From: Chris Down <chris@xxxxxxxxxxxxxx> Subject: mm, memcg: prevent memory.high load/store tearing A mem_cgroup's high attribute can be concurrently set at the same time as we are trying to read it -- for example, if we are in memory_high_write at the same time as we are trying to do high reclaim. Link: http://lkml.kernel.org/r/2f66f7038ed1d4688e59de72b627ae0ea52efa83.1584034301.git.chris@xxxxxxxxxxxxxx Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Roman Gushchin <guro@xxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) --- a/mm/memcontrol.c~mm-memcg-prevent-memoryhigh-load-store-tearing +++ a/mm/memcontrol.c @@ -2242,7 +2242,7 @@ static void reclaim_high(struct mem_cgro gfp_t gfp_mask) { do { - if (page_counter_read(&memcg->memory) <= memcg->high) + if (page_counter_read(&memcg->memory) <= READ_ONCE(memcg->high)) continue; memcg_memory_event(memcg, MEMCG_HIGH); try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, true); @@ -2582,7 +2582,7 @@ done_restock: * reclaim, the cost of mismatch is negligible. */ do { - if (page_counter_read(&memcg->memory) > memcg->high) { + if (page_counter_read(&memcg->memory) > READ_ONCE(memcg->high)) { /* Don't bother a random interrupted task */ if (in_interrupt()) { schedule_work(&memcg->high_work); @@ -4325,7 +4325,8 @@ void mem_cgroup_wb_stats(struct bdi_writ *pheadroom = PAGE_COUNTER_MAX; while ((parent = parent_mem_cgroup(memcg))) { - unsigned long ceiling = min(memcg->memory.max, memcg->high); + unsigned long ceiling = min(memcg->memory.max, + READ_ONCE(memcg->high)); unsigned long used = page_counter_read(&memcg->memory); *pheadroom = min(*pheadroom, ceiling - min(ceiling, used)); @@ -5047,7 +5048,7 @@ mem_cgroup_css_alloc(struct cgroup_subsy if (!memcg) return ERR_PTR(error); - memcg->high = PAGE_COUNTER_MAX; + WRITE_ONCE(memcg->high, PAGE_COUNTER_MAX); memcg->soft_limit = PAGE_COUNTER_MAX; if (parent) { memcg->swappiness = mem_cgroup_swappiness(parent); @@ -5200,7 +5201,7 @@ static void mem_cgroup_css_reset(struct page_counter_set_max(&memcg->tcpmem, PAGE_COUNTER_MAX); page_counter_set_min(&memcg->memory, 0); page_counter_set_low(&memcg->memory, 0); - memcg->high = PAGE_COUNTER_MAX; + WRITE_ONCE(memcg->high, PAGE_COUNTER_MAX); memcg->soft_limit = PAGE_COUNTER_MAX; memcg_wb_domain_size_changed(memcg); } @@ -6016,7 +6017,7 @@ static ssize_t memory_high_write(struct if (err) return err; - memcg->high = high; + WRITE_ONCE(memcg->high, high); for (;;) { unsigned long nr_pages = page_counter_read(&memcg->memory); _
