slub: use free_page instead of put_page for freeing kmalloc allocation

Glauber Costa · penberg · commit d9b7f22623b5 · 2012-08-16T09:25:03.000+03:00
When freeing objects, the slub allocator will most of the time free
empty pages by calling __free_pages(). But high-order kmalloc will be
diposed by means of put_page() instead. It makes no sense to call
put_page() in kernel pages that are provided by the object allocators,
so we shouldn't be doing this ourselves. Aside from the consistency
change, we don't change the flow too much. put_page()'s would call its
dtor function, which is __free_pages. We also already do all of the
Compound page tests ourselves, and the Mlock test we lose don't really
matter.

Signed-off-by: Glauber Costa &lt;glommer@parallels.com&gt;
Acked-by: Christoph Lameter &lt;cl@linux.com&gt;
CC: David Rientjes &lt;rientjes@google.com&gt;
CC: Pekka Enberg &lt;penberg@kernel.org&gt;
Signed-off-by: Pekka Enberg &lt;penberg@kernel.org&gt;
diff --git a/mm/slub.c b/mm/slub.c
@@ -3477,7 +3477,7 @@ void kfree(const void *x)
 	if (unlikely(!PageSlab(page))) {
 		BUG_ON(!PageCompound(page));
 		kmemleak_free(x);
-		put_page(page);
+		__free_pages(page, compound_order(page));
 		return;
 	}
 	slab_free(page->slab, page, object, _RET_IP_);

Original file line number	Diff line number	Diff line change
`@@ -3477,7 +3477,7 @@ void kfree(const void *x)`
`3477`	`3477`	`if (unlikely(!PageSlab(page))) {`
`3478`	`3478`	`BUG_ON(!PageCompound(page));`
`3479`	`3479`	`kmemleak_free(x);`
`3480`		`- put_page(page);`
	`3480`	`+ __free_pages(page, compound_order(page));`
`3481`	`3481`	`return;`
`3482`	`3482`	`}`
`3483`	`3483`	`slab_free(page->slab, page, object, _RET_IP_);`