The patch titled
Subject: mm/hugetlb: initialize hugetlb_usage in mm_init
has been added to the -mm tree. Its filename is
mm-hugetlb-initialize-hugetlb_usage-in-mm_init.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-initialize-hugetlb_usage-in-mm_init.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-initialize-hugetlb_usage-in-mm_init.patch
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------------------------------------------------------
From: Liu Zixian <liuzixian4@xxxxxxxxxx>
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@xxxxxxxxxx
Fixes: 5d317b2b6536 ("mm: hugetlb: proc: add HugetlbPages field to /proc/PID/status")
Signed-off-by: Liu Zixian <liuzixian4@xxxxxxxxxx>
Reviewed-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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
@@ -1052,6 +1052,7 @@ 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;
_
Patches currently in -mm which might be from liuzixian4@xxxxxxxxxx are
mm-hugetlb-initialize-hugetlb_usage-in-mm_init.patch
