linux-kernel - Re: [PATCH 4/4] kcore: remove noise from walk_memory

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Date:	Wed, 22 Jul 2009 14:21:03 +0800
From:	Amerigo Wang <xiyou.wangcong@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH 4/4] kcore: remove noise from walk_memory_resource

On Wed, Jul 22, 2009 at 02:12:27PM +0900, KAMEZAWA Hiroyuki wrote:
>From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>
>Originally, walk_memory_resource() was introduced to traverse all memory
>of "System RAM" for detecting memory hotplug/unplug range.
>For doing so, flags of IORESOUCE_MEM|IORESOURCE_BUSY was used and this
>was enough for memory hotplug because scanning range was controlled properly.
>
>But for using other purpose, /proc/kcore, this may includes some firmware
>area marked as IORESOURCE_BUSY | IORESOUCE_MEM. This patch makes the check
>strict to find out busy "System RAM".
>
>Note: PPC64 keeps their own walk_memory_resouce(), which walk through
>ppc64's lmb informaton. Because old kclist_add() is called per lmb,
>this patch makes no difference in behavior, finally.
>
>Changelog v2:
> - new patch from v2.
>
>Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>---
> kernel/resource.c |   18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
>Index: mmotm-2.6.31-Jul16/kernel/resource.c
>===================================================================
>--- mmotm-2.6.31-Jul16.orig/kernel/resource.c
>+++ mmotm-2.6.31-Jul16/kernel/resource.c
>@@ -237,10 +237,10 @@ EXPORT_SYMBOL(release_resource);
> #if !defined(CONFIG_ARCH_HAS_WALK_MEMORY)
> /*
>  * Finds the lowest memory reosurce exists within [res->start.res->end)
>- * the caller must specify res->start, res->end, res->flags.
>+ * the caller must specify res->start, res->end, res->flags and "name".
>  * If found, returns 0, res is overwritten, if not found, returns -1.
>  */
>-static int find_next_system_ram(struct resource *res)
>+static int find_next_system_ram(struct resource *res, char *name)
> {
> 	resource_size_t start, end;
> 	struct resource *p;
>@@ -256,6 +256,8 @@ static int find_next_system_ram(struct r
> 		/* system ram is just marked as IORESOURCE_MEM */
> 		if (p->flags != res->flags)
> 			continue;
>+		if (name && strcmp(p->name, name))
>+			continue;
> 		if (p->start > end) {
> 			p = NULL;
> 			break;
>@@ -273,19 +275,27 @@ static int find_next_system_ram(struct r
> 		res->end = p->end;
> 	return 0;
> }
>+
>+/*
>+ * This function calls callback against all memory range of "System RAM"
>+ * which are marked as IORESOURCE_MEM and IORESOUCE_BUSY.
>+ * Now, this function is only for "System RAM".


Then we should change its name, shouldn't we? :)

>+ */
> int
> walk_memory_resource(unsigned long start_pfn, unsigned long nr_pages, void *arg,
>-			int (*func)(unsigned long, unsigned long, void *))
>+		int (*func)(unsigned long, unsigned long, void *))


This line is a trivial change, I don't want to see it mixed with
the rest...


> {
> 	struct resource res;
> 	unsigned long pfn, len;
> 	u64 orig_end;
> 	int ret = -1;
>+
> 	res.start = (u64) start_pfn << PAGE_SHIFT;
> 	res.end = ((u64)(start_pfn + nr_pages) << PAGE_SHIFT) - 1;
> 	res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> 	orig_end = res.end;
>-	while ((res.start < res.end) && (find_next_system_ram(&res) >= 0)) {
>+	while ((res.start < res.end) &&
>+		(find_next_system_ram(&res, "System RAM") >= 0)) {
> 		pfn = (unsigned long)(res.start >> PAGE_SHIFT);
> 		len = (unsigned long)((res.end + 1 - res.start) >> PAGE_SHIFT);
> 		ret = (*func)(pfn, len, arg);
>
>--
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