configfs issues

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Hi all,

I've got some issues with using configfs in my module. The problem I ran into could be solved if configfs_group_operations->drop_item() would allow returning an error code. But I'll try to explain...

(1)
Say the user creates one object, let's say as objects/myobj1/. This object is dependent on some (shared) parameters which the user created under params/myparams1/. Now while myobj1/ is 'active', I don't want to let the user remove myparams1/. I can prevent this by making the user create a symlink(2) in the objects/myobj1/ directory to myparams1/, i.e. objects/myobj1/params/ -> ../../params/myparams1/, to denote its use. Now - if I have read the documentation correctly - the user cannot remove myparams1/ without removing the params/ link first. So fine, so good.

(2)
Next the user may create several objects which may be dependent on several params objects. Now I can solve this by creating a default group for each object, i.e. on myobj1 creation there is objects/myobj1/params/ automatically. In that directory the user may create symlink(2)s to several params/*/ dirs. Fine again.

(3)
Now what I want is the list of params an object uses to be an ordered list. I cannot do this because there is no intrinsic order in a filesystem. I can get the order by instead having an attribute called param_list which contains the ordered list of all params to use, e.g.
> cat param_list
 myparams2
 myparams4
 myparams1
However, this way I don't have any way to prevent the user from removing params because configfs_group_operations->drop_item() is void and does not allow me to return an error.

Question now: Do you think, ->drop_item() should be changed to allow returning an error? If not, what do you think would be an appropriate solution for the problem? (One solution would be that I trace back every object that uses the params to get dropped, and delete the according params entry from the object's params_list automatically... another would be, that I keep a reference on each params used, so they are deleted only from configfs but not from memory on removal, and rename the list entries to <removed> or whatever... both ideas I don't like too much.)

Thank you for any feedback!!!

PS: Please CC me on your replies, I'm not a LKML subscriber.
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