From 6cc4c3aa714bc58ec5d20f3054ca5f23534984d1 Mon Sep 17 00:00:00 2001 From: Tang Yizhou Date: Tue, 4 Mar 2025 19:03:18 +0800 Subject: writeback: fix calculations in trace_balance_dirty_pages() for cgwb In the commit dcc25ae76eb7 ("writeback: move global_dirty_limit into wb_domain") of the cgroup writeback backpressure propagation patchset, Tejun made some adaptations to trace_balance_dirty_pages() for cgroup writeback. However, this adaptation was incomplete and Tejun missed further adaptation in the subsequent patches. In the cgroup writeback scenario, if sdtc in balance_dirty_pages() is assigned to mdtc, then upon entering trace_balance_dirty_pages(), __entry->limit should be assigned based on the dirty_limit of the corresponding memcg's wb_domain, rather than global_wb_domain. To address this issue and simplify the implementation, introduce a 'limit' field in struct dirty_throttle_control to store the hard_limit value computed in wb_position_ratio() by calling hard_dirty_limit(). This field will then be used in trace_balance_dirty_pages() to assign the value to __entry->limit. Link: https://lkml.kernel.org/r/20250304110318.159567-4-yizhou.tang@shopee.com Fixes: dcc25ae76eb7 ("writeback: move global_dirty_limit into wb_domain") Signed-off-by: Tang Yizhou Acked-by: Tejun Heo Cc: Alexei Starovoitov Cc: Christian Brauner Cc: Jan Kara Cc: "Masami Hiramatsu (Google)" Cc: Matthew Wilcow (Oracle) Cc: Steven Rostedt Signed-off-by: Andrew Morton --- include/linux/writeback.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/writeback.h b/include/linux/writeback.h index 32095928365c..58bda3347914 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -326,6 +326,7 @@ struct dirty_throttle_control { unsigned long dirty; /* file_dirty + write + nfs */ unsigned long thresh; /* dirty threshold */ unsigned long bg_thresh; /* dirty background threshold */ + unsigned long limit; /* hard dirty limit */ unsigned long wb_dirty; /* per-wb counterparts */ unsigned long wb_thresh; -- cgit v1.2.3