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Fri, 26 Jan 2024 06:28:05 -0800 (PST) Received: from localhost ([2620:10d:c091:400::5:271e]) by smtp.gmail.com with ESMTPSA id nf6-20020a0562143b8600b0067cd5c86936sm540440qvb.79.2024.01.26.06.28.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jan 2024 06:28:05 -0800 (PST) Date: Fri, 26 Jan 2024 09:28:00 -0500 From: Johannes Weiner To: chengming.zhou@linux.dev Cc: yosryahmed@google.com, nphamcs@gmail.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chengming Zhou Subject: Re: [PATCH 1/2] mm/zswap: don't return LRU_SKIP if we have dropped lru lock Message-ID: <20240126142800.GF1567330@cmpxchg.org> References: <20240126083015.3557006-1-chengming.zhou@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240126083015.3557006-1-chengming.zhou@linux.dev> X-Rspamd-Queue-Id: 687CE40015 X-Rspam-User: X-Stat-Signature: q1hm6xrnu4zea9heyozo947mzy8q83c5 X-Rspamd-Server: rspam03 X-HE-Tag: 1706279286-405096 X-HE-Meta: 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 LenS6/Kz 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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 Fri, Jan 26, 2024 at 08:30:14AM +0000, chengming.zhou@linux.dev wrote: > From: Chengming Zhou > > 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. Good catch. Can you mention the possible consequences in the log? "Otherwise, the iteration might continue from a cursor position that was freed while the locks were dropped."? > 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") > Signed-off-by: Chengming Zhou Acked-by: Johannes Weiner