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Fri, 10 Apr 2026 10:41:49 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id W1JwBO3T2Gl0BwAAD6G6ig (envelope-from ); Fri, 10 Apr 2026 10:41:49 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id CCE51A0A81; Fri, 10 Apr 2026 12:41:48 +0200 (CEST) Date: Fri, 10 Apr 2026 12:41:48 +0200 From: Jan Kara To: Christoph Hellwig Cc: Jan Kara , Jeff Layton , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Mike Snitzer , Jens Axboe , Chuck Lever , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 1/3] mm: kick writeback flusher instead of inline flush for IOCB_DONTCACHE Message-ID: References: <20260408-dontcache-v2-0-948dec1e756b@kernel.org> <20260408-dontcache-v2-1-948dec1e756b@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Action: no action X-Rspamd-Queue-Id: EFEFE4000F X-Stat-Signature: rpmy4x6y1eihub3y8ayk1m6s5yo48cme X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1775817710-405686 X-HE-Meta: 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 yCjmdU07 Br0k4qmBzbT4qxHiIBdsbzcCWsoZO0D1/I+dAf4XM+90A+ULfweHzZzQsTI/koPfdsgK+34PL31xmyg3pgBY1XIpmoblcGlHhqhexi9KisKEKaqIPghzdHgqE7+WCyoXsQVP/S0heCAhuc5cyeXTJCKROQN3gAguBaruv+AmZMuuu6K7X68bj98741Vwt5xvmJzLfzdn663GtYicUNJAv/exDArIwPGWVVJvtHcUGW5X9iwfxQRCPTcTkEsaqbKxAQfFKvk4twV0EOVs+yJqSzT4svcYfvzIzN/0kUpdV8G8k0Bmkm115B4gevzjszWplSJPD8QyScGTYcqNVhzeebABulcI2WZ4fXZfIgr6zUPgGj8HfIpCdduFYnsCbTU/rN8fACrIWdJME2qI= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu 09-04-26 07:21:22, Christoph Hellwig wrote: > On Thu, Apr 09, 2026 at 09:21:36AM +0200, Jan Kara wrote: > > > So I think you'll want a new WB_start_dontcache bit, a new > > > get_nr_dontcache_pages() helper on a new node counter, etc. > > > > But I'm not sure how you imagine this would work without restricting > > writeback to particular inodes. Maybe we could mark inodes which have > > folios with dropbehind set and make flush worker only write such inodes? > > I'd only expedite writing by the number of pending dontcache folios. > It would still write the least recently dirtied inodes. So that may result in dontcache folios staying cached for quite some time if DONTCACHE and normal writes are mixed. But I agree over longer time it might just level out so maybe that's fine. Honza -- Jan Kara SUSE Labs, CR