Commit 5f24ce5f authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Linus Torvalds

thp: remove PG_buddy

PG_buddy can be converted to _mapcount == -2.  So the PG_compound_lock can
be added to page->flags without overflowing (because of the sparse section
bits increasing) with CONFIG_X86_PAE=y and CONFIG_X86_PAT=y.  This also
has to move the memory hotplug code from _mapcount to lru.next to avoid
any risk of clashes.  We can't use lru.next for PG_buddy removal, but
memory hotplug can use lru.next even more easily than the mapcount
instead.
Signed-off-by: default avatarAndrea Arcangeli <[email protected]>
Signed-off-by: default avatarAndrew Morton <[email protected]>
Signed-off-by: default avatarLinus Torvalds <[email protected]>
parent 21ae5b01
......@@ -116,15 +116,17 @@ u64 stable_page_flags(struct page *page)
if (PageHuge(page))
u |= 1 << KPF_HUGE;
u |= kpf_copy_bit(k, KPF_LOCKED, PG_locked);
/*
* Caveats on high order pages:
* PG_buddy will only be set on the head page; SLUB/SLQB do the same
* for PG_slab; SLOB won't set PG_slab at all on compound pages.
* Caveats on high order pages: page->_count will only be set
* -1 on the head page; SLUB/SLQB do the same for PG_slab;
* SLOB won't set PG_slab at all on compound pages.
*/
if (PageBuddy(page))
u |= 1 << KPF_BUDDY;
u |= kpf_copy_bit(k, KPF_LOCKED, PG_locked);
u |= kpf_copy_bit(k, KPF_SLAB, PG_slab);
u |= kpf_copy_bit(k, KPF_BUDDY, PG_buddy);
u |= kpf_copy_bit(k, KPF_ERROR, PG_error);
u |= kpf_copy_bit(k, KPF_DIRTY, PG_dirty);
......
......@@ -13,12 +13,16 @@ struct mem_section;
#ifdef CONFIG_MEMORY_HOTPLUG
/*
* Types for free bootmem.
* The normal smallest mapcount is -1. Here is smaller value than it.
* Types for free bootmem stored in page->lru.next. These have to be in
* some random range in unsigned long space for debugging purposes.
*/
#define SECTION_INFO (-1 - 1)
#define MIX_SECTION_INFO (-1 - 2)
#define NODE_INFO (-1 - 3)
enum {
MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE = 12,
SECTION_INFO = MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE,
MIX_SECTION_INFO,
NODE_INFO,
MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE = NODE_INFO,
};
/*
* pgdat resizing functions
......
......@@ -397,6 +397,27 @@ static inline void init_page_count(struct page *page)
atomic_set(&page->_count, 1);
}
/*
* PageBuddy() indicate that the page is free and in the buddy system
* (see mm/page_alloc.c).
*/
static inline int PageBuddy(struct page *page)
{
return atomic_read(&page->_mapcount) == -2;
}
static inline void __SetPageBuddy(struct page *page)
{
VM_BUG_ON(atomic_read(&page->_mapcount) != -1);
atomic_set(&page->_mapcount, -2);
}
static inline void __ClearPageBuddy(struct page *page)
{
VM_BUG_ON(!PageBuddy(page));
atomic_set(&page->_mapcount, -1);
}
void put_page(struct page *page);
void put_pages_list(struct list_head *pages);
......
......@@ -48,9 +48,6 @@
* struct page (these bits with information) are always mapped into kernel
* address space...
*
* PG_buddy is set to indicate that the page is free and in the buddy system
* (see mm/page_alloc.c).
*
* PG_hwpoison indicates that a page got corrupted in hardware and contains
* data with incorrect ECC bits that triggered a machine check. Accessing is
* not safe since it may cause another machine check. Don't touch!
