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/fs/proc/page.c b/fs/proc/page.c
index b06c674..6d8e6a9 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -116,15 +116,17 @@
if (PageHuge(page))
u |= 1 << KPF_HUGE;
+ /*
+ * 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);
- /*
- * 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.
- */
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);