Re: [PATCH 2/3] x86/mm: Simplify for-loop in free_init_pages()

Joe Perches
2012-07-14T22:38:18Z

On Sat, 2012-07-14 at 23:48 +0300, Pekka Enberg wrote:
> On Sat, Jul 14, 2012 at 11:43 PM, Joe Perches <joe@perches.com> wrote:
> > On Sat, 2012-07-14 at 13:36 -0700, Yinghai Lu wrote:
> >> On Sat, Jul 14, 2012 at 6:41 AM, Pekka Enberg <penberg@kernel.org> wrote:
> >> > As a cleanup, move initial "addr" assignment to the for-loop construct
> >> > in free_init_pages().
> >
> > Not really a good idea.
>
> Of course it's a good idea. The current code flow makes no sense.
>
> >> > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> > []
> >> > @@ -349,8 +349,6 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
> >> > if (begin >= end)
> >> > return;
> >> >
> >> > - addr = begin;
> >> > -
> >> > /*
> >> > * If debugging page accesses then do not free this memory but
> >> > * mark them not present - any buggy init-section access will
> >> > @@ -371,7 +369,7 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
> >> >
> >> > printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
> >> >
> >> > - for (; addr < end; addr += PAGE_SIZE) {
> >> > + for (addr = begin; addr < end; addr += PAGE_SIZE) {
> >> > ClearPageReserved(virt_to_page(addr));
> >> > init_page_count(virt_to_page(addr));
> >> > memset((void *)addr, POISON_FREE_INITMEM, PAGE_SIZE);
> >> > --
> >
> > Now there's an unused variable warning when CONFIG_DEBUG_PAGEALLOC
>
> Sure, that needs fixing. It'd probably be simplest to introduce a
> __free_init_pages() helper.
>

Perhaps:

arch/x86/mm/init.c | 14 ++++++--------
1 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index bc4e9d8..1023484 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -330,7 +330,6 @@ int devmem_is_allowed(unsigned long pagenr)

void free_init_pages(char *what, unsigned long begin, unsigned long end)
{
- unsigned long addr;
unsigned long begin_aligned, end_aligned;

/* Make sure boundaries are page aligned */
@@ -345,8 +344,6 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
if (begin >= end)
return;

- addr = begin;
-
/*
* If debugging page accesses then do not free this memory but
* mark them not present - any buggy init-section access will
@@ -367,12 +364,13 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)

printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);

- for (; addr < end; addr += PAGE_SIZE) {
- ClearPageReserved(virt_to_page(addr));
- init_page_count(virt_to_page(addr));
- memset((void *)addr, POISON_FREE_INITMEM, PAGE_SIZE);
- free_page(addr);
+ while (begin < end) {
+ ClearPageReserved(virt_to_page(begin));
+ init_page_count(virt_to_page(begin));
+ memset((void *)begin, POISON_FREE_INITMEM, PAGE_SIZE);
+ free_page(begin);
totalram_pages++;
+ begin += PAGE_SIZE;
}
#endif
}