dm ioctl: introduce flag indicating uevent was generated

Set a new DM_UEVENT_GENERATED_FLAG when returning from ioctls to
indicate that a uevent was actually generated.  This tells the userspace
caller that it may need to wait for the event to be processed.

Signed-off-by: Peter Rajnoha <prajnoha@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

3 files changed, 18 insertions, 12 deletions

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index e3cf568..d7500e1 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -285,7 +285,8 @@ retry:
 	up_write(&_hash_lock);
 }
 
-static int dm_hash_rename(uint32_t cookie, const char *old, const char *new)
+static int dm_hash_rename(uint32_t cookie, uint32_t *flags, const char *old,
+			  const char *new)
 {
 	char *new_name, *old_name;
 	struct hash_cell *hc;
@@ -344,7 +345,8 @@ static int dm_hash_rename(uint32_t cookie, const char *old, const char *new)
 		dm_table_put(table);
 	}
 
-	dm_kobject_uevent(hc->md, KOBJ_CHANGE, cookie);
+	if (!dm_kobject_uevent(hc->md, KOBJ_CHANGE, cookie))
+		*flags |= DM_UEVENT_GENERATED_FLAG;
 
 	dm_put(hc->md);
 	up_write(&_hash_lock);
@@ -736,10 +738,10 @@ static int dev_remove(struct dm_ioctl *param, size_t param_size)
 	__hash_remove(hc);
 	up_write(&_hash_lock);
 
-	dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr);
+	if (!dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr))
+		param->flags |= DM_UEVENT_GENERATED_FLAG;
 
 	dm_put(md);
-	param->data_size = 0;
 	return 0;
 }
 
@@ -773,7 +775,9 @@ static int dev_rename(struct dm_ioctl *param, size_t param_size)
 		return r;
 
 	param->data_size = 0;
-	return dm_hash_rename(param->event_nr, param->name, new_name);
+
+	return dm_hash_rename(param->event_nr, &param->flags, param->name,
+			      new_name);
 }
 
 static int dev_set_geometry(struct dm_ioctl *param, size_t param_size)
@@ -899,8 +903,8 @@ static int do_resume(struct dm_ioctl *param)
 
 	if (dm_suspended_md(md)) {
 		r = dm_resume(md);
-		if (!r)
-			dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr);
+		if (!r && !dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr))
+			param->flags |= DM_UEVENT_GENERATED_FLAG;
 	}
 
 	if (old_map)
@@ -1477,6 +1481,7 @@ static int validate_params(uint cmd, struct dm_ioctl *param)
 {
 	/* Always clear this flag */
 	param->flags &= ~DM_BUFFER_FULL_FLAG;
+	param->flags &= ~DM_UEVENT_GENERATED_FLAG;
 
 	/* Ignores parameters */
 	if (cmd == DM_REMOVE_ALL_CMD ||
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7199846..d21e128 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2618,18 +2618,19 @@ out:
 /*-----------------------------------------------------------------
  * Event notification.
  *---------------------------------------------------------------*/
-void dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
+int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
 		       unsigned cookie)
 {
 	char udev_cookie[DM_COOKIE_LENGTH];
 	char *envp[] = { udev_cookie, NULL };
 
 	if (!cookie)
-		kobject_uevent(&disk_to_dev(md->disk)->kobj, action);
+		return kobject_uevent(&disk_to_dev(md->disk)->kobj, action);
 	else {
 		snprintf(udev_cookie, DM_COOKIE_LENGTH, "%s=%u",
 			 DM_COOKIE_ENV_VAR_NAME, cookie);
-		kobject_uevent_env(&disk_to_dev(md->disk)->kobj, action, envp);
+		return kobject_uevent_env(&disk_to_dev(md->disk)->kobj,
+					  action, envp);
 	}
 }
 
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 8dadaa5..bad1724 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -125,8 +125,8 @@ void dm_stripe_exit(void);
 int dm_open_count(struct mapped_device *md);
 int dm_lock_for_deletion(struct mapped_device *md);
 
-void dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
-		       unsigned cookie);
+int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
+		      unsigned cookie);
 
 int dm_io_init(void);
 void dm_io_exit(void);