Re: [dm-devel] [PATCH 3/4] multipathd: pass in the type of reconfigure

[Martin Wilck <martin.wilck@suse.com>]

On Mon, 2021-09-20 at 18:21 -0500, Benjamin Marzinski wrote:
> This code doesn't actually change how multipathd reconfigures. It still
> does a weak reconfigure at the start, and full reconfigures later.

AFAICS it does change this, at least for the cases where reconfigure()
is called from ev_add_map() and missing_uev_wait_tick, where you call
schedule_reconfigure(false). The old code was using a static variable
and thus always doing a hard reconfigure when called more than once.

I'm find with this change (the old behavior was arguably wrong), but
the commit message should be clarified in this respect.

> But
> now schedule_reconfigure() takes the type of reconfigure to do, and
> that
> gets passed down to reconfigure(). If a full reconfigure has already
> been requested but not started, weak reconfigure requests will be
> upgraded. A future patch will enable users to control what kind of
> reconfigures happen.
> 
> Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
> ---
>  libmultipath/configure.c  |  2 +-
>  multipathd/cli_handlers.c |  2 +-
>  multipathd/main.c         | 62 ++++++++++++++++++++-------------------
>  multipathd/main.h         |  2 +-
>  4 files changed, 35 insertions(+), 33 deletions(-)
> 
> diff --git a/libmultipath/configure.c b/libmultipath/configure.c
> index 7edb355b..eb8ec1bd 100644
> --- a/libmultipath/configure.c
> +++ b/libmultipath/configure.c
> @@ -1098,7 +1098,7 @@ out:
>   * FORCE_RELOAD_NONE: existing maps aren't touched at all
>   * FORCE_RELOAD_YES: all maps are rebuilt from scratch and (re)loaded
> in DM
>   * FORCE_RELOAD_WEAK: existing maps are compared to the current conf
> and only
> - * reloaded in DM if there's a difference. This is useful during
> startup.
> + * reloaded in DM if there's a difference. This is normally
> sufficient.
>   */
>  int coalesce_paths (struct vectors *vecs, vector mpvec, char *refwwid,
>                     int force_reload, enum mpath_cmds cmd)
> diff --git a/multipathd/cli_handlers.c b/multipathd/cli_handlers.c
> index f59db3ab..b12a4e7e 100644
> --- a/multipathd/cli_handlers.c
> +++ b/multipathd/cli_handlers.c
> @@ -1012,7 +1012,7 @@ cli_reconfigure(void * v, struct strbuf *reply,
> void * data)
>  {
>         condlog(2, "reconfigure (operator)");
>  
> -       schedule_reconfigure();
> +       schedule_reconfigure(true);
>         return 0;
>  }
>  
> diff --git a/multipathd/main.c b/multipathd/main.c
> index 1ead0904..5c831e8d 100644
> --- a/multipathd/main.c
> +++ b/multipathd/main.c
> @@ -162,13 +162,6 @@ static bool get_delayed_reconfig(void)
>         return val;
>  }
>  
> -static void set_delayed_reconfig(bool val)
> -{
> -       pthread_mutex_lock(&config_lock);
> -       __delayed_reconfig = val;
> -       pthread_mutex_unlock(&config_lock);
> -}
> -
>  /*
>   * global copy of vecs for use in sig handlers
>   */
> @@ -290,7 +283,18 @@ enum daemon_status wait_for_state_change_if(enum
> daemon_status oldstate,
>  }
>  
>  /* Don't access this variable without holding config_lock */
> -static bool reconfigure_pending;
> +static enum force_reload_types reconfigure_pending =
> FORCE_RELOAD_NONE;
> +/* Only set while changing to DAEMON_CONFIGURE, and only access while
> + * reconfiguring in DAEMON_CONFIGURE */
> +static volatile enum force_reload_types reload_type =
> FORCE_RELOAD_NONE;
> +
> +static void enable_delayed_reconfig(enum force_reload_types type)
> +{
> +       pthread_mutex_lock(&config_lock);
> +       reconfigure_pending = type;
> +       __delayed_reconfig = true;
> +       pthread_mutex_unlock(&config_lock);
> +}
>  
>  /* must be called with config_lock held */
>  static void __post_config_state(enum daemon_status state)
> @@ -305,7 +309,8 @@ static void __post_config_state(enum daemon_status
> state)
>                  * In either case, child() will see DAEMON_CONFIGURE
>                  * again and start another reconfigure cycle.
>                  */
> -               if (reconfigure_pending && state == DAEMON_IDLE &&
> +               if (reconfigure_pending != FORCE_RELOAD_NONE &&
> +                   state == DAEMON_IDLE &&
>                     (old_state == DAEMON_CONFIGURE ||
>                      old_state == DAEMON_RUNNING)) {
>                         /*
> @@ -317,7 +322,8 @@ static void __post_config_state(enum daemon_status
> state)
>                         state = DAEMON_CONFIGURE;
>                 }
>                 if (state == DAEMON_CONFIGURE) {
> -                       reconfigure_pending = false;
> +                       reload_type = (reconfigure_pending ==
> FORCE_RELOAD_YES) ? FORCE_RELOAD_YES : FORCE_RELOAD_WEAK;
> +                       reconfigure_pending = FORCE_RELOAD_NONE;
>                         __delayed_reconfig = false;
>                 }
>                 running_state = state;
> @@ -334,20 +340,25 @@ void post_config_state(enum daemon_status state)
>         pthread_cleanup_pop(1);
>  }
>  
> -void schedule_reconfigure(void)
> +void schedule_reconfigure(bool force_reload_yes)
>  {
>         pthread_mutex_lock(&config_lock);
>         pthread_cleanup_push(config_cleanup, NULL);
> +       enum force_reload_types type;
> +
> +       type = (reconfigure_pending == FORCE_RELOAD_YES ||
> force_reload_yes) ?
> +              FORCE_RELOAD_YES : FORCE_RELOAD_WEAK;
>         switch (running_state)
>         {
>         case DAEMON_SHUTDOWN:
>                 break;
>         case DAEMON_IDLE:
> +               reconfigure_pending = type;
>                 __post_config_state(DAEMON_CONFIGURE);
>                 break;
>         case DAEMON_CONFIGURE:
>         case DAEMON_RUNNING:
> -               reconfigure_pending = true;
> +               reconfigure_pending = type;
>                 break;
>         default:
>                 break;
> @@ -812,7 +823,7 @@ ev_add_map (char * dev, const char * alias, struct
> vectors * vecs)
>                         if (get_delayed_reconfig() &&
>                             !need_to_delay_reconfig(vecs)) {
>                                 condlog(2, "reconfigure (delayed)");
> -                               schedule_reconfigure();
> +                               schedule_reconfigure(false);
>                                 return 0;
>                         }
>                 }
> @@ -1830,7 +1841,7 @@ missing_uev_wait_tick(struct vectors *vecs)
>         if (timed_out && get_delayed_reconfig() &&
>             !need_to_delay_reconfig(vecs)) {
>                 condlog(2, "reconfigure (delayed)");
> -               schedule_reconfigure();
> +               schedule_reconfigure(false);
>         }
>  }
>  
> @@ -2588,14 +2599,13 @@ checkerloop (void *ap)
>  }
>  
>  int
> -configure (struct vectors * vecs)
> +configure (struct vectors * vecs, enum force_reload_types type)
>  {
>         struct multipath * mpp;
>         struct path * pp;
>         vector mpvec;
>         int i, ret;
>         struct config *conf;
> -       static int force_reload = FORCE_RELOAD_WEAK;
>  
>         if (!vecs->pathvec && !(vecs->pathvec = vector_alloc())) {
>                 condlog(0, "couldn't allocate path vec in configure");
> @@ -2643,15 +2653,7 @@ configure (struct vectors * vecs)
>         if (should_exit())
>                 goto fail;
>  
> -       /*
> -        * create new set of maps & push changed ones into dm
> -        * In the first call, use FORCE_RELOAD_WEAK to avoid making
> -        * superfluous ACT_RELOAD ioctls. Later calls are done
> -        * with FORCE_RELOAD_YES.
> -        */
> -       ret = coalesce_paths(vecs, mpvec, NULL, force_reload,
> CMD_NONE);
> -       if (force_reload == FORCE_RELOAD_WEAK)
> -               force_reload = FORCE_RELOAD_YES;
> +       ret = coalesce_paths(vecs, mpvec, NULL, type, CMD_NONE);


Can we please rename this variable from "type" to "reload_type" here,
for the sake of readability? Likewise, in reconfigure()?

>         if (ret != CP_OK) {
>                 condlog(0, "configure failed while coalescing paths");
>                 goto fail;
> @@ -2729,7 +2731,7 @@ void rcu_free_config(struct rcu_head *head)
>  }
>  
>  int
> -reconfigure (struct vectors * vecs)
> +reconfigure (struct vectors * vecs, enum force_reload_types type)
>  {
>         struct config * old, *conf;
>  
> @@ -2763,7 +2765,7 @@ reconfigure (struct vectors * vecs)
>         rcu_assign_pointer(multipath_conf, conf);
>         call_rcu(&old->rcu, rcu_free_config);
>  
> -       configure(vecs);
> +       configure(vecs, type);
>  
>  
>         return 0;
> @@ -2815,7 +2817,7 @@ handle_signals(bool nonfatal)
>                 return;
>         if (reconfig_sig) {
>                 condlog(2, "reconfigure (signal)");
> -               schedule_reconfigure();
> +               schedule_reconfigure(true);
>         }
>         if (log_reset_sig) {
>                 condlog(2, "reset log (signal)");
> @@ -3274,9 +3276,9 @@ child (__attribute__((unused)) void *param)
>                         lock(&vecs->lock);
>                         pthread_testcancel();
>                         if (!need_to_delay_reconfig(vecs))
> -                               reconfigure(vecs);
> +                               reconfigure(vecs, reload_type);
>                         else
> -                               set_delayed_reconfig(true);
> +                               enable_delayed_reconfig(reload_type);
>                         lock_cleanup_pop(vecs->lock);
>                         post_config_state(DAEMON_IDLE);
>                 }
> diff --git a/multipathd/main.h b/multipathd/main.h
> index a1697a74..c8a1ce92 100644
> --- a/multipathd/main.h
> +++ b/multipathd/main.h
> @@ -37,7 +37,7 @@ void exit_daemon(void);
>  const char * daemon_status(void);
>  enum daemon_status wait_for_state_change_if(enum daemon_status
> oldstate,
>                                             unsigned long ms);
> -void schedule_reconfigure(void);
> +void schedule_reconfigure(bool reconfig_all);

For consistency, please consider using an "enum force_reload_types" as
argument to schedule_reconfigure() rather than a boolean.

Otherwise, the patch looks good.

Cheers
Martin


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