Okay thanks! So does this mean that you would suggest doing it with
bvec_kmap_local()?
Or are there other, maybe better, methods?
Thanks!
On 18/04/2022 04:59, Jens Axboe wrote:
On 4/14/22 8:15 AM, Jasper Surmont wrote:
I'm writing a device mapper target, and on a bio (read) request I want
to access (for example just logging) the data that was just read (by
providing a callback to bio->bio_end_io).
I've figured out I could read the data by using bvec_kmap_local() on
each bio_vec to get a pointer to the data. However, if my
understanding is correct this seems like an unefficient way: if the
bio just finished a read then shouldn't the data already be mapped
somewhere? If so, where?
Not necessarily - if you're doing passthrough or O_DIRECT IO, then
no mapping necessarily exists for any part of the IO.
