[PATCH for-rc 2/2] IB/mlx5: Fix how advise_mr() launches async work

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From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>

Work must hold a kref on the ib_device otherwise the dev pointer can
become free before the work runs.

Remove the bogus use of 'reg_state':
 - While in uverbs the reg_state is guaranteed to always be
   REGISTERED
 - Testing reg_state with no locking is bogus. Use ib_device_try_get()
   to get back into a region that prevents unregistration.

Fixes: 813e90b1aeaa ("IB/mlx5: Add advise_mr() support")
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
---
 drivers/infiniband/hw/mlx5/odp.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index 8d46b1dc56580f..a241a65834d4ca 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -1595,10 +1595,12 @@ static void mlx5_ib_prefetch_mr_work(struct work_struct *work)
 	struct prefetch_mr_work *w =
 		container_of(work, struct prefetch_mr_work, work);
 
-	if (w->dev->ib_dev.reg_state == IB_DEV_REGISTERED)
+	if (ib_device_try_get(&w->dev->ib_dev)) {
 		mlx5_ib_prefetch_sg_list(w->dev, w->pf_flags, w->sg_list,
 					 w->num_sge);
-
+		ib_device_put(&w->dev->ib_dev);
+	}
+	put_device(&w->dev->ib_dev.dev);
 	kfree(w);
 }
 
@@ -1617,15 +1619,13 @@ int mlx5_ib_advise_mr_prefetch(struct ib_pd *pd,
 		return mlx5_ib_prefetch_sg_list(dev, pf_flags, sg_list,
 						num_sge);
 
-	if (dev->ib_dev.reg_state != IB_DEV_REGISTERED)
-		return -ENODEV;
-
 	work = kvzalloc(struct_size(work, sg_list, num_sge), GFP_KERNEL);
 	if (!work)
 		return -ENOMEM;
 
 	memcpy(work->sg_list, sg_list, num_sge * sizeof(struct ib_sge));
 
+	get_device(&dev->ib_dev.dev);
 	work->dev = dev;
 	work->pf_flags = pf_flags;
 	work->num_sge = num_sge;
-- 
2.20.1




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