From: Liu Zixian liuzixian4@huawei.com Subject: mm/hugetlb: initialize hugetlb_usage in mm_init
After fork, the child process will get incorrect (2x) hugetlb_usage. If a process uses 5 2MB hugetlb pages in an anonymous mapping,
HugetlbPages: 10240 kB
and then forks, the child will show,
HugetlbPages: 20480 kB
The reason for double the amount is because hugetlb_usage will be copied from the parent and then increased when we copy page tables from parent to child. Child will have 2x actual usage.
Fix this by adding hugetlb_count_init in mm_init.
Link: https://lkml.kernel.org/r/20210826071742.877-1-liuzixian4@huawei.com Fixes: 5d317b2b6536 ("mm: hugetlb: proc: add HugetlbPages field to /proc/PID/status") Signed-off-by: Liu Zixian liuzixian4@huawei.com Reviewed-by: Naoya Horiguchi naoya.horiguchi@nec.com Reviewed-by: Mike Kravetz mike.kravetz@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
include/linux/hugetlb.h | 9 +++++++++ kernel/fork.c | 1 + 2 files changed, 10 insertions(+)
--- a/include/linux/hugetlb.h~mm-hugetlb-initialize-hugetlb_usage-in-mm_init +++ a/include/linux/hugetlb.h @@ -858,6 +858,11 @@ static inline spinlock_t *huge_pte_lockp
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); @@ -1042,6 +1047,10 @@ static inline spinlock_t *huge_pte_lockp return &mm->page_table_lock; }
+static inline void hugetlb_count_init(struct mm_struct *mm) +{ +} + static inline void hugetlb_report_usage(struct seq_file *f, struct mm_struct *m) { } --- a/kernel/fork.c~mm-hugetlb-initialize-hugetlb_usage-in-mm_init +++ a/kernel/fork.c @@ -1063,6 +1063,7 @@ static struct mm_struct *mm_init(struct mm->pmd_huge_pte = NULL; #endif mm_init_uprobes_state(mm); + hugetlb_count_init(mm);
if (current->mm) { mm->flags = current->mm->flags & MMF_INIT_MASK; _