Hi Junhui,

It seems I did not receive the patch version Acked by Ben,
Can you rebase and post please ?

Thanks.

On Thu, Feb 16, 2017 at 5:27 PM, Benjamin Marzinski <bmarzins@redhat.com> wrote:
On Thu, Feb 16, 2017 at 02:54:01PM +0800, tang.junhui@zte.com.cn wrote:
> From: "tang.junhui" <tang.junhui@zte.com.cn>

ACK

Thanks for all your work on this.
-Ben

>
> Change-Id: I3f81a55fff389f991f915927000b281d7e263cc5
> Signed-off-by: tang.junhui <tang.junhui@zte.com.cn>
>
> This patch used to improve processing efficiency for addition and deletion
> of multipath devices.
>
> This patch is tested pass by ZTE multipath automatic testing system.
> The modification reduces the system consumption(such as CPU) and shortens
> the processing time obviously in scene of massive multipath devices
> addition or deletion.
>
> The main processing flow of code is:
> 1) add uid_attrs configuration in the defaults section:
>    It is configured udev attribute which providing a unique path identifier
>    for corresponding type of path devices. If this field is configured and
>    matched with type of device, it would override any other methods providing
>    for device unique identifier in config file, and it would activate merging
>    uevents according to the identifier to promote effiecncy in processing
>    uevents. Tt has no default value, so defaultly only uevents filtering
>    works, and uevents merging does not works, if users want to identify path
>    by udev attribute and to activate merging uevents for SCSI and DAS device,
>    they can set it's value as:
>    "sd:ID_SERIAL dasd:ID_UID"
> 2) uevents accumulation in uevents burst scene:
>    wait one seconds for more uevents in uevent_listen() in uevents burst
>    situations
> 3) uevents preparing, filtering and merging:
>    discard unuse uevents and fetch path idendifier from uevents;
>    filter uevents;
>    merge uevents.
> 4) uevents proccessing:
>    proccess the merged uevents in uev->merge_node list without calling
>    domap();
>    proccess the last uevents uev with calling domap().
> ---
>  libmultipath/config.c      |   3 +
>  libmultipath/config.h      |   1 +
>  libmultipath/dict.c        |   3 +
>  libmultipath/discovery.c   |   5 +-
>  libmultipath/discovery.h   |   2 +-
>  libmultipath/list.h        |  41 ++++++
>  libmultipath/propsel.c     |   7 +
>  libmultipath/uevent.c      | 320 +++++++++++++++++++++++++++++++++++++++++++--
>  libmultipath/uevent.h      |   2 +
>  libmultipath/util.c        |  42 ++++++
>  libmultipath/util.h        |   1 +
>  multipath/multipath.conf.5 |  18 +++
>  multipathd/cli_handlers.c  |   4 +-
>  multipathd/main.c          |  93 +++++--------
>  multipathd/main.h          |   4 +-
>  15 files changed, 471 insertions(+), 75 deletions(-)
>
> diff --git a/libmultipath/config.c b/libmultipath/config.c
> index 15ddbd8..765e91d 100644
> --- a/libmultipath/config.c
> +++ b/libmultipath/config.c
> @@ -488,6 +488,9 @@ free_config (struct config * conf)
>       if (conf->uid_attribute)
>               FREE(conf->uid_attribute);
>
> +     if (conf->uid_attrs)
> +             FREE(conf->uid_attrs);
> +
>       if (conf->getuid)
>               FREE(conf->getuid);
>
> diff --git a/libmultipath/config.h b/libmultipath/config.h
> index 9670020..ab85930 100644
> --- a/libmultipath/config.h
> +++ b/libmultipath/config.h
> @@ -153,6 +153,7 @@ struct config {
>
>       char * multipath_dir;
>       char * selector;
> +     char * uid_attrs;
>       char * uid_attribute;
>       char * getuid;
>       char * features;
> diff --git a/libmultipath/dict.c b/libmultipath/dict.c
> index dc21846..0a531d1 100644
> --- a/libmultipath/dict.c
> +++ b/libmultipath/dict.c
> @@ -249,6 +249,8 @@ declare_ovr_snprint(selector, print_str)
>  declare_mp_handler(selector, set_str)
>  declare_mp_snprint(selector, print_str)
>
> +declare_def_handler(uid_attrs, set_str)
> +declare_def_snprint(uid_attrs, print_str)
>  declare_def_handler(uid_attribute, set_str)
>  declare_def_snprint_defstr(uid_attribute, print_str, DEFAULT_UID_ATTRIBUTE)
>  declare_ovr_handler(uid_attribute, set_str)
> @@ -1367,6 +1369,7 @@ init_keywords(vector keywords)
>       install_keyword("multipath_dir", &def_multipath_dir_handler, &snprint_def_multipath_dir);
>       install_keyword("path_selector", &def_selector_handler, &snprint_def_selector);
