Re: [PATCH RFC 12/24] nfsd: encoders and decoders for GET_DIR_DELEGATION

From: Chuck Lever
Date: Sun Mar 17 2024 - 11:35:53 EST

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On Fri, Mar 15, 2024 at 12:53:03PM -0400, Jeff Layton wrote:
> This adds basic infrastructure for handing GET_DIR_DELEGATION calls from
> clients, including the decoders and encoders. For now, the server side
> always just returns that the delegation is GDDR_UNAVAIL (and that we
> won't call back).
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/nfsd/nfs4proc.c | 30 ++++++++++++++++++++++
> fs/nfsd/nfs4xdr.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++--
> fs/nfsd/xdr4.h | 8 ++++++
> include/linux/nfs4.h | 5 ++++
> 4 files changed, 113 insertions(+), 2 deletions(-)

Just a handful of style preferences below.

> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 2927b1263f08..7973fe17bf3c 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -2173,6 +2173,18 @@ nfsd4_layout_verify(struct svc_export *exp, unsigned int layout_type)
> return nfsd4_layout_ops[layout_type];
> }
>
> +static __be32
> +nfsd4_get_dir_delegation(struct svc_rqst *rqstp,
> + struct nfsd4_compound_state *cstate,
> + union nfsd4_op_u *u)
> +{
> + struct nfsd4_get_dir_delegation *gdd = &u->get_dir_delegation;
> +
> + /* FIXME: actually return a delegation */
> + gdd->nf_status = GDD4_UNAVAIL;
> + return nfs_ok;
> +}
> +
> static __be32
> nfsd4_getdeviceinfo(struct svc_rqst *rqstp,
> struct nfsd4_compound_state *cstate, union nfsd4_op_u *u)
> @@ -3082,6 +3094,18 @@ static u32 nfsd4_copy_notify_rsize(const struct svc_rqst *rqstp,
> * sizeof(__be32);
> }
>
> +static u32 nfsd4_get_dir_delegation_rsize(const struct svc_rqst *rqstp,
> + const struct nfsd4_op *op)
> +{
> + return (op_encode_hdr_size +
> + 1 /* gddr_status */ +
> + op_encode_verifier_maxsz +
> + op_encode_stateid_maxsz +
> + 2 /* gddr_notification */ +
> + 2 /* gddr_child_attributes */ +
> + 2 /* gddr_dir_attributes */);
> +}
> +
> #ifdef CONFIG_NFSD_PNFS
> static u32 nfsd4_getdeviceinfo_rsize(const struct svc_rqst *rqstp,
> const struct nfsd4_op *op)
> @@ -3470,6 +3494,12 @@ static const struct nfsd4_operation nfsd4_ops[] = {
> .op_get_currentstateid = nfsd4_get_freestateid,
> .op_rsize_bop = nfsd4_only_status_rsize,
> },
> + [OP_GET_DIR_DELEGATION] = {
> + .op_func = nfsd4_get_dir_delegation,
> + .op_flags = OP_MODIFIES_SOMETHING,
> + .op_name = "OP_GET_DIR_DELEGATION",
> + .op_rsize_bop = nfsd4_get_dir_delegation_rsize,
> + },
> #ifdef CONFIG_NFSD_PNFS
> [OP_GETDEVICEINFO] = {
> .op_func = nfsd4_getdeviceinfo,
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index fac938f563ad..3718bef74e9f 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -1732,6 +1732,40 @@ nfsd4_decode_free_stateid(struct nfsd4_compoundargs *argp,
> return nfsd4_decode_stateid4(argp, &free_stateid->fr_stateid);
> }
>
> +static __be32
> +nfsd4_decode_get_dir_delegation(struct nfsd4_compoundargs *argp,
> + union nfsd4_op_u *u)
> +{
> + struct nfsd4_get_dir_delegation *gdd = &u->get_dir_delegation;
> + struct timespec64 ts;
> + u32 signal_deleg_avail;
> + u32 attrs[1];

I know this isn't how we've done XDR in the past, but I'd rather
see these dummy args as fields in struct nfsd4_get_dir_delegation,
and also move the comments about whether each argument is supported
to the putative nfsd4_proc_get_dir_delegation().

The actual implementation of GET_DIR_DELEGATION is in nfs4proc.c,
after all, not here. This is simply a translation function.

> + __be32 status;
> +
> + memset(gdd, 0, sizeof(*gdd));
> +
> + /* No signal_avail support for now (and maybe never) */
> + if (xdr_stream_decode_bool(argp->xdr, &signal_deleg_avail) < 0)
> + return nfserr_bad_xdr;
> + status = nfsd4_decode_bitmap4(argp, gdd->notification_types,
> + ARRAY_SIZE(gdd->notification_types));
> + if (status)
> + return status;
> +
> + /* For now, we don't support child or dir attr change notification */
> + status = nfsd4_decode_nfstime4(argp, &ts);
> + if (status)
> + return status;
> + /* No dir attr notification support yet either */
> + status = nfsd4_decode_nfstime4(argp, &ts);
> + if (status)
> + return status;
> + status = nfsd4_decode_bitmap4(argp, attrs, ARRAY_SIZE(attrs));
> + if (status)
> + return status;
> + return nfsd4_decode_bitmap4(argp, attrs, ARRAY_SIZE(attrs));
> +}
> +
> #ifdef CONFIG_NFSD_PNFS
> static __be32
> nfsd4_decode_getdeviceinfo(struct nfsd4_compoundargs *argp,
> @@ -2370,7 +2404,7 @@ static const nfsd4_dec nfsd4_dec_ops[] = {
> [OP_CREATE_SESSION] = nfsd4_decode_create_session,
> [OP_DESTROY_SESSION] = nfsd4_decode_destroy_session,
> [OP_FREE_STATEID] = nfsd4_decode_free_stateid,
> - [OP_GET_DIR_DELEGATION] = nfsd4_decode_notsupp,
> + [OP_GET_DIR_DELEGATION] = nfsd4_decode_get_dir_delegation,
> #ifdef CONFIG_NFSD_PNFS
> [OP_GETDEVICEINFO] = nfsd4_decode_getdeviceinfo,
> [OP_GETDEVICELIST] = nfsd4_decode_notsupp,
> @@ -5002,6 +5036,40 @@ nfsd4_encode_device_addr4(struct xdr_stream *xdr,
> return nfserr_toosmall;
> }
>
> +static __be32
> +nfsd4_encode_get_dir_delegation(struct nfsd4_compoundres *resp, __be32 nfserr,
> + union nfsd4_op_u *u)
> +{
> + struct xdr_stream *xdr = resp->xdr;
> + struct nfsd4_get_dir_delegation *gdd = &u->get_dir_delegation;
> +
> + /* Encode the GDDR_* status code */

