[PATCH] dm: new suspend/resume target methods

Some targets may perform io of their own volition, eg. a mirror
performing recovery, a cache target pulling in different chunks.  We
cannot let them perform this io while the device is suspended.  This
patch adds 2 new methods to the target type, which instruct the target
to suspend/resume itself.  All targets start in the suspended state,
so should expect an initial resume call.  Simple targets do not need
to implement these functions.

drivers/md/dm-table.c

@@ -776,6 +776,31 @@ void dm_table_add_wait_queue(struct dm_table *t, wait_queue_t *wq)
 	add_wait_queue(&t->eventq, wq);
 }
 
+void dm_table_suspend_targets(struct dm_table *t)
+{
+	int i;
+
+	for (i = 0; i < t->num_targets; i++) {
+		struct dm_target *ti = t->targets + i;
+
+		if (ti->type->suspend)
+			ti->type->suspend(ti);
+	}
+}
+
+void dm_table_resume_targets(struct dm_table *t)
+{
+	int i;
+
+	for (i = 0; i < t->num_targets; i++) {
+		struct dm_target *ti = t->targets + i;
+
+		if (ti->type->resume)
+			ti->type->resume(ti);
+	}
+}
+
+
 EXPORT_SYMBOL(dm_get_device);
 EXPORT_SYMBOL(dm_put_device);
 EXPORT_SYMBOL(dm_table_event);

drivers/md/dm.c

@@ -679,6 +679,7 @@ int dm_create(unsigned int minor, struct dm_table *table,
 		free_dev(md);
 		return r;
 	}
+	dm_table_resume_targets(md->map);
 
 	*result = md;
 	return 0;
@@ -693,6 +694,8 @@ void dm_put(struct mapped_device *md)
 {
 	if (atomic_dec_and_test(&md->holders)) {
 		DMWARN("destroying md");
+		if (!test_bit(DMF_SUSPENDED, &md->flags))
+			dm_table_suspend_targets(md->map);
 		__unbind(md);
 		free_dev(md);
 	}
@@ -782,6 +785,7 @@ int dm_suspend(struct mapped_device *md)
 	down_write(&md->lock);
 	remove_wait_queue(&md->wait, &wait);
 	set_bit(DMF_SUSPENDED, &md->flags);
+	dm_table_suspend_targets(md->map);
 	up_write(&md->lock);
 
 	return 0;
@@ -798,6 +802,7 @@ int dm_resume(struct mapped_device *md)
 		return -EINVAL;
 	}
 
+	dm_table_resume_targets(md->map);
 	clear_bit(DMF_SUSPENDED, &md->flags);
 	clear_bit(DMF_BLOCK_IO, &md->flags);
 	def = md->deferred;

drivers/md/dm.h

@@ -104,6 +104,8 @@ unsigned int dm_table_get_num_targets(struct dm_table *t);
 struct list_head *dm_table_get_devices(struct dm_table *t);
 int dm_table_get_mode(struct dm_table *t);
 void dm_table_add_wait_queue(struct dm_table *t, wait_queue_t *wq);
+void dm_table_suspend_targets(struct dm_table *t);
+void dm_table_resume_targets(struct dm_table *t);
 
 /*-----------------------------------------------------------------
  * A registry of target types.

include/linux/device-mapper.h

@@ -33,6 +33,10 @@ typedef void (*dm_dtr_fn) (struct dm_target *ti);
  * > 0: simple remap complete
  */
 typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio);
+
+typedef void (*dm_suspend_fn) (struct dm_target *ti);
+typedef void (*dm_resume_fn) (struct dm_target *ti);
+
 typedef int (*dm_status_fn) (struct dm_target *ti, status_type_t status_type,
 			     char *result, unsigned int maxlen);
 
@@ -56,6 +60,8 @@ struct target_type {
 	dm_ctr_fn ctr;
 	dm_dtr_fn dtr;
 	dm_map_fn map;
+	dm_suspend_fn suspend;
+	dm_resume_fn resume;
 	dm_status_fn status;
 };