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-rw-r--r--Documentation/cgroup-v2.txt6
-rw-r--r--mm/memcontrol.c38
2 files changed, 40 insertions, 4 deletions
diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
index e2f4e7948a66..8f1329a5f700 100644
--- a/Documentation/cgroup-v2.txt
+++ b/Documentation/cgroup-v2.txt
@@ -1387,6 +1387,12 @@ system than killing the group. Otherwise, memory.max is there to
limit this type of spillover and ultimately contain buggy or even
malicious applications.
+Setting the original memory.limit_in_bytes below the current usage was
+subject to a race condition, where concurrent charges could cause the
+limit setting to fail. memory.max on the other hand will first set the
+limit to prevent new charges, and then reclaim and OOM kill until the
+new limit is met - or the task writing to memory.max is killed.
+
The combined memory+swap accounting and limiting is replaced by real
control over swap space.
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f7c9b4cbdf01..8614e0d750e5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1236,7 +1236,7 @@ static unsigned long mem_cgroup_get_limit(struct mem_cgroup *memcg)
return limit;
}
-static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
+static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
int order)
{
struct oom_control oc = {
@@ -1314,6 +1314,7 @@ static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
}
unlock:
mutex_unlock(&oom_lock);
+ return chosen;
}
#if MAX_NUMNODES > 1
@@ -5029,6 +5030,8 @@ static ssize_t memory_max_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
+ unsigned int nr_reclaims = MEM_CGROUP_RECLAIM_RETRIES;
+ bool drained = false;
unsigned long max;
int err;
@@ -5037,9 +5040,36 @@ static ssize_t memory_max_write(struct kernfs_open_file *of,
if (err)
return err;
- err = mem_cgroup_resize_limit(memcg, max);
- if (err)
- return err;
+ xchg(&memcg->memory.limit, max);
+
+ for (;;) {
+ unsigned long nr_pages = page_counter_read(&memcg->memory);
+
+ if (nr_pages <= max)
+ break;
+
+ if (signal_pending(current)) {
+ err = -EINTR;
+ break;
+ }
+
+ if (!drained) {
+ drain_all_stock(memcg);
+ drained = true;
+ continue;
+ }
+
+ if (nr_reclaims) {
+ if (!try_to_free_mem_cgroup_pages(memcg, nr_pages - max,
+ GFP_KERNEL, true))
+ nr_reclaims--;
+ continue;
+ }
+
+ mem_cgroup_events(memcg, MEMCG_OOM, 1);
+ if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0))
+ break;
+ }
memcg_wb_domain_size_changed(memcg);
return nbytes;