On Thu, May 23, 2019 at 10:46:38AM -0700, John Hubbard wrote: > On 5/23/19 10:32 AM, Jason Gunthorpe wrote: > > On Thu, May 23, 2019 at 10:28:52AM -0700, Ira Weiny wrote: > > > > @@ -686,8 +686,8 @@ int ib_umem_odp_map_dma_pages(struct ib_umem_odp *umem_odp, u64 user_virt, > > > > * ib_umem_odp_map_dma_single_page(). > > > > */ > > > > if (npages - (j + 1) > 0) > > > > - release_pages(&local_page_list[j+1], > > > > - npages - (j + 1)); > > > > + put_user_pages(&local_page_list[j+1], > > > > + npages - (j + 1)); > > > > > > I don't know if we discussed this before but it looks like the use of > > > release_pages() was not entirely correct (or at least not necessary) here. So > > > I think this is ok. > > > > Oh? John switched it from a put_pages loop to release_pages() here: > > > > commit 75a3e6a3c129cddcc683538d8702c6ef998ec589 > > Author: John Hubbard <jhubbard@xxxxxxxxxx> > > Date: Mon Mar 4 11:46:45 2019 -0800 > > > > RDMA/umem: minor bug fix in error handling path > > 1. Bug fix: fix an off by one error in the code that cleans up if it fails > > to dma-map a page, after having done a get_user_pages_remote() on a > > range of pages. > > 2. Refinement: for that same cleanup code, release_pages() is better than > > put_page() in a loop. > > > > And now we are going to back something called put_pages() that > > implements the same for loop the above removed? > > > > Seems like we are going in circles?? John? > > > > put_user_pages() is meant to be a drop-in replacement for release_pages(), > so I made the above change as an interim step in moving the callsite from > a loop, to a single call. > > And at some point, it may be possible to find a way to optimize put_user_pages() > in a similar way to the batching that release_pages() does, that was part > of the plan for this. > > But I do see what you mean: in the interim, maybe put_user_pages() should > just be calling release_pages(), how does that change sound? It would have made it more consistent.. But it seems this isn't a functional problem in this patch Jason
