writeback: memcg dirty_throttle_control should be initialized with wb->memcg_completions
MDTC_INIT() is used to initialize dirty_throttle_control for memcg
domains. It used DTC_INIT_COMMON() to initialized mdtc->wb and
->wb_completions which is incorrect as DTC_INIT_COMMON() sets the
latter to wb->completions instead of wb->memcg_completions. This can
lead to wildly incorrect results when calculating the proportion of
dirty memory the memcg domain should get.
Remove DTC_INIT_COMMON() and update MDTC_INIT() to initialize
mdtc->wb_completions to wb->memcg_completions.
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: c2aa723a6093 ("writeback: implement memcg writeback domain based throttling")
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0f1a94e..56c0bff 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -145,9 +145,6 @@
unsigned long pos_ratio;
};
-#define DTC_INIT_COMMON(__wb) .wb = (__wb), \
- .wb_completions = &(__wb)->completions
-
/*
* Length of period for aging writeout fractions of bdis. This is an
* arbitrarily chosen number. The longer the period, the slower fractions will
@@ -157,12 +154,16 @@
#ifdef CONFIG_CGROUP_WRITEBACK
-#define GDTC_INIT(__wb) .dom = &global_wb_domain, \
- DTC_INIT_COMMON(__wb)
+#define GDTC_INIT(__wb) .wb = (__wb), \
+ .dom = &global_wb_domain, \
+ .wb_completions = &(__wb)->completions
+
#define GDTC_INIT_NO_WB .dom = &global_wb_domain
-#define MDTC_INIT(__wb, __gdtc) .dom = mem_cgroup_wb_domain(__wb), \
- .gdtc = __gdtc, \
- DTC_INIT_COMMON(__wb)
+
+#define MDTC_INIT(__wb, __gdtc) .wb = (__wb), \
+ .dom = mem_cgroup_wb_domain(__wb), \
+ .wb_completions = &(__wb)->memcg_completions, \
+ .gdtc = __gdtc
static bool mdtc_valid(struct dirty_throttle_control *dtc)
{
@@ -213,7 +214,8 @@
#else /* CONFIG_CGROUP_WRITEBACK */
-#define GDTC_INIT(__wb) DTC_INIT_COMMON(__wb)
+#define GDTC_INIT(__wb) .wb = (__wb), \
+ .wb_completions = &(__wb)->completions
#define GDTC_INIT_NO_WB
#define MDTC_INIT(__wb, __gdtc)
