Re: [PATCH 03/13] multipathd: allow map removal in do_sync_mpp()

[Benjamin Marzinski <bmarzins@redhat.com>]

On Sat, Dec 07, 2024 at 12:36:07AM +0100, Martin Wilck wrote:
> We previously didn't allow map removal inside the checker loop. But
> with the late updates to the checkerloop code, it should be safe to orphan
> paths and delete maps even in this situation. We remove such maps everywhere
> else in the code already, whenever refresh_multipath() or setup_multipath()
> is called.

Actually, thinking about this more, what do we get by proactively
deleting the multipath device if something goes wrong in the checker? If
we successfully reload a device, but can't sync it with the kernel,
that's one thing, But that was triggered by a change in the device, and
we know that when we reloaded the device, device-mapper was working. I'm
leery of possibly deleting the map because of a transient device-mapper
issue.  I'm not sure if on a check that we do repeatedly, we should
delete the device on an error.  We haven't in the past, and as far as I
know, it doesn't cause problems.  

Without a benefit to doing this, I'm not sure it makes sense.

-Ben

> 
> Signed-off-by: Martin Wilck <mwilck@suse.com>
> ---
>  multipathd/main.c | 43 ++++++++++++++++++++-----------------------
>  1 file changed, 20 insertions(+), 23 deletions(-)
> 
> diff --git a/multipathd/main.c b/multipathd/main.c
> index 4a28fbb..131dab6 100644
> --- a/multipathd/main.c
> +++ b/multipathd/main.c
> @@ -2446,34 +2446,30 @@ get_new_state(struct path *pp)
>  	return newstate;
>  }
>  
> -static void
> -do_sync_mpp(struct vectors * vecs, struct multipath *mpp)
> +/* Returns true if the mpp was deleted */
> +static int
> +do_sync_mpp(struct vectors *vecs, struct multipath *mpp)
>  {
> -	int i, ret;
> -	struct path *pp;
> +	int ret;
> +
> +	ret = refresh_multipath(vecs, mpp);
> +	if (ret)
> +		return ret;
>  
> -	ret = update_multipath_strings(mpp, vecs->pathvec);
> -	if (ret != DMP_OK) {
> -		condlog(1, "%s: %s", mpp->alias, ret == DMP_NOT_FOUND ?
> -			"device not found" :
> -			"couldn't synchronize with kernel state");
> -		vector_foreach_slot (mpp->paths, pp, i)
> -			pp->dmstate = PSTATE_UNDEF;
> -		return;
> -	}
>  	set_no_path_retry(mpp);
> +	return 0;
>  }
>  
> -static void
> +static int
>  sync_mpp(struct vectors * vecs, struct multipath *mpp, unsigned int ticks)
>  {
>  	if (mpp->sync_tick)
>  		mpp->sync_tick -= (mpp->sync_tick > ticks) ? ticks :
>  				  mpp->sync_tick;
>  	if (mpp->sync_tick)
> -		return;
> +		return 0;
>  
> -	do_sync_mpp(vecs, mpp);
> +	return do_sync_mpp(vecs, mpp);
>  }
>  
>  static int
> @@ -2513,12 +2509,10 @@ update_path_state (struct vectors * vecs, struct path * pp)
>  		return handle_path_wwid_change(pp, vecs)? CHECK_PATH_REMOVED :
>  							  CHECK_PATH_SKIPPED;
>  	}
> -	if (pp->mpp->synced_count == 0) {
> -		do_sync_mpp(vecs, pp->mpp);
> +	if (pp->mpp->synced_count == 0 && do_sync_mpp(vecs, pp->mpp))
>  		/* if update_multipath_strings orphaned the path, quit early */
> -		if (!pp->mpp)
> -			return CHECK_PATH_SKIPPED;
> -	}
> +		return CHECK_PATH_SKIPPED;
> +
>  	if ((newstate != PATH_UP && newstate != PATH_GHOST &&
>  	     newstate != PATH_PENDING) && (pp->state == PATH_DELAYED)) {
>  		/* If path state become failed again cancel path delay state */
> @@ -3018,8 +3012,11 @@ checkerloop (void *ap)
>  				mpp->synced_count = 0;
>  			if (checker_state == CHECKER_STARTING) {
>  				vector_foreach_slot(vecs->mpvec, mpp, i) {
> -					sync_mpp(vecs, mpp, ticks);
> -					mpp->prio_update = PRIO_UPDATE_NONE;
> +					if (sync_mpp(vecs, mpp, ticks))
> +						/* map deleted */
> +						i--;
> +					else
> +						mpp->prio_update = PRIO_UPDATE_NONE;
>  				}
>  				vector_foreach_slot(vecs->pathvec, pp, i)
>  					pp->is_checked = CHECK_PATH_UNCHECKED;
> -- 
> 2.47.0