On Wed, Oct 17, 2018 at 12:43:14AM +0200, Richard Weinberger wrote: > On Mon, Oct 15, 2018 at 8:56 AM Christoph Hellwig <hch@xxxxxx> wrote: > > > > There is no good reason to create a scatterlist in the ubd driver, > > it can just iterate the request directly. > > BTW: Does it make sense to drop blk_rq_map_sq from() > drivers/mtd/ubi/block.c too? > If so we have to allocate a temporary structure for the worker thread > for each segment, just like > UBD does already. I'm not sure if that is cheaper than blk_rq_map_sq(). UBI should not need a new per-thread structure, mostly because there are no threads involved. The scatterlist support in UBI only seems to exists for ubiblock, but it goes down a few layers. In the end all that could switch to a iov_iter-like setup and clean things up a lot, but it would be a fair amount of work.
