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Tue, 19 Dec 2023 20:30:32 -0800 (PST) Received: from localhost ([2620:10d:c092:400::4:42a4]) by smtp.gmail.com with ESMTPSA id wn7-20020a170907068700b00a23524df923sm3602794ejb.206.2023.12.19.20.30.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Dec 2023 20:30:32 -0800 (PST) Date: Wed, 20 Dec 2023 05:30:33 +0100 From: Johannes Weiner To: Yosry Ahmed Cc: Andrew Morton , Chengming Zhou , Nhat Pham , Chris Li , Seth Jennings , Dan Streetman , Vitaly Wool , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 5/5] mm/zswap: cleanup zswap_reclaim_entry() Message-ID: <20231220043033.GA23822@cmpxchg.org> References: <20231213-zswap-dstmem-v1-0-896763369d04@bytedance.com> <20231213-zswap-dstmem-v1-5-896763369d04@bytedance.com> <20231214142320.f5cf319e619dbb2127c423e9@linux-foundation.org> <20231218140313.GA19167@cmpxchg.org> <20231218145815.GA21073@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 734CD40009 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: so1rh5es1m3np4rb7g5sruq9usor7sss X-HE-Tag: 1703046634-768999 X-HE-Meta: U2FsdGVkX1+LZp2tNIQZs1igErqHlWlc86IUUKhE9P7TedypyRXu+orARoVFURZm9tbaBEVr2dr9ik8+5MonzJEfY8bW76PXZkIG6hLf5V1SB5xz3R5QUxqRHXwDb+a35GMhA79TOOubGw93KR9Gydd4rLeE90bEsJTGar4Risel6dc+FMgOHhgZO2lj0k1Il/TkXOVRnVwsQato1R4w34Qeq2BSmeXZcGifR7q5OWq0ckRcqXrnV8gyryQ4GRSt2g5uSSXfemSY7yzEIptbMiAYgWJgqXt8XH34QEcsugXkaCJuvkRrbSN0HF6hVR1FxwYK1RaXuRopZMGzvXliAuJv3OWs/dv1TvSQ6bS3TCBzdTkeagPHdj+RmYIVPfryDifu58sRP+KWSfnZBc0msvBplO+3dBduG4PDhShmCNzt97Bd8CJASSvu9wrJE9pPH9hctNFbQQkBKwtfsnlp/izc2YXrXjAF94Y/V9l+jQH5lx/QgmxKAHbzcu1LkafP4JWA6Gog8+OIzsjvmFeY3GY2YlPT/Grrb76sIsy3AgJywiE5vbLr6QFoTnYfOB5Kw1P78+9glh9ssLYTQL5Xi+BdtfvgsYLSPhvPtsySoNMFudsFfpA8CnHbziS5XgGzx3NzWdBoPs0zzx2DecjAk4LdkV7+6axkZJWDAI8/077XLwc6h85NRusrV9f8sru6R4MQycQtxzXuocG8BJBnWzcqJdIP4uFXv0O7gB+0qL4MtVxbrTRvaekGAIYuC8xpFiwQg4KzmtYTRfER5QJ/mUhBIIF38M58MNLeXQ//uA+g4ubZaAvre1q6ae3+BSjH5kJuNylR+Jt/IqqV2RS89+ro87YyWhLZflvwQbIuc+2mln1OvCWtDNd8SuA09VORxZazuIbOFpHVaTz+PloJ2d4qGwsg6CKMTNJpSn5FRBnjRn5QL6UGSQLQ/p1PYj+1+DdIQnuJ39eGGOyAbJR q2enHhOD nqgX+gyPV8gYt+prf0l6EKYRvxBqAOQyeA6ZEY9vJWWCJvLFpq2LOwpBAL8Zw2ruOMhVLcWxPSxzsM84nUhi8SebdvtKwywg4QNs9nw4ZFXyaDCMB5lSzsreWQxgptlFCiYp4fiLpT3XMR62sZ8oJu/dEA+/BJi3vJnpVwKcG34iV/Jxd+lSLKEMkb7++7y0+W4OkESIvwusXWeU1d1AoAkUCnV2eA53oDhD451U5bq6HAI5+WHXcImV0xVdGyYjLFw3wOZMGyxhR+xSvLf2WqAL7SAKpfNvE5dlMl2wc9uwZTSStL4Mg2/CaywJ6J1lzN3DiKR1MloQje9hHFxtBfgcRtKN7sLcy1XA6B1aBOZ1BIhw4Ikse97uIkyaUQM78RPQsJ9cuSj03emFVnphE1Zob3QwUF7TOJl6hXRLu26b0O8e/bRwHsmjCJ5hI4guLJINCU5g5KCvqFOjOoD/43eUqEg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000006, 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 Mon, Dec 18, 2023 at 12:52:40PM -0800, Yosry Ahmed wrote: > --- a/mm/zswap.c > +++ b/mm/zswap.c > @@ -1458,15 +1458,14 @@ static int zswap_writeback_entry(struct > zswap_entry *entry, > page = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol, > NO_INTERLEAVE_INDEX, &page_was_allocated, true); > if (!page) { > - /* > - * If we get here because the page is already in swapcache, a > - * load may be happening concurrently. It is safe and okay to > - * not free the entry. It is also okay to return !0. > - */ > return -ENOMEM; > } > > - /* Found an existing page, we raced with load/swapin */ > + /* > + * Found an existing page, we raced with load/swapin. We generally > + * writeback cold pages from zswap, and swapin means the page just > + * became hot. Skip this page and let the caller find another one. > + */ > if (!page_was_allocated) { > put_page(page); > return -EEXIST; ACK, that looks good to me! Thanks