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[PATCH] sparsemem hotplug base

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Make sparse's initalization be accessible at runtime.  This allows sparse
mappings to be created after boot in a hotplug situation.

This patch is separated from the previous one just to give an indication how
much of the sparse infrastructure is *just* for hotplug memory.

The section_mem_map doesn't really store a pointer.  It stores something that
is convenient to do some math against to get a pointer.  It isn't valid to
just do *section_mem_map, so I don't think it should be stored as a pointer.

There are a couple of things I'd like to store about a section.  First of all,
the fact that it is !NULL does not mean that it is present.  There could be
such a combination where section_mem_map *is* NULL, but the math gets you
properly to a real mem_map.  So, I don't think that check is safe.

Since we're storing 32-bit-aligned structures, we have a few bits in the
bottom of the pointer to play with.  Use one bit to encode whether there's
really a mem_map there, and the other one to tell whether there's a valid
section there.  We need to distinguish between the two because sometimes
there's a gap between when a section is discovered to be present and when we
can get the mem_map for it.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andy Whitcroft
2005-06-23 00:08:00 -07:00
committed by Linus Torvalds
parent 641c767389
commit 29751f6991
3 changed files with 125 additions and 27 deletions
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56
include/linux/mmzone.h
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@@ -476,11 +476,56 @@ extern struct pglist_data contig_page_data;
struct page;
struct mem_section {
struct page *section_mem_map;
/*
* This is, logically, a pointer to an array of struct
* pages. However, it is stored with some other magic.
* (see sparse.c::sparse_init_one_section())
*
* Making it a UL at least makes someone do a cast
* before using it wrong.
*/
unsigned long section_mem_map;
};
extern struct mem_section mem_section[NR_MEM_SECTIONS];
static inline struct mem_section *__nr_to_section(unsigned long nr)
{
return &mem_section[nr];
}
/*
* We use the lower bits of the mem_map pointer to store
* a little bit of information. There should be at least
* 3 bits here due to 32-bit alignment.
*/
#define SECTION_MARKED_PRESENT (1UL<<0)
#define SECTION_HAS_MEM_MAP (1UL<<1)
#define SECTION_MAP_LAST_BIT (1UL<<2)
#define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1))
static inline struct page *__section_mem_map_addr(struct mem_section *section)
{
unsigned long map = section->section_mem_map;
map &= SECTION_MAP_MASK;
return (struct page *)map;
}
static inline int valid_section(struct mem_section *section)
{
return (section->section_mem_map & SECTION_MARKED_PRESENT);
}
static inline int section_has_mem_map(struct mem_section *section)
{
return (section->section_mem_map & SECTION_HAS_MEM_MAP);
}
static inline int valid_section_nr(unsigned long nr)
{
return valid_section(__nr_to_section(nr));
}
/*
* Given a kernel address, find the home node of the underlying memory.
*/
@@ -488,24 +533,25 @@ extern struct mem_section mem_section[NR_MEM_SECTIONS];
static inline struct mem_section *__pfn_to_section(unsigned long pfn)
{
return &mem_section[pfn_to_section_nr(pfn)];
return __nr_to_section(pfn_to_section_nr(pfn));
}
#define pfn_to_page(pfn) \
({ \
unsigned long __pfn = (pfn); \
__pfn_to_section(__pfn)->section_mem_map + __pfn; \
__section_mem_map_addr(__pfn_to_section(__pfn)) + __pfn; \
})
#define page_to_pfn(page) \
({ \
page - mem_section[page_to_section(page)].section_mem_map; \
page - __section_mem_map_addr(__nr_to_section( \
page_to_section(page))); \
})
static inline int pfn_valid(unsigned long pfn)
{
if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
return 0;
return mem_section[pfn_to_section_nr(pfn)].section_mem_map != 0;
return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
}
/*