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bh=gP1SNSrFBlGtxxoCJK90VW8nMVu/mXcAmT+PUBPwbnY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RnJetQo5yXZtVIzdqT7I2bsQ2Q0rf/2IJ5s0/Hb4g88pYbpEhXK7vxpcNaUuXoAuc Tah5pthrBmltjyo2WhboHUg05bJ/kxhO8MjQ6zRpVuodxGkyevLleK9PtY4DDtRaP0 MGo15cv/8l/yM3wfJaiOv42xDzscEGvtKAvPt/l15lRqu2sRakJT7Taf6FNtiD3ijB I5GGiYRK16Z36NY3nPCfaMHD0yFovIei8pC3Bf2dmOOmCPHU3A4wwyvi2aQ3mj/mKp TZDaFIAGn1USMl61w7761TV9JG4lzLbwDEkOUo7j0kItsGL6oH1YweLO+x8TNdkjLn o+NGYn5w8sqOA== From: SeongJae Park To: Kairui Song Cc: linux-mm@kvack.org, Andrew Morton , "Huang, Ying" , Chris Li , Minchan Kim , Hugh Dickins , Johannes Weiner , Matthew Wilcox , Michal Hocko , Yosry Ahmed , David Hildenbrand , Yu Zhao , linux-kernel@vger.kernel.org, Kairui Song Subject: Re: [PATCH] mm/swap: fix race condition in direct swapin path Date: Mon, 5 Feb 2024 18:24:09 -0800 Message-Id: <20240206022409.202536-1-sj@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240205110959.4021-1-ryncsn@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: CB301140015 X-Stat-Signature: ppztz9c4wik9fsot9dkm54zwxjkxjtqu X-Rspam-User: X-HE-Tag: 1707186272-326961 X-HE-Meta: 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 WwNcwxG3 ZfEX1BRQXDOHGke416m5PMUEVw3c3LWpxIYvjzezLk7o5oCc9KJuXqtw4JZLef9RFXSS2MqqPlDLMPWItXVy6lqthpjvpIvR5+ll9F8bmYdF4HDx55nMGsLcqvhozO79NdlvSoLNfNXdEWZQe35Rauxi+Kg04bZbezuQ2fkcrVxefeDqKvVxBQhb1nOFyVG0KQWgALDM7nsQBWkxYQhFPqurgb4+GCuonHIjCMkUbP1wfiqk= 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: Hi Kairui, On Mon, 5 Feb 2024 19:09:59 +0800 Kairui Song wrote: [...] > mm/memory.c | 19 +++++++++++++++++++ > mm/swap.h | 5 +++++ > mm/swapfile.c | 16 ++++++++++++++++ > 3 files changed, 40 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index 7e1f4849463a..fd7c55a292f1 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3867,6 +3867,20 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > if (!folio) { > if (data_race(si->flags & SWP_SYNCHRONOUS_IO) && > __swap_count(entry) == 1) { > + /* > + * With swap count == 1, after we read the entry, > + * other threads could finish swapin first, free > + * the entry, then swapout the modified page using > + * the same entry. Now the content we just read is > + * stalled, and it's undetectable as pte_same() > + * returns true due to entry reuse. > + * > + * So pin the swap entry using the cache flag even > + * cache is not used. > + */ > + if (swapcache_prepare(entry)) > + goto out; > + I'm getting below build error after this patch. I guess maybe the code need to take care of CONFIG_SWAP unset case? .../mm/memory.c: In function 'do_swap_page': .../mm/memory.c:4004:8: error: implicit declaration of function 'swapcache_prepare'; did you mean 'swapcache_clear'? [-Werror=implicit-function-declaration] 4004 | if (swapcache_prepare(entry)) | ^~~~~~~~~~~~~~~~~ | swapcache_clear Thanks, SJ [...]