nilfs2: convert nilfs_page_mkwrite() to use a folio

Using the new folio APIs saves seven hidden calls to compound_head().

Link: https://lkml.kernel.org/r/20231114084436.2755-12-konishi.ryusuke@gmail.comSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/nilfs2/file.c

@@ -45,34 +45,36 @@ int nilfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 static vm_fault_t nilfs_page_mkwrite(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
-	struct page *page = vmf->page;
+	struct folio *folio = page_folio(vmf->page);
 	struct inode *inode = file_inode(vma->vm_file);
 	struct nilfs_transaction_info ti;
+	struct buffer_head *bh, *head;
 	int ret = 0;
 
 	if (unlikely(nilfs_near_disk_full(inode->i_sb->s_fs_info)))
 		return VM_FAULT_SIGBUS; /* -ENOSPC */
 
 	sb_start_pagefault(inode->i_sb);
-	lock_page(page);
-	if (page->mapping != inode->i_mapping ||
-	    page_offset(page) >= i_size_read(inode) || !PageUptodate(page)) {
-		unlock_page(page);
+	folio_lock(folio);
+	if (folio->mapping != inode->i_mapping ||
+	    folio_pos(folio) >= i_size_read(inode) ||
+	    !folio_test_uptodate(folio)) {
+		folio_unlock(folio);
 		ret = -EFAULT;	/* make the VM retry the fault */
 		goto out;
 	}
 
 	/*
-	 * check to see if the page is mapped already (no holes)
+	 * check to see if the folio is mapped already (no holes)
 	 */
-	if (PageMappedToDisk(page))
+	if (folio_test_mappedtodisk(folio))
 		goto mapped;
 
-	if (page_has_buffers(page)) {
-		struct buffer_head *bh, *head;
+	head = folio_buffers(folio);
+	if (head) {
 		int fully_mapped = 1;
 
-		bh = head = page_buffers(page);
+		bh = head;
 		do {
 			if (!buffer_mapped(bh)) {
 				fully_mapped = 0;
@@ -81,11 +83,11 @@ static vm_fault_t nilfs_page_mkwrite(struct vm_fault *vmf)
 		} while (bh = bh->b_this_page, bh != head);
 
 		if (fully_mapped) {
-			SetPageMappedToDisk(page);
+			folio_set_mappedtodisk(folio);
 			goto mapped;
 		}
 	}
-	unlock_page(page);
+	folio_unlock(folio);
 
 	/*
 	 * fill hole blocks
@@ -105,7 +107,7 @@ static vm_fault_t nilfs_page_mkwrite(struct vm_fault *vmf)
 	nilfs_transaction_commit(inode->i_sb);
 
  mapped:
-	wait_for_stable_page(page);
+	folio_wait_stable(folio);
  out:
 	sb_end_pagefault(inode->i_sb);
 	return vmf_fs_error(ret);