>       install_keyword("path_grouping_policy", &def_pgpolicy_handler, &snprint_def_pgpolicy);
> +     install_keyword("uid_attrs", &def_uid_attrs_handler, &snprint_def_uid_attrs);
>       install_keyword("uid_attribute", &def_uid_attribute_handler, &snprint_def_uid_attribute);
>       install_keyword("getuid_callout", &def_getuid_handler, &snprint_def_getuid);
>       install_keyword("prio", &def_prio_name_handler, &snprint_def_prio_name);
> diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
> index d1aec31..14904f2 100644
> --- a/libmultipath/discovery.c
> +++ b/libmultipath/discovery.c
> @@ -33,7 +33,7 @@
>
>  int
>  alloc_path_with_pathinfo (struct config *conf, struct udev_device *udevice,
> -                       int flag, struct path **pp_ptr)
> +                       char *wwid, int flag, struct path **pp_ptr)
>  {
>       int err = PATHINFO_FAILED;
>       struct path * pp;
> @@ -51,6 +51,9 @@ alloc_path_with_pathinfo (struct config *conf, struct udev_device *udevice,
>       if (!pp)
>               return PATHINFO_FAILED;
>
> +     if(wwid)
> +             strncpy(pp->wwid, wwid, sizeof(pp->wwid));
> +
>       if (safe_sprintf(pp->dev, "%s", devname)) {
>               condlog(0, "pp->dev too small");
>       } else {
> diff --git a/libmultipath/discovery.h b/libmultipath/discovery.h
> index 3039268..d16a69a 100644
> --- a/libmultipath/discovery.h
> +++ b/libmultipath/discovery.h
> @@ -37,7 +37,7 @@ int path_offline (struct path *);
>  int get_state (struct path * pp, struct config * conf, int daemon);
>  int pathinfo (struct path * pp, struct config * conf, int mask);
>  int alloc_path_with_pathinfo (struct config *conf, struct udev_device *udevice,
> -                           int flag, struct path **pp_ptr);
> +                           char *wwid, int flag, struct path **pp_ptr);
>  int store_pathinfo (vector pathvec, struct config *conf,
>                   struct udev_device *udevice, int flag,
>                   struct path **pp_ptr);
> diff --git a/libmultipath/list.h b/libmultipath/list.h
> index ceaa381..2b1dcf3 100644
> --- a/libmultipath/list.h
> +++ b/libmultipath/list.h
> @@ -317,4 +317,45 @@ static inline void list_splice_tail_init(struct list_head *list,
>            &pos->member != (head);                                    \
>            pos = n, n = list_entry(n->member.next, typeof(*n), member))
>
> +/**
> + * list_for_each_entry_reverse_safe - iterate backwards over list of given type safe against removal of list entry
> + * @pos:     the type * to use as a loop counter.
> + * @n:               another type * to use as temporary storage
> + * @head:    the head for your list.
> + * @member:  the name of the list_struct within the struct.
> + */
> +#define list_for_each_entry_reverse_safe(pos, n, head, member)          \
> +     for (pos = list_entry((head)->prev, typeof(*pos), member),      \
> +              n = list_entry(pos->member.prev, typeof(*pos), member);\
> +          &pos->member != (head);                                    \
> +          pos = n, n = list_entry(n->member.prev, typeof(*n), member))
> +
> +/**
> + * list_for_some_entry_safe - iterate list from the given begin node to the given end node safe against removal of list entry
> + * @pos:     the type * to use as a loop counter.
> + * @n:               another type * to use as temporary storage
> + * @from:    the begin node of the iteration.
> + * @to:              the end node of the iteration.
> + * @member:  the name of the list_struct within the struct.
> + */
> +#define list_for_some_entry_safe(pos, n, from, to, member)              \
> +     for (pos = list_entry((from)->next, typeof(*pos), member),      \
> +          n = list_entry(pos->member.next, typeof(*pos), member);    \
> +          &pos->member != (to);                                      \
> +          pos = n, n = list_entry(n->member.next, typeof(*n), member))
> +
> +/**
> + * list_for_some_entry_reverse_safe - iterate backwards list from the given begin node to the given end node safe against removal of list entry
> + * @pos:     the type * to use as a loop counter.
> + * @n:               another type * to use as temporary storage
> + * @from:    the begin node of the iteration.
> + * @to:              the end node of the iteration.
> + * @member:  the name of the list_struct within the struct.
