On Tue, 2023-06-06 at 15:13 -0500, Benjamin Marzinski wrote:
> need_switch_pathgroup() only checks if the currently used pathgroup
> is
> not the highest priority pathgroup. If it isn't, all multipathd does
> is
> instruct the kernel to switch to the correct pathgroup. However, the
> kernel treats the pathgroups as if they were ordered by priority.
> When
> the kernel runs out of paths to use in the currently selected
> pathgroup,
> it will start checking the pathgroups in order until it finds one
> with
> usable paths.
>
> need_switch_pathgroup() should also check if the pathgroups are out
> of
> order, and if so, multipathd should reload the map to reorder them
> correctly.
>
> Signed-off-by: Benjamin Marzinski <bmarzins@xxxxxxxxxx>
> ---
> multipathd/main.c | 69 ++++++++++++++++++++++++++++++++++++++-------
> --
> 1 file changed, 57 insertions(+), 12 deletions(-)
>
> diff --git a/multipathd/main.c b/multipathd/main.c
> index f603d143..05c74e9e 100644
> --- a/multipathd/main.c
> +++ b/multipathd/main.c
> @@ -395,11 +395,46 @@ void
> put_multipath_config(__attribute__((unused)) void *arg)
> rcu_read_unlock();
> }
>
> +/*
> + * The path group orderings that this function finds acceptible are
> different
> + * from now select_path_group determines the best pathgroup. The
> idea here is
> + * to only trigger a kernel reload when it is obvious that the
> pathgroups would
> + * be out of order, even if all the paths were usable. Thus
> pathgroups with
> + * PRIO_UNDEF are skipped, and the number of enabled paths doesn't
> matter here.
> + */
> +bool path_groups_in_order(struct multipath *mpp)
> +{
> + int i;
> + struct pathgroup *pgp;
> + bool seen_marginal_pg = false;
> + int last_prio = INT_MAX;
> +
> + if (VECTOR_SIZE(mpp->pg) < 2)
> + return true;
> +
> + vector_foreach_slot(mpp->pg, pgp, i) {
> + /* skip pgs with PRIO_UNDEF, since this is likely
> temporary */
> + if (!pgp->paths || pgp->priority == PRIO_UNDEF)
> + continue;
> + if (pgp->marginal && !seen_marginal_pg) {
> + last_prio = INT_MAX;
> + continue;
> + }
> + if (seen_marginal_pg && !pgp->marginal)
> + return false;
> + if (pgp->priority > last_prio)
> + return false;
> + last_prio = pgp->priority;
> + }
> + return true;
> +}
I still don't get the logic here. What's the point of using
seen_marginal_pg if it is always false? See my previous reply to v1 of
this patch.
Regards
Martin
> +
> static int
> -need_switch_pathgroup (struct multipath * mpp)
> +need_switch_pathgroup (struct multipath * mpp, bool *need_reload)
> {
> int bestpg;
>
> + *need_reload = false;
> if (!mpp)
> return 0;
>
> @@ -411,10 +446,9 @@ need_switch_pathgroup (struct multipath * mpp)
> return 0;
>
> mpp->bestpg = bestpg;
> - if (mpp->bestpg != mpp->nextpg)
> - return 1;
> + *need_reload = !path_groups_in_order(mpp);
>
> - return 0;
> + return (*need_reload || mpp->bestpg != mpp->nextpg);
> }
>
> static void
> @@ -1963,20 +1997,26 @@ ghost_delay_tick(struct vectors *vecs)
> }
>
> static void
> -deferred_failback_tick (vector mpvec)
> +deferred_failback_tick (struct vectors *vecs)
> {
> struct multipath * mpp;
> unsigned int i;
> + bool need_reload;
>
> - vector_foreach_slot (mpvec, mpp, i) {
> + vector_foreach_slot (vecs->mpvec, mpp, i) {
> /*
> * deferred failback getting sooner
> */
> if (mpp->pgfailback > 0 && mpp->failback_tick > 0) {
> mpp->failback_tick--;
>
> - if (!mpp->failback_tick &&
> need_switch_pathgroup(mpp))
> - switch_pathgroup(mpp);
> + if (!mpp->failback_tick &&
> + need_switch_pathgroup(mpp, &need_reload))
> {
> + if (need_reload)
> + reload_and_sync_map(mpp,
> vecs);
> + else
> + switch_pathgroup(mpp);
> + }
> }
> }
> }
> @@ -2219,6 +2259,7 @@ check_path (struct vectors * vecs, struct path
> * pp, unsigned int ticks)
> struct config *conf;
> int marginal_pathgroups, marginal_changed = 0;
> int ret;
> + bool need_reload;
>
> if (((pp->initialized == INIT_OK || pp->initialized ==
> INIT_PARTIAL ||
> pp->initialized == INIT_REQUESTED_UDEV) && !pp->mpp) ||
> @@ -2548,13 +2589,17 @@ check_path (struct vectors * vecs, struct
> path * pp, unsigned int ticks)
> condlog(2, "%s: path priorities changed. reloading",
> pp->mpp->alias);
> reload_and_sync_map(pp->mpp, vecs);
> - } else if (need_switch_pathgroup(pp->mpp)) {
> + } else if (need_switch_pathgroup(pp->mpp, &need_reload)) {
> if (pp->mpp->pgfailback > 0 &&
> (new_path_up || pp->mpp->failback_tick <= 0))
> pp->mpp->failback_tick = pp->mpp->pgfailback
> + 1;
> else if (pp->mpp->pgfailback == -FAILBACK_IMMEDIATE
> ||
> - (chkr_new_path_up &&
> followover_should_failback(pp)))
> - switch_pathgroup(pp->mpp);
> + (chkr_new_path_up &&
> followover_should_failback(pp))) {
> + if (need_reload)
> + reload_and_sync_map(pp->mpp, vecs);
> + else
> + switch_pathgroup(pp->mpp);
> + }
> }
> return 1;
> }
> @@ -2680,7 +2725,7 @@ unlock:
> pthread_cleanup_push(cleanup_lock, &vecs->lock);
> lock(&vecs->lock);
> pthread_testcancel();
> - deferred_failback_tick(vecs->mpvec);
> + deferred_failback_tick(vecs);
> retry_count_tick(vecs->mpvec);
> missing_uev_wait_tick(vecs);
> ghost_delay_tick(vecs);
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://listman.redhat.com/mailman/listinfo/dm-devel
