* [PATCH v2] mm/hugetlb: initialize hugetlb_usage in mm_init
@ 2021-08-26 7:17 Liu Zixian
2021-08-26 7:29 ` HORIGUCHI NAOYA(堀口 直也)
2021-08-26 16:19 ` Mike Kravetz
0 siblings, 2 replies; 3+ messages in thread
From: Liu Zixian @ 2021-08-26 7:17 UTC (permalink / raw)
To: linux-mm, mike.kravetz, akpm; +Cc: naoya.horiguchi, stable, wuxu.wu
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.
Fixes: 5d317b2b6536 ("mm: hugetlb: proc: add HugetlbPages field to
/proc/PID/status")
Signed-off-by: Liu Zixian <liuzixian4@huawei.com>
---
v2:
1. Create two hugetlb_count_init in hugetlb.h instead of using #ifdef
in fork.c
2. Add an example to clearify this issue.
---
include/linux/hugetlb.h | 9 +++++++++
kernel/fork.c | 1 +
2 files changed, 10 insertions(+)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index f7ca1a387..1faebe1cd 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);
@@ -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)
{
}
diff --git a/kernel/fork.c b/kernel/fork.c
index bc94b2cc5..0dbc96ade 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1050,6 +1050,7 @@ 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;
--
2.18.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] mm/hugetlb: initialize hugetlb_usage in mm_init
2021-08-26 7:17 [PATCH v2] mm/hugetlb: initialize hugetlb_usage in mm_init Liu Zixian
@ 2021-08-26 7:29 ` HORIGUCHI NAOYA(堀口 直也)
2021-08-26 16:19 ` Mike Kravetz
1 sibling, 0 replies; 3+ messages in thread
From: HORIGUCHI NAOYA(堀口 直也) @ 2021-08-26 7:29 UTC (permalink / raw)
To: Liu Zixian; +Cc: linux-mm, mike.kravetz, akpm, stable, wuxu.wu
On Thu, Aug 26, 2021 at 03:17:42PM +0800, Liu Zixian wrote:
> 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.
>
> Fixes: 5d317b2b6536 ("mm: hugetlb: proc: add HugetlbPages field to
> /proc/PID/status")
> Signed-off-by: Liu Zixian <liuzixian4@huawei.com>
Thank you for the fix.
Reviewed-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] mm/hugetlb: initialize hugetlb_usage in mm_init
2021-08-26 7:17 [PATCH v2] mm/hugetlb: initialize hugetlb_usage in mm_init Liu Zixian
2021-08-26 7:29 ` HORIGUCHI NAOYA(堀口 直也)
@ 2021-08-26 16:19 ` Mike Kravetz
1 sibling, 0 replies; 3+ messages in thread
From: Mike Kravetz @ 2021-08-26 16:19 UTC (permalink / raw)
To: Liu Zixian, linux-mm, akpm; +Cc: naoya.horiguchi, stable, wuxu.wu
On 8/26/21 12:17 AM, Liu Zixian wrote:
> 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.
>
> Fixes: 5d317b2b6536 ("mm: hugetlb: proc: add HugetlbPages field to
> /proc/PID/status")
> Signed-off-by: Liu Zixian <liuzixian4@huawei.com>
> ---
> v2:
> 1. Create two hugetlb_count_init in hugetlb.h instead of using #ifdef
> in fork.c
> 2. Add an example to clearify this issue.
> ---
> include/linux/hugetlb.h | 9 +++++++++
> kernel/fork.c | 1 +
> 2 files changed, 10 insertions(+)
Thanks,
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Andrew, can you add a CC stable?
--
Mike Kravetz
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-08-26 7:17 [PATCH v2] mm/hugetlb: initialize hugetlb_usage in mm_init Liu Zixian
2021-08-26 7:29 ` HORIGUCHI NAOYA(堀口 直也)
2021-08-26 16:19 ` Mike Kravetz
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