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Commit 50f8b92f authored by Song Liu's avatar Song Liu Committed by Linus Torvalds
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mm: thp: pass correct vm_flags to hugepage_vma_check() 

khugepaged_enter_vma_merge() passes a stale vma->vm_flags to
hugepage_vma_check().  The argument vm_flags contains the latest value.
Therefore, it is necessary to pass this vm_flags into
hugepage_vma_check().

With this bug, madvise(MADV_HUGEPAGE) for mmap files in shmem fails to
put memory in huge pages.  Here is an example of failed madvise():

   /* mount /dev/shm with huge=advise:
    *     mount -o remount,huge=advise /dev/shm */
   /* create file /dev/shm/huge */
   #define HUGE_FILE "/dev/shm/huge"

   fd = open(HUGE_FILE, O_RDONLY);
   ptr = mmap(NULL, FILE_SIZE, PROT_READ, MAP_PRIVATE, fd, 0);
   ret = madvise(ptr, FILE_SIZE, MADV_HUGEPAGE);

madvise() will return 0, but this memory region is never put in huge
page (check from /proc/meminfo: ShmemHugePages).

Link: http://lkml.kernel.org/r/20180629181752.792831-1-songliubraving@fb.com


Fixes: 02b75dc8160d ("mm: thp: register mm for khugepaged when merging vma for shmem")
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
Reviewed-by: default avatarRik van Riel <riel@surriel.com>
Reviewed-by: default avatarYang Shi <yang.shi@linux.alibaba.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a718e28f

mm/khugepaged.c

+8 −7
Original line number Diff line number Diff line
@@ -397,10 +397,11 @@ static inline int khugepaged_test_exit(struct mm_struct *mm) 
	return atomic_read(&mm->mm_users) == 0;

}



static bool hugepage_vma_check(struct vm_area_struct *vma)

static bool hugepage_vma_check(struct vm_area_struct *vma,

			       unsigned long vm_flags)

{

	if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||

	    (vma->vm_flags & VM_NOHUGEPAGE) ||

	if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||

	    (vm_flags & VM_NOHUGEPAGE) ||

	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))

		return false;

	if (shmem_file(vma->vm_file)) {
@@ -413,7 +414,7 @@ static bool hugepage_vma_check(struct vm_area_struct *vma) 
		return false;

	if (is_vma_temporary_stack(vma))

		return false;

	return !(vma->vm_flags & VM_NO_KHUGEPAGED);

	return !(vm_flags & VM_NO_KHUGEPAGED);

}



int __khugepaged_enter(struct mm_struct *mm)
@@ -458,7 +459,7 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 
	 * khugepaged does not yet work on non-shmem files or special

	 * mappings. And file-private shmem THP is not supported.

	 */

	if (!hugepage_vma_check(vma))

	if (!hugepage_vma_check(vma, vm_flags))

		return 0;



	hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
@@ -861,7 +862,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, 
	hend = vma->vm_end & HPAGE_PMD_MASK;

	if (address < hstart || address + HPAGE_PMD_SIZE > hend)

		return SCAN_ADDRESS_RANGE;

	if (!hugepage_vma_check(vma))

	if (!hugepage_vma_check(vma, vma->vm_flags))

		return SCAN_VMA_CHECK;

	return 0;

}
@@ -1695,7 +1696,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 
			progress++;

			break;

		}

		if (!hugepage_vma_check(vma)) {

		if (!hugepage_vma_check(vma, vma->vm_flags)) {

skip:

			progress++;

			continue;