Blktapctrl compatibility layer

I originally had just changed the NEWINTF ioctl to send over 48-bits
of information, which works on 64-bit but not on 32-bit (since the arg
is an unsigned long).  Additionally, the previous changes would break
an older userland against a new kernel.  For that reason, introduce a
new ioctl (NEWINTF_EXT) that fixes both of these problems.  This is
the dom0 userland side.

Signed-off-by: Chris Lalancette <clalance@redhat.com>

2 files changed, 25 insertions, 7 deletions

diff --git a/tools/blktap/drivers/blktapctrl.c b/tools/blktap/drivers/blktapctrl.c
index 88e30bbca9..337fc6b71f 100644
--- a/tools/blktap/drivers/blktapctrl.c
+++ b/tools/blktap/drivers/blktapctrl.c
@@ -123,12 +123,25 @@ static void make_blktap_dev(char *devname, int major, int minor)
 static int get_new_dev(int *major, int *minor, blkif_t *blkif)
 {
 	domid_translate_t tr;
+	domid_translate_ext_t tr_ext;
 	int ret;
 	char *devname;
 	
-	tr.domid = blkif->domid;
-        tr.busid = blkif->be_id;
-	ret = ioctl(ctlfd, BLKTAP_IOCTL_NEWINTF, tr );
+	if (blkif->be_id >= (1<<28)) {
+		/* new-style backend-id, so use the extended structure */
+		tr_ext.domid = blkif->domid;
+		tr_ext.busid = blkif->be_id;
+		ret = ioctl(ctlfd, BLKTAP_IOCTL_NEWINTF_EXT, &tr_ext);
+		DPRINTF("Sent domid %d and be_id %d\n", tr_ext.domid,
+			tr_ext.busid);
+	}
+	else {
+		/* old-style backend-id; use the old structure */
+		tr.domid = blkif->domid;
+		tr.busid = (unsigned short)blkif->be_id;
+		ret = ioctl(ctlfd, BLKTAP_IOCTL_NEWINTF, tr);
+		DPRINTF("Sent domid %d and be_id %d\n", tr.domid, tr.busid);
+	}
 	
 	if ( (ret <= 0)||(ret > MAX_TAP_DEV) ) {
 		DPRINTF("Incorrect Dev ID [%d]\n",ret);
@@ -145,9 +158,8 @@ static int get_new_dev(int *major, int *minor, blkif_t *blkif)
 	if (asprintf(&devname,"%s/%s%d",BLKTAP_DEV_DIR, BLKTAP_DEV_NAME, *minor) == -1)
 		return -1;
 	make_blktap_dev(devname,*major,*minor);	
-	DPRINTF("Received device id %d and major %d, "
-		"sent domid %d and be_id %d\n",
-		*minor, *major, tr.domid, tr.busid);
+	DPRINTF("Received device id %d and major %d\n",
+		*minor, *major);
 	return 0;
 }
 
diff --git a/tools/blktap/lib/blktaplib.h b/tools/blktap/lib/blktaplib.h
index 1bba363933..58a6fd897a 100644
--- a/tools/blktap/lib/blktaplib.h
+++ b/tools/blktap/lib/blktaplib.h
@@ -57,6 +57,7 @@
 #define BLKTAP_IOCTL_MAJOR	     7
 #define BLKTAP_QUERY_ALLOC_REQS      8
 #define BLKTAP_IOCTL_FREEINTF	     9
+#define BLKTAP_IOCTL_NEWINTF_EXT     50
 #define BLKTAP_IOCTL_PRINT_IDXS      100   
 
 /* blktap switching modes: (Set with BLKTAP_IOCTL_SETMODE)             */
@@ -161,9 +162,14 @@ typedef struct tapdev_info {
 
 typedef struct domid_translate {
 	unsigned short domid;
-	uint32_t busid;
+	unsigned short busid;
 } domid_translate_t ;
 
+typedef struct domid_translate_ext {
+	unsigned short domid;
+	uint32_t busid;
+} domid_translate_ext_t ;
+
 typedef struct image {
 	unsigned long long size;
 	unsigned long secsize;