mm/nommu: use alloc_pages_exact() rather than its own implementation

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.kim@lge.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Jungsoo Son <jungsoo.son@lge.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 22 deletions

diff --git a/mm/nommu.c b/mm/nommu.c
index cd519e1cd8a7..b51eadf6d952 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 = (void *)__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;