Re: [PATCH] drivers/scsi/st.c: add reference count and related fixes

[Brian King <brking@us.ibm.com>]

Kai Makisara wrote:
>>The primary change is adding a kref to the Scsi_Tape structure, to avoid
>>an oops when the tape drive is removed while open. This includes
>>scsi_tape_get/put routines and scsi_tape_release, and changes to st_open
>>and st_release. This is all based on the SCSI disk & CD reference
>>counting code.
>>
> 
> You have added a new kref for this. Have you considered using the 
> existing cdev refcounting instead of a separate kref?
> 
> (When the new character device code was introduced, I got the impression 
> that the proper way for the st would be to embed the struct into struct 
> scsi_tape and make the destructor. The scsi_tapes[] array would not be 
> necessary any more because the struct scsi_tape would be accessible through 
> containerof(inode->i_cdev, struct scsi_tape, cdev).
> (An array would be still necessary for tape number allocation.)
> I did not implement this at that time because there was no real need for 
> the change and it seemed too complex to test just for fun.)

I'm not sure how you would do this since there is currently no way to
embed data in a cdev. Also, since there are multiple cdevs per scsi_tape,
it seems cleaner to use a new kref.


-- 
Brian King
eServer Storage I/O
IBM Linux Technology Center