[PATCH] mm/hugetlb: initialize hugetlb_usage in mm_init

[Liu Zixian <liuzixian4@huawei.com>]

After fork, the new process will get incorrect hugetlb_usage.
The reason is dup_mm copies old_mm to the new one and mm_init
does not init hugetlb_usage.
Fix this by adding hugetlb_count_init in mm_init.

Signed-off-by: Liu Zixian <liuzixian4@huawei.com>
---
 include/linux/hugetlb.h | 5 +++++
 kernel/fork.c           | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index f7ca1a387..66ceabd66 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -858,6 +858,11 @@ static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
 
 void hugetlb_report_usage(struct seq_file *m, struct mm_struct *mm);
 
+static inline void hugetlb_count_init(struct mm_struct *mm)
+{
+	atomic_long_set(&mm->hugetlb_usage, 0);
+}
+
 static inline void hugetlb_count_add(long l, struct mm_struct *mm)
 {
 	atomic_long_add(l, &mm->hugetlb_usage);
diff --git a/kernel/fork.c b/kernel/fork.c
index bc94b2cc5..a9380081a 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1050,6 +1050,9 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 	mm->pmd_huge_pte = NULL;
 #endif
 	mm_init_uprobes_state(mm);
+#ifdef CONFIG_HUGETLB_PAGE
+	hugetlb_count_init(mm);
+#endif
 
 	if (current->mm) {
 		mm->flags = current->mm->flags & MMF_INIT_MASK;
-- 
2.18.1