mm: remove last argument of reuse_swap_page()

None of the callers care about the total_map_swapcount() any more.

Link: https://lkml.kernel.org/r/20211220205943.456187-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/swap.h

@@ -514,7 +514,7 @@ extern int __swp_swapcount(swp_entry_t entry);
 extern int swp_swapcount(swp_entry_t entry);
 extern struct swap_info_struct *page_swap_info(struct page *);
 extern struct swap_info_struct *swp_swap_info(swp_entry_t entry);
-extern bool reuse_swap_page(struct page *, int *);
+extern bool reuse_swap_page(struct page *);
 extern int try_to_free_swap(struct page *);
 struct backing_dev_info;
 extern int init_swap_address_space(unsigned int type, unsigned long nr_pages);
@@ -680,8 +680,8 @@ static inline int swp_swapcount(swp_entry_t entry)
 	return 0;
 }
 
-#define reuse_swap_page(page, total_map_swapcount) \
-	(page_trans_huge_mapcount(page, total_map_swapcount) == 1)
+#define reuse_swap_page(page) \
+	(page_trans_huge_mapcount(page, NULL) == 1)
 
 static inline int try_to_free_swap(struct page *page)
 {

mm/huge_memory.c

@@ -1322,7 +1322,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
 	 * We can only reuse the page if nobody else maps the huge page or it's
 	 * part.
 	 */
-	if (reuse_swap_page(page, NULL)) {
+	if (reuse_swap_page(page)) {
 		pmd_t entry;
 		entry = pmd_mkyoung(orig_pmd);
 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);

mm/khugepaged.c

@@ -681,7 +681,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 			goto out;
 		}
 		if (!pte_write(pteval) && PageSwapCache(page) &&
-				!reuse_swap_page(page, NULL)) {
+				!reuse_swap_page(page)) {
 			/*
 			 * Page is in the swap cache and cannot be re-used.
 			 * It cannot be collapsed into a THP.

mm/memory.c

@@ -3627,7 +3627,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
 	dec_mm_counter_fast(vma->vm_mm, MM_SWAPENTS);
 	pte = mk_pte(page, vma->vm_page_prot);
-	if ((vmf->flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) {
+	if ((vmf->flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
 		pte = maybe_mkwrite(pte_mkdirty(pte), vma);
 		vmf->flags &= ~FAULT_FLAG_WRITE;
 		ret |= VM_FAULT_WRITE;

mm/swapfile.c

@@ -1668,12 +1668,8 @@ static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
  * to it.  And as a side-effect, free up its swap: because the old content
  * on disk will never be read, and seeking back there to write new content
  * later would only waste time away from clustering.
- *
- * NOTE: total_map_swapcount should not be relied upon by the caller if
- * reuse_swap_page() returns false, but it may be always overwritten
- * (see the other implementation for CONFIG_SWAP=n).
  */
-bool reuse_swap_page(struct page *page, int *total_map_swapcount)
+bool reuse_swap_page(struct page *page)
 {
 	int count, total_mapcount, total_swapcount;
 
@@ -1682,8 +1678,6 @@ bool reuse_swap_page(struct page *page, int *total_map_swapcount)
 		return false;
 	count = page_trans_huge_map_swapcount(page, &total_mapcount,
 					      &total_swapcount);
-	if (total_map_swapcount)
-		*total_map_swapcount = total_mapcount + total_swapcount;
 	if (count == 1 && PageSwapCache(page) &&
 	    (likely(!PageTransCompound(page)) ||
 	     /* The remaining swap count will be freed soon */