+ mm-page_allocc-eliminate-null-test-and-memset-after-alloc_bootmem.patch added to -mm tree

+ mm-page_allocc-eliminate-null-test-and-memset-after-alloc_bootmem.patch added to -mm tree

[akpm]

The patch titled
     mm/page_alloc.c: eliminate NULL test and memset after alloc_bootmem
has been added to the -mm tree.  Its filename is
     mm-page_allocc-eliminate-null-test-and-memset-after-alloc_bootmem.patch

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See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this

The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
Subject: mm/page_alloc.c: eliminate NULL test and memset after alloc_bootmem
From: Julia Lawall <julia@diku.dk>

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>
---

 mm/page_alloc.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff -puN mm/page_alloc.c~mm-page_allocc-eliminate-null-test-and-memset-after-alloc_bootmem mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_allocc-eliminate-null-test-and-memset-after-alloc_bootmem
+++ a/mm/page_alloc.c
@@ -3396,10 +3396,8 @@ static void __init setup_usemap(struct p
 {
 	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,
_

Patches currently in -mm which might be from julia@diku.dk are

linux-next.patch
drivers-char-agp-add-missing-pci_dev_get.patch
drivers-mtd-maps-nettelc-use-array_size.patch
net-tipc-bcasth-use-array_size.patch
drivers-isdn-misdn-use-array_size.patch
drivers-pci-hotplug-add-missing-pci_dev_get.patch
drivers-message-fusion-use-array_size.patch
fs-namespacec-drop-code-after-return.patch
arch-arm-eliminate-null-test-and-memset-after-alloc_bootmem.patch
arch-avr32-eliminate-null-test-and-memset-after-alloc_bootmem.patch
arch-ia64-eliminate-null-test-and-memset-after-alloc_bootmem.patch
arch-powerpc-eliminate-null-test-and-memset-after-alloc_bootmem.patch
mm-page_allocc-eliminate-null-test-and-memset-after-alloc_bootmem.patch