mm: Use fixed constant in page_frag_alloc instead of size + 1

This patch replaces the size + 1 value introduced with the recent fix for 1
byte allocs with a constant value.

The idea here is to reduce code overhead as the previous logic would have
to read size into a register, then increment it, and write it back to
whatever field was being used. By using a constant we can avoid those
memory reads and arithmetic operations in favor of just encoding the
maximum value into the operation itself.

Fixes: 2c2ade81741c ("mm: page_alloc: fix ref bias in page_frag_alloc() for 1-byte allocs")
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 4 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 46285d28e43b..7f79b78bc829 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4675,11 +4675,11 @@ refill:
                 /* Even if we own the page, we do not use atomic_set().
                  * This would break get_page_unless_zero() users.
                  */
-                page_ref_add(page, size);
+                page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE);
 
                 /* reset page count bias and offset to start of new frag */
                 nc->pfmemalloc = page_is_pfmemalloc(page);
-                nc->pagecnt_bias = size + 1;
+                nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
                 nc->offset = size;
         }
 
@@ -4695,10 +4695,10 @@ refill:
                 size = nc->size;
 #endif
                 /* OK, page count is 0, we can safely set it */
-                set_page_count(page, size + 1);
+                set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);
 
                 /* reset page count bias and offset to start of new frag */
-                nc->pagecnt_bias = size + 1;
+                nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
                 offset = size - fragsz;
         }