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 B8B22E91297 for ; Thu, 5 Feb 2026 09:02:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2DC6D6B009B; Thu, 5 Feb 2026 04:02:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 29C996B00A4; Thu, 5 Feb 2026 04:02:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 15DDB6B00A6; Thu, 5 Feb 2026 04:02:32 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 051536B009B for ; Thu, 5 Feb 2026 04:02:32 -0500 (EST) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id A805258F72 for ; Thu, 5 Feb 2026 09:02:31 +0000 (UTC) X-FDA: 84409812102.25.FCF5732 Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) by imf17.hostedemail.com (Postfix) with ESMTP id D9B3040002 for ; Thu, 5 Feb 2026 09:02:29 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=gJvM0GXf; spf=pass (imf17.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.181 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=1770282150; 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=rVG4FBtA5C8lZDYA783TBUFJRw1YsphndfITKeVR5Jk=; b=B3F2ryB4POhnnZIoht0aq2VL157ki5SdSJRuuPPXaS26RxcEgJ+LFHvuAOOwdr8RI9mIch W4W0mzTuf7FwbNKb0xwN7xun4Ibs2cpNxkMVHmlsOeHznpo7cguQCKpBwiNafg7EioVEJi 1ReG1jvwBlzziMRi4Ou0dOsVRsoGreQ= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=gJvM0GXf; spf=pass (imf17.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.181 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=1770282150; a=rsa-sha256; cv=none; b=lYECcXEihy6QlXl2MIWsydxA7TcSXyPfTKRM/9h9jnJpguQ4ACdfW5HGEcTp24C8lmVwlc Um7GRPmXPAyM0OlEcGJ62A4JmtB8g94Kgf6d9wE3zcO11dBzwHRC4kInJTg4W4jcPRWs1F JN9k+0a280jSYdmeNLzUzv4R8udxJm0= 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=1770282148; 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=rVG4FBtA5C8lZDYA783TBUFJRw1YsphndfITKeVR5Jk=; b=gJvM0GXfYQygWkW4Ct+rwyYQkDXLMBc3fP697JvVIMEZedGgIR8TI28dyqAoOkaQ9blK/h D3CJvfPRZbVKCShjyWCz8Zde7Vf+fXSIeTOP19Qt4JAlKVhS0+PtMtGXKzjBbLVZkGJ8BM SDe5BdzPXCcuGS6rcjBS2ydOuV0l34Q= 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 Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v4 10/31] writeback: prevent memory cgroup release in writeback module Date: Thu, 5 Feb 2026 17:01:29 +0800 Message-ID: <46e2df6f69837b0f12e1ad1307c0f32334939dc5.1770279888.git.zhengqi.arch@bytedance.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: qpdexeij8xkeugqi9qy3433unn9fj1xh X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: D9B3040002 X-HE-Tag: 1770282149-949514 X-HE-Meta: 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 fJM3wLoU NbzFh6KHC0j+4IB7XEriCqrvGTuKipk0atSFiOVIslvdKcuNiQWu89kSJPTT385zzJZLVzKJAFnTKPprghaPgH8+ZMW5GCuTYD7YsujP+OaVANvuoGhRv6LJj4CS5Rfl820zZiBpiDkfcowm6b320zLOUvE06s59ZA6/kVj1VOrdTpZsktshdab5umSOlNVxmSACUJnnfjwqTGp1+IIgnCjbmsF7lm8Ogq1u4m5i1rH/JKtmzunwMlIY47mtete0IRk/Mi+X2tXpiOokzBhiA1Ocf7aI5ibguIAmdUn0LN0eWm0k= 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 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 68228bf89b82e..1a527ce28514d 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -279,15 +279,13 @@ 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 7b3d8f341ff10..6b987f7089ca4 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 9e7b00f1450e7..5508a4aced0cc 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -243,7 +243,7 @@ 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 @@ -253,14 +253,16 @@ 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