fs/nfsd/nfs4callback.c - kernel/msm-4.9 - Gitiles

 /*
  *  linux/fs/nfsd/nfs4callback.c
  *
  *  Copyright (c) 2001 The Regents of the University of Michigan.
  *  All rights reserved.
  *
  *  Kendrick Smith <kmsmith@umich.edu>
  *  Andy Adamson <andros@umich.edu>
  *
  *  Redistribution and use in source and binary forms, with or without
  *  modification, are permitted provided that the following conditions
  *  are met:
  *
  *  1. Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
  *     documentation and/or other materials provided with the distribution.
  *  3. Neither the name of the University nor the names of its
  *     contributors may be used to endorse or promote products derived
  *     from this software without specific prior written permission.
  *
  *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  *  DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  *  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  *  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include <linux/module.h>
 #include <linux/list.h>
 #include <linux/inet.h>
 #include <linux/errno.h>
 #include <linux/delay.h>
 #include <linux/sched.h>
 #include <linux/kthread.h>
 #include <linux/sunrpc/xdr.h>
 #include <linux/sunrpc/svc.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/nfsd/nfsd.h>
 #include <linux/nfsd/state.h>
 #include <linux/sunrpc/sched.h>
 #include <linux/nfs4.h>

 #define NFSDDBG_FACILITY                NFSDDBG_PROC

 #define NFSPROC4_CB_NULL 0
 #define NFSPROC4_CB_COMPOUND 1

 /* Index of predefined Linux callback client operations */

 enum {
         NFSPROC4_CLNT_CB_NULL = 0,
 	NFSPROC4_CLNT_CB_RECALL,
 };

 enum nfs_cb_opnum4 {
 	OP_CB_RECALL            = 4,
 };

 #define NFS4_MAXTAGLEN		20

 #define NFS4_enc_cb_null_sz		0
 #define NFS4_dec_cb_null_sz		0
 #define cb_compound_enc_hdr_sz		4
 #define cb_compound_dec_hdr_sz		(3 + (NFS4_MAXTAGLEN >> 2))
 #define op_enc_sz			1
 #define op_dec_sz			2
 #define enc_nfs4_fh_sz			(1 + (NFS4_FHSIZE >> 2))
 #define enc_stateid_sz			(NFS4_STATEID_SIZE >> 2)
 #define NFS4_enc_cb_recall_sz		(cb_compound_enc_hdr_sz +       \
 					1 + enc_stateid_sz +            \
 					enc_nfs4_fh_sz)

 #define NFS4_dec_cb_recall_sz		(cb_compound_dec_hdr_sz  +      \
 					op_dec_sz)

 /*
 * Generic encode routines from fs/nfs/nfs4xdr.c
 */
 static inline __be32 *
 xdr_writemem(__be32 *p, const void *ptr, int nbytes)
 {
 	int tmp = XDR_QUADLEN(nbytes);
 	if (!tmp)
 		return p;
 	p[tmp-1] = 0;
 	memcpy(p, ptr, nbytes);
 	return p + tmp;
 }

 #define WRITE32(n)               *p++ = htonl(n)
 #define WRITEMEM(ptr,nbytes)     do {                           \
 	p = xdr_writemem(p, ptr, nbytes);                       \
 } while (0)
 #define RESERVE_SPACE(nbytes)   do {                            \
 	p = xdr_reserve_space(xdr, nbytes);                     \
 	if (!p) dprintk("NFSD: RESERVE_SPACE(%d) failed in function %s\n", (int) (nbytes), __func__); \
 	BUG_ON(!p);                                             \
 } while (0)

 /*
  * Generic decode routines from fs/nfs/nfs4xdr.c
  */
 #define DECODE_TAIL                             \
 	status = 0;                             \
 out:                                            \
 	return status;                          \
 xdr_error:                                      \
 	dprintk("NFSD: xdr error! (%s:%d)\n", __FILE__, __LINE__); \
 	status = -EIO;                          \
 	goto out

 #define READ32(x)         (x) = ntohl(*p++)
 #define READ64(x)         do {                  \
 	(x) = (u64)ntohl(*p++) << 32;           \
 	(x) |= ntohl(*p++);                     \
 } while (0)
 #define READTIME(x)       do {                  \
 	p++;                                    \
 	(x.tv_sec) = ntohl(*p++);               \
 	(x.tv_nsec) = ntohl(*p++);              \
 } while (0)
 #define READ_BUF(nbytes)  do { \
 	p = xdr_inline_decode(xdr, nbytes); \
 	if (!p) { \
 		dprintk("NFSD: %s: reply buffer overflowed in line %d.\n", \
 			__func__, __LINE__); \
 		return -EIO; \
 	} \
 } while (0)

 struct nfs4_cb_compound_hdr {
 	int		status;
 	u32		ident;
 	u32		nops;
 	u32		taglen;
 	char *		tag;
 };

 static struct {
 int stat;
 int errno;
 } nfs_cb_errtbl[] = {
 	{ NFS4_OK,		0               },
 	{ NFS4ERR_PERM,		EPERM           },
 	{ NFS4ERR_NOENT,	ENOENT          },
 	{ NFS4ERR_IO,		EIO             },
 	{ NFS4ERR_NXIO,		ENXIO           },
 	{ NFS4ERR_ACCESS,	EACCES          },
 	{ NFS4ERR_EXIST,	EEXIST          },
 	{ NFS4ERR_XDEV,		EXDEV           },
 	{ NFS4ERR_NOTDIR,	ENOTDIR         },
 	{ NFS4ERR_ISDIR,	EISDIR          },
 	{ NFS4ERR_INVAL,	EINVAL          },
 	{ NFS4ERR_FBIG,		EFBIG           },
 	{ NFS4ERR_NOSPC,	ENOSPC          },
 	{ NFS4ERR_ROFS,		EROFS           },
 	{ NFS4ERR_MLINK,	EMLINK          },
 	{ NFS4ERR_NAMETOOLONG,	ENAMETOOLONG    },
 	{ NFS4ERR_NOTEMPTY,	ENOTEMPTY       },
 	{ NFS4ERR_DQUOT,	EDQUOT          },
 	{ NFS4ERR_STALE,	ESTALE          },
 	{ NFS4ERR_BADHANDLE,	EBADHANDLE      },
 	{ NFS4ERR_BAD_COOKIE,	EBADCOOKIE      },
 	{ NFS4ERR_NOTSUPP,	ENOTSUPP        },
 	{ NFS4ERR_TOOSMALL,	ETOOSMALL       },
 	{ NFS4ERR_SERVERFAULT,	ESERVERFAULT    },
 	{ NFS4ERR_BADTYPE,	EBADTYPE        },
 	{ NFS4ERR_LOCKED,	EAGAIN          },
 	{ NFS4ERR_RESOURCE,	EREMOTEIO       },
 	{ NFS4ERR_SYMLINK,	ELOOP           },
 	{ NFS4ERR_OP_ILLEGAL,	EOPNOTSUPP      },
 	{ NFS4ERR_DEADLOCK,	EDEADLK         },
 	{ -1,                   EIO             }
 };

 static int
 nfs_cb_stat_to_errno(int stat)
 {
 	int i;
 	for (i = 0; nfs_cb_errtbl[i].stat != -1; i++) {
 		if (nfs_cb_errtbl[i].stat == stat)
 			return nfs_cb_errtbl[i].errno;
 	}
 	/* If we cannot translate the error, the recovery routines should
 	* handle it.
 	* Note: remaining NFSv4 error codes have values > 10000, so should
 	* not conflict with native Linux error codes.
 	*/
 	return stat;
 }

 /*
  * XDR encode
  */

 static int
 encode_cb_compound_hdr(struct xdr_stream *xdr, struct nfs4_cb_compound_hdr *hdr)
 {
 	__be32 * p;

 	RESERVE_SPACE(16);
 	WRITE32(0);            /* tag length is always 0 */
 	WRITE32(NFS4_MINOR_VERSION);
 	WRITE32(hdr->ident);
 	WRITE32(hdr->nops);
 	return 0;
 }

 static int
 encode_cb_recall(struct xdr_stream *xdr, struct nfs4_cb_recall *cb_rec)
 {
 	__be32 *p;
 	int len = cb_rec->cbr_fh.fh_size;

