nilfs2: convert nilfs_lookup_dirty_data_buffers() to use filemap_get_folios_tag()

Convert function to use folios throughout. This is in preparation for
the removal of find_get_pages_range_tag(). This change removes 4 calls
to compound_head().

Link: https://lkml.kernel.org/r/20230104211448.4804-19-vishal.moola@gmail.comSigned-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/nilfs2/segment.c

@@ -680,7 +680,7 @@ static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode,
 					      loff_t start, loff_t end)
 {
 	struct address_space *mapping = inode->i_mapping;
-	struct pagevec pvec;
+	struct folio_batch fbatch;
 	pgoff_t index = 0, last = ULONG_MAX;
 	size_t ndirties = 0;
 	int i;
@@ -694,23 +694,26 @@ static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode,
 		index = start >> PAGE_SHIFT;
 		last = end >> PAGE_SHIFT;
 	}
-	pagevec_init(&pvec);
+	folio_batch_init(&fbatch);
  repeat:
 	if (unlikely(index > last) ||
-	    !pagevec_lookup_range_tag(&pvec, mapping, &index, last,
-				PAGECACHE_TAG_DIRTY))
+	      !filemap_get_folios_tag(mapping, &index, last,
+		      PAGECACHE_TAG_DIRTY, &fbatch))
 		return ndirties;
 
-	for (i = 0; i < pagevec_count(&pvec); i++) {
+	for (i = 0; i < folio_batch_count(&fbatch); i++) {
 		struct buffer_head *bh, *head;
-		struct page *page = pvec.pages[i];
+		struct folio *folio = fbatch.folios[i];
 
-		lock_page(page);
-		if (!page_has_buffers(page))
-			create_empty_buffers(page, i_blocksize(inode), 0);
-		unlock_page(page);
+		folio_lock(folio);
+		head = folio_buffers(folio);
+		if (!head) {
+			create_empty_buffers(&folio->page, i_blocksize(inode), 0);
+			head = folio_buffers(folio);
+		}
+		folio_unlock(folio);
 
-		bh = head = page_buffers(page);
+		bh = head;
 		do {
 			if (!buffer_dirty(bh) || buffer_async_write(bh))
 				continue;
@@ -718,13 +721,13 @@ static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode,
 			list_add_tail(&bh->b_assoc_buffers, listp);
 			ndirties++;
 			if (unlikely(ndirties >= nlimit)) {
-				pagevec_release(&pvec);
+				folio_batch_release(&fbatch);
 				cond_resched();
 				return ndirties;
 			}
 		} while (bh = bh->b_this_page, bh != head);
 	}
-	pagevec_release(&pvec);
+	folio_batch_release(&fbatch);
 	cond_resched();
 	goto repeat;
 }