* Re: [PATCH, RFC] ubd: remove use of blk_rq_map_sg [not found] <20181015065637.1860-1-hch@lst.de> @ 2018-10-16 22:43 ` Richard Weinberger 2018-10-17 6:14 ` Christoph Hellwig 0 siblings, 1 reply; 2+ messages in thread From: Richard Weinberger @ 2018-10-16 22:43 UTC (permalink / raw) To: Christoph Hellwig Cc: Richard Weinberger, Jens Axboe, linux-block, linux-um, linux-mtd @ lists . infradead . org On Mon, Oct 15, 2018 at 8:56 AM Christoph Hellwig <hch@lst.de> 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(). -- Thanks, //richard ^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH, RFC] ubd: remove use of blk_rq_map_sg 2018-10-16 22:43 ` [PATCH, RFC] ubd: remove use of blk_rq_map_sg Richard Weinberger @ 2018-10-17 6:14 ` Christoph Hellwig 0 siblings, 0 replies; 2+ messages in thread From: Christoph Hellwig @ 2018-10-17 6:14 UTC (permalink / raw) To: Richard Weinberger Cc: Christoph Hellwig, Richard Weinberger, Jens Axboe, linux-block, linux-um, linux-mtd @ lists . infradead . org 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@lst.de> 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. ^ permalink raw reply [flat|nested] 2+ messages in thread
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2018-10-16 22:43 ` [PATCH, RFC] ubd: remove use of blk_rq_map_sg Richard Weinberger
2018-10-17 6:14 ` Christoph Hellwig
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