On Thu, Sep 14, 2017 at 09:49:26PM +0200, Martin Wilck wrote: > Some multipath commands are dangerous to run while multipathd is running. > For example, "multipath -r" may apply a modified configuration to the kernel, > while multipathd is still using the old configuration, leading to > inconsistent state between multipathd and the kernel. > > It is safer to use equivalent multipathd client commands instead. > For now, do this only for "multipath -r", but other invocations > may be added in the future. Perhaps some day, all "multipath" > commands will be mapped to multipathd actions. > > Note that with delegation, "multipath -r" will not produce any > terminal output, so this may affect users who capture "multipath -r" > output for parsing it. It would be very hard to produce compatible output > to the normal multipath command for different verbosity levels. I > considered running "show topology" after "reconfigure", but the output > would have slightly different format and would only match -v2, anyway. > > I plan to convert more multipath commands, but that needs some more > thought. Some additional multipathd client commands need to be > implemented first. > > Changes wrt v2: > - use libmpathcmd rather than exec'ing multipathd (Ben Marzinski) > - pass more parameters from main program, preparing for other commands >
ACK -Ben > Signed-off-by: Martin Wilck <[email protected]> > --- > multipath/main.c | 62 > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 62 insertions(+) > > diff --git a/multipath/main.c b/multipath/main.c > index dede017e9202..48a75b6855d9 100644 > --- a/multipath/main.c > +++ b/multipath/main.c > @@ -502,6 +502,64 @@ get_dev_type(char *dev) { > return DEV_NONE; > } > > +/* > + * Some multipath commands are dangerous to run while multipathd is running. > + * For example, "multipath -r" may apply a modified configuration to the > kernel, > + * while multipathd is still using the old configuration, leading to > + * inconsistent state. > + * > + * It is safer to use equivalent multipathd client commands instead. > + */ > +int delegate_to_multipathd(enum mpath_cmds cmd, const char *dev, > + enum devtypes dev_type, const struct config *conf) > +{ > + int fd; > + char command[1024], *p, *reply; > + int n, r = 0; > + > + fd = mpath_connect(); > + if (fd == -1) > + return 0; > + > + p = command; > + *p = '\0'; > + n = sizeof(command); > + > + if (cmd == CMD_CREATE && conf->force_reload == FORCE_RELOAD_YES) { > + p += snprintf(p, n, "reconfigure"); > + } > + /* Add other translations here */ > + > + if (strlen(command) == 0) > + /* No command found, no need to delegate */ > + return 0; > + else if (p >= command + sizeof(command)) { > + condlog(0, "internal error - command buffer overflow"); > + r = -1; > + goto out; > + } > + > + condlog(3, "delegating command to multipathd"); > + r = mpath_process_cmd(fd, command, &reply, conf->uxsock_timeout); > + > + if (r == -1) { > + condlog(1, "error in multipath command %s: %s", > + command, strerror(errno)); > + goto out; > + } > + > + if (reply != NULL && *reply != '\0' && strcmp(reply, "ok\n")) > + printf("%s", reply); > + r = 1; > + > +out: > + FREE(reply); > + close(fd); > + if (r < 0) > + exit(1); > + return r; > +} > + > int > main (int argc, char *argv[]) > { > @@ -699,6 +757,10 @@ main (int argc, char *argv[]) > condlog(0, "the -w option requires a device"); > goto out; > } > + > + if (delegate_to_multipathd(cmd, dev, dev_type, conf)) > + exit(0); > + > if (cmd == CMD_RESET_WWIDS) { > struct multipath * mpp; > int i; > -- > 2.14.0 -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
