mm: memcontrol: restore proper dirty throttling when memory.high changes

Commit 86e304a2ec41 ("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.

Fixes: 86e304a2ec41 ("mm: memcontrol: try harder to set a new memory.high")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Chris Down <chris@chrisdown.name>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Link: http://lkml.kernel.org/r/20200728135210.379885-1-hannes@cmpxchg.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 369d9e1d8333011f003298722a2b297283791c28..856db3ba3093806de05d96199ff8ff41ab206b6b 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6273,6 +6273,8 @@ static ssize_t memory_high_write(struct kernfs_open_file *of,
 
        page_counter_set_high(&memcg->memory, high);
 
+       memcg_wb_domain_size_changed(memcg);
+
        return nbytes;
 }