On Mon 15-03-21 19:41:00, Johannes Weiner wrote:
> 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 <hannes@xxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> 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
--
Michal Hocko
SUSE Labs
