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Date:   Thu, 3 Sep 2020 13:21:48 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Leon Romanovsky <leon@kernel.org>
CC:     Doug Ledford <dledford@redhat.com>,
        Leon Romanovsky <leonro@mellanox.com>,
        <linux-rdma@vger.kernel.org>
Subject: Re: [PATCH rdma-next v1 13/13] RDMA/restrack: Drop valid restrack
 field as source of ambiguity
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References: <20200830101436.108487-1-leon@kernel.org>
 <20200830101436.108487-14-leon@kernel.org>
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On Sun, Aug 30, 2020 at 01:14:36PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@mellanox.com>
> 
> The valid field was needed to distinguish between supported/not
> supported QPs, after the create_qp was changed to support all types,
> that field can be dropped and the code simplified a little bit.
> 
> Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
>  drivers/infiniband/core/restrack.c | 29 ++++++++---------------------
>  include/rdma/restrack.h            |  9 ---------
>  2 files changed, 8 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/infiniband/core/restrack.c b/drivers/infiniband/core/restrack.c
> index 4caaa6312105..fb5345c8bd89 100644
> +++ b/drivers/infiniband/core/restrack.c
> @@ -143,7 +143,7 @@ static struct ib_device *res_to_dev(struct rdma_restrack_entry *res)
>  		return container_of(res, struct rdma_counter, res)->device;
>  	default:
>  		WARN_ONCE(true, "Wrong resource tracking type %u\n", res->type);
> -		return NULL;
> +		return ERR_PTR(-EINVAL);
>  	}
>  }
>  
> @@ -223,7 +223,7 @@ int __must_check rdma_restrack_add(struct rdma_restrack_entry *res)
>  	struct rdma_restrack_root *rt;
>  	int ret = 0;
>  
> -	if (!dev)
> +	if (IS_ERR_OR_NULL(dev))
>  		return -ENODEV;
>  
>  	if (res->no_track)
> @@ -261,10 +261,7 @@ int __must_check rdma_restrack_add(struct rdma_restrack_entry *res)
>  	}
>  
>  out:
> -	if (ret)
> -		return ret;
> -	res->valid = true;
> -	return 0;
> +	return ret;
>  }
>  EXPORT_SYMBOL(rdma_restrack_add);
>  
> @@ -323,25 +320,16 @@ EXPORT_SYMBOL(rdma_restrack_put);
>   */
>  void rdma_restrack_del(struct rdma_restrack_entry *res)
>  {
> +	struct ib_device *dev = res_to_dev(res);
>  	struct rdma_restrack_entry *old;
>  	struct rdma_restrack_root *rt;
> -	struct ib_device *dev;
>  
> -	if (!res->valid) {
> -		if (res->task) {
> -			put_task_struct(res->task);
> -			res->task = NULL;
> -		}
> -		return;
> -	}
> -
> -	if (res->no_track)
> +	WARN_ONCE(!dev && res->type != RDMA_RESTRACK_CM_ID,
> +		  "IB device should be set for restrack type %s",
> +		  type2str(res->type));
> +	if (res->no_track || IS_ERR_OR_NULL(dev))
>  		goto out;
>
> -	dev = res_to_dev(res);
> -	if (WARN_ON(!dev))
> -		return;
> -
>  	rt = &dev->res[res->type];
>  	old = xa_erase(&rt->xa, res->id);

How does this work without valid?

xa_alloc is called in rdma_restrack_add() and previously it was safe
to call res_track_del() on unadded things.

Now there are problems, like __ib_alloc_cq_user() does calls
restrack_del without doing restrack_ad()

> @@ -351,7 +339,6 @@ void rdma_restrack_del(struct rdma_restrack_entry *res)
>  	WARN_ON(old != res);

So this WARN_ON should trigger?

I don't think this can escape a bit that says that id is in the
xarray.

I'd say no_track is a flag to add to rdma_restrack_add(), not a bit in
the struct. The bit in the struct is 'valid' aka
'added_to_xarray'. The no_track flag simply doesn't set valid.

Jason