mm/hugetlb: initialize hugetlb_usage in mm_init

commit 13db8c50477d83ad3e3b9b0ae247e5cd833a7ae4 upstream.

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 5b68c9787f7c2ae832a9daaf0f2e6456d0591024..b9fbb6d4150e2fbaffcbad3cb8a02061aa79fa64 100644 (file)
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -722,6 +722,11 @@ 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);
@@ -897,6 +902,10 @@ 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 9705439439fe37abc001cc3d040fab6fb0f9c79a..3f96400a0ac61c96f17769208b093306346d90e7 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1037,6 +1037,7 @@ 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;