do_mmap_private() in nommu.c try to allocate physically contiguous pages
with arbitrary size in some cases and we now have good abstract function
to do exactly same thing, alloc_pages_exact(). So, change to use it.

There is no functional change.
This is the preparation step for support page owner feature accurately.

Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>
---
 mm/nommu.c |   33 +++++++++++----------------------
 1 file changed, 11 insertions(+), 22 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 2266a34..1b87c17 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1149,8 +1149,7 @@ static int do_mmap_private(struct vm_area_struct *vma,
                           unsigned long len,
                           unsigned long capabilities)
 {
-       struct page *pages;
-       unsigned long total, point, n;
+       unsigned long total, point;
        void *base;
        int ret, order;
 
@@ -1182,33 +1181,23 @@ static int do_mmap_private(struct vm_area_struct *vma,
        order = get_order(len);
        kdebug("alloc order %d for %lx", order, len);
 
-       pages = alloc_pages(GFP_KERNEL, order);
-       if (!pages)
-               goto enomem;
-
        total = 1 << order;
-       atomic_long_add(total, &mmap_pages_allocated);
-
        point = len >> PAGE_SHIFT;
 
-       /* we allocated a power-of-2 sized page set, so we may want to trim off
-        * the excess */
+       /* we don't want to allocate a power-of-2 sized page set */
        if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages) {
-               while (total > point) {
-                       order = ilog2(total - point);
-                       n = 1 << order;
-                       kdebug("shave %lu/%lu @%lu", n, total - point, total);
-                       atomic_long_sub(n, &mmap_pages_allocated);
-                       total -= n;
-                       set_page_refcounted(pages + total);
-                       __free_pages(pages + total, order);
-               }
+               total = point;
+               kdebug("try to alloc exact %lu pages", total);
+               base = alloc_pages_exact(len, GFP_KERNEL);
+       } else {
+               base = __get_free_pages(GFP_KERNEL, order);
        }
 
-       for (point = 1; point < total; point++)
-               set_page_refcounted(&pages[point]);
+       if (!base)
+               goto enomem;
+
+       atomic_long_add(total, &mmap_pages_allocated);
 
-       base = page_address(pages);
        region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY;
        region->vm_start = (unsigned long) base;
        region->vm_end   = region->vm_start + len;
-- 
1.7.9.5

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