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 B030ACCF9E0 for ; Tue, 28 Oct 2025 14:03:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1EE7280155; Tue, 28 Oct 2025 10:03:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 19F298013F; Tue, 28 Oct 2025 10:03:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0670880155; Tue, 28 Oct 2025 10:03:14 -0400 (EDT) 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 E37E68013F for ; Tue, 28 Oct 2025 10:03:14 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id B9E781604A6 for ; Tue, 28 Oct 2025 14:03:14 +0000 (UTC) X-FDA: 84047689908.20.77943BE Received: from out-185.mta0.migadu.com (out-185.mta0.migadu.com [91.218.175.185]) by imf06.hostedemail.com (Postfix) with ESMTP id 7F67318001F for ; Tue, 28 Oct 2025 14:03:12 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=bp6a9gAz; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf06.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.185 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1761660192; a=rsa-sha256; cv=none; b=tYTw1Ii5dafZmq5Rw6qoXF6UNtL3tjJvOn4DyIkAD+zMu7ZGlZs6H0BrfkmX45hCLUoghg ajmsgfjad2hXk9Pk3m/Im6liyuMer6stjJ3XW+cRtrd35o48lvt9/0aDz3mNnN1X79q3xY Pc0Jn6UmOlamx/P+XxNzOCfLsDitUa4= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=bp6a9gAz; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf06.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.185 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1761660192; 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=SdeP1C9lZUf/BHy9VyO6H/2ZkQY+8y2qy7tx97P5h/I=; b=U57r4pTLGxD37ZvDvIQ+qabsbCngMefbzaLktIjR14hAJAVFwZiLOH73efN3WahTrEIiPK qTI2itz44HVB1HgZ7u999BS3nFvBtxOdPyHMgMvX9xwEQyfKJrqRPh9UeVAAgbkVM5EP67 42AKCuAMSYRH9CoZk5MKSsypzXT93pY= 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=1761660189; 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=SdeP1C9lZUf/BHy9VyO6H/2ZkQY+8y2qy7tx97P5h/I=; b=bp6a9gAztickZhcVXAzCYe6KGXExJZWpvLQghvCnTrMnB8k9/ms5522DdHvjaBQXwl1RP/ 1YHo2+jDweAPtLcq9U1Cb3e57rrqkh4/RyV+G7msuW0Jz/HOa8JsbwwuEnjip7pOA7mM6l 35opjXquzD26S/pjcE8ZenFRa/5aYXs= 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@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v1 09/26] writeback: prevent memory cgroup release in writeback module Date: Tue, 28 Oct 2025 21:58:22 +0800 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: ss9qn8jy6y8i198iekjwdujzsafqwaq3 X-Rspamd-Queue-Id: 7F67318001F X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1761660192-210177 X-HE-Meta: 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 zwbiu32w W2dnJ0Mni2tsfneJ1OETUm604tmDp0tBdvmliaXsixLb/5Pdp5xh9ayvo+GuqisQDycjDDY1UTOqPFeSPcHTf/X2RXA+TTpF0Q03GHtrneAVmLtfepqfUZYgsZDgDoCJ8bR61g30Gv0EiFrMdqceTBxFfMQ8s3l/AEN1brfzsPdwUw8lC1727VqDJAkokiJ1s9F9+MAQE8sGxhcbQy2MIqmTezQ== 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 --- 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 2b35e80037fee..afd81fb8100cb 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -269,15 +269,13 @@ 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) @@ -968,16 +966,16 @@ 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->flags & CSS_ONLINE)) - return; + goto out; id = css->id; if (id == wbc->wb_id) { wbc->wb_bytes += bytes; - return; + goto out; } if (id == wbc->wb_lcand_id) @@ -990,6 +988,8 @@ 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 9fdbd4970021d..174e52d8e7039 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) @@ -1577,9 +1577,14 @@ 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 c08aff044e807..3680828727f23 100644 --- a/include/trace/events/writeback.h +++ b/include/trace/events/writeback.h @@ -295,7 +295,10 @@ 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 1da3ad77054d3..aa8945c4ee383 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -241,7 +241,7 @@ 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 @@ -251,14 +251,16 @@ 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