The commit is pushed to "branch-rh7-3.10.0-514.6.1.vz7.28.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git after rh7-3.10.0-514.6.1.vz7.28.6 ------> commit 31166ec0c438e0b8da2e41ba99661791f837e173 Author: Greg Thelen <gthe...@google.com> Date: Mon Feb 20 14:35:32 2017 +0400
ms/memcg: make mem_cgroup_read_stat() unsigned commit 484ebb3b8c8b27dd2171696462a3116edb9ff801 upstream. mem_cgroup_read_stat() returns a page count by summing per cpu page counters. The summing is racy wrt. updates, so a transient negative sum is possible. Callers don't want negative values: - mem_cgroup_wb_stats() doesn't want negative nr_dirty or nr_writeback. This could confuse dirty throttling. - oom reports and memory.stat shouldn't show confusing negative usage. - tree_usage() already avoids negatives. Avoid returning negative page counts from mem_cgroup_read_stat() and convert it to unsigned. [a...@linux-foundation.org: fix old typo while we're in there] Signed-off-by: Greg Thelen <gthe...@google.com> Cc: Johannes Weiner <han...@cmpxchg.org> Acked-by: Michal Hocko <mho...@suse.com> Cc: <sta...@vger.kernel.org> [4.2+] Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> https://jira.sw.ru/browse/PSBM-56256 Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com> --- mm/memcontrol.c | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 49b69f7..95b1c0c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -919,12 +919,14 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz) } /* + * Return page count for single (non recursive) @memcg. + * * Implementation Note: reading percpu statistics for memcg. * * Both of vmstat[] and percpu_counter has threshold and do periodic * synchronization to implement "quick" read. There are trade-off between * reading cost and precision of value. Then, we may have a chance to implement - * a periodic synchronizion of counter in memcg's counter. + * a periodic synchronization of counter in memcg's counter. * * But this _read() function is used for user interface now. The user accounts * memory usage by memory cgroup and he _always_ requires exact value because @@ -934,17 +936,24 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz) * * If there are kernel internal actions which can make use of some not-exact * value, and reading all cpu value can be performance bottleneck in some - * common workload, threashold and synchonization as vmstat[] should be + * common workload, threshold and synchronization as vmstat[] should be * implemented. */ -static long mem_cgroup_read_stat(struct mem_cgroup *memcg, - enum mem_cgroup_stat_index idx) +static unsigned long +mem_cgroup_read_stat(struct mem_cgroup *memcg, enum mem_cgroup_stat_index idx) { long val = 0; int cpu; + /* Per-cpu values can be negative, use a signed accumulator */ for_each_possible_cpu(cpu) val += per_cpu(memcg->stat->count[idx], cpu); + /* + * Summing races with updates, so val may be negative. Avoid exposing + * transient negative values. + */ + if (val < 0) + val = 0; return val; } @@ -1961,7 +1970,7 @@ done: for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) { if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account) continue; - pr_cont(" %s:%ldKB", mem_cgroup_stat_names[i], + pr_cont(" %s:%luKB", mem_cgroup_stat_names[i], K(mem_cgroup_read_stat(iter, i))); } @@ -4162,14 +4171,11 @@ static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *memcg, enum mem_cgroup_stat_index idx) { struct mem_cgroup *iter; - long val = 0; + unsigned long val = 0; - /* Per-cpu values can be negative, use a signed accumulator */ for_each_mem_cgroup_tree(iter, memcg) val += mem_cgroup_read_stat(iter, idx); - if (val < 0) /* race ? */ - val = 0; return val; } @@ -5050,7 +5056,7 @@ static int memcg_stat_show(struct cgroup *cont, struct cftype *cft, for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) { if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account) continue; - seq_printf(m, "%s %ld\n", mem_cgroup_stat_names[i], + seq_printf(m, "%s %lu\n", mem_cgroup_stat_names[i], mem_cgroup_read_stat(memcg, i) * PAGE_SIZE); } @@ -5075,13 +5081,13 @@ static int memcg_stat_show(struct cgroup *cont, struct cftype *cft, (u64)memsw * PAGE_SIZE); for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) { - long long val = 0; + unsigned long long val = 0; if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account) continue; for_each_mem_cgroup_tree(mi, memcg) val += mem_cgroup_read_stat(mi, i) * PAGE_SIZE; - seq_printf(m, "total_%s %lld\n", mem_cgroup_stat_names[i], val); + seq_printf(m, "total_%s %llu\n", mem_cgroup_stat_names[i], val); } for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++) { _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel