Tools: hv: vssdaemon: ignore the EBUSY on multiple freezing the same partition

index 6a213b8..1db9430 100644
@@ -44,21 +44,39 @@ static struct sockaddr_nl addr;
 #endif
 
 
-static int vss_do_freeze(char *dir, unsigned int cmd, char *fs_op)
+/* Don't use syslog() in the function since that can cause write to disk */
+static int vss_do_freeze(char *dir, unsigned int cmd)
 {
 	int ret, fd = open(dir, O_RDONLY);
 
 	if (fd < 0)
 		return 1;
+
 	ret = ioctl(fd, cmd, 0);
-	syslog(LOG_INFO, "VSS: %s of %s: %s\n", fs_op, dir, strerror(errno));
+
+	/*
+	 * If a partition is mounted more than once, only the first
+	 * FREEZE/THAW can succeed and the later ones will get
+	 * EBUSY/EINVAL respectively: there could be 2 cases:
+	 * 1) a user may mount the same partition to differnt directories
+	 *  by mistake or on purpose;
+	 * 2) The subvolume of btrfs appears to have the same partition
+	 * mounted more than once.
+	 */
+	if (ret) {
+		if ((cmd == FIFREEZE && errno == EBUSY) ||
+		    (cmd == FITHAW && errno == EINVAL)) {
+			close(fd);
+			return 0;
+		}
+	}
+
 	close(fd);
 	return !!ret;
 }
 
 static int vss_operate(int operation)
 {
-	char *fs_op;
 	char match[] = "/dev/";
 	FILE *mounts;
 	struct mntent *ent;

@@ -68,11 +86,9 @@ static int vss_operate(int operation)
 	switch (operation) {
 	case VSS_OP_FREEZE:
 		cmd = FIFREEZE;
-		fs_op = "freeze";
 		break;
 	case VSS_OP_THAW:
 		cmd = FITHAW;
-		fs_op = "thaw";
 		break;
 	default:
 		return -1;

@@ -93,15 +109,23 @@ static int vss_operate(int operation)
 			root_seen = 1;
 			continue;
 		}
-		error |= vss_do_freeze(ent->mnt_dir, cmd, fs_op);
+		error |= vss_do_freeze(ent->mnt_dir, cmd);
+		if (error && operation == VSS_OP_FREEZE)
+			goto err;
 	}
 	endmntent(mounts);
 
 	if (root_seen) {
-		error |= vss_do_freeze("/", cmd, fs_op);
+		error |= vss_do_freeze("/", cmd);
+		if (error && operation == VSS_OP_FREEZE)
+			goto err;
 	}
 
 	return error;
+err:
+	endmntent(mounts);
+	vss_operate(VSS_OP_THAW);
+	return error;
 }
 
 static int netlink_send(int fd, struct cn_msg *msg)

@@ -249,8 +273,16 @@ int main(void)
 		case VSS_OP_FREEZE:
 		case VSS_OP_THAW:
 			error = vss_operate(op);
-			if (error)
+			syslog(LOG_INFO, "VSS: op=%s: %s\n",
+				op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
+				error ? "failed" : "succeeded");
+
+			if (error) {
 				error = HV_E_FAIL;
+				syslog(LOG_ERR, "op=%d failed!", op);
+				syslog(LOG_ERR, "report it with these files:");
+				syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
+			}
 			break;
 		default:
 			syslog(LOG_ERR, "Illegal op:%d\n", op);