dm: consolidate target deregistration error handling

Change dm_unregister_target to return void and use BUG() for error
reporting.

dm_unregister_target can only fail because of programming bug in the
target driver. It can't fail because of user's behavior or disk errors.

This patch changes unregister_target to return void and use BUG if
someone tries to unregister non-registered target or unregister target
that is in use.

This patch removes code duplication (testing of error codes in all dm
targets) and reports bugs in just one place, in dm_unregister_target. In
some target drivers, these return codes were ignored, which could lead
to a situation where bugs could be missed.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 7 insertions, 8 deletions

diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
index 835cf95b857f..7decf10006e4 100644
--- a/drivers/md/dm-target.c
+++ b/drivers/md/dm-target.c
@@ -130,26 +130,26 @@ int dm_register_target(struct target_type *t)
         return rv;
 }
 
-int dm_unregister_target(struct target_type *t)
+void dm_unregister_target(struct target_type *t)
 {
         struct tt_internal *ti;
 
         down_write(&_lock);
         if (!(ti = __find_target_type(t->name))) {
-                up_write(&_lock);
-                return -EINVAL;
+                DMCRIT("Unregistering unrecognised target: %s", t->name);
+                BUG();
         }
 
         if (ti->use) {
-                up_write(&_lock);
-                return -ETXTBSY;
+                DMCRIT("Attempt to unregister target still in use: %s",
+                       t->name);
+                BUG();
         }
 
         list_del(&ti->list);
         kfree(ti);
 
         up_write(&_lock);
-        return 0;
 }
 
 /*
@@ -187,8 +187,7 @@ int __init dm_target_init(void)
 
 void dm_target_exit(void)
 {
-        if (dm_unregister_target(&error_target))
-                DMWARN("error target unregistration failed");
+        dm_unregister_target(&error_target);
 }
 
 EXPORT_SYMBOL(dm_register_target);