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Tue, 16 Sep 2025 21:41:20 -0700 (PDT) MIME-Version: 1.0 References: <20250916160100.31545-1-ryncsn@gmail.com> <20250916160100.31545-16-ryncsn@gmail.com> In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Wed, 17 Sep 2025 12:41:09 +0800 X-Gm-Features: AS18NWCg85JktjCHMlaLqxFptGC1bgva_j3Nzmnq8WvHDBi87jCKk26cFVpIEwo Message-ID: Subject: Re: [PATCH v4 15/15] mm, swap: use a single page for swap table when the size fits To: Kairui Song Cc: linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Hugh Dickins , Chris Li , Baoquan He , Nhat Pham , Kemeng Shi , Baolin Wang , Ying Huang , Johannes Weiner , David Hildenbrand , Yosry Ahmed , Lorenzo Stoakes , Zi Yan , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: B35DF1C0004 X-Stat-Signature: kpcwo87ktxnnatmkejej1t4gromzcp7y X-Rspam-User: X-HE-Tag: 1758084081-934959 X-HE-Meta: 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 RLWIm8TI +3Y0bnhjfHaPlkv2M/f7/M3QEltA6W3Oj2ibjvzVvqR3AV/k6zQFZO3bH0occ9oRw6pw70EYrySgyQkfcPZCYbECq6uZ93vOk0uGDPU8Em/4seEIi+5ClG15SrFFTVIwrciUa3e7IJ1Ubcb1KW/CML4m2huvh1CEgVgUVL0jJZt53uibrAKeRgnEzhecMVAYKcZV8XXb80JTStOO0SwlYl2Oc+GpNkX5eMa7CZ4wy5tocD+z7tTbya/NiUK7g5SAv919i161d2PcaobsN3AjNkN1GUexvXVQHsHmAYUROXTC83NQk4QWj6waMVyWVMiOgPQMpRO7iRfg0sysMT/jxpnYpS2sXrcZRI1+bF55nGRYE5l5sFd2PutjmD7UPnE4rf+q9iWqV/dwf/xhPmJT1Frn/NLcYNBdyjZgQ1/pwbysz17sTrfH37CzqQqF34ypBzPh14N8J61nqYGKJWQR5Q2FyAA== 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: > > > > > --- > > > +static void swap_table_free(struct swap_table *table) > > > +{ > > > + if (!SWP_TABLE_USE_PAGE) { > > > + kmem_cache_free(swap_table_cachep, table); > > > + return; > > > + } > > > + > > > + call_rcu(&(folio_page(virt_to_folio(table), 0)->rcu_head), > > > + swap_table_free_folio_rcu_cb); > > > +} > > > > Can=E2=80=99t it simply be: > > virt_to_page(table)->rcu_head ? > > I'm not sure if we prefer folios when possible? Not sure either, but even Mathew still sometimes suggests using PAGE: https://lore.kernel.org/lkml/aLrrQDCBzaMwwmA-@casper.infradead.org/ BTW, "(folio_page(folio), 0)" looks quite strange. I mean, why is it 0 instead of 1? Although we know it=E2=80=99s always one PAGE, 0 still seems strange. > > Either way is fine, they are identical for this use case. > Thanks Barry