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Subject[PATCH AUTOSEL 5.2 23/44] IB/mlx5: Fix implicit MR release flow
Date
From: Yishai Hadas <yishaih@mellanox.com>

[ Upstream commit f591822c3cf314442819486f45ff7dc1f690e0c0 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/infiniband/core/umem_odp.c | 4 ----
drivers/infiniband/hw/mlx5/odp.c | 24 +++++++++---------------
2 files changed, 9 insertions(+), 19 deletions(-)

diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
index e4b13a32692a9..5e5f7dd82c50d 100644
--- a/drivers/infiniband/core/umem_odp.c
+++ b/drivers/infiniband/core/umem_odp.c
@@ -114,10 +114,6 @@ 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->context->invalidate_range(umem_odp, ib_umem_start(umem),
ib_umem_end(umem));
diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index 91507a2e92900..d711f3e31fa74 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -581,7 +581,6 @@ 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;
@@ -596,7 +595,6 @@ 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;
}
@@ -684,19 +682,15 @@ 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);
}
}

--
2.20.1
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