From: Tejun Heo tj@kernel.org
[ 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 tj@kernel.org Cc: Jan Kara jack@suse.cz Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- 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 b16645b417d9..bd9474e82f38 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -714,6 +714,7 @@ 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;
/* @@ -725,7 +726,12 @@ 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;