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b=OdmgRg3qyn6J8aDsbqLaGp0YTTaluhiZhWbkHR3umhSBbE8aYtGUlHk/e/adSV9hW VkRWFb1ddniw7FTb+jOja5JusVe1kt63cNiVsMwknLtRRCRQ6apiwHp9HbeZivqfzV QHwRU4m05XBFBFW5uCuhh/x1oXdDQ2NMe9sF8BI7ax9S3W7rp944KLlnBccq4blXhZ ecX2zxqDsd403YnagGtHitK2eKdvWjCspHuoe1tSeiTulxdmSgVwhYpkTimAyqlV7u s+RU+pd7A4bcugMnk7Fjfk851NxzpT0KnjHdPWRO451TyVqifObRGPnCkAaxAJKjQo 74KzFLtsloFbQ== From: SeongJae Park To: "Jiayuan Chen" Cc: SeongJae Park , linux-mm@kvack.org, "Jiayuan Chen" , "Johannes Weiner" , "Michal Hocko" , "Roman Gushchin" , "Shakeel Butt" , "Muchun Song" , "Yosry Ahmed" , "Nhat Pham" , "Chengming Zhou" , "Andrew Morton" , "Nick Terrell" , "David Sterba" , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] mm: zswap: add per-memcg stat for incompressible pages Date: Thu, 5 Feb 2026 19:15:09 -0800 Message-ID: <20260206031509.68313-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 63A1640011 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: c7t9uecrs6ohk81ktmox1ut89iafa9zh X-HE-Tag: 1770347719-634987 X-HE-Meta: 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 uEo5zpxa 9utATTHvnWF0KtuTIJGtIyrNjOw85LVWiACnOrpXRHtXzlSImSRZ1UGzgkJv2tgdsPBg1y8cG+s0CBhhp/WAnGAoFsS6/LOxRAl9I+YUm7siKEqjPJXGIvoLlsDdYup2P1HT7fJQfITsi4LQkOeddid1Mt9B7l0d0t9LczzPNU1i0XO6pOepz07vdkoUJOACCpFemwIZH4WTm8JjDfzOQoa8Hscb6v1j8ikHNUlWOzFK1dpf3liftmpuxlBgl1sCcRyZ0yrnybyyyuXk= 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, 06 Feb 2026 02:47:58 +0000 "Jiayuan Chen" wrote: > February 6, 2026 at 10:21, "SeongJae Park" wrote: > > > > > > On Thu, 5 Feb 2026 13:30:12 +0800 Jiayuan Chen wrote: [...] > > > @@ -941,7 +941,7 @@ static bool zswap_decompress(struct zswap_entry *entry, struct folio *folio) > > > zs_obj_read_sg_begin(pool->zs_pool, entry->handle, input, entry->length); > > > > > > /* zswap entries of length PAGE_SIZE are not compressed. */ > > > - if (entry->length = PAGE_SIZE) { > > > + if (zswap_is_raw(entry->length)) { > > > WARN_ON_ONCE(input->length != PAGE_SIZE); > > > memcpy_from_sglist(kmap_local_folio(folio, 0), input, 0, PAGE_SIZE); > > > dlen = PAGE_SIZE; > > > > > Below this part, I show 'dlen = PAGE_SIZE'. Should it also be converted to > > use the helper function? > > > > The dlen variable represents the decompressed (plaintext) size. > Since we compress individual pages, the decompressed output should > always be PAGE_SIZE in normal cases. > > This check validates whether decompression produced the expected result, not whether the entry is incompressible. > > Using zswap_is_incomp() here would be semantically incorrect - the helper is meant to check if an > entry was stored without compression (i.e., compression failed to reduce size), while dlen = PAGE_SIZE > verifies the output of decompression is valid. You are right. Thank you for kindly correcting me. Thanks, SJ