Jens Axboe <jens.axboe@xxxxxxxxxx> writes:
> On Thu, Jun 11 2009, Kiyoshi Ueda wrote:
>> Hi Jens,
>>
>> This patch adds the following 2 interfaces for request-stacking drivers:
>>
>> - blk_rq_prep_clone(struct request *clone, struct request *orig,
>> struct bio_set *bs, gfp_t gfp_mask,
>> int (*bio_ctr)(struct bio *, struct bio*, void *),
>> void *data)
>> * Clones bios in the original request to the clone request
>> (bio_ctr is called for each cloned bios.)
>> * Copies attributes of the original request to the clone request.
>> The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not
>> copied.
>>
>> - blk_rq_unprep_clone(struct request *clone)
>> * Frees cloned bios from the clone request.
>>
>> Request stacking drivers (e.g. request-based dm) need to make a clone
>> request for a submitted request and dispatch it to other devices.
>>
>> To allocate request for the clone, request stacking drivers may not
>> be able to use blk_get_request() because the allocation may be done
>> in an irq-disabled context.
>> So blk_rq_prep_clone() takes a request allocated by the caller
>> as an argument.
>>
>> For each clone bio in the clone request, request stacking drivers
>> should be able to set up their own completion handler.
>> So blk_rq_prep_clone() takes a callback function which is called
>> for each clone bio, and a pointer for private data which is passed
>> to the callback.
>>
>> NOTE:
>> blk_rq_prep_clone() doesn't copy any actual data of the original
>> request. Pages are shared between original bios and cloned bios.
>> So caller must not complete the original request before the clone
>> request.
>
> This looks good to me now, I've applied it.
Is blk_rq_unprep_clone really the best name?
^^^^^^
Cheers,
Jeff
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