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Thu, 27 Aug 2026 07:46:09 -0400 (EDT) Date: Thu, 27 Aug 2026 12:46:08 +0100 From: Kiryl Shutsemau To: Hugh Dickins Cc: Andrew Morton , Ackerley Tng , Alexander Viro , Baolin Wang , Barry Song , Binbin Wu , Christian Brauner , Christoph Hellwig , Christoph Lameter , Claudio Imbrenda , David Hildenbrand , JP Kobryn , Jan Kara , Jens Axboe , Johannes Weiner , Kairui Song , Lance Yang , Leonardo Bras , Lorenzo Stoakes , Marcelo Tosatti , Matthew Wilcox , Mel Gorman , Miaohe Lin , Michal Hocko , Minchan Kim , Muchun Song , Oscar Salvador , Peter Zijlstra , Qi Zheng , Rik van Riel , Sebastian Andrzej Siewior , Shakeel Butt , Suren Baghdasaryan , Vlastimil Babka , Yang Shi , Yu Zhao , Zach O'Keefe , Zi Yan , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 04/25] mm/fbatch: lru bit set, no extra ref, while folio on per-cpu fbatch Message-ID: References: <14a16945-529b-8bc0-ab38-3ea97e54e223@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: CE65018000C X-Stat-Signature: r3hdoufc5wcr47w3mt6nm1sedcqzptbo X-HE-Tag: 1787831181-61049 X-HE-Meta: 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 4Dk8l5nS s1AWiYFl68BIg8hPgawya1yz4Lo5zuBSEvJYGDl0+m2fSzZjfclGVmLX/Yvu7KC0DS+ajuup0IIlR5sSp1huxOwO+6pV1ICKGvne3Visr//tHgYSLnk0Yu4Y5B7vRJSepWEIrgG2l06d6fimoCBGnUWPBSumPlYolIraMHzxIw1i19p1miXITrrpDgkMnMEq+TunKcRSuISsSK72AOWvipzfbmGd73fn+/rEkEtgXY00qLJCJ2o+DG35P29gDbakJR4KC/ANAg/TtRjB3w6HH8d/bQakxlBY82L/7mPWHdb/x1PawzDC9kOlwJsZiaoPW62xJZ1uDmwBt66T/is1Sj8IbxHkkNAmPwEPk Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 24, 2026 at 07:01:20AM -0700, Hugh Dickins wrote: > Treat folios on a per-cpu fbatch as if they were already on the lruvec: > with PG_lru set, without holding an extra reference. This will enable > the removal of most lru_add_drain() and lru_add_drain_all() calls soon. > > Recognize such a folio by 0x02 set in the folio->lru.next pointer by > folio_add_lru(). Hm. pfmemalloc (__GFP_MEMALLOC) thingy already claims the bit. Is it safe because such memory is never on LRU? Are pfmemalloc and PG_lru mutually exclusive? Do we want to be explicit about this? Like, folio/page_is_pfmemalloc() shouldn't return true for PG_lru folios/pages or something. -- Kiryl Shutsemau / Kirill A. Shutemov