Commit f591822c authored Aug 05, 2019 by Yishai Hadas Committed by Jason Gunthorpe Aug 07, 2019

IB/mlx5: Fix implicit MR release flow

Once implicit MR is being called to be released by
ib_umem_notifier_release() its leaves were marked as "dying".

However, when dereg_mr()->mlx5_ib_free_implicit_mr()->mr_leaf_free() is
called, it skips running the mr_leaf_free_action (i.e. umem_odp->work)
when those leaves were marked as "dying".

As such ib_umem_release() for the leaves won't be called and their MRs
will be leaked as well.

When an application exits/killed without calling dereg_mr we might hit the
above flow.

This fatal scenario is reported by WARN_ON() upon
mlx5_ib_dealloc_ucontext() as ibcontext->per_mm_list is not empty, the
call trace can be seen below.

Originally the "dying" mark as part of ib_umem_notifier_release() was
introduced to prevent pagefault_mr() from returning a success response
once this happened. However, we already have today the completion
mechanism so no need for that in those flows any more.  Even in case a
success response will be returned the firmware will not find the pages and
an error will be returned in the following call as a released mm will
cause ib_umem_odp_map_dma_pages() to permanently fail mmget_not_zero().

Fix the above issue by dropping the "dying" from the above flows.  The
other flows that are using "dying" are still needed it for their
synchronization purposes.

   WARNING: CPU: 1 PID: 7218 at
   drivers/infiniband/hw/mlx5/main.c:2004
		  mlx5_ib_dealloc_ucontext+0x84/0x90 [mlx5_ib]
   CPU: 1 PID: 7218 Comm: ibv_rc_pingpong Tainted: G     E
	       5.2.0-rc6+ #13
   Call Trace:
   uverbs_destroy_ufile_hw+0xb5/0x120 [ib_uverbs]
   ib_uverbs_close+0x1f/0x80 [ib_uverbs]
   __fput+0xbe/0x250
   task_work_run+0x88/0xa0
   do_exit+0x2cb/0xc30
   ? __fput+0x14b/0x250
   do_group_exit+0x39/0xb0
   get_signal+0x191/0x920
   ? _raw_spin_unlock_bh+0xa/0x20
   ? inet_csk_accept+0x229/0x2f0
   do_signal+0x36/0x5e0
   ? put_unused_fd+0x5b/0x70
   ? __sys_accept4+0x1a6/0x1e0
   ? inet_hash+0x35/0x40
   ? release_sock+0x43/0x90
   ? _raw_spin_unlock_bh+0xa/0x20
   ? inet_listen+0x9f/0x120
   exit_to_usermode_loop+0x5c/0xc6
   do_syscall_64+0x182/0x1b0
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 81713d37 ("IB/mlx5: Add implicit MR support")
Link: https://lore.kernel.org/r/20190805083010.21777-1-leon@kernel.org


Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Reviewed-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

parent e21a712a

drivers/infiniband/core/umem_odp.c

+0 −4

Original line number	Diff line number	Diff line
		@@ -112,10 +112,6 @@ static int ib_umem_notifier_release_trampoline(struct ib_umem_odp *umem_odp,
		* prevent any further fault handling on this MR.
		*/
		ib_umem_notifier_start_account(umem_odp);
		umem_odp->dying = 1;
		/* Make sure that the fact the umem is dying is out before we release
		* all pending page faults. */
		smp_wmb();
		complete_all(&umem_odp->notifier_completion);
		umem_odp->umem.context->invalidate_range(
		umem_odp, ib_umem_start(umem_odp), ib_umem_end(umem_odp));

drivers/infiniband/hw/mlx5/odp.c

+9 −15

Original line number	Diff line number	Diff line
		@@ -579,7 +579,6 @@ static int pagefault_mr(struct mlx5_ib_dev dev, struct mlx5_ib_mr mr,
		u32 flags)
		{
		int npages = 0, current_seq, page_shift, ret, np;
		bool implicit = false;
		struct ib_umem_odp *odp_mr = to_ib_umem_odp(mr->umem);
		bool downgrade = flags & MLX5_PF_FLAGS_DOWNGRADE;
		bool prefetch = flags & MLX5_PF_FLAGS_PREFETCH;
		@@ -594,7 +593,6 @@ static int pagefault_mr(struct mlx5_ib_dev dev, struct mlx5_ib_mr mr,
		if (IS_ERR(odp))
		return PTR_ERR(odp);
		mr = odp->private;
		implicit = true;
		} else {
		odp = odp_mr;
		}
		@@ -682,19 +680,15 @@ next_mr:

		out:
		if (ret == -EAGAIN) {
		if (implicit \|\| !odp->dying) {
		unsigned long timeout =
		msecs_to_jiffies(MMU_NOTIFIER_TIMEOUT);
		unsigned long timeout = msecs_to_jiffies(MMU_NOTIFIER_TIMEOUT);

		if (!wait_for_completion_timeout(
		&odp->notifier_completion,
		if (!wait_for_completion_timeout(&odp->notifier_completion,
		timeout)) {
		mlx5_ib_warn(dev, "timeout waiting for mmu notifier. seq %d against %d. notifiers_count=%d\n",
		current_seq, odp->notifiers_seq, odp->notifiers_count);
		}
		} else {
		/* The MR is being killed, kill the QP as well. */
		ret = -EFAULT;
		mlx5_ib_warn(
		dev,
		"timeout waiting for mmu notifier. seq %d against %d. notifiers_count=%d\n",
		current_seq, odp->notifiers_seq,
		odp->notifiers_count);
		}
		}

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