......@@ -96,7 +93,6 @@ enum pageflags {
PG_swapcache, /* Swap page: swp_entry_t in private */
PG_mappedtodisk, /* Has blocks allocated on-disk */
PG_reclaim, /* To be reclaimed asap */
PG_buddy, /* Page is free, on buddy lists */
PG_swapbacked, /* Page is backed by RAM/swap */
PG_unevictable, /* Page is "unevictable" */
#ifdef CONFIG_MMU
......@@ -233,7 +229,6 @@ PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
* risky: they bypass page accounting.
*/
TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
__PAGEFLAG(Buddy, buddy)
PAGEFLAG(MappedToDisk, mappedtodisk)
/* PG_readahead is only used for file reads; PG_reclaim is only for writes */
......@@ -461,7 +456,7 @@ static inline int PageTransCompound(struct page *page)
#define PAGE_FLAGS_CHECK_AT_FREE \
(1 << PG_lru | 1 << PG_locked | \
1 << PG_private | 1 << PG_private_2 | \
1 << PG_buddy | 1 << PG_writeback | 1 << PG_reserved | \
1 << PG_writeback | 1 << PG_reserved | \
1 << PG_slab | 1 << PG_swapcache | 1 << PG_active | \
1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON | \
__PG_COMPOUND_LOCK)
......
......@@ -82,9 +82,10 @@ static void release_memory_resource(struct resource *res)
#ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
#ifndef CONFIG_SPARSEMEM_VMEMMAP
static void get_page_bootmem(unsigned long info, struct page *page, int type)
static void get_page_bootmem(unsigned long info, struct page *page,
unsigned long type)
{
atomic_set(&page->_mapcount, type);
page->lru.next = (struct list_head *) type;
SetPagePrivate(page);
set_page_private(page, info);
atomic_inc(&page->_count);
......@@ -94,15 +95,16 @@ static void get_page_bootmem(unsigned long info, struct page *page, int type)
* so use __ref to tell modpost not to generate a warning */
void __ref put_page_bootmem(struct page *page)
{
int type;
unsigned long type;
type = atomic_read(&page->_mapcount);
BUG_ON(type >= -1);
type = (unsigned long) page->lru.next;
BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);
if (atomic_dec_return(&page->_count) == 1) {
ClearPagePrivate(page);
set_page_private(page, 0);
reset_page_mapcount(page);
INIT_LIST_HEAD(&page->lru);
__free_pages_bootmem(page, 0);
}
......
......@@ -449,8 +449,8 @@ __find_combined_index(unsigned long page_idx, unsigned int order)
* (c) a page and its buddy have the same order &&
* (d) a page and its buddy are in the same zone.
*
* For recording whether a page is in the buddy system, we use PG_buddy.
* Setting, clearing, and testing PG_buddy is serialized by zone->lock.
* For recording whether a page is in the buddy system, we set ->_mapcount -2.
* Setting, clearing, and testing _mapcount -2 is serialized by zone->lock.
*
* For recording page's order, we use page_private(page).
*/
......@@ -483,7 +483,7 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
* as necessary, plus some accounting needed to play nicely with other
* parts of the VM system.
* At each level, we keep a list of pages, which are heads of continuous
* free pages of length of (1 << order) and marked with PG_buddy. Page's
* free pages of length of (1 << order) and marked with _mapcount -2. Page's
* order is recorded in page_private(page) field.
* So when we are allocating or freeing one, we can derive the state of the
* other. That is, if we allocate a small block, and both were
......@@ -5574,7 +5574,6 @@ static struct trace_print_flags pageflag_names[] = {
{1UL << PG_swapcache, "swapcache" },
{1UL << PG_mappedtodisk, "mappedtodisk" },
{1UL << PG_reclaim, "reclaim" },
{1UL << PG_buddy, "buddy" },
{1UL << PG_swapbacked, "swapbacked" },
{1UL << PG_unevictable, "unevictable" },
#ifdef CONFIG_MMU
......
......@@ -671,10 +671,10 @@ static void __kfree_section_memmap(struct page *memmap, unsigned long 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;
unsigned long magic;
for (i = 0; i < nr_pages; i++, page++) {
magic = atomic_read(&page->_mapcount);
magic = (unsigned long) page->lru.next;
BUG_ON(magic == NODE_INFO);
......
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