xen/blktap-error-handling.patch

Index: xen-3.3.1-testing/tools/blktap/drivers/blktapctrl.c
===================================================================
--- xen-3.3.1-testing.orig/tools/blktap/drivers/blktapctrl.c
+++ xen-3.3.1-testing/tools/blktap/drivers/blktapctrl.c
@@ -662,9 +662,6 @@ static int blktapctrl_new_blkif(blkif_t
 
 	DPRINTF("Received a poll for a new vbd\n");
 	if ( ((blk=blkif->info) != NULL) && (blk->params != NULL) ) {
-		if (blktap_interface_create(ctlfd, &major, &minor, blkif) < 0)
-			return -1;
-
 		if (test_path(blk->params, &ptr, &type, &exist, &use_ioemu) != 0) {
                         DPRINTF("Error in blktap device string(%s).\n",
                                 blk->params);
@@ -693,10 +690,6 @@ static int blktapctrl_new_blkif(blkif_t
 			blkif->fds[WRITE] = exist->fds[WRITE];
 		}
 
-		add_disktype(blkif, type);
-		blkif->major = major;
-		blkif->minor = minor;
-
 		image = (image_t *)malloc(sizeof(image_t));
 		blkif->prv = (void *)image;
 		blkif->ops = &tapdisk_ops;
@@ -720,11 +713,18 @@ static int blktapctrl_new_blkif(blkif_t
 			goto fail;
 		}
 
+		if (blktap_interface_create(ctlfd, &major, &minor, blkif) < 0)
+			return -1;
+
+		blkif->major = major;
+		blkif->minor = minor;
+
+		add_disktype(blkif, type);
+
 	} else return -1;
 
 	return 0;
 fail:
-	ioctl(ctlfd, BLKTAP_IOCTL_FREEINTF, minor);
 	return -EINVAL;
 }
 
Index: xen-3.3.1-testing/tools/blktap/lib/xenbus.c
===================================================================
--- xen-3.3.1-testing.orig/tools/blktap/lib/xenbus.c
+++ xen-3.3.1-testing/tools/blktap/lib/xenbus.c
@@ -48,6 +48,7 @@
 #include <poll.h>
 #include <time.h>
 #include <sys/time.h>
+#include <unistd.h>
 #include "blktaplib.h"
 #include "list.h"
 #include "xs_api.h"
@@ -149,6 +150,37 @@ static int backend_remove(struct xs_hand
 	return 0;
 }
 
+static int check_image(struct backend_info *be, const char** errmsg)
+{
+	const char *path;
+	int mode;
+	blkif_t *blkif = be->blkif;
+	blkif_info_t *info = blkif->info;
+
+	/* Strip off the image type */
+	path = strchr(info->params, ':');
+	if (path == NULL)
+		path = info->params;
+	else
+		path++;
+
+	/* Check if the image exists and access is permitted */
+	mode = R_OK;
+	if (!be->readonly)
+		mode |= W_OK;
+	if (access(path, mode)) {
+		if (errno == ENOENT)
+			*errmsg = "File not found.";
+		else
+			*errmsg = "Insufficient file permissions.";
+		return -1;
+	}
+
+	/* TODO Check that the image is not attached to a different VM */
+
+	return 0;
+}
+
 static void ueblktap_setup(struct xs_handle *h, char *bepath)
 {
 	struct backend_info *be;
@@ -156,6 +188,7 @@ static void ueblktap_setup(struct xs_han
 	int len, er, deverr;
 	long int pdev = 0, handle;
 	blkif_info_t *blk;
+	const char* errmsg = NULL;
 	
 	be = be_lookup_be(bepath);
 	if (be == NULL)
@@ -211,6 +244,9 @@ static void ueblktap_setup(struct xs_han
 			be->pdev = pdev;
 		}
 
+		if (check_image(be, &errmsg))
+			goto fail;
+
 		er = blkif_init(be->blkif, handle, be->pdev, be->readonly);
 		if (er != 0) {
 			DPRINTF("Unable to open device %s\n",blk->params);
@@ -246,12 +282,21 @@ static void ueblktap_setup(struct xs_han
 	}
 
 	be->blkif->state = CONNECTED;
+	xs_printf(h, be->backpath, "hotplug-status", "connected");
+
 	DPRINTF("[SETUP] Complete\n\n");
 	goto close;
 	
 fail:
-	if ( (be != NULL) && (be->blkif != NULL) ) 
+	if (be) {
+		if (errmsg == NULL)
+			errmsg = "Setting up the backend failed. See the log "
+				"files in /var/log/xen/ for details.";
+		xs_printf(h, be->backpath, "hotplug-error", errmsg);
+		xs_printf(h, be->backpath, "hotplug-status", "error");
+
 		backend_remove(h, be);
+	}
 close:
 	if (path)
 		free(path);
@@ -286,7 +331,8 @@ static void ueblktap_probe(struct xs_han
 	len = strsep_len(bepath, '/', 7);
 	if (len < 0) 
 		goto free_be;
-	bepath[len] = '\0';
+	if (bepath[len] != '\0')
+		goto free_be;
 	
 	be = malloc(sizeof(*be));
 	if (!be) {
Index: xen-3.3.1-testing/tools/examples/xen-backend.rules
===================================================================
--- xen-3.3.1-testing.orig/tools/examples/xen-backend.rules
+++ xen-3.3.1-testing/tools/examples/xen-backend.rules
@@ -1,4 +1,3 @@
-SUBSYSTEM=="xen-backend", KERNEL=="tap*", RUN+="/etc/xen/scripts/blktap $env{ACTION}"
 SUBSYSTEM=="xen-backend", KERNEL=="vbd*", RUN+="/etc/xen/scripts/block $env{ACTION}"
 SUBSYSTEM=="xen-backend", KERNEL=="vtpm*", RUN+="/etc/xen/scripts/vtpm $env{ACTION}"
 SUBSYSTEM=="xen-backend", KERNEL=="vif*", ACTION=="online", RUN+="$env{script} online"