ocfs2: Convert ocfs2_read_folio() to use a folio

Use the folio API throughout.  There are a few places where we convert
back to a page to call into the rest of the filesystem, so folio usage
needs to be pushed down to those functions later.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

fs/ocfs2/aops.c

@@ -277,16 +277,14 @@ static int ocfs2_readpage_inline(struct inode *inode, struct page *page)
 
 static int ocfs2_read_folio(struct file *file, struct folio *folio)
 {
-	struct page *page = &folio->page;
-	struct inode *inode = page->mapping->host;
+	struct inode *inode = folio->mapping->host;
 	struct ocfs2_inode_info *oi = OCFS2_I(inode);
-	loff_t start = (loff_t)page->index << PAGE_SHIFT;
+	loff_t start = folio_pos(folio);
 	int ret, unlock = 1;
 
-	trace_ocfs2_readpage((unsigned long long)oi->ip_blkno,
-			     (page ? page->index : 0));
+	trace_ocfs2_readpage((unsigned long long)oi->ip_blkno, folio->index);
 
-	ret = ocfs2_inode_lock_with_page(inode, NULL, 0, page);
+	ret = ocfs2_inode_lock_with_page(inode, NULL, 0, &folio->page);
 	if (ret != 0) {
 		if (ret == AOP_TRUNCATED_PAGE)
 			unlock = 0;
@@ -296,11 +294,11 @@ static int ocfs2_read_folio(struct file *file, struct folio *folio)
 
 	if (down_read_trylock(&oi->ip_alloc_sem) == 0) {
 		/*
-		 * Unlock the page and cycle ip_alloc_sem so that we don't
+		 * Unlock the folio and cycle ip_alloc_sem so that we don't
 		 * busyloop waiting for ip_alloc_sem to unlock
 		 */
 		ret = AOP_TRUNCATED_PAGE;
-		unlock_page(page);
+		folio_unlock(folio);
 		unlock = 0;
 		down_read(&oi->ip_alloc_sem);
 		up_read(&oi->ip_alloc_sem);
@@ -313,21 +311,21 @@ static int ocfs2_read_folio(struct file *file, struct folio *folio)
 	 * block_read_full_folio->get_block freaks out if it is asked to read
 	 * beyond the end of a file, so we check here.  Callers
 	 * (generic_file_read, vm_ops->fault) are clever enough to check i_size
-	 * and notice that the page they just read isn't needed.
+	 * and notice that the folio they just read isn't needed.
 	 *
 	 * XXX sys_readahead() seems to get that wrong?
 	 */
 	if (start >= i_size_read(inode)) {
-		zero_user(page, 0, PAGE_SIZE);
-		SetPageUptodate(page);
+		folio_zero_segment(folio, 0, folio_size(folio));
+		folio_mark_uptodate(folio);
 		ret = 0;
 		goto out_alloc;
 	}
 
 	if (oi->ip_dyn_features & OCFS2_INLINE_DATA_FL)
-		ret = ocfs2_readpage_inline(inode, page);
+		ret = ocfs2_readpage_inline(inode, &folio->page);
 	else
-		ret = block_read_full_folio(page_folio(page), ocfs2_get_block);
+		ret = block_read_full_folio(folio, ocfs2_get_block);
 	unlock = 0;
 
 out_alloc:
@@ -336,7 +334,7 @@ static int ocfs2_read_folio(struct file *file, struct folio *folio)
 	ocfs2_inode_unlock(inode, 0);
 out:
 	if (unlock)
-		unlock_page(page);
+		folio_unlock(folio);
 	return ret;
 }