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Re: [PATCH] [MIPS] Hibernation: only save pages in system ram

To: Wu Zhangjin <wuzhangjin@gmail.com>
Subject: Re: [PATCH] [MIPS] Hibernation: only save pages in system ram
From: Ralf Baechle <ralf@linux-mips.org>
Date: Fri, 3 Jul 2009 00:22:05 +0100
Cc: LKML <linux-kernel@vger.kernel.org>, linux-mips@linux-mips.org, Pavel Machek <pavel@ucw.cz>, Wu Zhangjin <wuzj@lemote.com>
In-reply-to: <1246373570-21090-1-git-send-email-wuzhangjin@gmail.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1246373570-21090-1-git-send-email-wuzhangjin@gmail.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.18 (2008-05-17)
On Tue, Jun 30, 2009 at 10:52:50PM +0800, Wu Zhangjin wrote:

> From: Wu Zhangjin <wuzj@lemote.com>
> 
> when using hibernation(STD) with CONFIG_FLATMEM in linux-mips-64bit, it
> fails for the current mips-specific hibernation implementation save the
> pages in all of the memory space(except the nosave section) and make
> there will be not enough memory left to the STD task itself, and then
> fail. in reality, we only need to save the pages in system rams.
> 
> here is the reason why it fail:
> 
> kernel/power/snapshot.c:
> 
> static void mark_nosave_pages(struct memory_bitmap *bm)
> {
>               ...
>               if (pfn_valid(pfn)) {
>                       ...
>               }
> }
> 
> arch/mips/include/asm/page.h:
> 
>       ...
>       #ifdef CONFIG_FLATMEM
> 
>       #define pfn_valid(pfn)          ((pfn) >= ARCH_PFN_OFFSET && (pfn) < 
> max_mapnr)
> 
>       #elif defined(CONFIG_SPARSEMEM)
> 
>       /* pfn_valid is defined in linux/mmzone.h */
>       ...
> 
> we can rewrite pfn_valid(pfn) to fix this problem, but I really do not
> want to touch such a widely-used macro, so, I used another solution:
> 
> static struct page *saveable_page(struct zone *zone, unsigned long pfn)
> {
>       ...
>       if ( .... pfn_is_nosave(pfn)
>               return NULL;
>       ...
> }
> 
> and pfn_is_nosave is implemented in arch/mips/power/cpu.c, so, hacking
> this one is better.

No - pfn_valid() is broken, so it should be fixed.  Commit
752fbeb2e3555c0d236e992f1195fd7ce30e728d introduced the breakage.  It
seemed to assume that the valid range for PFNs doesn't start at 0 but
some higher number but got that entirely wrong..

#define ARCH_PFN_OFFSET         PFN_UP(PHYS_OFFSET)
#define pfn_valid(pfn)         ((pfn) >= ARCH_PFN_OFFSET && (pfn) < max_mapnr)

works nicely when PHYS_OFFSET is 0 - as for most MIPS systems and goes
horribly wrong otherwise.  So I suggest below patch.

  Ralf

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

 arch/mips/include/asm/page.h |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/arch/mips/include/asm/page.h b/arch/mips/include/asm/page.h
index dc0eaa7..96a14a4 100644
--- a/arch/mips/include/asm/page.h
+++ b/arch/mips/include/asm/page.h
@@ -165,7 +165,14 @@ typedef struct { unsigned long pgprot; } pgprot_t;
 
 #ifdef CONFIG_FLATMEM
 
-#define pfn_valid(pfn)         ((pfn) >= ARCH_PFN_OFFSET && (pfn) < max_mapnr)
+#define pfn_valid(pfn)                                                 \
+({                                                                     \
+       unsigned long __pfn = (pfn);                                    \
+       /* avoid <linux/bootmem.h> include hell */                      \
+       extern unsigned long min_low_pfn;                               \
+                                                                       \
+       __pfn >= min_low_pfn && __pfn < max_mapnr;                      \
+})
 
 #elif defined(CONFIG_SPARSEMEM)
 

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