[PATCH v3 23/34] NFSD: Use xdrgen XDR functions for the NFSv3 FSSTAT procedure

[Chuck Lever <cel@kernel.org>]

Replace the NFSPROC3_FSSTAT entry in the nfsd_procedures3 array with
an entry that dispatches the xdrgen-generated
nfs_svc_decode_FSSTAT3args and nfs_svc_encode_FSSTAT3res. A wrapper
structure bridges the generated xdrgen argument type and the legacy
svc_fh representation the NFSD VFS layer still uses. The result
wrapper carries a scratch kstatfs alongside the generated FSSTAT3res
type, which nfsd_statfs() fills before nfsd3_proc_fsstat() copies the
values into the encoded result.

The pc_argzero field is now set to zero for the NFSv3 FSSTAT
procedure. The xdrgen decoders are trusted to initialize all
arguments in the argp->xdrgen field, making the early defensive
memset unnecessary. The remaining argp fields are cleared as needed.

nfsd3_proc_fsstat() now sets the post-op attributes directly. This
makes it straightforward to confirm that the file handle is released
during every error flow.

nfs3svc_encode_fsstatres() no longer has any callers, so it is
removed, and with it the now-orphaned svcxdr_encode_fsstat3resok()
encode helper.

Signed-off-by: Chuck Lever <cel@kernel.org>
---
 fs/nfsd/nfs3proc.c | 71 +++++++++++++++++++++++++++++++++++-----------
 fs/nfsd/nfs3xdr.c  | 45 -----------------------------
 fs/nfsd/xdr3.h     |  6 ++--
 3 files changed, 57 insertions(+), 65 deletions(-)

diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 76963187de20..0650bfa960e8 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -193,6 +193,13 @@ struct LINK3args_wrapper {
 
 static_assert(offsetof(struct LINK3args_wrapper, xdrgen) == 0);
 
+struct FSSTAT3args_wrapper {
+	struct FSSTAT3args	xdrgen;
+	struct svc_fh		fh;
+};
+
+static_assert(offsetof(struct FSSTAT3args_wrapper, xdrgen) == 0);
+
 static int nfsd3_ftype3_to_mode(ftype3 ftype)
 {
 	switch (ftype) {
@@ -1555,18 +1562,47 @@ nfsd3_proc_readdirplus(struct svc_rqst *rqstp)
 	return rpc_success;
 }
 
-/*
- * Get file system stats
+/**
+ * nfsd3_proc_fsstat - FSSTAT: Get dynamic file system information
+ * @rqstp: RPC transaction context
+ *
+ * Return:
+ *   %rpc_success:		RPC executed successfully
+ *
+ * RPC synopsis:
+ *   FSSTAT3res NFSPROC3_FSSTAT(FSSTAT3args) = 18;
  */
-static __be32
-nfsd3_proc_fsstat(struct svc_rqst *rqstp)
+static __be32 nfsd3_proc_fsstat(struct svc_rqst *rqstp)
 {
-	struct nfsd_fhandle *argp = rqstp->rq_argp;
+	struct FSSTAT3args_wrapper *argp = rqstp->rq_argp;
 	struct nfsd3_fsstatres *resp = rqstp->rq_resp;
+	struct kstatfs *statp = &resp->stats;
+	struct svc_fh *fhp = &argp->fh;
 
-	resp->status = nfsd_statfs(rqstp, &argp->fh, &resp->stats, 0);
-	fh_put(&argp->fh);
-	resp->status = nfsd3_map_status(resp->status);
+	nfsd3_fh3_to_svc_fh(fhp, &argp->xdrgen.fsroot);
+
+	resp->xdrgen.status = nfsd_statfs(rqstp, fhp, statp, 0);
+
+	if (resp->xdrgen.status == nfs_ok) {
+		struct FSSTAT3resok *resok = &resp->xdrgen.u.resok;
+		u64 bs = statp->f_bsize;
+
+		resok->obj_attributes.attributes_follow = false;
+		resok->tbytes = bs * statp->f_blocks;
+		resok->fbytes = bs * statp->f_bfree;
+		resok->abytes = bs * statp->f_bavail;
+		resok->tfiles = statp->f_files;
+		resok->ffiles = statp->f_ffree;
+		resok->afiles = statp->f_ffree;
+		resok->invarsec = 0;
+	} else {
+		struct FSSTAT3resfail *resfail = &resp->xdrgen.u.resfail;
+
+		resp->xdrgen.status = nfsd3_map_status(resp->xdrgen.status);
+		resfail->obj_attributes.attributes_follow = false;
+	}
+
+	fh_put(fhp);
 	return rpc_success;
 }
 
