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[2603:7000:c01:2716:da5e:d3ff:fee7:26e7]) by smtp.gmail.com with ESMTPSA id nf8-20020a0562143b8800b0068c3b1bcf6bsm940617qvb.95.2024.02.02.08.28.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Feb 2024 08:28:34 -0800 (PST) Date: Fri, 2 Feb 2024 11:28:33 -0500 From: Johannes Weiner To: Chengming Zhou Cc: Nhat Pham , Andrew Morton , Yosry Ahmed , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 6/6] mm/zswap: zswap entry doesn't need refcount anymore Message-ID: <20240202162833.GG1227330@cmpxchg.org> References: <20240201-b4-zswap-invalidate-entry-v1-0-56ed496b6e55@bytedance.com> <20240201-b4-zswap-invalidate-entry-v1-6-56ed496b6e55@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240201-b4-zswap-invalidate-entry-v1-6-56ed496b6e55@bytedance.com> X-Rspamd-Queue-Id: 4D4F640018 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: izb4g6ttmihezczgzgfxm1cxm1npmawm X-HE-Tag: 1706891315-404292 X-HE-Meta: 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 gNWWZM6K 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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 Thu, Feb 01, 2024 at 03:49:06PM +0000, Chengming Zhou wrote: > Since we don't need to leave zswap entry on the zswap tree anymore, > we should remove it from tree once we find it from the tree. > > Then after using it, we can directly free it, no concurrent path > can find it from tree. Only the shrinker can see it from lru list, > which will also double check under tree lock, so no race problem. > > So we don't need refcount in zswap entry anymore and don't need to > take the spinlock for the second time to invalidate it. > > The side effect is that zswap_entry_free() maybe not happen in tree > spinlock, but it's ok since nothing need to be protected by the lock. > > Signed-off-by: Chengming Zhou Acked-by: Johannes Weiner