IB/mlx5: Fix implicit MR release flow

yishaih · jgunthorpe · commit f591822c3cf3 · 2019-08-07T15:36:43.000-03:00
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: 81713d3 ("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>
diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
@@ -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));
diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
@@ -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 @@ static int pagefault_mr(struct mlx5_ib_dev *dev, struct mlx5_ib_mr *mr,
 
 out:
 	if (ret == -EAGAIN) {
-		if (implicit || !odp->dying) {
-			unsigned long timeout =
-				msecs_to_jiffies(MMU_NOTIFIER_TIMEOUT);
-
-			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;
+		unsigned long timeout = msecs_to_jiffies(MMU_NOTIFIER_TIMEOUT);
+
+		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);
 		}
 	}
 
