btrfs: support subpage in endio_readpage_update_page_status()

To handle subpage status update, add the following:

- Use btrfs_page_*() subpage-aware helpers to update page status
  Now we can handle both cases well.

- No page unlock for subpage metadata
  Since subpage metadata doesn't utilize page locking at all, skip it.
  For subpage data locking, it's handled in later commits.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -2840,15 +2840,24 @@ static void endio_readpage_release_extent(struct processed_extent *processed,
 	processed->uptodate = uptodate;
 }
 
-static void endio_readpage_update_page_status(struct page *page, bool uptodate)
+static void endio_readpage_update_page_status(struct page *page, bool uptodate,
+					      u64 start, u32 len)
 {
+	struct btrfs_fs_info *fs_info = btrfs_sb(page->mapping->host->i_sb);
+
+	ASSERT(page_offset(page) <= start &&
+		start + len <= page_offset(page) + PAGE_SIZE);
+
 	if (uptodate) {
-		SetPageUptodate(page);
+		btrfs_page_set_uptodate(fs_info, page, start, len);
 	} else {
-		ClearPageUptodate(page);
-		SetPageError(page);
+		btrfs_page_clear_uptodate(fs_info, page, start, len);
+		btrfs_page_set_error(fs_info, page, start, len);
 	}
-	unlock_page(page);
+
+	if (fs_info->sectorsize == PAGE_SIZE)
+		unlock_page(page);
+	/* Subpage locking will be handled in later patches */
 }
 
 /*
@@ -2985,7 +2994,7 @@ static void end_bio_extent_readpage(struct bio *bio)
 		bio_offset += len;
 
 		/* Update page status and unlock */
-		endio_readpage_update_page_status(page, uptodate);
+		endio_readpage_update_page_status(page, uptodate, start, len);
 		endio_readpage_release_extent(&processed, BTRFS_I(inode),
 					      start, end, uptodate);
 	}