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: Song Liu <songliubraving@fb.com>
Reviewed-by: Rik van Riel <riel@surriel.com>
Reviewed-by: Yang 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 79d55e1..961cbe9 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -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;