FAILED: patch "[PATCH] mm/hugetlb: initialize hugetlb_usage in mm_init" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Sep 16, 2021

Subsystems (5)

Stable branch MM core Scheduler exec and binfmt +1 more subsystems

lore

Share & tools

lore

[email protected]

author maintainer

2021-09-16 12:57 UTC #0 lore raw

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 13db8c50477d83ad3e3b9b0ae247e5cd833a7ae4 Mon Sep 17 00:00:00 2001
From: Liu Zixian <[email protected]>
Date: Wed, 8 Sep 2021 18:10:05 -0700
Subject: [PATCH] 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/[email protected] open here

Fixes 5d317b2b6536 ("mm: hugetlb: proc: add HugetlbPages field to /proc/PID/status")

Signed-off-by Liu Zixian <[email protected]>

Reviewed-by Naoya Horiguchi <[email protected]>

Reviewed-by Mike Kravetz <[email protected]>

Cc <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Signed-off-by Linus Torvalds <[email protected]>

include/linux/hugetlb.h +9 -0

index f7ca1a3870ea..1faebe1cd0ed 100644
@@ -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)
 {
 }

kernel/fork.c +1 -0

index ff5be23800af..38681ad44c76 100644
@@ -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;