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

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 <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 21ae5b01

fs/proc/page.c

+8 −6
Original line number Diff line number Diff line
@@ -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);

include/linux/memory_hotplug.h

+9 −5
Original line number Diff line number Diff line
@@ -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

include/linux/mm.h

+21 −0
Original line number Diff line number Diff line
@@ -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);

include/linux/page-flags.h

+1 −6
Original line number Diff line number Diff line
@@ -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)

mm/memory_hotplug.c

+8 −6
Original line number Diff line number Diff line
@@ -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);

	}