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

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?


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.


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