+ mm-hugetlb-initialize-hugetlb_usage-in-mm_init.patch added to -mm tree

+ mm-hugetlb-initialize-hugetlb_usage-in-mm_init.patch added to -mm tree

[akpm]

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@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
@@ -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@huawei.com are

mm-hugetlb-initialize-hugetlb_usage-in-mm_init.patch