From nobody Fri Jan 2 13:27:17 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DAAE4CD8CBF for ; Wed, 11 Oct 2023 08:42:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345478AbjJKImk (ORCPT ); Wed, 11 Oct 2023 04:42:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42044 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344899AbjJKIme (ORCPT ); Wed, 11 Oct 2023 04:42:34 -0400 Received: from out30-113.freemail.mail.aliyun.com (out30-113.freemail.mail.aliyun.com [115.124.30.113]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 32EB994; Wed, 11 Oct 2023 01:42:32 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R221e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045170;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0VtwDfcD_1697013748; Received: from localhost(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0VtwDfcD_1697013748) by smtp.aliyun-inc.com; Wed, 11 Oct 2023 16:42:29 +0800 From: Jingbo Xu To: tj@kernel.org, guro@fb.com Cc: lizefan.x@bytedance.com, hannes@cmpxchg.org, cgroups@vger.kernel.org, jack@suse.cz, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, joseph.qi@linux.alibaba.com Subject: [PATCH] writeback, cgroup: switch inodes with dirty timestamps to release dying cgwbs Date: Wed, 11 Oct 2023 16:42:28 +0800 Message-Id: <20231011084228.77615-1-jefflexu@linux.alibaba.com> X-Mailer: git-send-email 2.19.1.6.gb485710b MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The cgwb cleanup routine will try to release the dying cgwb by switching the attached inodes. It fetches the attached inodes from wb->b_attached list, omitting the fact that inodes only with dirty timestamps reside in wb->b_dirty_time list, which is the case when lazytime is enabled. This causes enormous zombie memory cgroup when lazytime is enabled, as inodes with dirty timestamps can not be switched to a live cgwb for a long time. It is reasonable not to switch cgwb for inodes with dirty data, as otherwise it may break the bandwidth restrictions. However since the writeback of inode metadata is not accounted, let's also switch inodes with dirty timestamps to avoid zombie memory and block cgroups when laztytime is enabled. Fixs: c22d70a162d3 ("writeback, cgroup: release dying cgwbs by switching at= tached inodes") Signed-off-by: Jingbo Xu --- This issue is reported on our production environment (5.10 kernel with the dying cgwbs optimization[1] backported, and ext4 mounted with "-o relatime,lazytime"), while I can also reproduce it on the latest mainline kernel. [1] c22d70a162d3 ("writeback, cgroup: release dying cgwbs by switching attached inodes") --- fs/fs-writeback.c | 33 +++++++++++++++++++++------------ 1 file changed, 21 insertions(+), 12 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index c1af01b2c42d..89125760e4ad 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -613,6 +613,24 @@ static void inode_switch_wbs(struct inode *inode, int = new_wb_id) kfree(isw); } =20 +static bool isw_prepare_wbs_switch(struct inode_switch_wbs_context *isw, + struct list_head *list, int *nr) +{ + struct inode *inode; + + list_for_each_entry(inode, list, i_io_list) { + if (!inode_prepare_wbs_switch(inode, isw->new_wb)) + continue; + + isw->inodes[*nr] =3D inode; + (*nr)++; + + if (*nr >=3D WB_MAX_INODES_PER_ISW - 1) + return true; + } + return false; +} + /** * cleanup_offline_cgwb - detach associated inodes * @wb: target wb @@ -625,7 +643,6 @@ bool cleanup_offline_cgwb(struct bdi_writeback *wb) { struct cgroup_subsys_state *memcg_css; struct inode_switch_wbs_context *isw; - struct inode *inode; int nr; bool restart =3D false; =20 @@ -647,17 +664,9 @@ bool cleanup_offline_cgwb(struct bdi_writeback *wb) =20 nr =3D 0; spin_lock(&wb->list_lock); - list_for_each_entry(inode, &wb->b_attached, i_io_list) { - if (!inode_prepare_wbs_switch(inode, isw->new_wb)) - continue; - - isw->inodes[nr++] =3D inode; - - if (nr >=3D WB_MAX_INODES_PER_ISW - 1) { - restart =3D true; - break; - } - } + restart =3D isw_prepare_wbs_switch(isw, &wb->b_attached, &nr); + if (!restart) + restart =3D isw_prepare_wbs_switch(isw, &wb->b_dirty_time, &nr); spin_unlock(&wb->list_lock); =20 /* no attached inodes? bail out */ --=20 2.19.1.6.gb485710b