Re: [PATCH rdma-next] RDMA/rxe: Break endless pagefault loop for RO pages

[Leon Romanovsky <leon@kernel.org>]

On Thu, May 22, 2025 at 04:37:16PM +0300, Leon Romanovsky wrote:
> On Thu, May 22, 2025 at 10:29:02PM +0900, Daisuke Matsuda wrote:
> > 
> > On 2025/05/22 20:36, Leon Romanovsky wrote:
> > > From: Leon Romanovsky <leonro@nvidia.com>
> > > 
> > > RO pages has "perm" equal to 0, that caused to the situation
> > > where such pages were marked as needed to have fault and caused
> > > to infinite loop.
> > > 
> > > Fixes: eedd5b1276e7 ("RDMA/umem: Store ODP access mask information in PFN")
> > > Reported-by: Daisuke Matsuda <dskmtsd@gmail.com>
> > > Closes: https://lore.kernel.org/all/3e8f343f-7d66-4f7a-9f08-3910623e322f@gmail.com
> > > Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> > 
> > Tested-by: Daisuke Matsuda <dskmtsd@gmail.com>
> > 
> > Thank you!
> > This change fixes one of the two issues I reported.
> > The kernel module does not get stuck in rxe_ib_invalidate_range() anymore.
> > 
> > 
> > The remaining one is the stuck issue in uverbs_destroy_ufile_hw().
> > cf. https://lore.kernel.org/all/3e8f343f-7d66-4f7a-9f08-3910623e322f@gmail.com/
> 
> Thanks, I updated the link to point to https://lore.kernel.org/all/3016329a-4edd-4550-862f-b298a1b79a39@gmail.com/
> 
> > 
> > The issue occurs with test_odp_async_prefetch_rc_traffic, which is not yet
> > enabled in rxe. It might indicate that the root cause lies in ib_uverbs layer.
> 
> Unlikely, up till now, it indicated that driver didn't release some
> uverb object.

BTW, all places in RXE driver which do the following:
page = hmm_pfn_to_page(umem_odp->map.pfn_list[index]);
if (!page) {
...

are incorrect, hmm_pfn_to_page() will always return something.

Thanks