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 A3922F30951 for ; Thu, 5 Mar 2026 11:55:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 16CDF6B00A5; Thu, 5 Mar 2026 06:55:58 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1347B6B00A7; Thu, 5 Mar 2026 06:55:58 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 035BE6B00A8; Thu, 5 Mar 2026 06:55:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id E54B86B00A5 for ; Thu, 5 Mar 2026 06:55:57 -0500 (EST) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id ABAB0C2D1E for ; Thu, 5 Mar 2026 11:55:57 +0000 (UTC) X-FDA: 84511855554.06.07515F4 Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) by imf28.hostedemail.com (Postfix) with ESMTP id 5C21AC000B for ; Thu, 5 Mar 2026 11:55:54 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Pb6WKb5m; spf=pass (imf28.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=1772711754; 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=7g4zlvI4KL5BM3hQhoVvcLwONpSLS6QDIXKeCKwliro=; b=YAimTwtXLLYlef00WmsevSMg1UptJV3cb+VEv9aloM+K06W9F9kMT+X9Om1z2b/X8iEqoh Toy784FRNyhlEQe5g3A2k3HtXCIlK7Doo6CTNL+C0dF6JVSOAjZUIqARPasYfqNrNMzRwF rgzVtq4957uP1K/RdCnV+Yh9txVyfRM= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Pb6WKb5m; spf=pass (imf28.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=1772711754; a=rsa-sha256; cv=none; b=vCwisocANx4rcUnda/0GmSyj+mhniYCr3SGRaQu/q7DYBSLcbBzdv5rkou6ZF04fQc+jDN cHjha/xpMEzTZa4IqSXBIx7jrYL7ENWfxmuy2sUV7BxGYKKZu8eK6EVljPQDtdppt1i1p8 O5MGuLfGF9RzqL15IWU+JBFsmwBgtRY= 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=1772711752; 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=7g4zlvI4KL5BM3hQhoVvcLwONpSLS6QDIXKeCKwliro=; b=Pb6WKb5mz/1V1WY0eot4/pZLnwSOkyFz2Lzw8N3G+lPEzpxbDxUTlbXrGgDlF2tztpheTp 93mVBUBBnl/qzFMK1rAbrS6RsSXQ4dyPaLwlGTNCXmU152hwx4J4C1yCAIohg+SU0p/nz5 Pw2uIUZUgDgYZnRJlE3XqFM4pliL338= 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, bhe@redhat.com, usamaarif642@gmail.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v6 10/33] writeback: prevent memory cgroup release in writeback module Date: Thu, 5 Mar 2026 19:52:28 +0800 Message-ID: <645f99bc344575417f67def3744f975596df2793.1772711148.git.zhengqi.arch@bytedance.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 5C21AC000B X-Rspamd-Server: rspam07 X-Stat-Signature: y35m1s5b1rdzujnzooaktcmedwij3ziy X-Rspam-User: X-HE-Tag: 1772711754-703237 X-HE-Meta: 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 zRqmmtjs 7rDhpcN/CObp385GniP9mA7Z63QbzGVwPsEspmqdqQn0JnThhRaWCmmN4E5zk9Niw0GIddBS9Sdk+N7nnlrag4shHuaCSnzI9RkC+yvz//1cc/i7NZ47srDxhgNG+9U+eGPeMQBoudsuJhFGd7WC14W9PoQOZjQuM5EJpL0oJQX5M1u86ICENxkwQnd7JsZ5zDFZoCHYQDchVvTRMsfQHrLQa2YE+s7+E+gYv9c5oXvjzbzWkio+EhQRyKH+P6u1rclZMawEwppHuDDS5P0leQkQa3Chky22RoDDNlZXp8CPpHdA= 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 function get_mem_cgroup_css_from_folio() and the rcu read lock are employed to safeguard against the release of the memory cgroup. 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 Acked-by: Johannes Weiner Acked-by: Shakeel Butt --- fs/fs-writeback.c | 22 +++++++++++----------- include/linux/memcontrol.h | 9 +++++++-- include/trace/events/writeback.h | 3 +++ mm/memcontrol.c | 14 ++++++++------ 4 files changed, 29 insertions(+), 19 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 7c75ed7e89799..c3442a38450ca 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -280,15 +280,13 @@ void __inode_attach_wb(struct inode *inode, struct folio *folio) if (inode_cgwb_enabled(inode)) { struct cgroup_subsys_state *memcg_css; - if (folio) { - memcg_css = mem_cgroup_css_from_folio(folio); - wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC); - } else { - /* must pin memcg_css, see wb_get_create() */ + /* must pin memcg_css, see