NFSD: Get response size before operation for all RPCs

NFSD usess PAGE_SIZE as the reply size estimate for RPCs which don't
support op_rsize_bop(), A PAGE_SIZE (4096) is larger than many real
response sizes, eg, access (op_encode_hdr_size + 2), seek
(op_encode_hdr_size + 3).

This patch just adds op_rsize_bop() for all RPCs getting response size.

An overestimate is generally safe but the tighter estimates are probably
better.

Signed-off-by: Kinglong Mee <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

fs/nfsd/nfs4proc.c

···
 	return (op_encode_hdr_size + op_encode_stateid_maxsz)* sizeof(__be32);
 }
 
+static inline u32 nfsd4_access_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
+{
+	/* ac_supported, ac_resp_access */
+	return (op_encode_hdr_size + 2)* sizeof(__be32);
+}
+
 static inline u32 nfsd4_commit_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
 {
 	return (op_encode_hdr_size + op_encode_verifier_maxsz) * sizeof(__be32);
···
 	return ret;
 }
 
+static inline u32 nfsd4_getfh_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
+{
+	return (op_encode_hdr_size + 1) * sizeof(__be32) + NFS4_FHSIZE;
+}
+
 static inline u32 nfsd4_link_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
 {
 	return (op_encode_hdr_size + op_encode_change_info_maxsz)
···
 		XDR_QUADLEN(rlen)) * sizeof(__be32);
 }
 
+static inline u32 nfsd4_readlink_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
+{
+	return (op_encode_hdr_size + 1) * sizeof(__be32) + PAGE_SIZE;
+}
+
 static inline u32 nfsd4_remove_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
 {
 	return (op_encode_hdr_size + op_encode_change_info_maxsz)
···
 		+ XDR_QUADLEN(NFS4_MAX_SESSIONID_LEN) + 5) * sizeof(__be32);
 }
 
+static inline u32 nfsd4_test_stateid_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
+{
+	return (op_encode_hdr_size + 1 + op->u.test_stateid.ts_num_ids)
+		* sizeof(__be32);
+}
+
 static inline u32 nfsd4_setattr_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
 {
 	return (op_encode_hdr_size + nfs4_fattr_bitmap_maxsz) * sizeof(__be32);
+}
+
+static inline u32 nfsd4_secinfo_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
+{
+	return (op_encode_hdr_size + RPC_AUTH_MAXFLAVOR *
+		(4 + XDR_QUADLEN(GSS_OID_MAX_LEN))) * sizeof(__be32);
 }
 
 static inline u32 nfsd4_setclientid_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
···
 }
 
 #ifdef CONFIG_NFSD_PNFS
+static inline u32 nfsd4_getdeviceinfo_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
+{
+	u32 maxcount = 0, rlen = 0;
+
+	maxcount = svc_max_payload(rqstp);
+	rlen = min(op->u.getdeviceinfo.gd_maxcount, maxcount);
+
+	return (op_encode_hdr_size +
+		1 /* gd_layout_type*/ +
+		XDR_QUADLEN(rlen) +
+		2 /* gd_notify_types */) * sizeof(__be32);
+}
+
 /*
  * At this stage we don't really know what layout driver will handle the request,
  * so we need to define an arbitrary upper bound here.
···
 }
 #endif /* CONFIG_NFSD_PNFS */
 
