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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pQ9cJ-002Kgx-LM; Thu, 09 Feb 2023 16:17:47 +0000 Date: Thu, 9 Feb 2023 16:17:47 +0000 From: Matthew Wilcox To: Jan Kara Cc: linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, John Hubbard , David Howells , David Hildenbrand Subject: Re: [PATCH 1/5] mm: Do not reclaim private data from pinned page Message-ID: References: <20230209121046.25360-1-jack@suse.cz> <20230209123206.3548-1-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230209123206.3548-1-jack@suse.cz> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 668EB20023 X-Stat-Signature: fb6bbzcbdtyrnwdjtn6f86cd8x1qduau X-Rspam-User: X-HE-Tag: 1675959472-559651 X-HE-Meta: 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 FrUBweQK x4fl96KB4FTQfEtrmG89eKoIMdRi4bcf0b8bSUXeb8Ywa5EZCYjAxjZaor5ZI+6kCM4CT6beA3EVB2i9SCmy2OWvvN8/NWly5vBkhj91ihy6V8xLWfnyRGxIZbqRRCYe1dG7gS9BFUy/srCSNGaYIx/7J2Mm3sXib2OjzbejPDn3iKnn1kWD7qEYOduP4/8qKtEeSj/1pVPsXQXJU18IkOo/6ag== 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 Thu, Feb 09, 2023 at 01:31:53PM +0100, Jan Kara wrote: > If the page is pinned, there's no point in trying to reclaim it. > Furthermore if the page is from the page cache we don't want to reclaim > fs-private data from the page because the pinning process may be writing > to the page at any time and reclaiming fs private info on a dirty page > can upset the filesystem (see link below). > > Link: https://lore.kernel.org/linux-mm/20180103100430.GE4911@quack2.suse.cz OK, but now I'm confused. I've been told before that the reason we can't take pinned pages off the LRU list is that they need to be written back periodically for ... reasons. But now the pages are going to be skipped if they're found on the LRU list, so why is this better than taking them off the LRU list?