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[PATCH] sparsemem hotplug base 

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

56
include/linux/mmzone.h
View File

@ -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)));
}
/*

4
mm/page_alloc.c
View File

@ -1650,8 +1650,8 @@ void __init memmap_init_zone(unsigned long size, int nid, unsigned long zone,
unsigned long start_pfn)
{
struct page *page;
int end_pfn = start_pfn + size;
int pfn;
unsigned long end_pfn = start_pfn + size;
unsigned long pfn;
for (pfn = start_pfn; pfn < end_pfn; pfn++, page++) {
if (!early_pfn_valid(pfn))

92
mm/sparse.c
View File

@ -25,7 +25,7 @@ void memory_present(int nid, unsigned long start, unsigned long end)
for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
unsigned long section = pfn_to_section_nr(pfn);
if (!mem_section[section].section_mem_map)
mem_section[section].section_mem_map = (void *) -1;
mem_section[section].section_mem_map = SECTION_MARKED_PRESENT;
}
}
@ -50,6 +50,56 @@ unsigned long __init node_memmap_size_bytes(int nid, unsigned long start_pfn,
return nr_pages * sizeof(struct page);
}
/*
* Subtle, we encode the real pfn into the mem_map such that
* the identity pfn - section_mem_map will return the actual
* physical page frame number.
*/
static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long pnum)
{
return (unsigned long)(mem_map - (section_nr_to_pfn(pnum)));
}
/*
* We need this if we ever free the mem_maps. While not implemented yet,
* this function is included for parity with its sibling.
*/
static __attribute((unused))
struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pnum)
{
return ((struct page *)coded_mem_map) + section_nr_to_pfn(pnum);
}
static int sparse_init_one_section(struct mem_section *ms,
unsigned long pnum, struct page *mem_map)
{
if (!valid_section(ms))
return -EINVAL;
ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum);
return 1;
}
static struct page *sparse_early_mem_map_alloc(unsigned long pnum)
{
struct page *map;
int nid = early_pfn_to_nid(section_nr_to_pfn(pnum));
map = alloc_remap(nid, sizeof(struct page) * PAGES_PER_SECTION);
if (map)
return map;
map = alloc_bootmem_node(NODE_DATA(nid),
sizeof(struct page) * PAGES_PER_SECTION);
if (map)
return map;
printk(KERN_WARNING "%s: allocation failed\n", __FUNCTION__);
mem_section[pnum].section_mem_map = 0;
return NULL;
}
/*
* Allocate the accumulated non-linear sections, allocate a mem_map
* for each and record the physical to section mapping.
@ -58,28 +108,30 @@ void sparse_init(void)
{
unsigned long pnum;
struct page *map;
int nid;
for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
if (!mem_section[pnum].section_mem_map)
if (!valid_section_nr(pnum))
continue;
nid = early_pfn_to_nid(section_nr_to_pfn(pnum));
map = alloc_remap(nid, sizeof(struct page) * PAGES_PER_SECTION);
if (!map)
map = alloc_bootmem_node(NODE_DATA(nid),
sizeof(struct page) * PAGES_PER_SECTION);
if (!map) {
mem_section[pnum].section_mem_map = 0;
continue;
}
/*
* Subtle, we encode the real pfn into the mem_map such that
* the identity pfn - section_mem_map will return the actual
* physical page frame number.
*/
mem_section[pnum].section_mem_map = map -
section_nr_to_pfn(pnum);
map = sparse_early_mem_map_alloc(pnum);
if (map)
sparse_init_one_section(&mem_section[pnum], pnum, map);
}
}
/*
* returns the number of sections whose mem_maps were properly
* set. If this is <=0, then that means that the passed-in
* map was not consumed and must be freed.
*/
int sparse_add_one_section(unsigned long start_pfn, int nr_pages, struct page *map)
{
struct mem_section *ms = __pfn_to_section(start_pfn);
if (ms->section_mem_map & SECTION_MARKED_PRESENT)
return -EEXIST;
ms->section_mem_map |= SECTION_MARKED_PRESENT;
return sparse_init_one_section(ms, pfn_to_section_nr(start_pfn), map);
}