Re: [PATCH 1/1] infiniband/mm: convert put_page() to put_user_page*()

Jason Gunthorpe
2019-05-23T17:32:34Z

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@nvidia.com>
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?

Jason