[PATCH 3/6] mm: Convert page_to_pgoff() to page_pgoff()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Change the function signature to pass in the folio as all three
callers have it.  This removes a reference to page->index, which we're
trying to get rid of.  Also move page_pgoff() to mm/internal.h as
code outside mm has no business calling it.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/pagemap.h | 18 ------------------
 mm/internal.h           |  6 ++++++
 mm/memory-failure.c     |  4 ++--
 mm/rmap.c               |  2 +-
 4 files changed, 9 insertions(+), 21 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 483a191bb4df..1f295ef7d10d 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -913,24 +913,6 @@ static inline struct folio *read_mapping_folio(struct address_space *mapping,
 	return read_cache_folio(mapping, index, NULL, file);
 }
 
-/*
- * Get the offset in PAGE_SIZE (even for hugetlb pages).
- */
-static inline pgoff_t page_to_pgoff(struct page *page)
-{
-	struct page *head;
-
-	if (likely(!PageTransTail(page)))
-		return page->index;
-
-	head = compound_head(page);
-	/*
-	 *  We don't initialize ->index for tail pages: calculate based on
-	 *  head page
-	 */
-	return head->index + page - head;
-}
-
 /*
  * Return byte-offset into filesystem object for page.
  */
diff --git a/mm/internal.h b/mm/internal.h
index e511708b2be0..8dfd9527ac1e 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -919,6 +919,12 @@ void mlock_drain_remote(int cpu);
 
 extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma);
 
+static inline pgoff_t page_pgoff(const struct folio *folio,
+		const struct page *page)
+{
+	return folio->index + folio_page_idx(folio, page);
+}
+
 /**
  * vma_address - Find the virtual address a page range is mapped at
  * @vma: The vma which maps this object.
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 581d3e5c9117..572c742ecf48 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -617,7 +617,7 @@ static void collect_procs_anon(struct folio *folio, struct page *page,
 	if (av == NULL)	/* Not actually mapped anymore */
 		return;
 
-	pgoff = page_to_pgoff(page);
+	pgoff = page_pgoff(folio, page);
 	rcu_read_lock();
 	for_each_process(tsk) {
 		struct vm_area_struct *vma;
@@ -653,7 +653,7 @@ static void collect_procs_file(struct folio *folio, struct page *page,
 
 	i_mmap_lock_read(mapping);
 	rcu_read_lock();
-	pgoff = page_to_pgoff(page);
+	pgoff = page_pgoff(folio, page);
 	for_each_process(tsk) {
 		struct task_struct *t = task_early_kill(tsk, force_early);
 		unsigned long addr;
diff --git a/mm/rmap.c b/mm/rmap.c
index 886bf67ba382..ba1920291ac6 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1266,7 +1266,7 @@ static void __page_check_anon_rmap(struct folio *folio, struct page *page,
 	 */
 	VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root,
 			folio);
-	VM_BUG_ON_PAGE(page_to_pgoff(page) != linear_page_index(vma, address),
+	VM_BUG_ON_PAGE(page_pgoff(folio, page) != linear_page_index(vma, address),
 		       page);
 }
 
-- 
2.43.0