From b7d66bbc8ad38a40ec758da0383a0e2a9694e205 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 13 Jun 2019 15:30:41 -0700 Subject: [PATCH] blkcg, writeback: dead memcgs shouldn't contribute to writeback ownership arbitration [ Upstream commit 6631142229005e1b1c311a09efe9fb3cfdac8559 ] wbc_account_io() collects information on cgroup ownership of writeback pages to determine which cgroup should own the inode. Pages can stay associated with dead memcgs but we want to avoid attributing IOs to dead blkcgs as much as possible as the association is likely to be stale. However, currently, pages associated with dead memcgs contribute to the accounting delaying and/or confusing the arbitration. Fix it by ignoring pages associated with dead memcgs. Signed-off-by: Tejun Heo Cc: Jan Kara Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- fs/fs-writeback.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 9544e2f8b79f..7ee86d8f313d 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -721,6 +721,7 @@ void wbc_detach_inode(struct writeback_control *wbc) void wbc_account_io(struct writeback_control *wbc, struct page *page, size_t bytes) { + struct cgroup_subsys_state *css; int id; /* @@ -732,7 +733,12 @@ void wbc_account_io(struct writeback_control *wbc, struct page *page, if (!wbc->wb) return; - id = mem_cgroup_css_from_page(page)->id; + css = mem_cgroup_css_from_page(page); + /* dead cgroups shouldn't contribute to inode ownership arbitration */ + if (!(css->flags & CSS_ONLINE)) + return; + + id = css->id; if (id == wbc->wb_id) { wbc->wb_bytes += bytes; -- GitLab