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?
thanks,
--
John Hubbard
NVIDIA
