linux-kernel - Re: + hotplug-memory-adding-non-section-aligned-memory-is-bad.patch added to -mm tree

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Date:	Tue, 1 Apr 2008 09:48:24 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, mm-commits@...r.kernel.org,
	jeremy@...p.org, clameter@....com, dave@...ux.vnet.ibm.com,
	jeremy.fitzhardinge@...rix.com, mingo@...e.hu, tglx@...utronix.de,
	y-goto@...fujitsu.com
Subject: Re: + hotplug-memory-adding-non-section-aligned-memory-is-bad.patch
 added to -mm tree

Hi, Andrew.

This patch got NACK from Goto-san. 
("Ok" I said was my mistake. sorry.)

Regards,
-Kame


On Mon, 31 Mar 2008 14:33:37 -0700
akpm@...ux-foundation.org wrote:

> 
> The patch titled
>      Subject: [PATCH 2 of 4] hotplug-memory: adding non-section-aligned memory is bad
> has been added to the -mm tree.  Its filename is
>      hotplug-memory-adding-non-section-aligned-memory-is-bad.patch
> 
> Before you just go and hit "reply", please:
>    a) Consider who else should be cc'ed
>    b) Prefer to cc a suitable mailing list as well
>    c) Ideally: find the original patch on the mailing list and do a
>       reply-to-all to that, adding suitable additional cc's
> 
> *** Remember to use Documentation/SubmitChecklist when testing your code ***
> 
> See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
> out what to do about this
> 
> The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
> 
> ------------------------------------------------------
> Subject: Subject: [PATCH 2 of 4] hotplug-memory: adding non-section-aligned memory is bad
> From: Jeremy Fitzhardinge <jeremy@...p.org>
> 
> Adding non-section-aligned memory will cause bad results, because page
> structures are only built on section-aligned boundaries.  Also, memory
> whose size isn't a multiple of the section size is silently ignored.
> 
> This patch adds a couple of WARN_ONs to help confused programmers work
> out what's going wrong when they hotplug memory without being aware of
> these constraints.
> 
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Cc: Yasunori Goto <y-goto@...fujitsu.com>
> Cc: Christoph Lameter <clameter@....com>
> Cc: Dave Hansen <dave@...ux.vnet.ibm.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
> 
>  include/linux/mmzone.h |    3 +++
>  mm/memory_hotplug.c    |    5 +++++
>  2 files changed, 8 insertions(+)
> 
> diff -puN include/linux/mmzone.h~hotplug-memory-adding-non-section-aligned-memory-is-bad include/linux/mmzone.h
> --- a/include/linux/mmzone.h~hotplug-memory-adding-non-section-aligned-memory-is-bad
> +++ a/include/linux/mmzone.h
> @@ -829,6 +829,9 @@ static inline unsigned long early_pfn_to
>  #define PAGES_PER_SECTION       (1UL << PFN_SECTION_SHIFT)
>  #define PAGE_SECTION_MASK	(~(PAGES_PER_SECTION-1))
>  
> +#define SECTION_SIZE		(1UL << SECTION_SIZE_BITS)
> +#define SECTION_SIZE_MASK	(SECTION_SIZE - 1)
> +
>  #define SECTION_BLOCKFLAGS_BITS \
>  	((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)
>  
> diff -puN mm/memory_hotplug.c~hotplug-memory-adding-non-section-aligned-memory-is-bad mm/memory_hotplug.c
> --- a/mm/memory_hotplug.c~hotplug-memory-adding-non-section-aligned-memory-is-bad
> +++ a/mm/memory_hotplug.c
> @@ -301,6 +301,11 @@ int add_memory_resource(int nid, struct 
>  	u64 start = res->start;
>  	u64 size = res->end - res->start + 1;
>  
> +	/* Adding non-section-aligned memory will give unexpected
> +	   and unintuitive results. */
> +	WARN_ON((start & SECTION_SIZE_MASK) != 0);
> +	WARN_ON((size & SECTION_SIZE_MASK) != 0);
> +
>  	if (!node_online(nid)) {
>  		pgdat = hotadd_new_pgdat(nid, start);
>  		if (!pgdat)
> _
> 
> Patches currently in -mm which might be from jeremy@...p.org are
> 
> origin.patch
> git-x86.patch
> sparsemem-vmemmap-does-not-need-section-bits.patch
> kbuild-create-a-way-to-create-preprocessor-constants-from-c-expressions.patch
> pageflags-use-an-enum-for-the-flags.patch
> pageflags-get-rid-of-flags_reserved.patch
> pageflags-introduce-macros-to-generate-page-flag-functions.patch
> pageflags-convert-to-the-use-of-new-macros.patch
> pageflags-use-proper-page-flag-functions-in-xen.patch
> pageflags-eliminate-pg_xxx-aliases.patch
> hotplug-memory-add-add_memory_resource.patch
> hotplug-memory-adding-non-section-aligned-memory-is-bad.patch
> sparsemem-reduce-i386-pae-section-size.patch
> paravirt_ops-dont-steal-memory-resources-in-paravirt_disable_iospace.patch
> xen-make-blkif_getgeo-static.patch
> 
> --
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