linux-kernel - [PATCH 5/14] arch/m68k/mm/Sun3mmu.c: Eliminate NULL test and memset after alloc

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Message-ID: <Pine.LNX.4.64.0806241022410.26777@ask.diku.dk>
Date:	Tue, 24 Jun 2008 10:23:07 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	akinobu.mita@...il.com, geert@...ux-m68k.org,
	zippel@...ux-m68k.org, linux-m68k@...ts.linux-m68k.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH 5/14] arch/m68k/mm/Sun3mmu.c: Eliminate NULL test and memset
 after alloc_bootmem

From: Julia Lawall <julia@...u.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.

 arch/m68k/mm/sun3mmu.c |    1 -
 1 file changed, 1 deletion(-)

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

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

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

@@
expression E,E1;
@@

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

Signed-off-by: Julia Lawall <julia@...u.dk>
---

diff -u -p a/arch/m68k/mm/sun3mmu.c b/arch/m68k/mm/sun3mmu.c
--- a/arch/m68k/mm/sun3mmu.c
+++ b/arch/m68k/mm/sun3mmu.c
@@ -53,7 +53,6 @@ void __init paging_init(void)
 	wp_works_ok = 0;
 #endif
 	empty_zero_page = alloc_bootmem_pages(PAGE_SIZE);
-	memset(empty_zero_page, 0, PAGE_SIZE);
 
 	address = PAGE_OFFSET;
 	pg_dir = swapper_pg_dir;
--
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