mm: Add folio_raw_mapping()

Convert __page_rmapping to folio_raw_mapping and move it to mm/internal.h.
It's only a couple of instructions (load and mask), so it's definitely
going to be cheaper to inline it than call it.  Leave page_rmapping
out of line.  Change page_anon_vma() to not call folio_raw_mapping() --
it's more efficient to do the subtraction than the mask.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>

1 files changed, 7 insertions, 0 deletions

diff --git a/mm/internal.h b/mm/internal.h
index 1a84484f8650..187a032fed4d 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -34,6 +34,13 @@
 
 void page_writeback_init(void);
 
+static inline void *folio_raw_mapping(struct folio *folio)
+{
+	unsigned long mapping = (unsigned long)folio->mapping;
+
+	return (void *)(mapping & ~PAGE_MAPPING_FLAGS);
+}
+
 vm_fault_t do_swap_page(struct vm_fault *vmf);
 void folio_rotate_reclaimable(struct folio *folio);