 	RESERVE_SPACE(12+sizeof(cb_rec->cbr_stateid) + len);
 	WRITE32(OP_CB_RECALL);
 	WRITE32(cb_rec->cbr_stateid.si_generation);
 	WRITEMEM(&cb_rec->cbr_stateid.si_opaque, sizeof(stateid_opaque_t));
 	WRITE32(cb_rec->cbr_trunc);
 	WRITE32(len);
 	WRITEMEM(&cb_rec->cbr_fh.fh_base, len);
 	return 0;
 }

 static int
 nfs4_xdr_enc_cb_null(struct rpc_rqst *req, __be32 *p)
 {
 	struct xdr_stream xdrs, *xdr = &xdrs;

 	xdr_init_encode(&xdrs, &req->rq_snd_buf, p);
         RESERVE_SPACE(0);
 	return 0;
 }

 static int
 nfs4_xdr_enc_cb_recall(struct rpc_rqst *req, __be32 *p, struct nfs4_cb_recall *args)
 {
 	struct xdr_stream xdr;
 	struct nfs4_cb_compound_hdr hdr = {
 		.ident = args->cbr_ident,
 		.nops   = 1,
 	};

 	xdr_init_encode(&xdr, &req->rq_snd_buf, p);
 	encode_cb_compound_hdr(&xdr, &hdr);
 	return (encode_cb_recall(&xdr, args));
 }


 static int
 decode_cb_compound_hdr(struct xdr_stream *xdr, struct nfs4_cb_compound_hdr *hdr){
         __be32 *p;

         READ_BUF(8);
         READ32(hdr->status);
         READ32(hdr->taglen);
         READ_BUF(hdr->taglen + 4);
         hdr->tag = (char *)p;
         p += XDR_QUADLEN(hdr->taglen);
         READ32(hdr->nops);
         return 0;
 }

 static int
 decode_cb_op_hdr(struct xdr_stream *xdr, enum nfs_opnum4 expected)
 {
 	__be32 *p;
 	u32 op;
 	int32_t nfserr;

 	READ_BUF(8);
 	READ32(op);
 	if (op != expected) {
 		dprintk("NFSD: decode_cb_op_hdr: Callback server returned "
 		         " operation %d but we issued a request for %d\n",
 		         op, expected);
 		return -EIO;
 	}
 	READ32(nfserr);
 	if (nfserr != NFS_OK)
 		return -nfs_cb_stat_to_errno(nfserr);
 	return 0;
 }

 static int
 nfs4_xdr_dec_cb_null(struct rpc_rqst *req, __be32 *p)
 {
 	return 0;
 }

 static int
 nfs4_xdr_dec_cb_recall(struct rpc_rqst *rqstp, __be32 *p)
 {
 	struct xdr_stream xdr;
 	struct nfs4_cb_compound_hdr hdr;
 	int status;

 	xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, p);
 	status = decode_cb_compound_hdr(&xdr, &hdr);
 	if (status)
 		goto out;
 	status = decode_cb_op_hdr(&xdr, OP_CB_RECALL);
 out:
 	return status;
 }

 /*
  * RPC procedure tables
  */
 #define PROC(proc, call, argtype, restype)                              \
 [NFSPROC4_CLNT_##proc] = {                                      	\
         .p_proc   = NFSPROC4_CB_##call,					\
         .p_encode = (kxdrproc_t) nfs4_xdr_##argtype,                    \
         .p_decode = (kxdrproc_t) nfs4_xdr_##restype,                    \
         .p_arglen = NFS4_##argtype##_sz,                                \
         .p_replen = NFS4_##restype##_sz,                                \
         .p_statidx = NFSPROC4_CB_##call,				\
 	.p_name   = #proc,                                              \
 }

 static struct rpc_procinfo     nfs4_cb_procedures[] = {
     PROC(CB_NULL,      NULL,     enc_cb_null,     dec_cb_null),
     PROC(CB_RECALL,    COMPOUND,   enc_cb_recall,      dec_cb_recall),
 };

 static struct rpc_version       nfs_cb_version4 = {
         .number                 = 1,
         .nrprocs                = ARRAY_SIZE(nfs4_cb_procedures),
         .procs                  = nfs4_cb_procedures
 };

 static struct rpc_version *	nfs_cb_version[] = {
 	NULL,
 	&nfs_cb_version4,
 };

 static struct rpc_program cb_program;

 static struct rpc_stat cb_stats = {
 		.program	= &cb_program
 };

 #define NFS4_CALLBACK 0x40000000
 static struct rpc_program cb_program = {
 		.name 		= "nfs4_cb",
 		.number		= NFS4_CALLBACK,
 		.nrvers		= ARRAY_SIZE(nfs_cb_version),
 		.version	= nfs_cb_version,
 		.stats		= &cb_stats,
 		.pipe_dir_name  = "/nfsd4_cb",
 };