> + */
> +#define list_for_some_entry_reverse_safe(pos, n, from, to, member)      \
> +     for (pos = list_entry((from)->prev, typeof(*pos), member),      \
> +          n = list_entry(pos->member.prev, typeof(*pos), member);    \
> +          &pos->member != (to);                                      \
> +          pos = n, n = list_entry(n->member.prev, typeof(*n), member))
> +
>  #endif /* _LIST_H */
> diff --git a/libmultipath/propsel.c b/libmultipath/propsel.c
> index c0bc616..c47bd08 100644
> --- a/libmultipath/propsel.c
> +++ b/libmultipath/propsel.c
> @@ -18,6 +18,7 @@
>  #include "prio.h"
>  #include "discovery.h"
>  #include "dict.h"
> +#include "util.h"
>  #include "prioritizers/alua_rtpg.h"
>  #include <inttypes.h>
>
> @@ -339,6 +340,12 @@ int select_getuid(struct config *conf, struct path *pp)
>  {
>       char *origin;
>
> +     pp->uid_attribute = parse_uid_attribute_by_attrs(conf->uid_attrs, pp->dev);
> +     if (pp->uid_attribute) {
> +             origin = "(setting: multipath.conf defaults section)";
> +             goto out;
> +     }
> +
>       pp_set_ovr(getuid);
>       pp_set_ovr(uid_attribute);
>       pp_set_hwe(getuid);
> diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
> index 7edcce1..6e2527b 100644
> --- a/libmultipath/uevent.c
> +++ b/libmultipath/uevent.c
> @@ -24,6 +24,7 @@
>
>  #include <unistd.h>
>  #include <stdio.h>
> +#include <stdbool.h>
>  #include <errno.h>
>  #include <stdlib.h>
>  #include <stddef.h>
> @@ -38,6 +39,7 @@
>  #include <linux/netlink.h>
>  #include <pthread.h>
>  #include <sys/mman.h>
> +#include <sys/time.h>
>  #include <libudev.h>
>  #include <errno.h>
>
> @@ -46,6 +48,14 @@
>  #include "list.h"
>  #include "uevent.h"
>  #include "vector.h"
> +#include "structs.h"
> +#include "util.h"
> +#include "config.h"
> +#include "blacklist.h"
> +
> +#define MAX_ACCUMULATION_COUNT 2048
> +#define MAX_ACCUMULATION_TIME 30*1000
> +#define MIN_BURST_SPEED 10
>
>  typedef int (uev_trigger)(struct uevent *, void * trigger_data);
>
> @@ -72,48 +82,301 @@ struct uevent * alloc_uevent (void)
>  {
>       struct uevent *uev = MALLOC(sizeof(struct uevent));
>
> -     if (uev)
> +     if (uev) {
>               INIT_LIST_HEAD(&uev->node);
> +             INIT_LIST_HEAD(&uev->merge_node);
> +     }
>
>       return uev;
>  }
>
>  void
> -service_uevq(struct list_head *tmpq)
> +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 (my_uev_trigger && my_uev_trigger(uev, my_trigger_data))
> -                     condlog(0, "uevent trigger error");
> -
>               if (uev->udev)
>                       udev_device_unref(uev->udev);
>               FREE(uev);
>       }
>  }
>
> -static void uevent_cleanup(void *arg)
> +void
> +uevent_get_wwid(struct uevent *uev)
>  {
> -     struct udev *udev = arg;
> +     int i;
> +     char *uid_attribute;
> +     struct config * conf;
>
> -     condlog(3, "Releasing uevent_listen() resources");
> -     udev_unref(udev);
> +     conf = get_multipath_config();
> +     uid_attribute = parse_uid_attribute_by_attrs(conf->uid_attrs, uev->kernel);
> +     put_multipath_config(conf);
> +
> +     if (!uid_attribute)
> +             return;
> +
> +     for (i = 0; uev->envp[i] != NULL; i++) {
> +             if (!strncmp(uev->envp[i], uid_attribute, strlen(uid_attribute)) &&
> +                 strlen(uev->envp[i]) > strlen(uid_attribute) &&
> +                 uev->envp[i][strlen(uid_attribute)] == '=') {
> +                     uev->wwid = uev->envp[i] + strlen(uid_attribute) + 1;
> +                     break;
> +             }
> +     }
> +     free(uid_attribute);
> +}
> +
> +bool
> +uevent_need_merge(void)
> +{
> +     struct config * conf;
> +     bool need_merge = false;
> +
> +     conf = get_multipath_config();
> +     if (conf->uid_attrs)
> +             need_merge = true;
> +     put_multipath_config(conf);
> +
> +     return need_merge;
> +}
> +
> +bool
> +uevent_can_discard(struct uevent *uev)
> +{
> +     char *tmp;
> +     char a[11], b[11];
> +     struct config * conf;
> +
> +     /*
> +      * keep only block devices, discard partitions
> +      */
> +     tmp = strstr(uev->devpath, "/block/");
> +     if (tmp == NULL){
> +             condlog(4, "no /block/ in '%s'", uev->devpath);
> +             return true;
> +     }
> +     if (sscanf(tmp, "/block/%10s", a) != 1 ||
> +         sscanf(tmp, "/block/%10[^/]/%10s", a, b) == 2) {
> +             condlog(4, "discard event on %s", uev->devpath);
> +             return true;
> +     }
> +
> +     /*
> +      * do not filter dm devices by devnode
> +      */
> +     if (!strncmp(uev->kernel, "dm-", 3))
