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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1t9TnL-00000009B9r-1HO5; Fri, 08 Nov 2024 18:33:19 +0000 Date: Fri, 8 Nov 2024 18:33:19 +0000 From: Matthew Wilcox To: Jens Axboe Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, hannes@cmpxchg.org, clm@meta.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 08/13] fs: add read support for RWF_UNCACHED Message-ID: References: <20241108174505.1214230-1-axboe@kernel.dk> <20241108174505.1214230-9-axboe@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241108174505.1214230-9-axboe@kernel.dk> X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: D20C4C0014 X-Stat-Signature: t7pou3dehfhi9ur1t6351te1ktie3fwr X-Rspam-User: X-HE-Tag: 1731090763-682403 X-HE-Meta: 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 lU7SWs6N BrkmQRZ2xNMN4sjoxfO75D+TC1veM4jlw9hSaiKtwbGekVfN2kVUWYjmjNcKA8Fv5om1z/1SKIOVBy/TX8BQrSVosYTzM0wGYTRL52nZNb7PrjyDNduRACIcU0RBzBsEFwfNSyaJYnK91F+N+aCNtUuw27s/rkRC1AVlWlx59mBL/UQvk+TcfX5yXedrlbCYR7Io7/K9/ZBazACUVzIn9T6Ms/vr3OYGCn+UUC03oB3yk+lmOW+EqPqj25b3ZTvGbssxWMS3VSK/fFYik/WNlbyqU2A== 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 Fri, Nov 08, 2024 at 10:43:31AM -0700, Jens Axboe wrote: > +++ b/mm/swap.c > @@ -472,6 +472,8 @@ static void folio_inc_refs(struct folio *folio) > */ > void folio_mark_accessed(struct folio *folio) > { > + if (folio_test_uncached(folio)) > + return; > if (lru_gen_enabled()) { This feels like it might be a problem. If, eg, process A is doing uncached IO and process B comes along and, say, mmap()s it, I think we'll need to clear the uncached flag in order to have things work correctly. It's a performance problem, not a correctness problem.