On 08/29/2017 12:05 AM, 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.
>
> Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
> ---
> Makefile.inc | 2 +-
> multipath/main.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 74 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile.inc b/Makefile.inc
> index 29c290a2..d012b3d7 100644
> --- a/Makefile.inc
> +++ b/Makefile.inc
> @@ -90,7 +90,7 @@ OPTFLAGS = -O2 -g -pipe -Wall -Wextra -Wformat=2 -Werror=implicit-int \
> -Wp,-D_FORTIFY_SOURCE=2 $(STACKPROT) \
> --param=ssp-buffer-size=4
>
> -CFLAGS = $(OPTFLAGS) -DLIB_STRING=\"${LIB}\" -DRUN_DIR=\"${RUN}\"
> +CFLAGS = $(OPTFLAGS) -D BIN_DIR=\"$(bindir)\" -DLIB_STRING=\"${LIB}\" -DRUN_DIR=\"${RUN}\"
> BIN_CFLAGS = -fPIE -DPIE
> LIB_CFLAGS = -fPIC
> SHARED_FLAGS = -shared
> diff --git a/multipath/main.c b/multipath/main.c
> index dede017e..b54aa9bb 100644
> --- a/multipath/main.c
> +++ b/multipath/main.c
> @@ -502,6 +502,74 @@ 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 struct config *conf)
> +{
> +#define DELEGATE_MAX_ARGS 5
> + int fd = mpath_connect();
> + char mpd_path[PATH_MAX];
> + char *argv[DELEGATE_MAX_ARGS];
> + char log[4096], *p;
> + char verbosity[2] = { '0', '\0' };
> + int idx = 1, cmd_idx, sz, n, i;
> +
> + if (fd == -1)
> + return 0;
> + close(fd);
> +
> + if (conf->verbosity > 0 && conf->verbosity < 8)
> + verbosity[0] = '0' + conf->verbosity;
> + argv[idx++] = "-v";
> + argv[idx++] = verbosity;
> +
> + cmd_idx = idx;
> + if (cmd == CMD_CREATE && conf->force_reload == FORCE_RELOAD_YES) {
> + argv[idx++] = "reconfigure";
> + } /* Add other translations here */
> +
> + if (idx == cmd_idx)
> + /* No command found, no need to delegate */
> + return 0;
> + else if (idx >= DELEGATE_MAX_ARGS) {
> + condlog(0, "internal error - argv overflow");
> + exit(1);
> + }
> +
> + argv[idx] = NULL;
> + snprintf(mpd_path, sizeof(mpd_path), "%s/%s", BIN_DIR, "multipathd");
> + argv[0] = mpd_path;
> +
> + condlog(1, "delegating command to multipathd");
> +
> + sz = sizeof(log);
> + p = log;
> + i = 0;
> + n = snprintf(p, sz, "command: %s", argv[i++]);
> + while (i < idx && n < sz) {
> + sz -= n;
> + p += n;
> + n = snprintf(p, sz, " %s", argv[i++]);
> + }
> + condlog(2, "%s", log);
> + if (n >= sz)
> + condlog(2, "(command on previous line was truncated)");
> +
> + if (execv(mpd_path, argv) == -1) {
> + condlog(0, "failed to execute multipathd: %s", strerror(errno));
> + exit(1);
> + }
> +
> + /* not reached */
> + return 1;
> +}
> +
> int
> main (int argc, char *argv[])
> {
> @@ -695,10 +763,15 @@ main (int argc, char *argv[])
> } else
> mpath_disconnect(fd);
> }
> +
> if (cmd == CMD_REMOVE_WWID && !dev) {
> condlog(0, "the -w option requires a device");
> goto out;
> }
> +
> + if (delegate_to_multipathd(cmd, conf))
> + exit(0); /* not reached */
> +
> if (cmd == CMD_RESET_WWIDS) {
> struct multipath * mpp;
> int i;
>
Good idea.
We should be adding '-t' to it, too; after all, where's the point in
having multipath presenting you with a different table as the daemon is
using?
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@xxxxxxx +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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