netdev - Re: [PATCH] RDMA: Add rdma_connect

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Date:   Mon, 26 Oct 2020 09:01:20 -0700
From:   santosh.shilimkar@...cle.com
To:     Jason Gunthorpe <jgg@...dia.com>,
        Danil Kipnis <danil.kipnis@...ud.ionos.com>,
        Doug Ledford <dledford@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Jack Wang <jinpu.wang@...ud.ionos.com>,
        Keith Busch <kbusch@...nel.org>,
        linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
        Max Gurtovoy <mgurtovoy@...dia.com>, netdev@...r.kernel.org,
        rds-devel@....oracle.com, Sagi Grimberg <sagi@...mberg.me>
Cc:     Guoqing Jiang <guoqing.jiang@...ud.ionos.com>,
        Leon Romanovsky <leonro@...dia.com>
Subject: Re: [PATCH] RDMA: Add rdma_connect_locked()



On 10/26/20 7:25 AM, Jason Gunthorpe wrote:
> There are two flows for handling RDMA_CM_EVENT_ROUTE_RESOLVED, either the
> handler triggers a completion and another thread does rdma_connect() or
> the handler directly calls rdma_connect().
> 
> In all cases rdma_connect() needs to hold the handler_mutex, but when
> handler's are invoked this is already held by the core code. This causes
> ULPs using the 2nd method to deadlock.
> 
> Provide a rdma_connect_locked() and have all ULPs call it from their
> handlers.
> 
> Reported-by: Guoqing Jiang <guoqing.jiang@...ud.ionos.com>
> Fixes: 2a7cec538169 ("RDMA/cma: Fix locking for the RDMA_CM_CONNECT state"
> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
> ---

[....]

> diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c
> index 06603dd1c8aa38..b36b60668b1da9 100644
> --- a/net/rds/ib_cm.c
> +++ b/net/rds/ib_cm.c
> @@ -956,9 +956,10 @@ int rds_ib_cm_initiate_connect(struct rdma_cm_id *cm_id, bool isv6)
>   	rds_ib_cm_fill_conn_param(conn, &conn_param, &dp,
>   				  conn->c_proposed_version,
>   				  UINT_MAX, UINT_MAX, isv6);
> -	ret = rdma_connect(cm_id, &conn_param);
> +	ret = rdma_connect_locked(cm_id, &conn_param);
>   	if (ret)
> -		rds_ib_conn_error(conn, "rdma_connect failed (%d)\n", ret);
> +		rds_ib_conn_error(conn, "rdma_connect_locked failed (%d)\n",
> +				  ret);
>   
>   out:
>   	/* Beware - returning non-zero tells the rdma_cm to destroy
> 
For RDS part,
Acked-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>