> +             return false;
> +     /*
> +      * filter paths devices by devnode
> +      */
> +     conf = get_multipath_config();
> +     if (filter_devnode(conf->blist_devnode, conf->elist_devnode,
> +                        uev->kernel) > 0) {
> +             put_multipath_config(conf);
> +             return true;
> +     }
> +     put_multipath_config(conf);
> +
> +     return false;
> +}
> +
> +bool
> +uevent_can_filter(struct uevent *earlier, struct uevent *later)
> +{
> +
> +     /*
> +      * filter earlier uvents if path has removed later. Eg:
> +      * "add path1 |chang path1 |add path2 |remove path1"
> +      * can filter as:
> +      * "add path2 |remove path1"
> +      * uevents "add path1" and "chang path1" are filtered out
> +      */
> +     if (!strcmp(earlier->kernel, later->kernel) &&
> +             !strcmp(later->action, "remove") &&
> +             strncmp(later->kernel, "dm-", 3)) {
> +             return true;
> +     }
> +
> +     /*
> +      * filter change uvents if add uevents exist. Eg:
> +      * "change path1| add path1 |add path2"
> +      * can filter as:
> +      * "add path1 |add path2"
> +      * uevent "chang path1" is filtered out
> +      */
> +     if (!strcmp(earlier->kernel, later->kernel) &&
> +             !strcmp(earlier->action, "change") &&
> +             !strcmp(later->action, "add") &&
> +             strncmp(later->kernel, "dm-", 3)) {
> +             return true;
> +     }
> +
> +     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
> -uevq_cleanup(struct list_head *tmpq)
> +uevent_prepare(struct list_head *tmpq)
> +{
> +     struct uevent *uev, *tmp;
> +
> +     list_for_each_entry_reverse_safe(uev, tmp, tmpq, node) {
> +             if (uevent_can_discard(uev)) {
> +                     list_del_init(&uev->node);
> +                     if (uev->udev)
> +                             udev_device_unref(uev->udev);
> +                     FREE(uev);
> +                     continue;
> +             }
> +
> +             if (strncmp(uev->kernel, "dm-", 3) &&
> +                 uevent_need_merge())
> +                     uevent_get_wwid(uev);
> +     }
> +}
> +
> +void
> +uevent_filter(struct uevent *later, struct list_head *tmpq)
> +{
> +     struct uevent *earlier, *tmp;
> +
> +     list_for_some_entry_reverse_safe(earlier, tmp, &later->node, tmpq, node) {
> +             /*
> +              * filter unnessary earlier uevents
> +              * by the later uevent
> +              */
> +             if (uevent_can_filter(earlier, later)) {
> +                     condlog(2, "uevent: %s-%s has filtered by uevent: %s-%s",
> +                             earlier->kernel, earlier->action,
> +                             later->kernel, later->action);
> +
> +                     list_del_init(&earlier->node);
> +                     if (earlier->udev)
> +                             udev_device_unref(earlier->udev);
> +                     FREE(earlier);
> +             }
> +     }
> +}
> +
> +void
> +uevent_merge(struct uevent *later, struct list_head *tmpq)
> +{
> +     struct uevent *earlier, *tmp;
> +
> +     list_for_some_entry_reverse_safe(earlier, tmp, &later->node, tmpq, node) {
> +             if (merge_need_stop(earlier, later))
> +                     break;
> +             /*
> +              * merge earlier uevents to the later uevent
> +              */
> +             if (uevent_can_merge(earlier, later)) {
> +                     condlog(2, "merged uevent: %s-%s-%s with uevent: %s-%s-%s",
> +                             earlier->action, earlier->kernel, earlier->wwid,
> +                             later->action, later->kernel, later->wwid);
> +
> +                     list_move(&earlier->node, &later->merge_node);
> +             }
> +     }
> +}
> +
> +void
> +merge_uevq(struct list_head *tmpq)
> +{
> +     struct uevent *later;
> +
> +     uevent_prepare(tmpq);
> +     list_for_each_entry_reverse(later, tmpq, node) {
> +             uevent_filter(later, tmpq);
> +             if(uevent_need_merge())
> +                     uevent_merge(later, tmpq);
> +     }
> +}
> +
> +void
> +service_uevq(struct list_head *tmpq)
>  {
>       struct uevent *uev, *tmp;
>
>       list_for_each_entry_safe(uev, tmp, tmpq, node) {
>               list_del_init(&uev->node);
> +
> +             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);
>       }
>  }
>
> +static void uevent_cleanup(void *arg)
> +{
> +     struct udev *udev = arg;
> +
> +     condlog(3, "Releasing uevent_listen() resources");
> +     udev_unref(udev);
> +}
> +
>  /*
>   * Service the uevent queue.
