mm: use alloc_pages_exact() in alloc_large_system_hash() to avoid duplicated logic

alloc_large_system_hash() has logic for freeing pages at the end of an
excessively large power-of-two buffer that is a duplicate of what is in
alloc_pages_exact().  This patch converts alloc_large_system_hash() to use
alloc_pages_exact().

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 17 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 85759cdd6973..8ca06d87dc1f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4699,26 +4699,13 @@ void *__init alloc_large_system_hash(const char *tablename,
                 else if (hashdist)
                         table = __vmalloc(size, GFP_ATOMIC, PAGE_KERNEL);
                 else {
-                        unsigned long order = get_order(size);
-
-                        if (order < MAX_ORDER)
-                                table = (void *)__get_free_pages(GFP_ATOMIC,
-                                                                order);
                         /*
                          * If bucketsize is not a power-of-two, we may free
-                         * some pages at the end of hash table.
+                         * some pages at the end of hash table which
+                         * alloc_pages_exact() automatically does
                          */
-                        if (table) {
-                                unsigned long alloc_end = (unsigned long)table +
-                                                (PAGE_SIZE << order);
-                                unsigned long used = (unsigned long)table +
-                                                PAGE_ALIGN(size);
-                                split_page(virt_to_page(table), order);
-                                while (used < alloc_end) {
-                                        free_page(used);
-                                        used += PAGE_SIZE;
-                                }
-                        }
+                        if (get_order(size) < MAX_ORDER)
+                                table = alloc_pages_exact(size, GFP_ATOMIC);
                 }
         } while (!table && size > PAGE_SIZE && --log2qty);