Re: [Patch 005/005](memory hotplug) free memmaps allocated by bootmem

From: Yasunori Goto
Date: Mon Jun 16 2008 - 10:25:54 EST



> > Index: current/mm/sparse.c
> > ===================================================================
> > --- current.orig/mm/sparse.c 2008-04-07 20:13:25.000000000 +0900
> > +++ current/mm/sparse.c 2008-04-07 20:27:20.000000000 +0900
> > @@ -8,6 +8,7 @@
> > #include <linux/module.h>
> > #include <linux/spinlock.h>
> > #include <linux/vmalloc.h>
> > +#include "internal.h"
> > #include <asm/dma.h>
> > #include <asm/pgalloc.h>
> > #include <asm/pgtable.h>
> > @@ -360,6 +361,9 @@
> > {
> > return; /* XXX: Not implemented yet */
> > }
> > +static void free_map_bootmem(struct page *page, unsigned long nr_pages)
> > +{
> > +}
> > #else
> > static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
> > {
> > @@ -397,17 +401,47 @@
> > free_pages((unsigned long)memmap,
> > get_order(sizeof(struct page) * nr_pages));
> > }
> > +
> > +static void free_map_bootmem(struct page *page, unsigned long nr_pages)
> > +{
> > + unsigned long maps_section_nr, removing_section_nr, i;
> > + int magic;
> > +
> > + for (i = 0; i < nr_pages; i++, page++) {
> > + magic = atomic_read(&page->_mapcount);
> > +
> > + BUG_ON(magic == NODE_INFO);
>
> Are we sure the node area was big enough to never allocate usemap's into
> it and change the magic to MIX? I saw you make the section information
> page sized but not the others.

I don't think this is finish for removing whole of node. Just preparing.
I would like to make section removing at first rather than node.

> > +
> > + maps_section_nr = pfn_to_section_nr(page_to_pfn(page));
> > + removing_section_nr = page->private;
> > +
> > + /*
> > + * When this function is called, the removing section is
> > + * logical offlined state. This means all pages are isolated
> > + * from page allocator. If removing section's memmap is placed
> > + * on the same section, it must not be freed.
> > + * If it is freed, page allocator may allocate it which will
> > + * be removed physically soon.
> > + */
> > + if (maps_section_nr != removing_section_nr)
> > + put_page_bootmem(page);
>
> Would the section memmap have its own get_page_bootmem reference here?
> Would that not protect it from release?

It's not protected.



> > Index: current/mm/page_alloc.c
> > ===================================================================
> > --- current.orig/mm/page_alloc.c 2008-04-07 20:12:55.000000000 +0900
> > +++ current/mm/page_alloc.c 2008-04-07 20:13:29.000000000 +0900
> > @@ -568,7 +568,7 @@
> > /*
> > * permit the bootmem allocator to evade page validation on high-order frees
> > */
> > -void __init __free_pages_bootmem(struct page *page, unsigned int order)
> > +void __free_pages_bootmem(struct page *page, unsigned int order)
>
> not __meminit or something?

Ah, yes. I'll fix it.

Thanks for comments.

Bye.

--
Yasunori Goto


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