[PATCH 3/7] slub: Do not use c->page on free

[Christoph Lameter]

Avoid using the page struct address on free by just doing an
address comparison. That is easily doable now that the page address
is available in the page struct and we already have the page struct
address of the object to be freed calculated.

Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>

Index: linux/mm/slub.c
===================================================================
--- linux.orig/mm/slub.c	2014-12-09 12:25:45.770405462 -0600
+++ linux/mm/slub.c	2014-12-09 12:25:45.766405582 -0600
@@ -2625,6 +2625,13 @@ slab_empty:
 	discard_slab(s, page);
 }
 
+static bool same_slab_page(struct kmem_cache *s, struct page *page, void *p)
+{
+	long d = p - page->address;
+
+	return d > 0 && d < (1 << MAX_ORDER) && d < (compound_order(page) << PAGE_SHIFT);
+}
+
 /*
  * Fastpath with forced inlining to produce a kfree and kmem_cache_free that
  * can perform fastpath freeing without additional function calls.
@@ -2658,7 +2665,7 @@ redo:
 	tid = c->tid;
 	preempt_enable();
 
-	if (likely(page == c->page)) {
+	if (likely(same_slab_page(s, page, c->freelist))) {
 		set_freepointer(s, object, c->freelist);
 
 		if (unlikely(!this_cpu_cmpxchg_double(

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