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 <mwilck@xxxxxxxx>
> ---
> 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
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
