Steal the write_pidfile function from xenstored_core, and use it to ensure

that blktapctrl only starts once.

Signed-off-by: Ewan Mellor <ewan@xensource.com>

diff --git a/tools/blktap/drivers/blktapctrl.c b/tools/blktap/drivers/blktapctrl.c
index cb2258af42f5ed0305af43535815e3a94d974ce7..b16ab516b5523ce0628316d29940688966589c02 100644 (file)
--- a/tools/blktap/drivers/blktapctrl.c
+++ b/tools/blktap/drivers/blktapctrl.c
@@ -57,6 +57,8 @@
 #include "blktapctrl.h"
 #include "tapdisk.h"
 
+#define PIDFILE "/var/run/blktapctrl.pid"
+
 #define NUM_POLL_FDS 2
 #define MSG_SIZE 4096
 #define MAX_TIMEOUT 10
@@ -622,6 +624,29 @@ static void print_drivers(void)
                DPRINTF("Found driver: [%s]\n",dtypes[i]->name);
 } 
 
+static void write_pidfile(long pid)
+{
+       char buf[100];
+       int len;
+       int fd;
+
+       fd = open(PIDFILE, O_RDWR | O_CREAT, 0600);
+       if (fd == -1) {
+               DPRINTF("Opening pid file failed (%d)\n", errno);
+               exit(1);
+       }
+
+       /* We exit silently if daemon already running. */
+       if (lockf(fd, F_TLOCK, 0) == -1)
+               exit(0);
+
+       len = sprintf(buf, "%ld\n", pid);
+       if (write(fd, buf, len) != len) {
+               DPRINTF("Writing pid file failed (%d)\n", errno);
+               exit(1);
+       }
+}
+
 int main(int argc, char *argv[])
 {
        char *devname;
@@ -681,6 +706,7 @@ int main(int argc, char *argv[])
        ioctl(ctlfd, BLKTAP_IOCTL_SETMODE, BLKTAP_MODE_INTERPOSE );
 
        process = getpid();
+       write_pidfile(process);
        ret = ioctl(ctlfd, BLKTAP_IOCTL_SENDPID, process );
 
        /*Static pollhooks*/
@@ -716,3 +742,13 @@ int main(int argc, char *argv[])
        closelog();
        return -1;
 }
+
+/*
+ * Local variables:
+ *  c-file-style: "linux"
+ *  indent-tabs-mode: t
+ *  c-indent-level: 8
+ *  c-basic-offset: 8
+ *  tab-width: 8
+ * End:
+ */