On 2020/5/15 12:06, Matthew Wilcox wrote:

On Thu, May 07, 2020 at 03:50:56PM +0800, Zhen Lei wrote:

quoted

@@ -266,7 +266,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
 
 static sector_t swap_page_sector(struct page *page)
 {
-	return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9);
+	return npage_to_sectors((sector_t)__page_file_index(page));

If you make npage_to_sectors() a proper function instead of a macro,
you can do the casting inside the function instead of in the callers
(which is prone to bugs).

Oh, yes. __page_file_index(page) maybe called many times in marco, althouth currently
it is not. So that, not all are suitable for page_to_sector(). And for this example,
still need to use "<< PAGE_SECTORS_SHIFT".

Also, this is a great example of why page_to_sector() was a better name
than npage_to_sectors().  This function doesn't return a count of sectors,
it returns a sector number within the swap device.

OK, so I will change to page_to_sector()/sector_to_page().

.