diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 39619fd6d6aa..3b671e9bf684 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2000,6 +2000,13 @@ noinline_for_stack bool find_lock_delalloc_range(struct inode *inode,
 	/* step one, find a bunch of delalloc bytes starting at start */
 	delalloc_start = *start;
 	delalloc_end = 0;
+
+	/*
+	 * If @max_bytes is smaller than a block, btrfs_find_delalloc_range() can
+	 * return early without handling any dirty ranges.
+	 */
+	ASSERT(max_bytes >= fs_info->sectorsize);
+
 	found = btrfs_find_delalloc_range(tree, &delalloc_start, &delalloc_end,
 					  max_bytes, &cached_state);
 	if (!found || delalloc_end <= *start) {
@@ -2028,13 +2035,14 @@ noinline_for_stack bool find_lock_delalloc_range(struct inode *inode,
 				  delalloc_start, delalloc_end);
 	ASSERT(!ret || ret == -EAGAIN);
 	if (ret == -EAGAIN) {
-		/* some of the pages are gone, lets avoid looping by
-		 * shortening the size of the delalloc range we're searching
+		/*
+		 * Some of the pages are gone, lets avoid looping by
+		 * shortening the size of the delalloc range we're searching.
 		 */
 		free_extent_state(cached_state);
 		cached_state = NULL;
 		if (!loops) {
-			max_bytes = PAGE_SIZE;
+			max_bytes = fs_info->sectorsize;
 			loops = 1;
 			goto again;
 		} else {