diff --git a/sys/geom/geom_io.c b/sys/geom/geom_io.c
--- a/sys/geom/geom_io.c
+++ b/sys/geom/geom_io.c
@@ -199,12 +199,12 @@
 		/*
 		 *  BIO_ORDERED flag may be used by disk drivers to enforce
 		 *  ordering restrictions, so this flag needs to be cloned.
-		 *  BIO_UNMAPPED and BIO_VLIST should be inherited, to properly
-		 *  indicate which way the buffer is passed.
+		 *  BIO_UNMAPPED, BIO_VLIST, and BIO_SWAP should be inherited,
+		 *  to properly indicate which way the buffer is passed.
 		 *  Other bio flags are not suitable for cloning.
 		 */
 		bp2->bio_flags = bp->bio_flags &
-		    (BIO_ORDERED | BIO_UNMAPPED | BIO_VLIST);
+		    (BIO_ORDERED | BIO_UNMAPPED | BIO_VLIST | BIO_SWAP);
 		bp2->bio_length = bp->bio_length;
 		bp2->bio_offset = bp->bio_offset;
 		bp2->bio_data = bp->bio_data;
@@ -238,7 +238,7 @@
 	struct bio *bp2;
 
 	bp2 = uma_zalloc(biozone, M_WAITOK | M_ZERO);
-	bp2->bio_flags = bp->bio_flags & (BIO_UNMAPPED | BIO_VLIST);
+	bp2->bio_flags = bp->bio_flags & (BIO_UNMAPPED | BIO_VLIST | BIO_SWAP);
 	bp2->bio_parent = bp;
 	bp2->bio_cmd = bp->bio_cmd;
 	bp2->bio_length = bp->bio_length;
diff --git a/sys/sys/bio.h b/sys/sys/bio.h
--- a/sys/sys/bio.h
+++ b/sys/sys/bio.h
@@ -67,8 +67,9 @@
 #define	BIO_UNMAPPED	0x10
 #define	BIO_TRANSIENT_MAPPING	0x20
 #define	BIO_VLIST	0x40
+#define	BIO_SWAP	0x200	/* Swap-related I/O */
 
-#define	PRINT_BIO_FLAGS "\20\7vlist\6transient_mapping\5unmapped" \
+#define	PRINT_BIO_FLAGS "\20\12swap\7vlist\6transient_mapping\5unmapped" \
 	"\4ordered\3onqueue\2done\1error"
 
 #define BIO_SPEEDUP_WRITE	0x4000	/* Resource shortage at upper layers */
diff --git a/sys/vm/swap_pager.c b/sys/vm/swap_pager.c
--- a/sys/vm/swap_pager.c
+++ b/sys/vm/swap_pager.c
@@ -2893,6 +2893,7 @@
 	bio->bio_offset = (bp->b_blkno - sp->sw_first) * PAGE_SIZE;
 	bio->bio_length = bp->b_bcount;
 	bio->bio_done = swapgeom_done;
+	bio->bio_flags |= BIO_SWAP;
 	if (!buf_mapped(bp)) {
 		bio->bio_ma = bp->b_pages;
 		bio->bio_data = unmapped_buf;