+
+static inline u32 nfsd4_seek_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
+{
+	return (op_encode_hdr_size + 3) * sizeof(__be32);
+}
+
 static struct nfsd4_operation nfsd4_ops[] = {
 	[OP_ACCESS] = {
 		.op_func = (nfsd4op_func)nfsd4_access,
 		.op_name = "OP_ACCESS",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_access_rsize,
 	},
 	[OP_CLOSE] = {
 		.op_func = (nfsd4op_func)nfsd4_close,
···
 	[OP_GETFH] = {
 		.op_func = (nfsd4op_func)nfsd4_getfh,
 		.op_name = "OP_GETFH",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_getfh_rsize,
 	},
 	[OP_LINK] = {
 		.op_func = (nfsd4op_func)nfsd4_link,
···
 	[OP_LOCKT] = {
 		.op_func = (nfsd4op_func)nfsd4_lockt,
 		.op_name = "OP_LOCKT",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_lock_rsize,
 	},
 	[OP_LOCKU] = {
 		.op_func = (nfsd4op_func)nfsd4_locku,
···
 		.op_func = (nfsd4op_func)nfsd4_lookup,
 		.op_flags = OP_HANDLES_WRONGSEC | OP_CLEAR_STATEID,
 		.op_name = "OP_LOOKUP",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_only_status_rsize,
 	},
 	[OP_LOOKUPP] = {
 		.op_func = (nfsd4op_func)nfsd4_lookupp,
 		.op_flags = OP_HANDLES_WRONGSEC | OP_CLEAR_STATEID,
 		.op_name = "OP_LOOKUPP",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_only_status_rsize,
 	},
 	[OP_NVERIFY] = {
 		.op_func = (nfsd4op_func)nfsd4_nverify,
 		.op_name = "OP_NVERIFY",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_only_status_rsize,
 	},
 	[OP_OPEN] = {
 		.op_func = (nfsd4op_func)nfsd4_open,
···
 	[OP_READLINK] = {
 		.op_func = (nfsd4op_func)nfsd4_readlink,
 		.op_name = "OP_READLINK",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_readlink_rsize,
 	},
 	[OP_REMOVE] = {
 		.op_func = (nfsd4op_func)nfsd4_remove,
···
 		.op_func = (nfsd4op_func)nfsd4_secinfo,
 		.op_flags = OP_HANDLES_WRONGSEC,
 		.op_name = "OP_SECINFO",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_secinfo_rsize,
 	},
 	[OP_SETATTR] = {
 		.op_func = (nfsd4op_func)nfsd4_setattr,
···
 	[OP_VERIFY] = {
 		.op_func = (nfsd4op_func)nfsd4_verify,
 		.op_name = "OP_VERIFY",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_only_status_rsize,
 	},
 	[OP_WRITE] = {
 		.op_func = (nfsd4op_func)nfsd4_write,
···
 		.op_func = (nfsd4op_func)nfsd4_secinfo_no_name,
 		.op_flags = OP_HANDLES_WRONGSEC,
 		.op_name = "OP_SECINFO_NO_NAME",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_secinfo_rsize,
 	},
 	[OP_TEST_STATEID] = {
 		.op_func = (nfsd4op_func)nfsd4_test_stateid,
 		.op_flags = ALLOWED_WITHOUT_FH,
 		.op_name = "OP_TEST_STATEID",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_test_stateid_rsize,
 	},
 	[OP_FREE_STATEID] = {
 		.op_func = (nfsd4op_func)nfsd4_free_stateid,
···
 		.op_func = (nfsd4op_func)nfsd4_getdeviceinfo,
 		.op_flags = ALLOWED_WITHOUT_FH,
 		.op_name = "OP_GETDEVICEINFO",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_getdeviceinfo_rsize,
 	},
 	[OP_LAYOUTGET] = {
 		.op_func = (nfsd4op_func)nfsd4_layoutget,
···
 	[OP_SEEK] = {
 		.op_func = (nfsd4op_func)nfsd4_seek,
 		.op_name = "OP_SEEK",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_seek_rsize,
 	},
 };
 
···
 
 int nfsd4_max_reply(struct svc_rqst *rqstp, struct nfsd4_op *op)
 {
-	struct nfsd4_operation *opdesc;
-	nfsd4op_rsize estimator;
-
 	if (op->opnum == OP_ILLEGAL)
 		return op_encode_hdr_size * sizeof(__be32);
-	opdesc = OPDESC(op);
-	estimator = opdesc->op_rsize_bop;
-	return estimator ? estimator(rqstp, op) : PAGE_SIZE;
+
+	BUG_ON(OPDESC(op)->op_rsize_bop == NULL);
+	return OPDESC(op)->op_rsize_bop(rqstp, op);
 }
 
 void warn_on_nonidempotent_op(struct nfsd4_op *op)