mm: remove vma_address()

Convert the three remaining callers to call vma_pgoff_address() directly. 
This removes an ambiguity where we'd check just one page if passed a tail
page and all N pages if passed a head page.

Also add better kernel-doc for vma_pgoff_address().

Link: https://lkml.kernel.org/r/20240328225831.1765286-3-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/internal.h

@@ -804,9 +804,14 @@ void mlock_drain_remote(int cpu);
 
 extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma);
 
-/*
- * Return the start of user virtual address at the specific offset within
- * a vma.
+/**
+ * vma_pgoff_address - Find the virtual address a page range is mapped at
+ * @pgoff: The page offset within its object.
+ * @nr_pages: The number of pages to consider.
+ * @vma: The vma which maps this object.
+ *
+ * If any page in this range is mapped by this VMA, return the first address
+ * where any of these pages appear.  Otherwise, return -EFAULT.
  */
 static inline unsigned long
 vma_pgoff_address(pgoff_t pgoff, unsigned long nr_pages,
@@ -829,18 +834,6 @@ vma_pgoff_address(pgoff_t pgoff, unsigned long nr_pages,
 	return address;
 }
 
-/*
- * Return the start of user virtual address of a page within a vma.
- * Returns -EFAULT if all of the page is outside the range of vma.
- * If page is a compound head, the entire compound page is considered.
- */
-static inline unsigned long
-vma_address(struct page *page, struct vm_area_struct *vma)
-{
-	VM_BUG_ON_PAGE(PageKsm(page), page);	/* KSM page->index unusable */
-	return vma_pgoff_address(page_to_pgoff(page), compound_nr(page), vma);
-}
-
 /*
  * Then at what user virtual address will none of the range be found in vma?
  * Assumes that vma_address() already returned a good starting address.

mm/rmap.c

@@ -775,6 +775,8 @@ static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 {
 	struct folio *folio = page_folio(page);
+	pgoff_t pgoff;
+
 	if (folio_test_anon(folio)) {
 		struct anon_vma *page__anon_vma = folio_anon_vma(folio);
 		/*
@@ -790,7 +792,9 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 		return -EFAULT;
 	}
 
-	return vma_address(page, vma);
+	/* The !page__anon_vma above handles KSM folios */
+	pgoff = folio->index + folio_page_idx(folio, page);
+	return vma_pgoff_address(pgoff, 1, vma);
 }
 
 /*
@@ -2588,7 +2592,8 @@ static void rmap_walk_anon(struct folio *folio,
 	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
 			pgoff_start, pgoff_end) {
 		struct vm_area_struct *vma = avc->vma;
-		unsigned long address = vma_address(&folio->page, vma);
+		unsigned long address = vma_pgoff_address(pgoff_start,
+				folio_nr_pages(folio), vma);
 
 		VM_BUG_ON_VMA(address == -EFAULT, vma);
 		cond_resched();
@@ -2649,7 +2654,8 @@ static void rmap_walk_file(struct folio *folio,
 lookup:
 	vma_interval_tree_foreach(vma, &mapping->i_mmap,
 			pgoff_start, pgoff_end) {
-		unsigned long address = vma_address(&folio->page, vma);
+		unsigned long address = vma_pgoff_address(pgoff_start,
+			       folio_nr_pages(folio), vma);
 
 		VM_BUG_ON_VMA(address == -EFAULT, vma);
 		cond_resched();