>   */
> @@ -142,6 +405,7 @@ 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");
> @@ -442,11 +706,43 @@ struct uevent *uevent_from_udev_device(struct udev_device *dev)
>       return uev;
>  }
>
> +bool uevent_burst(struct timeval *start_time, int events)
> +{
> +     struct timeval diff_time, end_time;
> +     unsigned long speed;
> +     unsigned long eclipse_ms;
> +
> +     if(events > MAX_ACCUMULATION_COUNT) {
> +             condlog(2, "burst got %u uevents, too much uevents, stopped", events);
> +             return false;
> +     }
> +
> +     gettimeofday(&end_time, NULL);
> +     timersub(&end_time, start_time, &diff_time);
> +
> +     eclipse_ms = diff_time.tv_sec * 1000 + diff_time.tv_usec / 1000;
> +
> +     if (eclipse_ms == 0)
> +             return true;
> +
> +     if (eclipse_ms > MAX_ACCUMULATION_TIME) {
> +             condlog(2, "burst continued %lu ms, too long time, stopped", eclipse_ms);
> +             return false;
> +     }
> +
> +     speed = (events * 1000) / eclipse_ms;
> +     if (speed > MIN_BURST_SPEED)
> +             return true;
> +
> +     return false;
> +}
> +
>  int uevent_listen(struct udev *udev)
>  {
>       int err = 2;
>       struct udev_monitor *monitor = NULL;
>       int fd, socket_flags, events;
> +     struct timeval start_time;
>       int need_failback = 1;
>       int timeout = 30;
>       LIST_HEAD(uevlisten_tmp);
> @@ -500,6 +796,7 @@ int uevent_listen(struct udev *udev)
>       }
>
>       events = 0;
> +     gettimeofday(&start_time, NULL);
>       while (1) {
>               struct uevent *uev;
>               struct udev_device *dev;
> @@ -514,7 +811,7 @@ int uevent_listen(struct udev *udev)
>               errno = 0;
>               fdcount = poll(&ev_poll, 1, poll_timeout);
>               if (fdcount && ev_poll.revents & POLLIN) {
> -                     timeout = 0;
> +                     timeout = uevent_burst(&start_time, events + 1) ? 1 : 0;
>                       dev = udev_monitor_receive_device(monitor);
>                       if (!dev) {
>                               condlog(0, "failed getting udev device");
> @@ -547,6 +844,7 @@ int uevent_listen(struct udev *udev)
>                       pthread_mutex_unlock(uevq_lockp);
>                       events = 0;
>               }
> +             gettimeofday(&start_time, NULL);
>               timeout = 30;
>       }
>       need_failback = 0;
> diff --git a/libmultipath/uevent.h b/libmultipath/uevent.h
> index 9d22dcd..61a4207 100644
> --- a/libmultipath/uevent.h
> +++ b/libmultipath/uevent.h
> @@ -17,11 +17,13 @@ struct udev;
>
>  struct uevent {
>       struct list_head node;
> +     struct list_head merge_node;
>       struct udev_device *udev;
>       char buffer[HOTPLUG_BUFFER_SIZE + OBJECT_SIZE];
>       char *devpath;
>       char *action;
>       char *kernel;
> +     char *wwid;
>       unsigned long seqnum;
>       char *envp[HOTPLUG_NUM_ENVP];
>  };
> diff --git a/libmultipath/util.c b/libmultipath/util.c
> index 03a5738..e1e83cf 100644
> --- a/libmultipath/util.c
> +++ b/libmultipath/util.c
> @@ -261,6 +261,48 @@ dev_t parse_devt(const char *dev_t)
>       return makedev(maj, min);
>  }
>
> +char *parse_uid_attribute_by_attrs(char *uid_attrs, char *path_dev)
> +{
> +     char *uid_attribute;
> +     char *uid_attr_record;
> +     char *dev;
> +     char *attr;
> +     char *tmp;
> +     int  count;
> +
> +     if(!uid_attrs || !path_dev)
> +             return NULL;
> +
> +     count = get_word(uid_attrs, &uid_attr_record);
> +     while (uid_attr_record) {
> +             tmp = strrchr(uid_attr_record, ':');
> +             if (!tmp) {
> +                     free(uid_attr_record);
> +                     if (!count)
> +                             break;
> +                     uid_attrs += count;
> +                     count = get_word(uid_attrs, &uid_attr_record);
> +                     continue;
> +             }
> +             dev = uid_attr_record;
> +             attr = tmp + 1;
> +             *tmp = '\0';
> +
> +             if(!strncmp(path_dev, dev, strlen(dev))) {
