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* Re: [PATCH 09/12] multipathd: merge uevents before proccessing
From: tang.junhui @ 2017-01-04  3:29 UTC (permalink / raw)
  To: Benjamin Marzinski
  Cc: bart.vanassche, dm-devel, mwilck, tang.wenjun3, zhang.kai16
In-Reply-To: <20170104003049.GF2732@octiron.msp.redhat.com>

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Hello Ben,

Yes, a *_safe list traversal method can meet the needs,
I will modify it and simplify the codes.

Thanks,
Tang Junhui

发件人:         "Benjamin Marzinski" <bmarzins@redhat.com>
收件人:         tang.junhui@zte.com.cn, 
抄送:   tang.wenjun3@zte.com.cn, zhang.kai16@zte.com.cn, 
dm-devel@redhat.com, bart.vanassche@sandisk.com, mwilck@suse.com
日期:   2017/01/04 08:39
主题:   Re: [dm-devel] [PATCH 09/12] multipathd: merge uevents before 
proccessing
发件人: dm-devel-bounces@redhat.com

On Tue, Dec 27, 2016 at 04:03:26PM +0800, tang.junhui@zte.com.cn wrote:
> From: tang.junhui <tang.junhui@zte.com.cn>
> 
> These uevents are going to be merged:
> 1) uevents come from paths and
> 2) uevents type is same and
> 3) uevents type is addition or deletion and
> 4) uevents wwid is same.

This is just a nit, and I might be missing something subtle here, but it
seems like instead of adding list_for_some_entry_reverse, and then
breaking the abstraction to manually get previous entries, you could
have just added list_for_some_entry_reverse_safe in your earlier patch,
and hid the work of traversing a list while removing elements behind the
well understood abstraction of a *_safe list traversal method.

