On 27/04/17 04:11 PM, Jason Gunthorpe wrote: > On Thu, Apr 27, 2017 at 03:53:37PM -0600, Logan Gunthorpe wrote: > Well, that is in the current form, with more users it would make sense > to optimize for the single page case, eg by providing the existing > call, providing a faster single-page-only variant of the copy, perhaps > even one that is inlined. Ok, does it make sense then to have an sg_copy_page_to_buffer (or some such... I'm having trouble thinking of a sane name that isn't too long). That just does k(un)map_atomic and memcpy? I could try that if it makes sense to people. >> Switching the for_each_sg to sg_miter is probably the nicer solution as >> it takes care of the mapping and the offset/length accounting for you >> and will have similar performance. > > sg_miter will still fail when the sg contains __iomem, however I would > expect that the sg_copy will work with iomem, by using the __iomem > memcpy variant. Yes, that's true. Any sg_miters that ever see iomem will need to be converted to support it. This isn't much different than the other kmap(sg_page()) users I was converting that will also fail if they see iomem. Though, I suspect an sg_miter user would be easier to convert to iomem than a random kmap user. Logan
