diff options
| -rw-r--r-- | mdmon.8 | 98 | ||||
| -rw-r--r-- | mdmon.c | 94 |
2 files changed, 56 insertions, 136 deletions
@@ -5,7 +5,7 @@ mdmon \- monitor MD external metadata arrays .SH SYNOPSIS -.BI mdmon " CONTAINER [NEWROOT | PID]" +.BI mdmon " [--all] [--takeover] CONTAINER" .SH OVERVIEW The 2.6.27 kernel brings the ability to support external metadata arrays. @@ -128,66 +128,35 @@ device>/<member index>" if the array is to remain readonly. CONTAINER The .B container -device to monitor. It can be a full path like /dev/md/container, a simple md -device name like md127, or -.I \-\-all - which tells -.I mdmon -to scan for containers and launch an -.I mdmon -instance for each one found. +device to monitor. It can be a full path like /dev/md/container, or a +simple md device name like md127. .TP -[NEWROOT] -In order to support an external metadata raid array as the rootfs -.I mdmon -needs to be started in the initramfs environment. Once the initramfs -environment mounts the final rootfs -.I mdmon -needs to be restarted in the new namespace. When NEWROOT is specified -.I mdmon -will terminate any -.I mdmon -instances that are running in the current namespace, -.IR chroot (2) -to NEWROOT, and continue monitoring the container. - -Alternately the new -.I mdmon -can be started after the new root has been installed with -.I pivotroot -by passing -.B / -as the NEWROOT. For -.I mdmon -to be able to find and kill the old -.I mdmon -there must be some part of the filesystem that persists from before -the -.I pivotroot -to afterwards. This can be -.B /var/run/mdadm -or some other directory. The default other directory is -.B /lib/init/rw/mdadm -but this can easily be changed when -.I mdmon -is compiled. -If -.I mdmon -cannot store the pid file in -.B /var/run/mdadm -it will store it in the other directory until -.B /var/run/mdadm -becomes available, or until it is killed. +.B \-\-takeover +This instructs +.I mdmon +to replace any active +.I mdmon +which is currently monitoring the array. This is primarily used late +in the boot process to replace any +.I mdmon +which was started from an +.B initramfs +before the root filesystem was mounted. This avoids holding a +reference on that +.B initramfs +indefinitely and ensures that the +.I pid +and +.I sock +files used to communicate with +.I mdmon +are in a standard place. .TP -[PID] -If the second argument to -.I mdmon -does not start with a slash it is assumed to be the pid of a previous -instance of -.I mdmon -to kill. This is used internally by -.I mdmon -to pass the pid across a chroot/exec and should not be used otherwise. +.B \-\-all +This tells mdmon to find any active containers and start monitoring +each of them if appropriate. This is normally used with +.B \-\-takeover +late in the boot sequence. .PP Note that @@ -200,17 +169,16 @@ RAID arrays. The only times it is run other that by is when the boot scripts need to restart it after mounting the new root filesystem. -.SH EXMAPLES +.SH EXAMPLES -.B " mdmon --all /" +.B " mdmon \-\-all \-\-takeover" .br Any .I mdmon which is currently running is killed and a new instance is started. -This should be run early in the boot sequence after a -.I pivotroot -to the final root filesystem, but before that filesystem is remounted -read-write. +This should be run late in the boot sequence and particularly after +.B /var +is mounted and writable. .SH SEE ALSO .IR mdadm (8), .IR md (4). @@ -254,28 +254,31 @@ void usage(void) exit(2); } -static int mdmon(char *devname, int devnum, int must_fork, char *switchroot); +static int mdmon(char *devname, int devnum, int must_fork, int takeover); int main(int argc, char *argv[]) { char *container_name = NULL; - char *switchroot = NULL; int devnum; char *devname; int status = 0; - - switch (argc) { - case 3: - switchroot = argv[2]; - case 2: - container_name = argv[1]; - break; - default: - usage(); + int arg; + int all = 0; + int takeover = 0; + + for (arg = 1; arg < argc; arg++) { + if (strcmp(argv[arg], "--all") == 0 || + strcmp(argv[arg], "/proc/mdstat") == 0) + all = 1; + else if (strcmp(argv[arg], "--takeover") == 0) + takeover = 1; + else if (container_name == NULL) + container_name = argv[arg]; + else + usage(); } - if (strcmp(container_name, "/proc/mdstat") == 0 || - strcmp(container_name, "--all") == 0) { + if (all) { struct mdstat_ent *mdstat, *e; /* launch an mdmon instance for each container found */ @@ -292,7 +295,7 @@ int main(int argc, char *argv[]) sprintf(container_name, "%s", devname); } status |= mdmon(devname, e->devnum, 1, - switchroot); + takeover); } } free_mdstat(mdstat); @@ -320,10 +323,10 @@ int main(int argc, char *argv[]) container_name); exit(1); } - return mdmon(devname, devnum, do_fork(), switchroot); + return mdmon(devname, devnum, do_fork(), takeover); } -static int mdmon(char *devname, int devnum, int must_fork, char *switchroot) +static int mdmon(char *devname, int devnum, int must_fork, int takeover) { int mdfd; struct mdinfo *mdi, *di; @@ -336,50 +339,7 @@ static int mdmon(char *devname, int devnum, int must_fork, char *switchroot) pid_t victim = -1; int victim_sock = -1; - dprintf("starting mdmon for %s in %s\n", - devname, switchroot ? : "/"); - - /* switchroot is either a path name starting with '/', or a - * pid of the original mdmon (we have already done the chroot). - * In the latter case, stdin is a socket connected to the original - * mdmon. - */ - - /* try to spawn mdmon instances from the target file system */ - if (switchroot && switchroot[0] == '/' && - strcmp(switchroot, "/") != 0) { - pid_t pid; - char buf[20]; - - switch (fork()) { - case 0: - victim = mdmon_pid(devnum); - victim_sock = connect_monitor(devname); - if (chroot(switchroot) != 0) { - fprintf(stderr, "mdmon: failed to chroot to '%s': %s\n", - switchroot, strerror(errno)); - exit(4); - } - ignore = chdir("/"); - sprintf(buf, "%d", victim); - if (victim_sock) { - close(0); - dup(victim_sock); - close(victim_sock); - } - execl("/sbin/mdmon", "mdmon", devname, buf, NULL); - exit(1); - case -1: - return 1; - default: - pid = wait(&status); - if (pid > -1 && WIFEXITED(status) && - WEXITSTATUS(status) == 0) - return 0; - else - return 1; - } - } + dprintf("starting mdmon for %s\n", devname); mdfd = open_dev(devnum); if (mdfd < 0) { @@ -486,17 +446,9 @@ static int mdmon(char *devname, int devnum, int must_fork, char *switchroot) act.sa_handler = SIG_IGN; sigaction(SIGPIPE, &act, NULL); - if (switchroot) { - /* we assume we assume that /sys /proc /dev are available in - * the new root - */ - if (switchroot[0] == '/') { - victim = mdmon_pid(container->devnum); - victim_sock = connect_monitor(container->devname); - } else { - victim = atoi(switchroot); - victim_sock = 0; - } + if (takeover) { + victim = mdmon_pid(container->devnum); + victim_sock = connect_monitor(container->devname); } ignore = chdir("/"); |