mm: drop page_index and simplify folio_index

There are two helpers for retrieving the index within address space for
mixed usage of swap cache and page cache:

- page_index
- folio_index

This commit drops page_index, as we have eliminated all users, and
converts folio_index's helper __page_file_index to use folio to avoid the
page conversion.

Link: https://lkml.kernel.org/r/20240521175854.96038-11-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Anna Schumaker <anna@kernel.org>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Marc Dionne <marc.dionne@auristor.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Xiubo Li <xiubli@redhat.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index b3e5e384e330..348c4d3ae078 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3449,12 +3449,11 @@ struct address_space *swapcache_mapping(struct folio *folio)
 }
 EXPORT_SYMBOL_GPL(swapcache_mapping);
 
-pgoff_t __page_file_index(struct page *page)
+pgoff_t __folio_swap_cache_index(struct folio *folio)
 {
-	swp_entry_t swap = page_swap_entry(page);
-	return swp_offset(swap);
+	return swp_offset(folio->swap);
 }
-EXPORT_SYMBOL_GPL(__page_file_index);
+EXPORT_SYMBOL_GPL(__folio_swap_cache_index);
 
 /*
  * add_swap_count_continuation - called when a swap count is duplicated