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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rfABQ-000000045RB-0ZNr; Wed, 28 Feb 2024 03:00:36 +0000 Date: Wed, 28 Feb 2024 03:00:36 +0000 From: Matthew Wilcox To: Kent Overstreet Cc: Linus Torvalds , Dave Chinner , Luis Chamberlain , lsf-pc@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm , Daniel Gomez , Pankaj Raghav , Jens Axboe , Christoph Hellwig , Chris Mason , Johannes Weiner Subject: Re: [LSF/MM/BPF TOPIC] Measuring limits and enhancing buffered IO Message-ID: References: <4rde5abojkj6neokif4j6z4bgkqwztowfiiklpvxramiuhvzjb@ts5af6w4bl4t> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4rde5abojkj6neokif4j6z4bgkqwztowfiiklpvxramiuhvzjb@ts5af6w4bl4t> X-Rspam-User: X-Stat-Signature: gkpr3i6ujtqfyg6w3swre5apxqgcxdi5 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 65030A0019 X-HE-Tag: 1709089249-247581 X-HE-Meta: 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 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 Tue, Feb 27, 2024 at 09:22:26PM -0500, Kent Overstreet wrote: > Which does raise the question of if we've ever attempted to define a > lock ordering on folios. I suspect not, since folio lock doesn't even > seem to have lockdep support. We even wrote it down! /* * To avoid deadlocks between range_cyclic writeback and callers * that hold pages in PageWriteback to aggregate I/O until * the writeback iteration finishes, we do not loop back to the * start of the file. Doing so causes a page lock/page * writeback access order inversion - we should only ever lock * multiple pages in ascending page->index order, and looping * back to the start of the file violates that rule and causes * deadlocks. */ (I'll take the AR to put this somewhere better like in the folio_lock() kernel-doc)