Let's clarify a bit by extending the comments.

Signed-off-by: David Hildenbrand (Red Hat) <david@kernel.org>
---
 mm/balloon_compaction.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index 03c5dbabb1565..85eea88cea083 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -222,7 +222,11 @@ static void balloon_page_putback(struct page *page)
 	struct balloon_dev_info *b_dev_info = balloon_page_device(page);
 	unsigned long flags;
 
-	/* Isolated balloon pages cannot get deflated. */
+	/*
+	 * When we isolated the page, the page was still inflated in a balloon
+	 * device. As isolated balloon pages cannot get deflated, we still have
+	 * a balloon device here.
+	 */
 	if (WARN_ON_ONCE(!b_dev_info))
 		return;
 
@@ -241,7 +245,11 @@ static int balloon_page_migrate(struct page *newpage, struct page *page,
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
 	VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
 
-	/* Isolated balloon pages cannot get deflated. */
+	/*
+	 * When we isolated the page, the page was still inflated in a balloon
+	 * device. As isolated balloon pages cannot get deflated, we still have
+	 * a balloon device here.
+	 */
 	if (WARN_ON_ONCE(!balloon))
 		return -EAGAIN;
 
-- 
2.52.0