-Ben

> 
> Change-Id: I05ee057391c092aa0c5f989b7a4f9cb550bb4d98
> Signed-off-by: tang.junhui <tang.junhui@zte.com.cn>
> ---
>  libmultipath/uevent.c | 125 
+++++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 114 insertions(+), 11 deletions(-)
> 
> diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
> index b0b05e9..114068c 100644
> --- a/libmultipath/uevent.c
> +++ b/libmultipath/uevent.c
> @@ -85,6 +85,20 @@ struct uevent * alloc_uevent (void)
>                return uev;
>  }
> 
> +void
> +uevq_cleanup(struct list_head *tmpq)
> +{
> +              struct uevent *uev, *tmp;
> +
> +              list_for_each_entry_safe(uev, tmp, tmpq, node) {
> +                              list_del_init(&uev->node);
> +
> +                              if (uev->udev)
> + udev_device_unref(uev->udev);
> +                              FREE(uev);
> +              }
> +}
> +
>  bool
>  uevent_can_discard(char *devpath, char *kernel)
>  {
> @@ -125,6 +139,103 @@ uevent_can_discard(char *devpath, char *kernel)
>                return false;
>  }
> 
> +bool
> +merge_need_stop(struct uevent *earlier, struct uevent *later)
> +{
> +              /*
> +               * dm uevent do not try to merge with left uevents
> +               */
> +              if (!strncmp(later->kernel, "dm-", 3))
> +                              return true;
> +
> +              /*
> +               * we can not make a jugement without wwid,
> +               * so it is sensible to stop merging
> +               */
> +              if (!earlier->wwid || !later->wwid)
> +                              return true;
> +              /*
> +               * uevents merging stoped
> +               * when we meet an opposite action uevent from the same 
LUN to AVOID
> +               * "add path1 |remove path1 |add path2 |remove path2 |add 
path3"
> +               * to merge as "remove path1, path2" and "add path1, 
path2, path3"
> +               * OR
> +               * "remove path1 |add path1 |remove path2 |add path2 
|remove path3"
> +               * to merge as "add path1, path2" and "remove path1, 
path2, path3"
> +               * SO
> +               * when we meet a non-change uevent from the same LUN
> +               * with the same wwid and different action
> +               * it would be better to stop merging.
> +               */
> +              if (!strcmp(earlier->wwid, later->wwid) &&
> +                  strcmp(earlier->action, later->action) &&
> +                  strcmp(earlier->action, "change") &&
> +                  strcmp(later->action, "change"))
> +                              return true;
> +
> +              return false;
> +}
> +
> +bool
> +uevent_can_merge(struct uevent *earlier, struct uevent *later)
> +{
> +              /* merge paths uevents
> +               * whose wwids exsit and are same
> +               * and actions are same,
> +               * and actions are addition or deletion
> +               */
> +              if (earlier->wwid && later->wwid &&
> +                  !strcmp(earlier->wwid, later->wwid) &&
> +                  !strcmp(earlier->action, later->action) &&
> +                  strncmp(earlier->action, "change", 6) &&
> +                  strncmp(earlier->kernel, "dm-", 3)) {
> +                              return true;
> +              }
> +
> +              return false;
> +}
> +
> +void
> +uevent_merge(struct uevent *later, struct list_head *tmpq)
> +{
> +              struct uevent *earlier, *temp;
> +              /*
> +               * compare the uevent with earlier uevents
> +               */
> +              list_for_some_entry_reverse(earlier, &later->node, tmpq, 
node) {
> +next_earlier_node:
> +                              if (merge_need_stop(earlier, later))
> +                                              break;
> +                              /*
> +                               * try to merge earlier uevents to the 
later uevent
> +                               */
> +                              if (uevent_can_merge(earlier, later)) {
> +                                              condlog(3, "merged 
uevent: %s-%s-%s with uevent: %s-%s-%s",
> + earlier->action, earlier->kernel, earlier->wwid,
> + later->action, later->kernel, later->wwid);
> +                                              temp = earlier;
> +
> +                                              earlier = 
list_entry(earlier->node.prev, typeof(struct uevent), node);
> +                                              list_move(&temp->node, 
&later->merge_node);
> +
> +                                              if (earlier == 
list_entry(tmpq, typeof(struct uevent), node))
> +                                                              break;
> +                                              else
> +                                                              goto 
next_earlier_node;
> +                              }
> +              }
> +}
> +
> +void
> +merge_uevq(struct list_head *tmpq)
> +{
> +              struct uevent *later;
> +
> +              list_for_each_entry_reverse(later, tmpq, node) {
> +                              uevent_merge(later, tmpq);
> +              }
> +}
> +
>  void
>  service_uevq(struct list_head *tmpq)
>  {
> @@ -136,6 +247,8 @@ service_uevq(struct list_head *tmpq)
>                                if (my_uev_trigger && my_uev_trigger(uev, 
my_trigger_data))
>                                                condlog(0, "uevent 
trigger error");
> 
> +                              uevq_cleanup(&uev->merge_node);
> +
>                                if (uev->udev)
> udev_device_unref(uev->udev);
>                                FREE(uev);
> @@ -150,17 +263,6 @@ static void uevent_cleanup(void *arg)
>                udev_unref(udev);
>  }
> 
> -void
> -uevq_cleanup(struct list_head *tmpq)
> -{
> -              struct uevent *uev, *tmp;
> -
> -              list_for_each_entry_safe(uev, tmp, tmpq, node) {
> -                              list_del_init(&uev->node);
> -                              FREE(uev);
> -              }
> -}
> -
>  /*
>   * Service the uevent queue.
>   */
> @@ -189,6 +291,7 @@ int uevent_dispatch(int (*uev_trigger)(struct uevent 
*, void * trigger_data),
>                                pthread_mutex_unlock(uevq_lockp);
>                                if (!my_uev_trigger)
>                                                break;
> +                              merge_uevq(&uevq_tmp);
>                                service_uevq(&uevq_tmp);
>                }
>                condlog(3, "Terminating uev service queue");
> -- 
> 2.8.1.windows.1
> 

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