From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9DDA3D29FEC for ; Wed, 14 Jan 2026 11:33:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 113DB6B0089; Wed, 14 Jan 2026 06:33:27 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 0B7E76B008C; Wed, 14 Jan 2026 06:33:27 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EFC2F6B0098; Wed, 14 Jan 2026 06:33:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id DF5436B0089 for ; Wed, 14 Jan 2026 06:33:26 -0500 (EST) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id AAF18160473 for ; Wed, 14 Jan 2026 11:33:26 +0000 (UTC) X-FDA: 84330358812.27.A69A4EB Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) by imf07.hostedemail.com (Postfix) with ESMTP id E8A5540010 for ; Wed, 14 Jan 2026 11:33:24 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=PQYKnHnA; spf=pass (imf07.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.174 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1768390405; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=RYKmKzTmoDz+3hblYyrmsVqHSYCX4thxKqFjYci068E=; b=0uDyyGuhQPpU6cNMiXM3rwrU0MdDILP8qNYuBPrEKhV9Nal/IrZSrgzeMMvxWxJ9NbGjKL bjo1vcXqBuH+zUE6UHruJYnmpOcWujoSTylFHa4CXiyWDFqIWTRt+iJsgJY4IJPeKOlxot 4NyxQmDrYwTz9p771CDanNVAbjBXUlo= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=PQYKnHnA; spf=pass (imf07.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.174 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1768390405; a=rsa-sha256; cv=none; b=UnINyyQkakoTEN8amz6Nx8U4rPy8JCBfb6yBq7a/TNE/rT258wYExWhFnHXRuIEdgLobxm 5GNyjkKgd87kYLMEQj7vJKgDSHCWzTDQDO+3BQqh2e1NmrPsz6c3sPsZBFfRN9ylcLWPq5 sXo3bddOM8WapandqguSFORNf8Iuzi8= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1768390403; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RYKmKzTmoDz+3hblYyrmsVqHSYCX4thxKqFjYci068E=; b=PQYKnHnA/WXohtXcryy3wCAj7dsUJLBy+6Tqf/8flvNyDOr20PD6qxaTtXxWRo9MQ4FOcl WrXlqIg/jPG8B4awfWDFo++s/vr7h/24OIZVjg5p164uKuULgP5+510o0zDWvZHAPo1bzy czy9TwQVzj3XPiK3SeV0DSsBhpTqEhQ= From: Qi Zheng To: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, yosry.ahmed@linux.dev, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v3 08/30] mm: memcontrol: prevent memory cgroup release in get_mem_cgroup_from_folio() Date: Wed, 14 Jan 2026 19:32:35 +0800 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: E8A5540010 X-Stat-Signature: 44e19gxkko1y3nji9879zn8rjr96m4rs X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1768390404-522302 X-HE-Meta: U2FsdGVkX18KLkRHUTi4OIg7Y260XQ+l1Nld7GthFEi4i3bJsEPDisZxtrV40xPppxOX3URtJwUrJNv62rRhBW2AeAadGpZ3G3B84Zp0rbSAI1hnTtr622tVdE+D+D9vxwIeqE0JmRhhcJb2DKlhMvQDN5fSJxwSHGcbBEPRyPiLWUnRh9nVAut5WeFW4iWbFpW92d9YVTCwrLE5OELx4N92fSh3XJp3FVjNRUcAS/HHKdVqohGS6rJGJp5lwAjLynKyK1CWbHt/3UyR7FXbXLL1MLmXU1GACIvmIEt7Zp+0TwxKkKmM+CdNv8Ynhk6sbd28iULocKlfkgnLrLw8Rnf4SYLIYufFSrjdx0Z9SmANViFRsdKnOIagpmwR6b+QDtxND4zX5W4Utec/mXL4WU936r0Ft4xbz2Ky13nydOPM5FxInvpJPCyKEO3SVCO0ZOrnjX2GzrFqq5N5lDvcpfddrfEPeL8CUvIa16WDGm5lrkbYMafVm3pGyDa8i3cS9aOj/VCyMpaJwX6DnMVXXS4I+PaSSfgnYI2bI25vjmEtdHYfWVp37INrIoETkuz8B0O3HiSLUluOcwCYOG4IJWfoCHCHNwo9cfudbgbIYGB82e55d8pDo+idqOo/07smUHUn3M5xzQcZUlt70G1KNJhYKOWi5y+Jo5tYvJeKfRkiaEz37eFDs2xtQtCKcoa+0XPfjBwSowW0sFqgyYp5kDlrM7zvfrBPBY+NVefOSDBK8AO7EQsnSAcG5KvH5YTxk1wnLmK/uvRmloGfo23mhceeaZMxVRa+Gq76P3h6PaPGDTiXRVlX8v9DstPrqqamcVLpFZv8d/KNVzzbWCo0WcE/gVBjMspW3YM8mll+nID6ma8nhKTEgP966GoBEuIpAsy4k7l2EgyDKZVYk+W6kiKLr9yWTtfRxF6wA4kSeH2wrCjz0q5nPeWtFNaBdeEsb2FKg4Ixg2PQa0+plWr DloTDbwp /EyLlUd0p91vKT0uy0f2cnAOvaJDDC90BNZVBQLbLjT5KEL9e4Nw7rxHRvOAzkEN5mkVytFLsXLvzCId2PTf+ZJBw7DrJbT5+ctkVIS677apxSYRQLO3KSQv35GyDfsCCE5KkFifWV3jwubsjpbdlaVw9RH9o24+lo8LimbnkdKdgfE68lLNtRekLhslEFQ4ULLD24tR7PGTSNTPMQE+hrY2vMrsb1dNDWP7AXhar7+qrvNRX83RdVhs/euVhDGU/1ZiD 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: From: Muchun Song In the near future, a folio will no longer pin its corresponding memory cgroup. To ensure safety, it will only be appropriate to hold the rcu read lock or acquire a reference to the memory cgroup returned by folio_memcg(), thereby preventing it from being released. In the current patch, the rcu read lock is employed to safeguard against the release of the memory cgroup in get_mem_cgroup_from_folio(). This serves as a preparatory measure for the reparenting of the LRU pages. Signed-off-by: Muchun Song Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo --- mm/memcontrol.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 982c9f5cf72cb..0458fc2e810ff 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -991,14 +991,18 @@ struct mem_cgroup *get_mem_cgroup_from_current(void) */ struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio) { - struct mem_cgroup *memcg = folio_memcg(folio); + struct mem_cgroup *memcg; if (mem_cgroup_disabled()) return NULL; + if (!folio_memcg_charged(folio)) + return root_mem_cgroup; + rcu_read_lock(); - if (!memcg || WARN_ON_ONCE(!css_tryget(&memcg->css))) - memcg = root_mem_cgroup; + do { + memcg = folio_memcg(folio); + } while (unlikely(!css_tryget(&memcg->css))); rcu_read_unlock(); return memcg; } -- 2.20.1