linux-kernel - Re: [PATCH] coredump_filter: add hugepage core dumping

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Message-ID: <48C48520.9070206@hitachi.com>
Date:	Mon, 08 Sep 2008 10:51:28 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Hugh Dickins <hugh@...itas.com>,
	William Irwin <wli@...omorphy.com>,
	Adam Litke <agl@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, roland@...hat.com,
	sugita <yumiko.sugita.yf@...achi.com>,
	Satoshi OSHIMA <satoshi.oshima.fk@...achi.com>
Subject: Re: [PATCH] coredump_filter: add hugepage core dumping

[Added CC to Roland McGrath]

Mel Gorman wrote:

>>--- a/Documentation/filesystems/proc.txt
>>+++ b/Documentation/filesystems/proc.txt
>>@@ -2389,11 +2389,12 @@ will be dumped when the <pid> process is
>> of memory types. If a bit of the bitmask is set, memory segments of the
>> corresponding memory type are dumped, otherwise they are not dumped.
>> 
>>-The following 4 memory types are supported:
>>+The following 5 memory types are supported:
>>   - (bit 0) anonymous private memory
>>   - (bit 1) anonymous shared memory
>>   - (bit 2) file-backed private memory
>>   - (bit 3) file-backed shared memory
>>+  - (bit 5) hugetlb memory
> 
> It's not your fault, but the meaning of bit 4 appears to be
> undocumented. Offhand, does anyone know if this is intentional?

I think it was just forgotten to be updated.  Bit 4 was introduced
by Roland McGrath, and it means elf header pages in file-backed
private VMAs are dumped even if bit 2 is cleared.

Thanks,


Subject: [PATCH] coredump_filter: add description of bit 4

There is no description of bit 4 of coredump_filter in the
documentation.  This patch adds it.

Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
CC: Roland McGrath <roland@...hat.com>
---
 Documentation/filesystems/proc.txt |    2 ++
 1 file changed, 2 insertions(+)

Index: linux-2.6.27-rc5/Documentation/filesystems/proc.txt
===================================================================
--- linux-2.6.27-rc5.orig/Documentation/filesystems/proc.txt
+++ linux-2.6.27-rc5/Documentation/filesystems/proc.txt
@@ -2394,6 +2394,8 @@ The following 4 memory types are support
   - (bit 1) anonymous shared memory
   - (bit 2) file-backed private memory
   - (bit 3) file-backed shared memory
+  - (bit 4) ELF header pages in file-backed private memory areas (it is
+            effective only if the bit 2 is cleared)
 
   Note that MMIO pages such as frame buffer are never dumped and vDSO pages
   are always dumped regardless of the bitmask status.



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