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: 81713d3788d2 ("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
index 2a75c6f..c0e15db 100644 (file)
--- 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
index 81da820..1d257d1 100644 (file)
--- 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 @@ next_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);
                }
        }