[lustre-devel] [PATCH v2 07/29] lustre: obd: collect all resource releasing for obj_type.

James Simmons jsimmons at infradead.org
Wed May 22 11:51:57 PDT 2019

>>  int class_register_type(struct obd_ops *dt_ops, struct md_ops *md_ops,
>> @@ -181,10 +163,17 @@ int class_register_type(struct obd_ops *dt_ops, 
>struct md_ops *md_ops,
>>  		return -EEXIST;
>>  	}
>> -	rc = -ENOMEM;
>>  	type = kzalloc(sizeof(*type), GFP_NOFS);
>>  	if (!type)
>> -		return rc;
>> +		return -ENOMEM;
>> +
>> +	type->typ_kobj.kset = lustre_kset;
>> +	rc = kobject_init_and_add(&type->typ_kobj, &class_ktype,
>> +				  &lustre_kset->kobj, "%s", name);
>I don't know that I would actually cause a problem, but I don't like
>"add"ing and object (above) before fully initializing it (below).  So
>I've kept the split from my version where kobject_init() happens early
>and kobject_add() happens later.
>I've included the other changes that you made.

The reason I did it that way was to handle the server case down the road.
So for the case when both client and server are on the same node, and yes
people do such setups for testing this is important.

Consider the case we have both the lov and lod layer on a single node. 
Both layers attempt to create "lov" obd_type. When the lov module loads 
first then a complete obd_type is created. Once lod loads then it just 
uses real lov obd_type and creates the needed symlinks. You end up with

ls -al /sys/fs/lustre/lov/
total 0
drwxr-xr-x  2 root root 0 May 22 14:27 .
drwxr-xr-x 14 root root 0 May 22 14:27 ..
lrwxrwxrwx  1 root root 0 May 22 14:27 lustre-MDT0000-mdtlov -> 
lrwxrwxrwx  1 root root 0 May 22 14:27 lustre-MDT0002-mdtlov -> 

Plus the real lov obd devices.

Now if lod loads first then the lod module creates a "lov" obd_type
using class_create_symlink() but is not fully initialized nor does
it need to be. If the client lov module is present and it loads then
it takes the "lov" obd_type create by the lod and finishes initializing

Looking at the final code and added in server case:

        type = class_search_type(name);
        if (type) {
		if (strcmp(name, LUSTRE_LOV_NAME) == 0 ||
                    strcmp(name, LUSTRE_OSC_NAME) == 0)
                        goto dir_exist;
		CDEBUG(D_IOCTL, "Type %s already registered\n", name);
                return -EEXIST;

        type = kzalloc(sizeof(*type), GFP_NOFS);
        if (!type)
                return rc;

        type->typ_kobj.kset = lustre_kset;
        kobject_init(&type->typ_kobj, &class_ktype);

        type->typ_dt_ops = dt_ops;  /* lov obd_type is never set to the 
				     * correct values if lod created it.
        type->typ_md_ops = md_ops;

        rc = kobject_add(&type->typ_kobj, &lustre_kset->kobj, "%s", name);
        if (rc)
                goto failed;

        type->typ_debugfs_entry = debugfs_create_dir(type->typ_name,

Now if this needed for the later module handling patches I guess we could

	if (strcmp(name, LUSTRE_LOV_NAME) == 0 ||
            strcmp(name, LUSTRE_OSC_NAME) == 0) {
		type->typ_dt_ops = dt_ops;
		type->typ_md_ops = md_ops;
		goto dir_exist;

Is that the case?

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