diff --git a/mm/readahead.c b/mm/readahead.c
index 87609bd117f999155ce9a4318cc07dd50996a5f4..69757a624982310818b566dbac34ee38c5cfa883 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -164,20 +164,10 @@ static void read_pages(struct readahead_control *rac)
 
 	if (aops->readahead) {
 		aops->readahead(rac);
-		/*
-		 * Clean up the remaining folios.  The sizes in ->ra
-		 * may be used to size the next readahead, so make sure
-		 * they accurately reflect what happened.
-		 */
+		/* Clean up the remaining folios. */
 		while ((folio = readahead_folio(rac)) != NULL) {
-			unsigned long nr = folio_nr_pages(folio);
-
 			folio_get(folio);
-			rac->ra->size -= nr;
-			if (rac->ra->async_size >= nr) {
-				rac->ra->async_size -= nr;
-				filemap_remove_folio(folio);
-			}
+			filemap_remove_folio(folio);
 			folio_unlock(folio);
 			folio_put(folio);
 		}
@@ -497,7 +487,8 @@ void page_cache_ra_order(struct readahead_control *ractl,
 		struct file_ra_state *ra, unsigned int new_order)
 {
 	struct address_space *mapping = ractl->mapping;
-	pgoff_t index = readahead_index(ractl);
+	pgoff_t start = readahead_index(ractl);
+	pgoff_t index = start;
 	pgoff_t limit = (i_size_read(mapping->host) - 1) >> PAGE_SHIFT;
 	pgoff_t mark = index + ra->size - ra->async_size;
 	unsigned int nofs;
@@ -556,12 +547,18 @@ void page_cache_ra_order(struct readahead_control *ractl,
 	/*
 	 * If there were already pages in the page cache, then we may have
 	 * left some gaps.  Let the regular readahead code take care of this
-	 * situation.
+	 * situation below.
 	 */
 	if (!err)
 		return;
 fallback:
-	do_page_cache_ra(ractl, ra->size, ra->async_size);
+	/*
+	 * ->readahead() may have updated readahead window size so we have to
+	 * check there's still something to read.
+	 */
+	if (ra->size > index - start)
+		do_page_cache_ra(ractl, ra->size - (index - start),
+				 ra->async_size);
 }
 
 /*
@@ -597,7 +594,7 @@ static void ondemand_readahead(struct readahead_control *ractl,
 	 */
 	expected = round_down(ra->start + ra->size - ra->async_size,
 			1UL << order);
-	if (index == expected || index == (ra->start + ra->size)) {
+	if (folio && index == expected) {
 		ra->start += ra->size;
 		/*
 		 * In the case of MADV_HUGEPAGE, the actual size might exceed