In other encoders, I've used simply the name of the field as it is
in the RFC as a documenting comment. That's more clear, and is
easily grep-able. So:

/* gddrnf_status */

> + if (xdr_stream_encode_u32(xdr, gdd->nf_status) != XDR_UNIT)
> + return nfserr_resource;
> +
> + /* if it's GDD4_UNAVAIL then we're (almost) done */
> + if (gdd->nf_status == GDD4_UNAVAIL) {

I prefer using a switch for XDR unions. That makes our
implementation look more like the XDR definition; easier for humans
to audit and modify.

> + /* We never call back */
> + return nfsd4_encode_bool(xdr, false);

Again, let's move this boolean to struct nfsd4_get_dir_delegation to
enable nfsd4_proc_get_dir_delegation to decide in the future.

> + }
> +
> + /* GDD4_OK case */

If a switch is used, then this comment becomes a real piece of
self-verifying code:

case GDD4_OK:

> + nfserr = nfsd4_encode_verifier4(xdr, &gdd->cookieverf);
> + if (nfserr)
> + return nfserr;
> + nfserr = nfsd4_encode_stateid4(xdr, &gdd->stateid);
> + if (nfserr)
> + return nfserr;
> + /* No notifications (yet) */
> + nfserr = nfsd4_encode_bitmap4(xdr, 0, 0, 0);
> + if (nfserr)
> + return nfserr;
> + nfserr = nfsd4_encode_bitmap4(xdr, 0, 0, 0);
> + if (nfserr)
> + return nfserr;
> + return nfsd4_encode_bitmap4(xdr, 0, 0, 0);

All these as well can go in struct nfsd4_get_dir_delegation.

> +}
> +
> static __be32
> nfsd4_encode_getdeviceinfo(struct nfsd4_compoundres *resp, __be32 nfserr,
> union nfsd4_op_u *u)
> @@ -5580,7 +5648,7 @@ static const nfsd4_enc nfsd4_enc_ops[] = {
> [OP_CREATE_SESSION] = nfsd4_encode_create_session,
> [OP_DESTROY_SESSION] = nfsd4_encode_noop,
> [OP_FREE_STATEID] = nfsd4_encode_noop,
> - [OP_GET_DIR_DELEGATION] = nfsd4_encode_noop,
> + [OP_GET_DIR_DELEGATION] = nfsd4_encode_get_dir_delegation,
> #ifdef CONFIG_NFSD_PNFS
> [OP_GETDEVICEINFO] = nfsd4_encode_getdeviceinfo,
> [OP_GETDEVICELIST] = nfsd4_encode_noop,
> diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
> index 415516c1b27e..27de75f32dea 100644
> --- a/fs/nfsd/xdr4.h
> +++ b/fs/nfsd/xdr4.h
> @@ -518,6 +518,13 @@ struct nfsd4_free_stateid {
> stateid_t fr_stateid; /* request */
> };
>
> +struct nfsd4_get_dir_delegation {
> + u32 notification_types[1]; /* request */
> + u32 nf_status; /* response */
> + nfs4_verifier cookieverf; /* response */
> + stateid_t stateid; /* response */
> +};
> +
> /* also used for NVERIFY */
> struct nfsd4_verify {
> u32 ve_bmval[3]; /* request */
> @@ -797,6 +804,7 @@ struct nfsd4_op {
> struct nfsd4_reclaim_complete reclaim_complete;
> struct nfsd4_test_stateid test_stateid;
> struct nfsd4_free_stateid free_stateid;
> + struct nfsd4_get_dir_delegation get_dir_delegation;
> struct nfsd4_getdeviceinfo getdeviceinfo;
> struct nfsd4_layoutget layoutget;
> struct nfsd4_layoutcommit layoutcommit;
> diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
> index ef8d2d618d5b..11ad088b411d 100644
> --- a/include/linux/nfs4.h
> +++ b/include/linux/nfs4.h
> @@ -701,6 +701,11 @@ enum state_protect_how4 {
> SP4_SSV = 2
> };
>
> +enum get_dir_delegation_non_fatal_res {
> + GDD4_OK = 0,
> + GDD4_UNAVAIL = 1
> +};
> +
> enum pnfs_layouttype {
> LAYOUT_NFSV4_1_FILES = 1,
> LAYOUT_OSD2_OBJECTS = 2,
>
> --
> 2.44.0
>

--
Chuck Lever

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Next in thread: Jeff Layton: "Re: [PATCH RFC 12/24] nfsd: encoders and decoders for GET_DIR_DELEGATION"
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