diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -5269,6 +5269,16 @@
 	}
 }
 
+struct memdesc
+memdesc_buf(struct buf *bp)
+{
+	if (!buf_mapped(bp))
+		return (memdesc_vmpages(bp->b_pages, bp->b_bufsize,
+		    (vm_offset_t)bp->b_offset & PAGE_MASK));
+
+	return (memdesc_vaddr(bp->b_data, bp->b_bufsize));
+}
+
 struct memdesc
 memdesc_bio(struct bio *bio)
 {
diff --git a/sys/sys/memdesc.h b/sys/sys/memdesc.h
--- a/sys/sys/memdesc.h
+++ b/sys/sys/memdesc.h
@@ -30,6 +30,7 @@
 #define	_SYS_MEMDESC_H_
 
 struct bio;
+struct buf;
 struct bus_dma_segment;
 struct uio;
 struct mbuf;
@@ -150,6 +151,7 @@
 	return (mem);
 }
 
+struct memdesc	memdesc_buf(struct buf *bp);
 struct memdesc	memdesc_bio(struct bio *bio);
 struct memdesc	memdesc_ccb(union ccb *ccb);