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SubjectRe: [Patch](memory hotplug) Fix compile error for i386 with NUMA config
Hi David-san.

> On Sat, 9 Dec 2006, Yasunori Goto wrote:
>
> > Hello.
> >
> > This patch is to fix compile error when config memory hotplug
> > with numa on i386.
> >
> > The cause of compile error was missing of arch_add_memory(), remove_memory(),
> > and memory_add_physaddr_to_nid() when NUMA config is on.
> >
> > This is for 2.6.19, and I tested no compile error of it.
> >
> > Please apply.
> >
> > Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
> >
> > ---
> > arch/i386/mm/discontig.c | 17 +++++++++++++++++
> > arch/i386/mm/init.c | 4 +---
> > 2 files changed, 18 insertions(+), 3 deletions(-)
> >
> > Index: linux-2.6.19/arch/i386/mm/init.c
> > ===================================================================
> > --- linux-2.6.19.orig/arch/i386/mm/init.c 2006-12-04 20:06:32.000000000 +0900
> > +++ linux-2.6.19/arch/i386/mm/init.c 2006-12-04 21:09:49.000000000 +0900
> > @@ -681,10 +681,9 @@
> > * memory to the highmem for now.
> > */
> > #ifdef CONFIG_MEMORY_HOTPLUG
> > -#ifndef CONFIG_NEED_MULTIPLE_NODES
> > int arch_add_memory(int nid, u64 start, u64 size)
> > {
> > - struct pglist_data *pgdata = &contig_page_data;
> > + struct pglist_data *pgdata = NODE_DATA(nid);
> > struct zone *zone = pgdata->node_zones + ZONE_HIGHMEM;
> > unsigned long start_pfn = start >> PAGE_SHIFT;
> > unsigned long nr_pages = size >> PAGE_SHIFT;
> > @@ -697,7 +696,6 @@
> > return -EINVAL;
> > }
> > #endif
> > -#endif
> >
> > kmem_cache_t *pgd_cache;
> > kmem_cache_t *pmd_cache;
>
> The reason for the #ifndef CONFIG_NEED_MULTIPLE_NODES check seems to
> solely exist for excluding the NUMA case, so it doesn't appear as though
> this is the correct fix since your changelog indicates a compile problem
> with a NUMA build. This hypothesis is supported by the comment which
> conveniently appears just before arch_add_memory which _explicitly_ states
> that the following is for non-NUMA cases.

No.
Other arch's arch_add_memory() and remove_memory() have been already
used for NUMA case too. But i386 didn't do it because just
contig_page_data is used.
Current NODE_DATA() macro is defined both case appropriately.
So, this #ifdef is redundant now.

(See: http://marc.theaimsgroup.com/?l=linux-mm&m=116494983531221&w=2)

>
> > Index: linux-2.6.19/arch/i386/mm/discontig.c
> > ===================================================================
> > --- linux-2.6.19.orig/arch/i386/mm/discontig.c 2006-12-04 20:06:32.000000000 +0900
> > +++ linux-2.6.19/arch/i386/mm/discontig.c 2006-12-09 17:30:24.000000000 +0900
> > @@ -405,3 +405,20 @@
> > totalram_pages += totalhigh_pages;
> > #endif
> > }
> > +
> > +#ifdef CONFIG_MEMORY_HOTPLUG
> > +/* This is the case that there is no _PXM on DSDT for added memory */
> > +int memory_add_physaddr_to_nid(u64 addr)
> > +{
> > + int nid;
> > + unsigned long pfn = addr >> PAGE_SHIFT;
> > +
> > + for (nid = 0; nid < MAX_NUMNODES; nid++){
> > + if (node_start_pfn[nid] <= pfn &&
> > + pfn < node_end_pfn[nid])
> > + return nid;
> > + }
> > +
> > + return 0;
> > +}
> > +#endif
> >
>
> memory_add_physaddr_to_nid is only declared as extern in
> include/linux/memory_hotplug.h in the CONFIG_NUMA case so this also
> doesn't appear as the correct fix but probably worked for your compile
> since you had CONFIG_MEMORY_HOTPLUG enabled.

memory_add_physaddr_to_nid() is used for memory hotplug to
find node id for new memory when ACPI's DSDT doesn't define
_PXM for new memory. So, when CONFIG_MEMORY_HOTPLUG is not set,
this function is not used.

Bye.

--
Yasunori Goto


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