From ea6fac901ca35cea057b734b3818334ee54e14a2 Mon Sep 17 00:00:00 2001 From: Jingbo Xu Date: Sat, 14 Oct 2023 20:55:11 +0800 Subject: [PATCH] writeback, cgroup: switch inodes with dirty timestamps to release dying cgwbs [ Upstream commit 6654408a33e6297d8e1d2773409431d487399b95 ] 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 for, let's also switch inodes with dirty timestamps to avoid zombie memory and block cgroups when laztytime is enabled. Fixes: c22d70a162d3 ("writeback, cgroup: release dying cgwbs by switching attached inodes") Reviewed-by: Jan Kara Signed-off-by: Jingbo Xu Link: https://lore.kernel.org/r/20231014125511.102978-1-jefflexu@linux.alibaba.com Acked-by: Tejun Heo Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin --- fs/fs-writeback.c | 41 +++++++++++++++++++++++++++++------------ 1 file changed, 29 insertions(+), 12 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index c1af01b..1767493 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -613,6 +613,24 @@ out_free: kfree(isw); } +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] = inode; + (*nr)++; + + if (*nr >= 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 = false; @@ -647,17 +664,17 @@ bool cleanup_offline_cgwb(struct bdi_writeback *wb) nr = 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++] = inode; - - if (nr >= WB_MAX_INODES_PER_ISW - 1) { - restart = true; - break; - } - } + /* + * In addition to the inodes that have completed writeback, also switch + * cgwbs for those inodes only with dirty timestamps. Otherwise, those + * inodes won't be written back for a long time when lazytime is + * enabled, and thus pinning the dying cgwbs. It won't break the + * bandwidth restrictions, as writeback of inode metadata is not + * accounted for. + */ + restart = isw_prepare_wbs_switch(isw, &wb->b_attached, &nr); + if (!restart) + restart = isw_prepare_wbs_switch(isw, &wb->b_dirty_time, &nr); spin_unlock(&wb->list_lock); /* no attached inodes? bail out */ -- 2.7.4