> +                     uid_attribute = STRDUP(attr);
> +                     free(uid_attr_record);
> +                     return uid_attribute;
> +             }
> +
> +             free(uid_attr_record);
> +             if (!count)
> +                     break;
> +             uid_attrs += count;
> +             count = get_word(uid_attrs, &uid_attr_record);
> +     }
> +     return NULL;
> +}
> +
>  void
>  setup_thread_attr(pthread_attr_t *attr, size_t stacksize, int detached)
>  {
> diff --git a/libmultipath/util.h b/libmultipath/util.h
> index f3b37ee..793f2b7 100644
> --- a/libmultipath/util.h
> +++ b/libmultipath/util.h
> @@ -12,6 +12,7 @@ size_t strlcat(char *dst, const char *src, size_t size);
>  int devt2devname (char *, int, char *);
>  dev_t parse_devt(const char *dev_t);
>  char *convert_dev(char *dev, int is_path_device);
> +char *parse_uid_attribute_by_attrs(char *uid_attrs, char *path_dev);
>  void setup_thread_attr(pthread_attr_t *attr, size_t stacksize, int detached);
>
>  #define safe_sprintf(var, format, args...)   \
> diff --git a/multipath/multipath.conf.5 b/multipath/multipath.conf.5
> index 36589f5..63c63c2 100644
> --- a/multipath/multipath.conf.5
> +++ b/multipath/multipath.conf.5
> @@ -209,6 +209,24 @@ The default is: \fBfailover\fR
>  .
>  .
>  .TP
> +.B uid_attrs
> +The udev attribute providing a unique path identifier for corresponding
> +type of path devices. If this field is configured and matched with type
> +of device, it would override any other methods providing for device
> +unique identifier in config file, and it would activate merging uevents
> +according to the identifier to promote effiecncy in processing uevents.
> +Tt has no default value, if you want to identify path by udev attribute
> +and to activate merging uevents for SCSI and DAS device, you can set
> +it's value as:
> +.RS
> +.TP
> +\fBuid_attrs "sd:ID_SERIAL dasd:ID_UID"\fR
> +.TP
> +The default is: \fB<unset>\fR
> +.RE
> +.
> +.
> +.TP
>  .B uid_attribute
>  The udev attribute providing a unique path identifier.
>  .RS
> diff --git a/multipathd/cli_handlers.c b/multipathd/cli_handlers.c
> index b0eeca6..12f85de 100644
> --- a/multipathd/cli_handlers.c
> +++ b/multipathd/cli_handlers.c
> @@ -670,7 +670,7 @@ cli_add_path (void * v, char ** reply, int * len, void * data)
>               pp->checkint = conf->checkint;
>       }
>       put_multipath_config(conf);
> -     return ev_add_path(pp, vecs);
> +     return ev_add_path(pp, vecs, 1);
>  blacklisted:
>       *reply = strdup("blacklisted\n");
>       *len = strlen(*reply) + 1;
> @@ -692,7 +692,7 @@ cli_del_path (void * v, char ** reply, int * len, void * data)
>               condlog(0, "%s: path already removed", param);
>               return 1;
>       }
> -     return ev_remove_path(pp, vecs);
> +     return ev_remove_path(pp, vecs, 1);
>  }
>
>  int
> diff --git a/multipathd/main.c b/multipathd/main.c
> index adc3258..e513f7d 100644
> --- a/multipathd/main.c
> +++ b/multipathd/main.c
> @@ -608,7 +608,7 @@ ev_remove_map (char * devname, char * alias, int minor, struct vectors * vecs)
>  }
>
>  static int
> -uev_add_path (struct uevent *uev, struct vectors * vecs)
> +uev_add_path (struct uevent *uev, struct vectors * vecs, int need_do_map)
>  {
>       struct path *pp;
>       int ret = 0, i;
> @@ -641,7 +641,7 @@ uev_add_path (struct uevent *uev, struct vectors * vecs)
>                                    DI_ALL | DI_BLACKLIST);
>                       put_multipath_config(conf);
>                       if (r == PATHINFO_OK)
> -                             ret = ev_add_path(pp, vecs);
> +                             ret = ev_add_path(pp, vecs, need_do_map);
>                       else if (r == PATHINFO_SKIPPED) {
>                               condlog(3, "%s: remove blacklisted path",
>                                       uev->kernel);
> @@ -665,7 +665,7 @@ uev_add_path (struct uevent *uev, struct vectors * vecs)
>        */
>       conf = get_multipath_config();
>       ret = alloc_path_with_pathinfo(conf, uev->udev,
> -                                    DI_ALL, &pp);
