btrfs: use the folio iterator in btrfs_end_super_write()

Iterate over folios instead of bvecs.  Switch the order of unlock and put
to be the usual order; we know this folio can't be put until it's been
waited for, but that's fragile.  Remove the calls to ClearPageUptodate /
SetPageUptodate -- if PAGE_SIZE is larger than BTRFS_SUPER_INFO_SIZE,
we'd be marking the entire folio uptodate without having actually
initialised all the bytes in the page.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -3626,28 +3626,21 @@ ALLOW_ERROR_INJECTION(open_ctree, ERRNO);
 static void btrfs_end_super_write(struct bio *bio)
 {
 	struct btrfs_device *device = bio->bi_private;
-	struct bio_vec *bvec;
-	struct bvec_iter_all iter_all;
-	struct page *page;
-
-	bio_for_each_segment_all(bvec, bio, iter_all) {
-		page = bvec->bv_page;
+	struct folio_iter fi;
 
+	bio_for_each_folio_all(fi, bio) {
 		if (bio->bi_status) {
 			btrfs_warn_rl_in_rcu(device->fs_info,
-				"lost page write due to IO error on %s (%d)",
+				"lost super block write due to IO error on %s (%d)",
 				btrfs_dev_name(device),
 				blk_status_to_errno(bio->bi_status));
-			ClearPageUptodate(page);
-			SetPageError(page);
+			folio_set_error(fi.folio);
 			btrfs_dev_stat_inc_and_print(device,
 						     BTRFS_DEV_STAT_WRITE_ERRS);
-		} else {
-			SetPageUptodate(page);
 		}
 
-		put_page(page);
-		unlock_page(page);
+		folio_unlock(fi.folio);
+		folio_put(fi.folio);
 	}
 
 	bio_put(bio);