dm: replace -EEXIST with -EBUSY

[ Upstream commit b13ef36 ]

The -EEXIST error code is reserved by the module loading infrastructure
to indicate that a module is already loaded. When a module's init
function returns -EEXIST, userspace tools like kmod interpret this as
"module already loaded" and treat the operation as successful, returning
0 to the user even though the module initialization actually failed.

This follows the precedent set by commit 54416fd ("netfilter:
conntrack: helper: Replace -EEXIST by -EBUSY") which fixed the same
issue in nf_conntrack_helper_register().

Affected modules:
  * dm_cache dm_clone dm_integrity dm_mirror dm_multipath dm_pcache
  * dm_vdo dm-ps-round-robin dm_historical_service_time dm_io_affinity
  * dm_queue_length dm_service_time dm_snapshot

Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: dagomez137

drivers/md/dm-exception-store.c

@@ -116,7 +116,7 @@ int dm_exception_store_type_register(struct dm_exception_store_type *type)
 	if (!__find_exception_store_type(type->name))
 		list_add(&type->list, &_exception_store_types);
 	else
-		r = -EEXIST;
+		r = -EBUSY;
 	spin_unlock(&_lock);
 
 	return r;

drivers/md/dm-log.c

@@ -121,7 +121,7 @@ int dm_dirty_log_type_register(struct dm_dirty_log_type *type)
 	if (!__find_dirty_log_type(type->name))
 		list_add(&type->list, &_log_types);
 	else
-		r = -EEXIST;
+		r = -EBUSY;
 	spin_unlock(&_lock);
 
 	return r;

drivers/md/dm-path-selector.c

@@ -107,7 +107,7 @@ int dm_register_path_selector(struct path_selector_type *pst)
 
 	if (__find_path_selector_type(pst->name)) {
 		kfree(psi);
-		r = -EEXIST;
+		r = -EBUSY;
 	} else
 		list_add(&psi->list, &_path_selectors);
 

drivers/md/dm-target.c

@@ -88,7 +88,7 @@ int dm_register_target(struct target_type *tt)
 	if (__find_target_type(tt->name)) {
 		DMERR("%s: '%s' target already registered",
 		      __func__, tt->name);
-		rv = -EEXIST;
+		rv = -EBUSY;
 	} else {
 		list_add(&tt->list, &_targets);
 	}