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mdmon: improve switchroot handling. 

The change to get mdmon to re-exec itself from the switchroot
filesystem broken switchroot in various ways.  This fixes it.

If the switchroot path is not '/', mdmon will find the pid and
socket for the monitor, chroot to the new root, and exec mdmon
passing the pid in argv[2] and the socket in stdin.

If the switchroot path is actually a number, mdmon will not chroot,
but will kill that pid before taking over the array.

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2010-01-29 12:14:17 +11:00
parent af7ca33487
commit e98ef22509
1 changed files with 43 additions and 22 deletions
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65
mdmon.c
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@ -368,15 +368,35 @@ static int mdmon(char *devname, int devnum, int must_fork, char *switchroot)
dprintf("starting mdmon for %s in %s\n",
devname, switchroot ? : "/");
/* try to spawn mdmon instances from the target file system */
if (switchroot && strcmp(switchroot, "/") != 0) {
char path[1024];
pid_t pid;
/* 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];
sprintf(path, "%s/sbin/mdmon", switchroot);
switch (fork()) {
case 0:
execl(path, "mdmon", devname, NULL);
victim = devname2mdmon(devname);
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;
@ -499,12 +519,12 @@ static int mdmon(char *devname, int devnum, int must_fork, char *switchroot)
/* we assume we assume that /sys /proc /dev are available in
* the new root
*/
victim = devname2mdmon(container->devname);
victim_sock = connect_monitor(container->devname);
if (chroot(switchroot) != 0) {
fprintf(stderr, "mdmon: failed to chroot to '%s': %s\n",
switchroot, strerror(errno));
exit(4);
if (switchroot[0] == '/') {
victim = devname2mdmon(container->devname);
victim_sock = connect_monitor(container->devname);
} else {
victim = atoi(switchroot);
victim_sock = 0;
}
}
@ -532,16 +552,6 @@ static int mdmon(char *devname, int devnum, int must_fork, char *switchroot)
getppid());
close(pfd[1]);
setsid();
close(0);
open("/dev/null", O_RDWR);
close(1);
ignore = dup(0);
#ifndef DEBUG
close(2);
ignore = dup(0);
#endif
mlockall(MCL_CURRENT | MCL_FUTURE);
if (clone_monitor(container) < 0) {
@ -554,6 +564,17 @@ static int mdmon(char *devname, int devnum, int must_fork, char *switchroot)
try_kill_monitor(victim, container->devname, victim_sock);
close(victim_sock);
}
setsid();
close(0);
open("/dev/null", O_RDWR);
close(1);
ignore = dup(0);
#ifndef DEBUG
close(2);
ignore = dup(0);
#endif
do_manager(container);
exit(0);