[dm-devel] questions about device-mappers XXXX-map funtion()

[Jon Bendtsen]

Kevin Corry wrote:
> On Sunday 07 September 2003 06:31, Jon Bendtsen wrote:
> 
>>Me and a friend are trying to built encryption into LVM2, and are
>>currently in the process of making a dm-crypt mapping target.
>>(it is also a university project).
>>
>>We copy a bio, not cloning. After this we encrypt the data in the bio,
>>bio_data(), and use submit_bio() to store it at the disk. But the
>>original bio are still written to disk, so we are looking for a way
>>to cancel the writing of this original bio?
> 
> 
> Jon,
> 
> What is your map function returning? If you return 1, then DM will assume you 
> simply adjusted the bi_sector and bi_dev fields, and it will continue 
> submitting the request to the lower-level device. If you return 0, DM assumes 
> your target module is taking ownership of the bio, and does not perform any 
> additional processing on that bio. In this case your code will be responsible 
> for either submitting that bio, or eventually calling bio_endio() on the bio.

Thanks we'll try that.



JonB