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Cc:     Calum Mackay <calum.mackay@oracle.com>, linux-nfs@vger.kernel.org
Subject: Re: [PATCH v2] NFS: allow deprecation of NFS UDP protocol
To:     Olga Kornievskaia <olga.kornievskaia@gmail.com>,
        trond.myklebust@hammerspace.com, anna.schumaker@netapp.com
References: <20191121160651.5317-1-olga.kornievskaia@gmail.com>
From:   Calum Mackay <calum.mackay@oracle.com>
Organization: Oracle
Message-ID: <ce430173-8fc0-564a-eb51-f79698920436@oracle.com>
Date:   Thu, 21 Nov 2019 23:16:52 +0000
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hi Olga,

On 21/11/2019 4:06 pm, Olga Kornievskaia wrote:
> From: Olga Kornievskaia <kolga@netapp.com>
> 
> Add a kernel config CONFIG_NFS_DISABLE_UDP_SUPPORT to disallow NFS
> UDP mounts and enable it by default.
> 
> Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
> ---
>   fs/nfs/Kconfig  | 10 ++++++++++
>   fs/nfs/client.c |  4 ++++
>   fs/nfs/super.c  |  4 ++++
>   3 files changed, 18 insertions(+)
> 
> diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
> index 295a7a2..ba5a681 100644
> --- a/fs/nfs/Kconfig
> +++ b/fs/nfs/Kconfig
> @@ -196,3 +196,13 @@ config NFS_DEBUG
>   	depends on NFS_FS && SUNRPC_DEBUG
>   	select CRC32
>   	default y
> +
> +config NFS_DISABLE_UDP_SUPPORT
> +	bool "NFS: Disable NFS UDP protocol support"
> +	depends on NFS_FS
> +	default y
> +	help
> +	  Choose Y here to disable the use of NFS over UDP. NFS over UDP
> +	  on modern networks (1Gb+) can lead to data corruption caused by
> +	  fragmentation during high loads.
> +	  The default is N because many deployments still use UDP.

You've changed the default to 'y' for v2, but you've left in the 'N' 
comment.


> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index 02110a3..24ca314 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -474,6 +474,7 @@ void nfs_init_timeout_values(struct rpc_timeout *to, int proto,
>   			to->to_maxval = to->to_initval;
>   		to->to_exponential = 0;
>   		break;
> +#ifdef CONFIG_NFS_DISABLE_UDP_SUPPORT
>   	case XPRT_TRANSPORT_UDP:
>   		if (retrans == NFS_UNSPEC_RETRANS)
>   			to->to_retries = NFS_DEF_UDP_RETRANS;
> @@ -484,6 +485,7 @@ void nfs_init_timeout_values(struct rpc_timeout *to, int proto,
>   		to->to_maxval = NFS_MAX_UDP_TIMEOUT;
>   		to->to_exponential = 1;
>   		break;
> +#endif

Should the first two of your added ifdefs be ifndefs?

cheers,
calum.

>   	default:
>   		BUG();
>   	}
> @@ -580,8 +582,10 @@ static int nfs_start_lockd(struct nfs_server *server)
>   		default:
>   			nlm_init.protocol = IPPROTO_TCP;
>   			break;
> +#ifdef CONFIG_NFS_DISABLE_UDP_SUPPORT
>   		case XPRT_TRANSPORT_UDP:
>   			nlm_init.protocol = IPPROTO_UDP;
> +#endif
>   	}
>   
>   	host = nlmclnt_init(&nlm_init);
> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> index a84df7d6..f68346d 100644
> --- a/fs/nfs/super.c
> +++ b/fs/nfs/super.c
> @@ -2204,6 +2204,10 @@ static int nfs_validate_text_mount_data(void *options,
>   #endif /* CONFIG_NFS_V4 */
>   	} else {
>   		nfs_set_mount_transport_protocol(args);
> +#ifdef CONFIG_NFS_DISABLE_UDP_SUPPORT
> +		if (args->nfs_server.protocol == XPRT_TRANSPORT_UDP)
> +			goto out_invalid_transport_udp;
> +#endif
>   		if (args->nfs_server.protocol == XPRT_TRANSPORT_RDMA)
>   			port = NFS_RDMA_PORT;
>   	}
>