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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Olga Kornievskaia <olga.kornievskaia@gmail.com>
CC:     "trond.myklebust@hammerspace.com" <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH v1] NFSv4.1 provide mount option to toggle trunking
 discovery
Thread-Topic: [PATCH v1] NFSv4.1 provide mount option to toggle trunking
 discovery
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Date:   Thu, 24 Feb 2022 15:30:52 +0000
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References: <20220223174041.77887-1-olga.kornievskaia@gmail.com>
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> On Feb 23, 2022, at 12:40 PM, Olga Kornievskaia <olga.kornievskaia@gmail.=
com> wrote:
>=20
> From: Olga Kornievskaia <kolga@netapp.com>
>=20
> Introduce a new mount option -- trunkdiscovery,notrunkdiscovery -- to
> toggle whether or not the client will engage in actively discovery
> of trunking locations.

An alternative solution might be to change the client's
probe to treat NFS4ERR_DELAY as "no trunking information
available" and then allow operation to proceed on the
known good transport.

I can't think of a reason why normal operation needs to
stop until this request succeeds...?


> Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
> ---
> fs/nfs/client.c           | 3 ++-
> fs/nfs/fs_context.c       | 8 ++++++++
> include/linux/nfs_fs_sb.h | 1 +
> 3 files changed, 11 insertions(+), 1 deletion(-)
>=20
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index d1f34229e11a..84c080ddfd01 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -857,7 +857,8 @@ static int nfs_probe_fsinfo(struct nfs_server *server=
, struct nfs_fh *mntfh, str
> 	}
>=20
> 	if (clp->rpc_ops->discover_trunking !=3D NULL &&
> -			(server->caps & NFS_CAP_FS_LOCATIONS)) {
> +			(server->caps & NFS_CAP_FS_LOCATIONS &&
> +			 !(server->flags & NFS_MOUNT_NOTRUNK_DISCOVERY))) {
> 		error =3D clp->rpc_ops->discover_trunking(server, mntfh);
> 		if (error < 0)
> 			return error;
> diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c
> index ea17fa1f31ec..ad1448a63aa0 100644
> --- a/fs/nfs/fs_context.c
> +++ b/fs/nfs/fs_context.c
> @@ -80,6 +80,7 @@ enum nfs_param {
> 	Opt_source,
> 	Opt_tcp,
> 	Opt_timeo,
> +	Opt_trunkdiscovery,
> 	Opt_udp,
> 	Opt_v,
> 	Opt_vers,
> @@ -180,6 +181,7 @@ static const struct fs_parameter_spec nfs_fs_paramete=
rs[] =3D {
> 	fsparam_string("source",	Opt_source),
> 	fsparam_flag  ("tcp",		Opt_tcp),
> 	fsparam_u32   ("timeo",		Opt_timeo),
> +	fsparam_flag_no("trunkdiscovery", Opt_trunkdiscovery),
> 	fsparam_flag  ("udp",		Opt_udp),
> 	fsparam_flag  ("v2",		Opt_v),
> 	fsparam_flag  ("v3",		Opt_v),
> @@ -529,6 +531,12 @@ static int nfs_fs_context_parse_param(struct fs_cont=
ext *fc,
> 		else
> 			ctx->flags &=3D ~NFS_MOUNT_NOCTO;
> 		break;
> +	case Opt_trunkdiscovery:
> +		if (result.negated)
> +			ctx->flags |=3D NFS_MOUNT_NOTRUNK_DISCOVERY;
> +		else
> +			ctx->flags &=3D ~NFS_MOUNT_NOTRUNK_DISCOVERY;
> +		break;
> 	case Opt_ac:
> 		if (result.negated)
> 			ctx->flags |=3D NFS_MOUNT_NOAC;
> diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
> index ca0959e51e81..d0920d7f5f9e 100644
> --- a/include/linux/nfs_fs_sb.h
> +++ b/include/linux/nfs_fs_sb.h
> @@ -151,6 +151,7 @@ struct nfs_server {
> #define NFS_MOUNT_SOFTREVAL		0x800000
> #define NFS_MOUNT_WRITE_EAGER		0x01000000
> #define NFS_MOUNT_WRITE_WAIT		0x02000000
> +#define NFS_MOUNT_NOTRUNK_DISCOVERY	0x04000000
>=20
> 	unsigned int		fattr_valid;	/* Valid attributes */
> 	unsigned int		caps;		/* server capabilities */
> --=20
> 2.27.0
>=20

--
Chuck Lever