mm/slob: Use free_page instead of put_page for page-size kmalloc allocations

When freeing objects, the slob allocator currently free empty pages
calling __free_pages(). However, page-size kmallocs are disposed
using put_page() instead.

It makes no sense to call put_page() for kernel pages that are provided
by the object allocator, so we shouldn't be doing this ourselves.

This is based on:
commit d9b7f22623
Author: Glauber Costa <[email protected]>
slub: use free_page instead of put_page for freeing kmalloc allocation

Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Matt Mackall <[email protected]>
Acked-by: Glauber Costa <[email protected]>
Signed-off-by: Ezequiel Garcia <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>

mm/slob.c

@@ -500,7 +500,7 @@ void kfree(const void *block)
 		unsigned int *m = (unsigned int *)(block - align);
 		slob_free(m, *m + align);
 	} else
-		put_page(sp);
+		__free_pages(sp, compound_order(sp));
 }
 EXPORT_SYMBOL(kfree);