[dm-devel] [PATCH 10/15] libmultipath: change how the checker async is set

[Benjamin Marzinski]

On Sat, Jan 18, 2020 at 12:43:49PM -0500, John Stoffel wrote:
> >>>>> "Benjamin" == Benjamin Marzinski <bmarzins at redhat.com> writes:
> 
> Benjamin> The way that the checkers async mode worked in multipathd didn't make
> Benjamin> much sense. When multipathd starts up, all checker classes are in the
> Benjamin> sync mode, and any pathinfo() calls on devices would run the checker in
> Benjamin> sync mode. However, the First time a checker class was used in
> Benjamin> checkerloop, it would set that checker class to async (assuming
> Benjamin> force_sync wasn't set).  After that, no matter when a checker from that
> Benjamin> class was called, it would always run in async mode.  Multipathd doesn't
> Benjamin> need to run checkers in sync mode at all, so don't.
> 
> Sorry, I had a hard time parsing this description, especially the last
> sentence.  Do you mean that checkers should default to async then,
> instead of sync mode?  And from looking at the code, don't you mean
> that you force sync mode?  I guess the question is whether checker
> classes should default sync, or async.  And if they move to async,
> should they stay there?
>     

Sorry. I mean that right now multipathd runs the checkers from pathinfo(),
wait_for_pending_paths() and check_path(). When multipathd starts, all
checkers are in sync mode. The first time a checker is run from
check_path(), it is switched to async mode, and stays there for the rest
of the time multipathd is runing.

There is no need for multipathd to run checkers in sync mode at all, so
we shouldn't be doing so for these first checks.

-Ben

> 
> 
> Benjamin> Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
> Benjamin> ---
> Benjamin>  libmpathpersist/mpath_persist.c |  2 +-
> Benjamin>  libmultipath/discovery.c        | 10 ++++------
> Benjamin>  multipath/main.c                |  1 +
> Benjamin>  3 files changed, 6 insertions(+), 7 deletions(-)
> 
> Benjamin> diff --git a/libmpathpersist/mpath_persist.c b/libmpathpersist/mpath_persist.c
> Benjamin> index 603cfc3b..b2238f00 100644
> Benjamin> --- a/libmpathpersist/mpath_persist.c
> Benjamin> +++ b/libmpathpersist/mpath_persist.c
> Benjamin> @@ -47,7 +47,7 @@ mpath_lib_init (void)
> Benjamin>  		condlog(0, "Failed to initialize multipath config.");
> Benjamin>  		return NULL;
> Benjamin>  	}
> Benjamin> -
> Benjamin> +	conf->force_sync = 1;
> Benjamin>  	set_max_fds(conf->max_fds);
>  
> Benjamin>  	return conf;
> Benjamin> diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
> Benjamin> index d2773c3a..1ab093f4 100644
> Benjamin> --- a/libmultipath/discovery.c
> Benjamin> +++ b/libmultipath/discovery.c
> Benjamin> @@ -1643,12 +1643,10 @@ get_state (struct path * pp, struct config *conf, int daemon, int oldstate)
> Benjamin>  	if (pp->mpp && !c->mpcontext)
> Benjamin>  		checker_mp_init(c, &pp->mpp->mpcontext);
> Benjamin>  	checker_clear_message(c);
> Benjamin> -	if (daemon) {
> Benjamin> -		if (conf->force_sync == 0)
> Benjamin> -			checker_set_async(c);
> Benjamin> -		else
> Benjamin> -			checker_set_sync(c);
> Benjamin> -	}
> Benjamin> +	if (conf->force_sync == 0)
> Benjamin> +		checker_set_async(c);
> Benjamin> +	else
> Benjamin> +		checker_set_sync(c);
> Benjamin>  	if (!conf->checker_timeout &&
> Benjamin>  	    sysfs_get_timeout(pp, &(c->timeout)) <= 0)
> c-> timeout = DEF_TIMEOUT;
> Benjamin> diff --git a/multipath/main.c b/multipath/main.c
> Benjamin> index 4f4d8e89..aebabd9b 100644
> Benjamin> --- a/multipath/main.c
> Benjamin> +++ b/multipath/main.c
> Benjamin> @@ -905,6 +905,7 @@ main (int argc, char *argv[])
> Benjamin>  		exit(RTVL_FAIL);
> Benjamin>  	multipath_conf = conf;
> conf-> retrigger_tries = 0;
> Benjamin> +	conf->force_sync = 1;
> Benjamin>  	while ((arg = getopt(argc, argv, ":adcChl::FfM:v:p:b:BrR:itTquUwW")) != EOF ) {
> Benjamin>  		switch(arg) {
> Benjamin>  		case 1: printf("optarg : %s\n",optarg);
> Benjamin> -- 
> Benjamin> 2.17.2
> 
> Benjamin> --
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> Benjamin> dm-devel at redhat.com
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