[PATCH] mm: memcontrol: switch to rstat fix

[Johannes Weiner]

Fix a sleep in atomic section problem: wb_writeback() takes a spinlock
and calls wb_over_bg_thresh() -> mem_cgroup_wb_stats, but the regular
rstat flushing function called from in there does lockbreaking and may
sleep. Switch to the atomic variant, cgroup_rstat_irqsafe().

To be consistent with other memcg flush calls, but without adding
another memcg wrapper, inline and drop memcg_flush_vmstats() instead.

Signed-off-by: Johannes Weiner <han...@cmpxchg.org>
---
 mm/memcontrol.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f7fb12d3c2fc..9091913ec877 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -757,11 +757,6 @@ mem_cgroup_largest_soft_limit_node(struct 
mem_cgroup_tree_per_node *mctz)
        return mz;
 }
 
-static void memcg_flush_vmstats(struct mem_cgroup *memcg)
-{
-       cgroup_rstat_flush(memcg->css.cgroup);
-}
-
 /**
  * __mod_memcg_state - update cgroup memory statistics
  * @memcg: the memory cgroup
@@ -1572,7 +1567,7 @@ static char *memory_stat_format(struct mem_cgroup *memcg)
         *
         * Current memory state:
         */
-       memcg_flush_vmstats(memcg);
+       cgroup_rstat_flush(memcg->css.cgroup);
 
        for (i = 0; i < ARRAY_SIZE(memory_stats); i++) {
                u64 size;
@@ -3523,7 +3518,7 @@ static unsigned long mem_cgroup_usage(struct mem_cgroup 
*memcg, bool swap)
        unsigned long val;
 
        if (mem_cgroup_is_root(memcg)) {
-               memcg_flush_vmstats(memcg);
+               cgroup_rstat_flush(memcg->css.cgroup);
                val = memcg_page_state(memcg, NR_FILE_PAGES) +
                        memcg_page_state(memcg, NR_ANON_MAPPED);
                if (swap)
@@ -3925,7 +3920,7 @@ static int memcg_numa_stat_show(struct seq_file *m, void 
*v)
        int nid;
        struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
 
-       memcg_flush_vmstats(memcg);
+       cgroup_rstat_flush(memcg->css.cgroup);
 
        for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {
                seq_printf(m, "%s=%lu", stat->name,
@@ -3997,7 +3992,7 @@ static int memcg_stat_show(struct seq_file *m, void *v)
 
        BUILD_BUG_ON(ARRAY_SIZE(memcg1_stat_names) != ARRAY_SIZE(memcg1_stats));
 
-       memcg_flush_vmstats(memcg);
+       cgroup_rstat_flush(memcg->css.cgroup);
 
        for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) {
                unsigned long nr;
@@ -4500,7 +4495,7 @@ void mem_cgroup_wb_stats(struct bdi_writeback *wb, 
unsigned long *pfilepages,
        struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css);
        struct mem_cgroup *parent;
 
-       memcg_flush_vmstats(memcg);
+       cgroup_rstat_flush_irqsafe(memcg->css.cgroup);
 
        *pdirty = memcg_page_state(memcg, NR_FILE_DIRTY);
        *pwriteback = memcg_page_state(memcg, NR_WRITEBACK);
-- 
2.30.1