xen/snapshot-ioemu-restore.patch

Index: xen-4.0.0-testing/tools/blktap/drivers/blktapctrl.c
===================================================================
--- xen-4.0.0-testing.orig/tools/blktap/drivers/blktapctrl.c
+++ xen-4.0.0-testing/tools/blktap/drivers/blktapctrl.c
@@ -348,6 +348,7 @@ static int write_msg(int fd, int msgtype
 		msg_dev = (msg_newdev_t *)(buf + sizeof(msg_hdr_t));
 		msg_dev->devnum = blkif->minor;
 		msg_dev->domid = blkif->domid;
+		msg_dev->be_id = blkif->be_id;
 
 		break;
 
Index: xen-4.0.0-testing/tools/blktap/lib/blktaplib.h
===================================================================
--- xen-4.0.0-testing.orig/tools/blktap/lib/blktaplib.h
+++ xen-4.0.0-testing/tools/blktap/lib/blktaplib.h
@@ -189,6 +189,7 @@ typedef struct msg_hdr {
 typedef struct msg_newdev {
 	uint8_t     devnum;
 	uint16_t    domid;
+	uint32_t    be_id;
 } msg_newdev_t;
 
 typedef struct msg_pid {
Index: xen-4.0.0-testing/tools/ioemu-remote/hw/xen_blktap.c
===================================================================
--- xen-4.0.0-testing.orig/tools/ioemu-remote/hw/xen_blktap.c
+++ xen-4.0.0-testing/tools/ioemu-remote/hw/xen_blktap.c
@@ -67,6 +67,8 @@ int write_fd;
 static pid_t process;
 fd_list_entry_t *fd_start = NULL;
 
+extern char* get_snapshot_name(int devid);
+
 static void handle_blktap_iomsg(void* private);
 
 struct aiocb_info {
@@ -500,6 +502,10 @@ static void handle_blktap_ctrlmsg(void*
 
 	char buf[MSG_SIZE];
 
+#ifndef QEMU_TOOL
+	char *snapshot;
+#endif
+
 	length = read(read_fd, buf, MSG_SIZE);
 
 	if (length > 0 && length >= sizeof(msg_hdr_t)) 
@@ -555,7 +561,39 @@ static void handle_blktap_ctrlmsg(void*
 			if (s != NULL) {
 				ret = ((map_new_dev(s, msg_dev->devnum) 
 					== msg_dev->devnum ? 0: -1));
-			}	
+			}
+
+#ifndef QEMU_TOOL
+			fprintf(stderr, "Reading snapshot name for %d\n", msg_dev->be_id);
+			snapshot = get_snapshot_name(msg_dev->be_id);
+			if (snapshot) {
+				fprintf(stderr, "Using snapshot %s\n", snapshot);
+				ret = bdrv_snapshot_goto(s->bs, snapshot);
+				switch (ret) {
+				case 0:
+					/* Success */
+					break;
+				case -ENOTSUP:
+					if (s->flags & TD_RDONLY) {
+						fprintf(stderr, "Snapshots not supported for "
+							"image format of a read-only image\n");
+					} else {
+						fprintf(stderr, "Snapshots not supported "
+							"for this image format");
+						ret = -1;
+					}
+					break;
+				case -ENOENT:
+					fprintf(stderr, "No such snapshot");
+					ret = -1;
+					break;
+				default:
+					fprintf(stderr, "Could not load snapshot");
+					ret = -1;
+					break;
+				}
+			}
+#endif
 
 			memset(buf, 0x00, MSG_SIZE); 
 			msglen = sizeof(msg_hdr_t);
Index: xen-4.0.0-testing/tools/ioemu-remote/xenstore.c
===================================================================
--- xen-4.0.0-testing.orig/tools/ioemu-remote/xenstore.c
+++ xen-4.0.0-testing/tools/ioemu-remote/xenstore.c
@@ -103,6 +103,8 @@ int xenstore_watch_new_callback(const ch
 }
 
 
+char* get_snapshot_name(int devid);
+
 static int pasprintf(char **buf, const char *fmt, ...)
 {
     va_list ap;
@@ -644,8 +646,33 @@ void xenstore_parse_domain_config(int hv
 		}
 	    }
             pstrcpy(bs->filename, sizeof(bs->filename), params);
-            if (bdrv_open2(bs, params, BDRV_O_CACHE_WB /* snapshot and write-back */, format) < 0)
+            if (bdrv_open2(bs, params, BDRV_O_CACHE_WB /* snapshot and write-back */, format) < 0) {
                 fprintf(stderr, "qemu: could not open vbd '%s' or hard disk image '%s' (drv '%s' format '%s')\n", buf, params, drv ? drv : "?", format ? format->format_name : "0");
+            } else {
+                char* snapshot = get_snapshot_name(atoi(e_danger[i]));
+                if (snapshot) {
+                    fprintf(stderr, "Using snapshot %s\n", snapshot);
+                    ret = bdrv_snapshot_goto(bs, snapshot);
+                    switch (ret) {
+                    case 0:
+                        /* Success */
+                        break;
+                    case -ENOTSUP:
+                        /* Don't abort here (could be read-only ISO) */
+                        fprintf(stderr, "Snapshots are not supported for "
+                            "this image file format\n");
+                        break;
+                    case -ENOENT:
+                        fprintf(stderr, "No such snapshot, skipping this "
+                            "image file\n");
+                        continue;
+                    default:
+                        fprintf(stderr, "Could not load snapshot, skipping"
+                            " this image file\n");
+                        continue;
+                    }
+                }
+            }
         }
 
 #endif
@@ -779,6 +806,23 @@ int xenstore_parse_disable_pf_config ()
     return disable_pf;
 }
 
+
+char* get_snapshot_name(int devid)
+{
+    char* path = NULL;
+    char* name = NULL;
+    unsigned int len;
+
+    if (pasprintf(&path,
+            "/local/domain/0/backend/tap/%u/%u/snapshot", domid, devid) == -1)
+        return NULL;
+    name = xs_read(xsh, XBT_NULL, path, &len);
+
+    free(path);
+    return name;
+}
+
+
 int xenstore_fd(void)
 {
     if (xsh)