> +                                    uev->wwid, DI_ALL, &pp);
>       put_multipath_config(conf);
>       if (!pp) {
>               if (ret == PATHINFO_SKIPPED)
> @@ -681,7 +681,7 @@ uev_add_path (struct uevent *uev, struct vectors * vecs)
>               conf = get_multipath_config();
>               pp->checkint = conf->checkint;
>               put_multipath_config(conf);
> -             ret = ev_add_path(pp, vecs);
> +             ret = ev_add_path(pp, vecs, need_do_map);
>       } else {
>               condlog(0, "%s: failed to store path info, "
>                       "dropping event",
> @@ -699,7 +699,7 @@ uev_add_path (struct uevent *uev, struct vectors * vecs)
>   * 1: error
>   */
>  int
> -ev_add_path (struct path * pp, struct vectors * vecs)
> +ev_add_path (struct path * pp, struct vectors * vecs, int need_do_map)
>  {
>       struct multipath * mpp;
>       char params[PARAMS_SIZE] = {0};
> @@ -767,6 +767,13 @@ rescan:
>       /* persistent reservation check*/
>       mpath_pr_event_handle(pp);
>
> +     if (!need_do_map)
> +             return 0;
> +
> +     if (!dm_map_present(mpp->alias)) {
> +             mpp->action = ACT_CREATE;
> +             start_waiter = 1;
> +     }
>       /*
>        * push the map to the device-mapper
>        */
> @@ -833,7 +840,7 @@ fail:
>  }
>
>  static int
> -uev_remove_path (struct uevent *uev, struct vectors * vecs)
> +uev_remove_path (struct uevent *uev, struct vectors * vecs, int need_do_map)
>  {
>       struct path *pp;
>       int ret;
> @@ -844,7 +851,7 @@ uev_remove_path (struct uevent *uev, struct vectors * vecs)
>       pthread_testcancel();
>       pp = find_path_by_dev(vecs->pathvec, uev->kernel);
>       if (pp)
> -             ret = ev_remove_path(pp, vecs);
> +             ret = ev_remove_path(pp, vecs, need_do_map);
>       lock_cleanup_pop(vecs->lock);
>       if (!pp) {
>               /* Not an error; path might have been purged earlier */
> @@ -855,7 +862,7 @@ uev_remove_path (struct uevent *uev, struct vectors * vecs)
>  }
>
>  int
> -ev_remove_path (struct path *pp, struct vectors * vecs)
> +ev_remove_path (struct path *pp, struct vectors * vecs, int need_do_map)
>  {
>       struct multipath * mpp;
>       int i, retval = 0;
> @@ -918,6 +925,8 @@ ev_remove_path (struct path *pp, struct vectors * vecs)
>                       goto out;
>               }
>
> +             if (!need_do_map)
> +                     goto out;
>               /*
>                * reload the map
>                */
> @@ -995,7 +1004,7 @@ uev_update_path (struct uevent *uev, struct vectors * vecs)
>               }
>
>               if (pp->initialized == INIT_REQUESTED_UDEV)
> -                     retval = uev_add_path(uev, vecs);
> +                     retval = uev_add_path(uev, vecs, 1);
>               else if (mpp && ro >= 0) {
>                       condlog(2, "%s: update path write_protect to '%d' (uevent)", uev->kernel, ro);
>
> @@ -1016,7 +1025,7 @@ out:
>                       int flag = DI_SYSFS | DI_WWID;
>
>                       conf = get_multipath_config();
> -                     retval = alloc_path_with_pathinfo(conf, uev->udev, flag, NULL);
> +                     retval = alloc_path_with_pathinfo(conf, uev->udev, uev->wwid, flag, NULL);
>                       put_multipath_config(conf);
>
>                       if (retval == PATHINFO_SKIPPED) {
> @@ -1077,40 +1086,15 @@ uxsock_trigger (char * str, char ** reply, int * len, void * trigger_data)
>       return r;
>  }
>
> -static int
> -uev_discard(char * devpath)
> -{
> -     char *tmp;
> -     char a[11], b[11];
> -
> -     /*
> -      * keep only block devices, discard partitions
> -      */
> -     tmp = strstr(devpath, "/block/");
> -     if (tmp == NULL){
> -             condlog(4, "no /block/ in '%s'", devpath);
> -             return 1;
> -     }
> -     if (sscanf(tmp, "/block/%10s", a) != 1 ||
> -         sscanf(tmp, "/block/%10[^/]/%10s", a, b) == 2) {
> -             condlog(4, "discard event on %s", devpath);
> -             return 1;
> -     }
> -     return 0;
> -}
> -
>  int
>  uev_trigger (struct uevent * uev, void * trigger_data)
