[PATCH v5 11/12] mm: drop page_index and simplify folio_index

[Kairui Song <ryncsn@gmail.com>]

From: Kairui Song <kasong@tencent.com>

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 convertion.

Signed-off-by: Kairui Song <kasong@tencent.com>
---
 include/linux/mm.h      | 13 -------------
 include/linux/pagemap.h |  8 ++++----
 mm/swapfile.c           |  7 +++----
 3 files changed, 7 insertions(+), 21 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9849dfda44d4..e2718cac0fda 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2290,19 +2290,6 @@ static inline void *folio_address(const struct folio *folio)
 	return page_address(&folio->page);
 }
 
-extern pgoff_t __page_file_index(struct page *page);
-
-/*
- * Return the pagecache index of the passed page.  Regular pagecache pages
- * use ->index whereas swapcache pages use swp_offset(->private)
- */
-static inline pgoff_t page_index(struct page *page)
-{
-	if (unlikely(PageSwapCache(page)))
-		return __page_file_index(page);
-	return page->index;
-}
-
 /*
  * Return true only if the page has been allocated with
  * ALLOC_NO_WATERMARKS and the low watermark was not
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a324582ea702..0cfa5810cde3 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -778,7 +778,7 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
 			mapping_gfp_mask(mapping));
 }
 
-#define swapcache_index(folio)	__page_file_index(&(folio)->page)
+extern pgoff_t __folio_swap_cache_index(struct folio *folio);
 
 /**
  * folio_index - File index of a folio.
@@ -793,9 +793,9 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
  */
 static inline pgoff_t folio_index(struct folio *folio)
 {
-        if (unlikely(folio_test_swapcache(folio)))
-                return swapcache_index(folio);
-        return folio->index;
+	if (unlikely(folio_test_swapcache(folio)))
+		return __folio_swap_cache_index(folio);
+	return folio->index;
 }
 
 /**
diff --git a/mm/swapfile.c b/mm/swapfile.c
index f6ca215fb92f..0b0ae6e8c764 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3474,12 +3474,11 @@ 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
-- 
2.45.0