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Mon, 29 Jan 2024 16:09:06 -0800 (PST) Date: Tue, 30 Jan 2024 00:09:04 +0000 In-Reply-To: <20240126-zswap-writeback-race-v2-1-b10479847099@bytedance.com> Mime-Version: 1.0 References: <20240126-zswap-writeback-race-v2-0-b10479847099@bytedance.com> <20240126-zswap-writeback-race-v2-1-b10479847099@bytedance.com> Message-ID: Subject: Re: [PATCH v2 1/3] mm/zswap: don't return LRU_SKIP if we have dropped lru lock From: Yosry Ahmed To: Chengming Zhou Cc: Johannes Weiner , Nhat Pham , Andrew Morton , Chris Li , linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="us-ascii" X-Rspamd-Queue-Id: EC86D1C001A X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: bwrd8yk7i1du3qm1xq61wsd31o5mzhku X-HE-Tag: 1706573347-488467 X-HE-Meta: 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 8LitABPe ZLq8jtHhvcO5+84EJbBiTeMXfZjaKjr0CAPoDsbhz6H0Q6RBHYFKf5BeLQyvDjLdiNs8GDDTYSlJbZ7leh7YzfBOKQU/MJ+aNRW0P5PKgC0YelZxd1wAOTEFKanVllHrzcZ438ATx+y8Jr5vvdMvSkfU1ZxazPAuOItKn+4nyHF66Hyeo6DwEeS3YBr42276Pv2fCrWwYvL9BErmJMjMCY/s38TTmx2VioeXesJtGv3tcc29kBVYtdaB6t7cTazRNgSZWbrAD4ihLivpNtl/iB1rIc7h0SageR5u4BDfg8knn/uSIWuSzBNT8JusHqMabcrkrKgNDA16pWe5BbGG1nNm5Yz/qyFyE99VH3yQm6s77R3raaqBspzM6It3PK2f+beenY4zwOhwULR/wg4U+yV3h9z+bRLSwsy1EAlRFuTiEi36R17KCtt3oufa2hturMVQ0aE9W/C1/LR2lCtxYISfM88hCsdkhsCLKndUrjY/fNXM8aaBsMsymiFtSwmDfzQeQaBUAqscOxZyNWBIrvhsQwZyk0UIkZqS/XbG0IRCg3XLAVZPDoV8gvgRUhgM2D2Y/UOvCNZf+MwOrFv5baVhrnKG+qBTRQu0P083foawRJbZxh5KZuKYBgYPmyZdy+n+kTr31nUpnqfCcGJghkWkMGy01Lu1mCmmeWERgN8FdQfIvFs5iqfT6dcHLXkKwcxWK6TrCeB8zT6/33Yg+T61Ni+tjGg5gSbrg1fnsHbiNwLLkYQ28UxrCi9Sp/OvZiZWv7/vheIAtZNkC9vdytPUWPqzbr/fEii61lQ58pVAoOw9WQ5oPfr4pXf0hWDr8hqWE8Mod/852ltQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000426, 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 Sun, Jan 28, 2024 at 01:28:49PM +0000, Chengming Zhou wrote: > LRU_SKIP can only be returned if we don't ever dropped lru lock, or > we need to return LRU_RETRY to restart from the head of lru list. > > Otherwise, the iteration might continue from a cursor position that > was freed while the locks were dropped. Does this warrant a stable backport? > > Actually we may need to introduce another LRU_STOP to really terminate > the ongoing shrinking scan process, when we encounter a warm page > already in the swap cache. The current list_lru implementation > doesn't have this function to early break from __list_lru_walk_one. > > Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure") > Acked-by: Johannes Weiner > Reviewed-by: Nhat Pham > Signed-off-by: Chengming Zhou Acked-by: Yosry Ahmed