>  {
>       int r = 0;
>       struct vectors * vecs;
> -     struct config *conf;
> +     struct uevent *merge_uev, *tmp;
>
>       vecs = (struct vectors *)trigger_data;
>
> -     if (uev_discard(uev->devpath))
> -             return 0;
> -
>       pthread_cleanup_push(config_cleanup, NULL);
>       pthread_mutex_lock(&config_lock);
>       if (running_state != DAEMON_IDLE &&
> @@ -1139,28 +1123,21 @@ uev_trigger (struct uevent * uev, void * trigger_data)
>       }
>
>       /*
> -      * path add/remove event
> +      * path add/remove/change event, add/remove maybe merged
>        */
> -     conf = get_multipath_config();
> -     if (filter_devnode(conf->blist_devnode, conf->elist_devnode,
> -                        uev->kernel) > 0) {
> -             put_multipath_config(conf);
> -             goto out;
> +     list_for_each_entry_safe(merge_uev, tmp, &uev->merge_node, node) {
> +             if (!strncmp(merge_uev->action, "add", 3))
> +                     r += uev_add_path(merge_uev, vecs, 0);
> +             if (!strncmp(merge_uev->action, "remove", 6))
> +                     r += uev_remove_path(merge_uev, vecs, 0);
>       }
> -     put_multipath_config(conf);
>
> -     if (!strncmp(uev->action, "add", 3)) {
> -             r = uev_add_path(uev, vecs);
> -             goto out;
> -     }
> -     if (!strncmp(uev->action, "remove", 6)) {
> -             r = uev_remove_path(uev, vecs);
> -             goto out;
> -     }
> -     if (!strncmp(uev->action, "change", 6)) {
> -             r = uev_update_path(uev, vecs);
> -             goto out;
> -     }
> +     if (!strncmp(uev->action, "add", 3))
> +             r += uev_add_path(uev, vecs, 1);
> +     if (!strncmp(uev->action, "remove", 6))
> +             r += uev_remove_path(uev, vecs, 1);
> +     if (!strncmp(uev->action, "change", 6))
> +             r += uev_update_path(uev, vecs);
>
>  out:
>       return r;
> @@ -1570,7 +1547,7 @@ check_path (struct vectors * vecs, struct path * pp, int ticks)
>                       conf = get_multipath_config();
>                       ret = pathinfo(pp, conf, DI_ALL | DI_BLACKLIST);
>                       if (ret == PATHINFO_OK) {
> -                             ev_add_path(pp, vecs);
> +                             ev_add_path(pp, vecs, 1);
>                               pp->tick = 1;
>                       } else if (ret == PATHINFO_SKIPPED) {
>                               put_multipath_config(conf);
> @@ -1686,7 +1663,7 @@ check_path (struct vectors * vecs, struct path * pp, int ticks)
>               }
>               if (!disable_reinstate && reinstate_path(pp, add_active)) {
>                       condlog(3, "%s: reload map", pp->dev);
> -                     ev_add_path(pp, vecs);
> +                     ev_add_path(pp, vecs, 1);
>                       pp->tick = 1;
>                       return 0;
>               }
> @@ -1709,7 +1686,7 @@ check_path (struct vectors * vecs, struct path * pp, int ticks)
>                       /* Clear IO errors */
>                       if (reinstate_path(pp, 0)) {
>                               condlog(3, "%s: reload map", pp->dev);
> -                             ev_add_path(pp, vecs);
> +                             ev_add_path(pp, vecs, 1);
>                               pp->tick = 1;
>                               return 0;
>                       }
> diff --git a/multipathd/main.h b/multipathd/main.h
> index f72580d..094b04f 100644
> --- a/multipathd/main.h
> +++ b/multipathd/main.h
> @@ -22,8 +22,8 @@ void exit_daemon(void);
>  const char * daemon_status(void);
>  int need_to_delay_reconfig (struct vectors *);
>  int reconfigure (struct vectors *);
> -int ev_add_path (struct path *, struct vectors *);
> -int ev_remove_path (struct path *, struct vectors *);
> +int ev_add_path (struct path *, struct vectors *, int);
> +int ev_remove_path (struct path *, struct vectors *, int);
>  int ev_add_map (char *, char *, struct vectors *);
>  int ev_remove_map (char *, char *, int, struct vectors *);
>  void sync_map_state (struct multipath *);
> --
> 2.8.1.windows.1
>