dm: uevent generate events

This patch adds support for the dm_path_event dm_send_event functions which
create and send udev events.

Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

5 files changed, 295 insertions, 0 deletions

diff --git a/Documentation/device-mapper/dm-uevent.txt b/Documentation/device-mapper/dm-uevent.txt
new file mode 100644
index 000000000000..07edbd85c714
--- /dev/null
+++ b/Documentation/device-mapper/dm-uevent.txt
@@ -0,0 +1,97 @@
+The device-mapper uevent code adds the capability to device-mapper to create
+and send kobject uevents (uevents).  Previously device-mapper events were only
+available through the ioctl interface.  The advantage of the uevents interface
+is the event contains environment attributes providing increased context for
+the event avoiding the need to query the state of the device-mapper device after
+the event is received.
+
+There are two functions currently for device-mapper events.  The first function
+listed creates the event and the second function sends the event(s).
+
+void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti,
+                    const char *path, unsigned nr_valid_paths)
+
+void dm_send_uevents(struct list_head *events, struct kobject *kobj)
+
+
+The variables added to the uevent environment are:
+
+Variable Name: DM_TARGET
+Uevent Action(s): KOBJ_CHANGE
+Type: string
+Description:
+Value: Name of device-mapper target that generated the event.
+
+Variable Name: DM_ACTION
+Uevent Action(s): KOBJ_CHANGE
+Type: string
+Description:
+Value: Device-mapper specific action that caused the uevent action.
+        PATH_FAILED - A path has failed.
+        PATH_REINSTATED - A path has been reinstated.
+
+Variable Name: DM_SEQNUM
+Uevent Action(s): KOBJ_CHANGE
+Type: unsigned integer
+Description: A sequence number for this specific device-mapper device.
+Value: Valid unsigned integer range.
+
+Variable Name: DM_PATH
+Uevent Action(s): KOBJ_CHANGE
+Type: string
+Description: Major and minor number of the path device pertaining to this
+event.
+Value: Path name in the form of "Major:Minor"
+
+Variable Name: DM_NR_VALID_PATHS
+Uevent Action(s): KOBJ_CHANGE
+Type: unsigned integer
+Description:
+Value: Valid unsigned integer range.
+
+Variable Name: DM_NAME
+Uevent Action(s): KOBJ_CHANGE
+Type: string
+Description: Name of the device-mapper device.
+Value: Name
+
+Variable Name: DM_UUID
+Uevent Action(s): KOBJ_CHANGE
+Type: string
+Description: UUID of the device-mapper device.
+Value: UUID. (Empty string if there isn't one.)
+
+An example of the uevents generated as captured by udevmonitor is shown
+below.
+
+1.) Path failure.
+UEVENT[1192521009.711215] change@/block/dm-3
+ACTION=change
+DEVPATH=/block/dm-3
+SUBSYSTEM=block
+DM_TARGET=multipath
+DM_ACTION=PATH_FAILED
+DM_SEQNUM=1
+DM_PATH=8:32
+DM_NR_VALID_PATHS=0
+DM_NAME=mpath2
+DM_UUID=mpath-35333333000002328
+MINOR=3
+MAJOR=253
+SEQNUM=1130
+
+2.) Path reinstate.
+UEVENT[1192521132.989927] change@/block/dm-3
+ACTION=change
+DEVPATH=/block/dm-3
+SUBSYSTEM=block
+DM_TARGET=multipath
+DM_ACTION=PATH_REINSTATED
+DM_SEQNUM=2
+DM_PATH=8:32
+DM_NR_VALID_PATHS=1
+DM_NAME=mpath2
+DM_UUID=mpath-35333333000002328
+MINOR=3
+MAJOR=253
+SEQNUM=1131
diff --git a/drivers/md/dm-uevent.c b/drivers/md/dm-uevent.c
index 53200c96bcb4..50377e5dc2a3 100644
--- a/drivers/md/dm-uevent.c
+++ b/drivers/md/dm-uevent.c
@@ -21,12 +21,22 @@
 #include <linux/list.h>
 #include <linux/slab.h>
 #include <linux/kobject.h>
+#include <linux/dm-ioctl.h>
 
 #include "dm.h"
 #include "dm-uevent.h"
 
 #define DM_MSG_PREFIX "uevent"
 
+static const struct {
+        enum dm_uevent_type type;
+        enum kobject_action action;
+        char *name;
+} _dm_uevent_type_names[] = {
+        {DM_UEVENT_PATH_FAILED, KOBJ_CHANGE, "PATH_FAILED"},
+        {DM_UEVENT_PATH_REINSTATED, KOBJ_CHANGE, "PATH_REINSTATED"},
+};
+
 static struct kmem_cache *_dm_event_cache;
 
 struct dm_uevent {
@@ -34,6 +44,8 @@ struct dm_uevent {
         enum kobject_action action;
         struct kobj_uevent_env ku_env;
         struct list_head elist;
+        char name[DM_NAME_LEN];
+        char uuid[DM_UUID_LEN];
 };
 
 static void dm_uevent_free(struct dm_uevent *event)
@@ -55,6 +67,144 @@ static struct dm_uevent *dm_uevent_alloc(struct mapped_device *md)
         return event;
 }
 
