjm/CdZF5j1JRte7cQ6D4SkMec+oi4qCwb4Tvh1/xUDXYKItBD4h3iRi9mtEriKfqI4uWWVASKcg5mP+QRKmELMcCuiEmWsycPVTMuEZNczLEiEgsw/S69PAtqcaBCmB2+xtCbIUett6vCv A4NJ5/Lm RQG7Jj0g/mVDc9ykE4hh0HrCsjNiRk70BH46CA0aPlTZVRp3b/3mFIC4fxFCcIG7mp3Y2T//TEfFUdXfdBf2BDSeNjwv07BS7vAkVFQbVyogsQkaAy75bDxu8k4p/J1Ph2L+ADSRkWwB9wCHELP9999MoXoITNQ647kIGHQMwuSUwADloOylR12bs0smlWetBOhewZ7b7DaG/YpS6Vfy+PSr5VCc52e9QLDKs 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 Thu, Mar 27, 2025 at 11:04:57AM -0400, Zi Yan wrote: > On Fri Mar 7, 2025 at 8:54 AM EST, Matthew Wilcox (Oracle) wrote: > > The writepage callback is going away; filesystems must implement > > migrate_folio or else dirty folios will not be migratable. > > What is the impact of this? Are there any filesystem that has > a_ops->writepage() without migrate_folio()? I wonder if it could make > the un-migratable problem worse[1] when such FS exists. As Christoph and I have been going through filesystems removing their ->writepage operations, we've been careful to add ->migrate_folio callbacks at the same time. But we haven't fixed any out-of-tree filesystems, and we can't fix the filesystems which will be written in the future. So maybe what we should do is WARN_ON_ONCE() for filesystems which have a ->writepages, but do not have a ->migrate_folio()? > > static int fallback_migrate_folio(struct address_space *mapping, > > struct folio *dst, struct folio *src, enum migrate_mode mode) > > { > > - if (folio_test_dirty(src)) { > > - /* Only writeback folios in full synchronous migration */ > > - switch (mode) { > > - case MIGRATE_SYNC: > > - break; > > - default: > > - return -EBUSY; > > - } > > - return writeout(mapping, src); > > - } > > Now fallback_migrate_folio() no longer writes out page for FS, so it is > the responsibilty of migrate_folio()? ->migrate_folio() doesn't need to write out the page. It can migrate dirty folios (just not folios currently under writeback, obviously)