6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jingbo Xu jefflexu@linux.alibaba.com
[ 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 jack@suse.cz Signed-off-by: Jingbo Xu jefflexu@linux.alibaba.com Link: https://lore.kernel.org/r/20231014125511.102978-1-jefflexu@linux.alibaba.com Acked-by: Tejun Heo tj@kernel.org Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 c1af01b2c42d7..1767493dffda7 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); }
+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 */