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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: 5d317b2b65 ("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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Liu Zixian 2021-09-08 18:10:05 -07:00 committed by Linus Torvalds
parent 4b42fb2136
commit 13db8c5047
2 changed files with 10 additions and 0 deletions
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9
include/linux/hugetlb.h
View File

@ -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);
@ -1042,6 +1047,10 @@ static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
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)
{
}

1
kernel/fork.c
View File

@ -1063,6 +1063,7 @@ 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);
hugetlb_count_init(mm);
if (current->mm) {
mm->flags = current->mm->flags & MMF_INIT_MASK;