Commit 46870b23 authored by Jason Gunthorpe's avatar Jason Gunthorpe
Browse files

RDMA/odp: Remove broken debugging call to invalidate_range 

invalidate_range() also obtains the umem_mutex which is being held at this
point, so if this path were was ever called it would deadlock. Thus
conclude the debugging never triggers and rework it into a simple WARN_ON
and leave things as they are.

While here add a note to explain how we could possibly get inconsistent
page pointers.

Link: https://lore.kernel.org/r/20191009160934.3143-16-jgg@ziepe.ca


Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
parent 09689703

drivers/infiniband/core/umem_odp.c

+19 −19
Original line number Diff line number Diff line
@@ -508,7 +508,6 @@ static int ib_umem_odp_map_dma_single_page( 
{

	struct ib_device *dev = umem_odp->umem.ibdev;

	dma_addr_t dma_addr;

	int remove_existing_mapping = 0;

	int ret = 0;



	/*
@@ -534,28 +533,29 @@ static int ib_umem_odp_map_dma_single_page( 
	} else if (umem_odp->page_list[page_index] == page) {

		umem_odp->dma_list[page_index] |= access_mask;

	} else {

		pr_err("error: got different pages in IB device and from get_user_pages. IB device page: %p, gup page: %p\n",

		/*

		 * This is a race here where we could have done:

		 *

		 *         CPU0                             CPU1

		 *   get_user_pages()

		 *                                       invalidate()

		 *                                       page_fault()

		 *   mutex_lock(umem_mutex)

		 *    page from GUP != page in ODP

		 *

		 * It should be prevented by the retry test above as reading

		 * the seq number should be reliable under the

		 * umem_mutex. Thus something is really not working right if

		 * things get here.

		 */

		WARN(true,

		     "Got different pages in IB device and from get_user_pages. IB device page: %p, gup page: %p\n",

		     umem_odp->page_list[page_index], page);

		/* Better remove the mapping now, to prevent any further

		 * damage. */

		remove_existing_mapping = 1;

		ret = -EAGAIN;

	}



out:

	put_user_page(page);



	if (remove_existing_mapping) {

		ib_umem_notifier_start_account(umem_odp);

		dev->ops.invalidate_range(

			umem_odp,

			ib_umem_start(umem_odp) +

				(page_index << umem_odp->page_shift),

			ib_umem_start(umem_odp) +

				((page_index + 1) << umem_odp->page_shift));

		ib_umem_notifier_end_account(umem_odp);

		ret = -EAGAIN;

	}



	return ret;

}

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