[patch 091/163] mm: memcontrol: restore proper dirty throttling when memory.high changes

Andrew Morton
2020-08-07T06:22:15Z

From: Johannes Weiner <hannes@cmpxchg.org>
Subject: mm: memcontrol: restore proper dirty throttling when memory.high changes

Commit 8c8c383c04f6 ("mm: memcontrol: try harder to set a new
memory.high") inadvertently removed a callback to recalculate the
writeback cache size in light of a newly configured memory.high limit.

Without letting the writeback cache know about a potentially heavily
reduced limit, it may permit too many dirty pages, which can cause
unnecessary reclaim latencies or even avoidable OOM situations.

This was spotted while reading the code, it hasn't knowingly caused any
problems in practice so far.

Link: http://lkml.kernel.org/r/20200728135210.379885-1-hannes@cmpxchg.org
Fixes: 8c8c383c04f6 ("mm: memcontrol: try harder to set a new memory.high")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/memcontrol.c | 2 ++
1 file changed, 2 insertions(+)

--- a/mm/memcontrol.c~mm-memcontrol-restore-proper-dirty-throttling-when-memoryhigh-changes
+++ a/mm/memcontrol.c
@@ -6273,6 +6273,8 @@ static ssize_t memory_high_write(struct

page_counter_set_high(&memcg->memory, high);

+ memcg_wb_domain_size_changed(memcg);
+
return nbytes;
}

_