+static struct dm_uevent *dm_build_path_uevent(struct mapped_device *md,
+                                              struct dm_target *ti,
+                                              enum kobject_action action,
+                                              const char *dm_action,
+                                              const char *path,
+                                              unsigned nr_valid_paths)
+{
+        struct dm_uevent *event;
+
+        event = dm_uevent_alloc(md);
+        if (!event) {
+                DMERR("%s: dm_uevent_alloc() failed", __FUNCTION__);
+                goto err_nomem;
+        }
+
+        event->action = action;
+
+        if (add_uevent_var(&event->ku_env, "DM_TARGET=%s", ti->type->name)) {
+                DMERR("%s: add_uevent_var() for DM_TARGET failed",
+                      __FUNCTION__);
+                goto err_add;
+        }
+
+        if (add_uevent_var(&event->ku_env, "DM_ACTION=%s", dm_action)) {
+                DMERR("%s: add_uevent_var() for DM_ACTION failed",
+                      __FUNCTION__);
+                goto err_add;
+        }
+
+        if (add_uevent_var(&event->ku_env, "DM_SEQNUM=%u",
+                           dm_next_uevent_seq(md))) {
+                DMERR("%s: add_uevent_var() for DM_SEQNUM failed",
+                      __FUNCTION__);
+                goto err_add;
+        }
+
+        if (add_uevent_var(&event->ku_env, "DM_PATH=%s", path)) {
+                DMERR("%s: add_uevent_var() for DM_PATH failed", __FUNCTION__);
+                goto err_add;
+        }
+
+        if (add_uevent_var(&event->ku_env, "DM_NR_VALID_PATHS=%d",
+                           nr_valid_paths)) {
+                DMERR("%s: add_uevent_var() for DM_NR_VALID_PATHS failed",
+                      __FUNCTION__);
+                goto err_add;
+        }
+
+        return event;
+
+err_add:
+        dm_uevent_free(event);
+err_nomem:
+        return ERR_PTR(-ENOMEM);
+}
+
+/**
+ * dm_send_uevents - send uevents for given list
+ *
+ * @events:     list of events to send
+ * @kobj:       kobject generating event
+ *
+ */
+void dm_send_uevents(struct list_head *events, struct kobject *kobj)
+{
+        int r;
+        struct dm_uevent *event, *next;
+
+        list_for_each_entry_safe(event, next, events, elist) {
+                list_del_init(&event->elist);
+
+                /*
+                 * Need to call dm_copy_name_and_uuid from here for now.
+                 * Context of previous var adds and locking used for
+                 * hash_cell not compatable.
+                 */
+                if (dm_copy_name_and_uuid(event->md, event->name,
+                                          event->uuid)) {
+                        DMERR("%s: dm_copy_name_and_uuid() failed",
+                              __FUNCTION__);
+                        goto uevent_free;
+                }
+
+                if (add_uevent_var(&event->ku_env, "DM_NAME=%s", event->name)) {
+                        DMERR("%s: add_uevent_var() for DM_NAME failed",
+                              __FUNCTION__);
+                        goto uevent_free;
+                }
+
+                if (add_uevent_var(&event->ku_env, "DM_UUID=%s", event->uuid)) {
+                        DMERR("%s: add_uevent_var() for DM_UUID failed",
+                              __FUNCTION__);
+                        goto uevent_free;
+                }
+
+                r = kobject_uevent_env(kobj, event->action, event->ku_env.envp);
+                if (r)
+                        DMERR("%s: kobject_uevent_env failed", __FUNCTION__);
+uevent_free:
+                dm_uevent_free(event);
+        }
+}
+EXPORT_SYMBOL_GPL(dm_send_uevents);
+
+/**
+ * dm_path_uevent - called to create a new path event and queue it
+ *
+ * @event_type: path event type enum
+ * @ti:                 pointer to a dm_target
+ * @path:               string containing pathname
+ * @nr_valid_paths:     number of valid paths remaining
+ *
+ */
+void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti,
+                   const char *path, unsigned nr_valid_paths)
+{
+        struct mapped_device *md = dm_table_get_md(ti->table);
+        struct dm_uevent *event;
+
+        if (event_type >= ARRAY_SIZE(_dm_uevent_type_names)) {
+                DMERR("%s: Invalid event_type %d", __FUNCTION__, event_type);
+                goto out;
+        }
+
+        event = dm_build_path_uevent(md, ti,
+                                     _dm_uevent_type_names[event_type].action,
+                                     _dm_uevent_type_names[event_type].name,
+                                     path, nr_valid_paths);
+        if (IS_ERR(event))
+                goto out;
+
+        dm_uevent_add(md, &event->elist);
+
+out:
+        dm_put(md);
+}
+EXPORT_SYMBOL_GPL(dm_path_uevent);
+
 int dm_uevent_init(void)
 {
         _dm_event_cache = KMEM_CACHE(dm_uevent, 0);
diff --git a/drivers/md/dm-uevent.h b/drivers/md/dm-uevent.h
index 9d776836489b..2eccc8bd671a 100644
--- a/drivers/md/dm-uevent.h
+++ b/drivers/md/dm-uevent.h
@@ -21,10 +21,19 @@
 #ifndef DM_UEVENT_H
 #define DM_UEVENT_H
 