wb_get_create() */ + if (folio) + memcg_css = get_mem_cgroup_css_from_folio(folio); + else memcg_css = task_get_css(current, memory_cgrp_id); - wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC); - css_put(memcg_css); - } + wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC); + css_put(memcg_css); } if (!wb) @@ -979,16 +977,16 @@ void wbc_account_cgroup_owner(struct writeback_control *wbc, struct folio *folio if (!wbc->wb || wbc->no_cgroup_owner) return; - css = mem_cgroup_css_from_folio(folio); + css = get_mem_cgroup_css_from_folio(folio); /* dead cgroups shouldn't contribute to inode ownership arbitration */ if (!css_is_online(css)) - return; + goto out; id = css->id; if (id == wbc->wb_id) { wbc->wb_bytes += bytes; - return; + goto out; } if (id == wbc->wb_lcand_id) @@ -1001,6 +999,8 @@ void wbc_account_cgroup_owner(struct writeback_control *wbc, struct folio *folio wbc->wb_tcand_bytes += bytes; else wbc->wb_tcand_bytes -= min(bytes, wbc->wb_tcand_bytes); +out: + css_put(css); } EXPORT_SYMBOL_GPL(wbc_account_cgroup_owner); diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index f4b6158b77d8e..20d38262b984b 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -895,7 +895,7 @@ static inline bool mm_match_cgroup(struct mm_struct *mm, return match; } -struct cgroup_subsys_state *mem_cgroup_css_from_folio(struct folio *folio); +struct cgroup_subsys_state *get_mem_cgroup_css_from_folio(struct folio *folio); ino_t page_cgroup_ino(struct page *page); static inline bool mem_cgroup_online(struct mem_cgroup *memcg) @@ -1564,9 +1564,14 @@ static inline void mem_cgroup_track_foreign_dirty(struct folio *folio, if (mem_cgroup_disabled()) return; + if (!folio_memcg_charged(folio)) + return; + + rcu_read_lock(); memcg = folio_memcg(folio); - if (unlikely(memcg && &memcg->css != wb->memcg_css)) + if (unlikely(&memcg->css != wb->memcg_css)) mem_cgroup_track_foreign_dirty_slowpath(folio, wb); + rcu_read_unlock(); } void mem_cgroup_flush_foreign(struct bdi_writeback *wb); diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h index 4d3d8c8f3a1bc..b849b8cc96b1e 100644 --- a/include/trace/events/writeback.h +++ b/include/trace/events/writeback.h @@ -294,7 +294,10 @@ TRACE_EVENT(track_foreign_dirty, __entry->ino = inode ? inode->i_ino : 0; __entry->memcg_id = wb->memcg_css->id; __entry->cgroup_ino = __trace_wb_assign_cgroup(wb); + + rcu_read_lock(); __entry->page_cgroup_ino = cgroup_ino(folio_memcg(folio)->css.cgroup); + rcu_read_unlock(); ), TP_printk("bdi %s[%llu]: ino=%lu memcg_id=%u cgroup_ino=%lu page_cgroup_ino=%lu", diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 4820919c0d219..a4bb8b8b2c457 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -244,7 +244,7 @@ DEFINE_STATIC_KEY_FALSE(memcg_bpf_enabled_key); EXPORT_SYMBOL(memcg_bpf_enabled_key); /** - * mem_cgroup_css_from_folio - css of the memcg associated with a folio + * get_mem_cgroup_css_from_folio - acquire a css of the memcg associated with a folio * @folio: folio of interest * * If memcg is bound to the default hierarchy, css of the memcg associated @@ -254,14 +254,16 @@ EXPORT_SYMBOL(memcg_bpf_enabled_key); * If memcg is bound to a traditional hierarchy, the css of root_mem_cgroup * is returned. */ -struct cgroup_subsys_state *mem_cgroup_css_from_folio(struct folio *folio) +struct cgroup_subsys_state *get_mem_cgroup_css_from_folio(struct folio *folio) { - struct mem_cgroup *memcg = folio_memcg(folio); + struct mem_cgroup *memcg; - if (!memcg || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) - memcg = root_mem_cgroup; + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) + return &root_mem_cgroup->css; - return &memcg->css; + memcg = get_mem_cgroup_from_folio(folio); + + return memcg ? &memcg->css : &root_mem_cgroup->css; } /** -- 2.20.1