mm/page_alloc.c: eliminate NULL test and memset after alloc_bootmem

As noted by Akinobu Mita in patch b1fceac2b9e04d278316b2faddf276015fc06e3b,
alloc_bootmem and related functions never return NULL and always return a
zeroed region of memory.  Thus a NULL test or memset after calls to these
functions is unnecessary.

This was fixed using the following semantic patch.
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
expression E;
statement S;
@@

E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\|alloc_bootmem_node\|alloc_bootmem_low_pages_node\|alloc_bootmem_pages_node\)(...)
... when != E
(
- BUG_ON (E == NULL);
|
- if (E == NULL) S
)

@@
expression E,E1;
@@

E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\|alloc_bootmem_node\|alloc_bootmem_low_pages_node\|alloc_bootmem_pages_node\)(...)
... when != E
- memset(E,0,E1);
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 3 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2f644c3e3da3..ce2a026219bc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3381,10 +3381,8 @@ static void __init setup_usemap(struct pglist_data *pgdat,
 {
         unsigned long usemapsize = usemap_size(zonesize);
         zone->pageblock_flags = NULL;
-        if (usemapsize) {
+        if (usemapsize)
                 zone->pageblock_flags = alloc_bootmem_node(pgdat, usemapsize);
-                memset(zone->pageblock_flags, 0, usemapsize);
-        }
 }
 #else
 static void inline setup_usemap(struct pglist_data *pgdat,