+enum dm_uevent_type {
+        DM_UEVENT_PATH_FAILED,
+        DM_UEVENT_PATH_REINSTATED,
+};
+
 #ifdef CONFIG_DM_UEVENT
 
 extern int dm_uevent_init(void);
 extern void dm_uevent_exit(void);
+extern void dm_send_uevents(struct list_head *events, struct kobject *kobj);
+extern void dm_path_uevent(enum dm_uevent_type event_type,
+                           struct dm_target *ti, const char *path,
+                           unsigned nr_valid_paths);
 
 #else
 
@@ -35,6 +44,15 @@ static inline int dm_uevent_init(void)
 static inline void dm_uevent_exit(void)
 {
 }
+static inline void dm_send_uevents(struct list_head *events,
+                                   struct kobject *kobj)
+{
+}
+static inline void dm_path_uevent(enum dm_uevent_type event_type,
+                                  struct dm_target *ti, const char *path,
+                                  unsigned nr_valid_paths)
+{
+}
 
 #endif  /* CONFIG_DM_UEVENT */
 
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index bb5c1eaca52b..07cbbb8eb3e0 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -113,6 +113,9 @@ struct mapped_device {
          */
         atomic_t event_nr;
         wait_queue_head_t eventq;
+        atomic_t uevent_seq;
+        struct list_head uevent_list;
+        spinlock_t uevent_lock; /* Protect access to uevent_list */
 
         /*
          * freeze/thaw support require holding onto a super block
@@ -985,6 +988,9 @@ static struct mapped_device *alloc_dev(int minor)
         atomic_set(&md->holders, 1);
         atomic_set(&md->open_count, 0);
         atomic_set(&md->event_nr, 0);
+        atomic_set(&md->uevent_seq, 0);
+        INIT_LIST_HEAD(&md->uevent_list);
+        spin_lock_init(&md->uevent_lock);
 
         md->queue = blk_alloc_queue(GFP_KERNEL);
         if (!md->queue)
@@ -1083,8 +1089,16 @@ static void free_dev(struct mapped_device *md)
  */
 static void event_callback(void *context)
 {
+        unsigned long flags;
+        LIST_HEAD(uevents);
         struct mapped_device *md = (struct mapped_device *) context;
 
+        spin_lock_irqsave(&md->uevent_lock, flags);
+        list_splice_init(&md->uevent_list, &uevents);
+        spin_unlock_irqrestore(&md->uevent_lock, flags);
+
+        dm_send_uevents(&uevents, &md->disk->kobj);
+
         atomic_inc(&md->event_nr);
         wake_up(&md->eventq);
 }
@@ -1502,6 +1516,11 @@ out:
 /*-----------------------------------------------------------------
  * Event notification.
  *---------------------------------------------------------------*/
+uint32_t dm_next_uevent_seq(struct mapped_device *md)
+{
+        return atomic_add_return(1, &md->uevent_seq);
+}
+
 uint32_t dm_get_event_nr(struct mapped_device *md)
 {
         return atomic_read(&md->event_nr);
@@ -1513,6 +1532,15 @@ int dm_wait_event(struct mapped_device *md, int event_nr)
                         (event_nr != atomic_read(&md->event_nr)));
 }
 
+void dm_uevent_add(struct mapped_device *md, struct list_head *elist)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&md->uevent_lock, flags);
+        list_add(elist, &md->uevent_list);
+        spin_unlock_irqrestore(&md->uevent_lock, flags);
+}
+
 /*
  * The gendisk is only valid as long as you have a reference
  * count on 'md'.
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 8b3c7cdc599c..37c66d1254b5 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -183,6 +183,8 @@ int dm_resume(struct mapped_device *md);
  */
 uint32_t dm_get_event_nr(struct mapped_device *md);
 int dm_wait_event(struct mapped_device *md, int event_nr);
+uint32_t dm_next_uevent_seq(struct mapped_device *md);
+void dm_uevent_add(struct mapped_device *md, struct list_head *elist);
 
 /*
  * Info functions.