Commit b676b293 authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds

mm, thp: fix mapped pages avoiding unevictable list on mlock

When a transparent hugepage is mapped and it is included in an mlock()
range, follow_page() incorrectly avoids setting the page's mlock bit and
moving it to the unevictable lru.

This is evident if you try to mlock(), munlock(), and then mlock() a
range again.  Currently:

	#define MAP_SIZE	(4 << 30)	/* 4GB */

	void *ptr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE,
	mlock(ptr, MAP_SIZE);

		$ grep -E "Unevictable|Inactive\(anon" /proc/meminfo
		Inactive(anon):     6304 kB
		Unevictable:     4213924 kB

	munlock(ptr, MAP_SIZE);

		Inactive(anon):  4186252 kB
		Unevictable:       19652 kB

	mlock(ptr, MAP_SIZE);

		Inactive(anon):  4198556 kB
		Unevictable:       21684 kB

Notice that less than 2MB was added to the unevictable list; this is
because these pages in the range are not transparent hugepages since the
4GB range was allocated with mmap() and has no specific alignment.  If
posix_memalign() were used instead, unevictable would not have grown at
all on the second mlock().

The fix is to call mlock_vma_page() so that the mlock bit is set and the
page is added to the unevictable list.  With this patch:

	mlock(ptr, MAP_SIZE);

		Inactive(anon):     4056 kB
		Unevictable:     4213940 kB

	munlock(ptr, MAP_SIZE);

		Inactive(anon):  4198268 kB
		Unevictable:       19636 kB

	mlock(ptr, MAP_SIZE);

		Inactive(anon):     4008 kB
		Unevictable:     4213940 kB
Signed-off-by: default avatarDavid Rientjes <>
Acked-by: default avatarHugh Dickins <>
Reviewed-by: default avatarAndrea Arcangeli <>
Cc: Naoya Horiguchi <>
Cc: KAMEZAWA Hiroyuki <>
Cc: Johannes Weiner <>
Cc: Michel Lespinasse <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent e90bdb7f
......@@ -11,7 +11,7 @@ extern int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
extern int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd,
pmd_t orig_pmd);
extern struct page *follow_trans_huge_pmd(struct mm_struct *mm,
extern struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
unsigned long addr,
pmd_t *pmd,
unsigned int flags);
......@@ -971,11 +971,12 @@ out_unlock:
return ret;
struct page *follow_trans_huge_pmd(struct mm_struct *mm,
struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
unsigned long addr,
pmd_t *pmd,
unsigned int flags)
struct mm_struct *mm = vma->vm_mm;
struct page *page = NULL;
......@@ -998,6 +999,14 @@ struct page *follow_trans_huge_pmd(struct mm_struct *mm,
_pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
if (page->mapping && trylock_page(page)) {
if (page->mapping)
page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
if (flags & FOLL_GET)
......@@ -1528,7 +1528,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
wait_split_huge_page(vma->anon_vma, pmd);
} else {
page = follow_trans_huge_pmd(mm, address,
page = follow_trans_huge_pmd(vma, address,
pmd, flags);
goto out;
Markdown is supported
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment