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From:   ronnie sahlberg <ronniesahlberg@gmail.com>
Date:   Sat, 31 Mar 2018 08:23:48 +1000
Message-ID: <CAN05THTrte19yRdyAOHvcjhxmOW=auh=z5nvVXsqcLxbmYn7Dg@mail.gmail.com>
Subject: Re: [PATCH 1/2] cifs: smbd: avoid reconnect lockup
To:     Long Li <longli@microsoft.com>
Cc:     Steve French <sfrench@samba.org>,
        linux-cifs <linux-cifs@vger.kernel.org>,
        "samba-technical@lists.samba.org" <samba-technical@lists.samba.org>,
        LKML <linux-kernel@vger.kernel.org>
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Looks good to me (both patches)

Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

On Sat, Mar 31, 2018 at 8:16 AM, Long Li <longli@linuxonhyperv.com> wrote:
> From: Long Li <longli@microsoft.com>
>
> During transport reconnect, other processes may have registered memory
> and blocked on transport. This creates a deadlock situation because the
> transport resources can't be freed, and reconnect is blocked.
>
> Fix this by returning to upper layer on timeout. Before returning,
> transport status is set to reconnecting so other processes will release
> memory registration resources.
>
> Upper layer will retry the reconnect. This is not in fast I/O path so
> setting the timeout to 5 seconds.
>
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>  fs/cifs/smbdirect.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
> index 5aa0b54..3f7883e 100644
> --- a/fs/cifs/smbdirect.c
> +++ b/fs/cifs/smbdirect.c
> @@ -1498,8 +1498,8 @@ int smbd_reconnect(struct TCP_Server_Info *server)
>         log_rdma_event(INFO, "reconnecting rdma session\n");
>
>         if (!server->smbd_conn) {
> -               log_rdma_event(ERR, "rdma session already destroyed\n");
> -               return -EINVAL;
> +               log_rdma_event(INFO, "rdma session already destroyed\n");
> +               goto create_conn;
>         }
>
>         /*
> @@ -1512,15 +1512,19 @@ int smbd_reconnect(struct TCP_Server_Info *server)
>         }
>
>         /* wait until the transport is destroyed */
> -       wait_event(server->smbd_conn->wait_destroy,
> -               server->smbd_conn->transport_status == SMBD_DESTROYED);
> +       if (!wait_event_timeout(server->smbd_conn->wait_destroy,
> +               server->smbd_conn->transport_status == SMBD_DESTROYED, 5*HZ))
> +               return -EAGAIN;
>
>         destroy_workqueue(server->smbd_conn->workqueue);
>         kfree(server->smbd_conn);
>
> +create_conn:
>         log_rdma_event(INFO, "creating rdma session\n");
>         server->smbd_conn = smbd_get_connection(
>                 server, (struct sockaddr *) &server->dstaddr);
> +       log_rdma_event(INFO, "created rdma session info=%p\n",
> +               server->smbd_conn);
>
>         return server->smbd_conn ? 0 : -ENOENT;
>  }
> --
> 2.7.4
>
> --
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