mm: introduce pure page table freeing function

commit 0189429 upstream.

The pages used for ptdescs are currently freed back to the allocator in a
single location.  They will shortly be freed from a second location.

Create a simple helper that just frees them back to the allocator.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Dave Hansen <[email protected]>
Signed-off-by: Lu Baolu <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Reviewed-by: Kevin Tian <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Acked-by: Mike Rapoport (Microsoft) <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Betkov <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Jean-Philippe Brucker <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Liam Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Robin Murohy <[email protected]>
Cc: Thomas Gleinxer <[email protected]>
Cc: "Uladzislau Rezki (Sony)" <[email protected]>
Cc: Vasant Hegde <[email protected]>
Cc: Vinicius Costa Gomes <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Yi Lai <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: hansendc

include/linux/mm.h

@@ -3031,6 +3031,13 @@ static inline struct ptdesc *pagetable_alloc_noprof(gfp_t gfp, unsigned int orde
 }
 #define pagetable_alloc(...)	alloc_hooks(pagetable_alloc_noprof(__VA_ARGS__))
 
+static inline void __pagetable_free(struct ptdesc *pt)
+{
+	struct page *page = ptdesc_page(pt);
+
+	__free_pages(page, compound_order(page));
+}
+
 /**
  * pagetable_free - Free pagetables
  * @pt:	The page table descriptor
@@ -3040,12 +3047,10 @@ static inline struct ptdesc *pagetable_alloc_noprof(gfp_t gfp, unsigned int orde
  */
 static inline void pagetable_free(struct ptdesc *pt)
 {
-	struct page *page = ptdesc_page(pt);
-
 	if (ptdesc_test_kernel(pt))
 		ptdesc_clear_kernel(pt);
 
-	__free_pages(page, compound_order(page));
+	__pagetable_free(pt);
 }
 
 #if defined(CONFIG_SPLIT_PTE_PTLOCKS)