mm, hugetlb_cgroup: round limit_in_bytes down to hugepage size

The page_counter rounds limits down to page size values.  This makes
sense, except in the case of hugetlb_cgroup where it's not possible to
charge partial hugepages.  If the hugetlb_cgroup margin is less than the
hugepage size being charged, it will fail as expected.

Round the hugetlb_cgroup limit down to hugepage size, since it is the
effective limit of the cgroup.

For consistency, round down PAGE_COUNTER_MAX as well when a
hugetlb_cgroup is created: this prevents error reports when a user
cannot restore the value to the kernel default.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nikolay Borisov <kernel@kyup.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index d8fb10de0f1449f0cd912aaa65d6887c338b20aa..eec1150125b9857f3f84185d1d5beeff64ec034f 100644 (file)
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -67,26 +67,42 @@ static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup *h_cg)
        return false;
 }
 
+static void hugetlb_cgroup_init(struct hugetlb_cgroup *h_cgroup,
+                               struct hugetlb_cgroup *parent_h_cgroup)
+{
+       int idx;
+
+       for (idx = 0; idx < HUGE_MAX_HSTATE; idx++) {
+               struct page_counter *counter = &h_cgroup->hugepage[idx];
+               struct page_counter *parent = NULL;
+               unsigned long limit;
+               int ret;
+
+               if (parent_h_cgroup)
+                       parent = &parent_h_cgroup->hugepage[idx];
+               page_counter_init(counter, parent);
+
+               limit = round_down(PAGE_COUNTER_MAX,
+                                  1 << huge_page_order(&hstates[idx]));
+               ret = page_counter_limit(counter, limit);
+               VM_BUG_ON(ret);
+       }
+}
+
 static struct cgroup_subsys_state *
 hugetlb_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
 {
        struct hugetlb_cgroup *parent_h_cgroup = hugetlb_cgroup_from_css(parent_css);
        struct hugetlb_cgroup *h_cgroup;
-       int idx;
 
        h_cgroup = kzalloc(sizeof(*h_cgroup), GFP_KERNEL);
        if (!h_cgroup)
                return ERR_PTR(-ENOMEM);
 
-       if (parent_h_cgroup) {
-               for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)
-                       page_counter_init(&h_cgroup->hugepage[idx],
-                                         &parent_h_cgroup->hugepage[idx]);
-       } else {
+       if (!parent_h_cgroup)
                root_h_cgroup = h_cgroup;
-               for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)
-                       page_counter_init(&h_cgroup->hugepage[idx], NULL);
-       }
+
+       hugetlb_cgroup_init(h_cgroup, parent_h_cgroup);
        return &h_cgroup->css;
 }
 
@@ -285,6 +301,7 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
                return ret;
 
        idx = MEMFILE_IDX(of_cft(of)->private);
+       nr_pages = round_down(nr_pages, 1 << huge_page_order(&hstates[idx]));
 
        switch (MEMFILE_ATTR(of_cft(of)->private)) {
        case RES_LIMIT: