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

[Benjamin Marzinski <bmarzins@redhat.com>]

On Mon, Nov 15, 2021 at 04:23:54PM +0000, Martin Wilck wrote:
> 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.

Sure.

-Ben

> 
> > 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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