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: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 4ca1241..0db8037 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -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 @@
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 @@
* 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 @@
#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)