@@ -1924,15 +1960,15 @@ static const struct svc_procedure nfsd_procedures3[22] = {
 		.pc_name = "READDIRPLUS",
 	},
 	[NFSPROC3_FSSTAT] = {
-		.pc_func = nfsd3_proc_fsstat,
-		.pc_decode = nfs3svc_decode_fhandleargs,
-		.pc_encode = nfs3svc_encode_fsstatres,
-		.pc_argsize = sizeof(struct nfsd3_fhandleargs),
-		.pc_argzero = sizeof(struct nfsd3_fhandleargs),
-		.pc_ressize = sizeof(struct nfsd3_fsstatres),
-		.pc_cachetype = RC_NOCACHE,
-		.pc_xdrressize = ST+pAT+2*6+1,
-		.pc_name = "FSSTAT",
+		.pc_func	= nfsd3_proc_fsstat,
+		.pc_decode	= nfs_svc_decode_FSSTAT3args,
+		.pc_encode	= nfs_svc_encode_FSSTAT3res,
+		.pc_argsize	= sizeof(struct FSSTAT3args_wrapper),
+		.pc_argzero	= 0,
+		.pc_ressize	= sizeof(struct nfsd3_fsstatres),
+		.pc_cachetype	= RC_NOCACHE,
+		.pc_xdrressize	= NFS3_FSSTAT3res_sz,
+		.pc_name	= "FSSTAT",
 	},
 	[NFSPROC3_FSINFO] = {
 		.pc_func = nfsd3_proc_fsinfo,
@@ -2006,6 +2042,7 @@ union nfsd3_xdrstore {
 	struct READ3res			readres;
 	struct nfsd3_writeres		writeres;
 	struct nfsd3_readdirres		readdirres;
+	struct FSSTAT3args_wrapper	fsstatargs;
 	struct nfsd3_fsstatres		fsstatres;
 	struct nfsd3_fsinfores		fsinfores;
 	struct nfsd3_pathconfres	pathconfres;
diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 59e89b7f9d19..0ca671bdd1c8 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -620,51 +620,6 @@ int nfs3svc_encode_entryplus3(void *data, const char *name, int namlen,
 	return -EINVAL;
 }
 
-static bool
-svcxdr_encode_fsstat3resok(struct xdr_stream *xdr,
-			   const struct nfsd3_fsstatres *resp)
-{
-	const struct kstatfs *s = &resp->stats;
-	u64 bs = s->f_bsize;
-	__be32 *p;
-
-	p = xdr_reserve_space(xdr, XDR_UNIT * 13);
-	if (!p)
-		return false;
-	p = xdr_encode_hyper(p, bs * s->f_blocks);	/* total bytes */
-	p = xdr_encode_hyper(p, bs * s->f_bfree);	/* free bytes */
-	p = xdr_encode_hyper(p, bs * s->f_bavail);	/* user available bytes */
-	p = xdr_encode_hyper(p, s->f_files);		/* total inodes */
-	p = xdr_encode_hyper(p, s->f_ffree);		/* free inodes */
-	p = xdr_encode_hyper(p, s->f_ffree);		/* user available inodes */
-	*p = cpu_to_be32(resp->invarsec);		/* mean unchanged time */
-
-	return true;
-}
-
-/* FSSTAT */
-bool
-nfs3svc_encode_fsstatres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
-{
-	struct nfsd3_fsstatres *resp = rqstp->rq_resp;
-
-	if (!svcxdr_encode_nfsstat3(xdr, resp->status))
-		return false;
-	switch (resp->status) {
-	case nfs_ok:
-		if (!svcxdr_encode_post_op_attr(rqstp, xdr, &nfs3svc_null_fh))
-			return false;
-		if (!svcxdr_encode_fsstat3resok(xdr, resp))
-			return false;
-		break;
-	default:
-		if (!svcxdr_encode_post_op_attr(rqstp, xdr, &nfs3svc_null_fh))
-			return false;
-	}
-
-	return true;
-}
-
 static bool
 svcxdr_encode_fsinfo3resok(struct xdr_stream *xdr,
 			   const struct nfsd3_fsinfores *resp)
diff --git a/fs/nfsd/xdr3.h b/fs/nfsd/xdr3.h
index 9a2bdd5a0da5..577a4beaafc3 100644
--- a/fs/nfsd/xdr3.h
+++ b/fs/nfsd/xdr3.h
@@ -86,11 +86,12 @@ struct nfsd3_readdirres {
 };
 
 struct nfsd3_fsstatres {
-	__be32			status;
+	struct FSSTAT3res	xdrgen;
 	struct kstatfs		stats;
-	__u32			invarsec;
 };
 
+static_assert(offsetof(struct nfsd3_fsstatres, xdrgen) == 0);
+
 struct nfsd3_fsinfores {
 	__be32			status;
 	__u32			f_rtmax;
@@ -136,7 +137,6 @@ bool nfs3svc_decode_commitargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 
 bool nfs3svc_encode_accessres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 bool nfs3svc_encode_readdirres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
-bool nfs3svc_encode_fsstatres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 bool nfs3svc_encode_fsinfores(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 bool nfs3svc_encode_pathconfres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 bool nfs3svc_encode_commitres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
-- 
2.55.0