3 files changed, 16 insertions, 2 deletions

diff --git a/sys/dev/ata/ata-disk.c b/sys/dev/ata/ata-disk.c
index 598d6dfa1220..619f1fed4a52 100644
--- a/sys/dev/ata/ata-disk.c
+++ b/sys/dev/ata/ata-disk.c
@@ -301,6 +301,13 @@ adstrategy(struct buf *bp)
     struct ad_softc *adp = bp->b_dev->si_drv1;
     int32_t s;
 
+    /* if it's a null transfer, return immediatly. */
+    if (bp->b_bcount == 0) {
+	bp->b_resid = 0;
+	biodone(bp);
+	return;
+    }
+
     s = splbio();
     bufqdisksort(&adp->queue, bp);
     ad_start(adp);
diff --git a/sys/dev/ata/atapi-cd.c b/sys/dev/ata/atapi-cd.c
index 40eb4b6296c8..50632f7b17a8 100644
--- a/sys/dev/ata/atapi-cd.c
+++ b/sys/dev/ata/atapi-cd.c
@@ -1030,7 +1030,7 @@ acdstrategy(struct buf *bp)
 	return;
     }
 #endif
-
+    /* if it's a null transfer, return immediatly. */
     if (bp->b_bcount == 0) {
 	bp->b_resid = 0;
 	biodone(bp);
diff --git a/sys/dev/ata/atapi-fd.c b/sys/dev/ata/atapi-fd.c
index 6c45f6f9969b..f8e32917d671 100644
--- a/sys/dev/ata/atapi-fd.c
+++ b/sys/dev/ata/atapi-fd.c
@@ -254,6 +254,13 @@ afdstrategy(struct buf *bp)
     struct afd_softc *fdp = bp->b_dev->si_drv1;
     int32_t s;
 
+    /* if it's a null transfer, return immediatly. */
+    if (bp->b_bcount == 0) {
+	bp->b_resid = 0;
+	biodone(bp);
+	return;
+    }
+
     s = splbio();
     bufq_insert_tail(&fdp->buf_queue, bp);
     afd_start(fdp);
@@ -267,7 +274,7 @@ afd_start(struct afd_softc *fdp)
     u_int32_t lba, count;
     int8_t ccb[16];
     int8_t *data_ptr;
-    
+
     if (!bp)
 	return;