 /* Reference counting, callback cleanup, etc., all look racy as heck.
  * And why is cb_set an atomic? */

 static int do_probe_callback(void *data)
 {
 	struct nfs4_client *clp = data;
 	struct sockaddr_in	addr;
 	struct nfs4_callback    *cb = &clp->cl_callback;
 	struct rpc_timeout	timeparms = {
 		.to_initval	= (NFSD_LEASE_TIME/4) * HZ,
 		.to_retries	= 5,
 		.to_maxval	= (NFSD_LEASE_TIME/2) * HZ,
 		.to_exponential	= 1,
 	};
 	struct rpc_create_args args = {
 		.protocol	= IPPROTO_TCP,
 		.address	= (struct sockaddr *)&addr,
 		.addrsize	= sizeof(addr),
 		.timeout	= &timeparms,
 		.program	= &cb_program,
 		.prognumber	= cb->cb_prog,
 		.version	= nfs_cb_version[1]->number,
 		.authflavor	= clp->cl_flavor,
 		.flags		= (RPC_CLNT_CREATE_NOPING | RPC_CLNT_CREATE_QUIET),
 		.client_name    = clp->cl_principal,
 	};
 	struct rpc_message msg = {
 		.rpc_proc       = &nfs4_cb_procedures[NFSPROC4_CLNT_CB_NULL],
 		.rpc_argp       = clp,
 	};
 	struct rpc_clnt *client;
 	int status;

 	if (!clp->cl_principal && (clp->cl_flavor >= RPC_AUTH_GSS_KRB5)) {
 		status = nfserr_cb_path_down;
 		goto out_err;
 	}

 	/* Initialize address */
 	memset(&addr, 0, sizeof(addr));
 	addr.sin_family = AF_INET;
 	addr.sin_port = htons(cb->cb_port);
 	addr.sin_addr.s_addr = htonl(cb->cb_addr);

 	/* Create RPC client */
 	client = rpc_create(&args);
 	if (IS_ERR(client)) {
 		dprintk("NFSD: couldn't create callback client\n");
 		status = PTR_ERR(client);
 		goto out_err;
 	}

 	status = rpc_call_sync(client, &msg, RPC_TASK_SOFT);

 	if (status)
 		goto out_release_client;

 	cb->cb_client = client;
 	atomic_set(&cb->cb_set, 1);
 	put_nfs4_client(clp);
 	return 0;
 out_release_client:
 	rpc_shutdown_client(client);
 out_err:
 	dprintk("NFSD: warning: no callback path to client %.*s\n",
 		(int)clp->cl_name.len, clp->cl_name.data);
 	put_nfs4_client(clp);
 	return status;
 }

 /*
  * Set up the callback client and put a NFSPROC4_CB_NULL on the wire...
  */
 void
 nfsd4_probe_callback(struct nfs4_client *clp)
 {
 	struct task_struct *t;

 	BUG_ON(atomic_read(&clp->cl_callback.cb_set));

 	/* the task holds a reference to the nfs4_client struct */
 	atomic_inc(&clp->cl_count);

 	t = kthread_run(do_probe_callback, clp, "nfs4_cb_probe");

 	if (IS_ERR(t))
 		atomic_dec(&clp->cl_count);

 	return;
 }

 /*
  * called with dp->dl_count inc'ed.
  */
 void
 nfsd4_cb_recall(struct nfs4_delegation *dp)
 {
 	struct nfs4_client *clp = dp->dl_client;
 	struct rpc_clnt *clnt = clp->cl_callback.cb_client;
 	struct nfs4_cb_recall *cbr = &dp->dl_recall;
 	struct rpc_message msg = {
 		.rpc_proc = &nfs4_cb_procedures[NFSPROC4_CLNT_CB_RECALL],
 		.rpc_argp = cbr,
 	};
 	int retries = 1;
 	int status = 0;

 	cbr->cbr_trunc = 0; /* XXX need to implement truncate optimization */
 	cbr->cbr_dp = dp;

 	status = rpc_call_sync(clnt, &msg, RPC_TASK_SOFT);
 	while (retries--) {
 		switch (status) {
 			case -EIO:
 				/* Network partition? */
 				atomic_set(&clp->cl_callback.cb_set, 0);
 			case -EBADHANDLE:
 			case -NFS4ERR_BAD_STATEID:
 				/* Race: client probably got cb_recall
 				 * before open reply granting delegation */
 				break;
 			default:
 				goto out_put_cred;
 		}
 		ssleep(2);
 		status = rpc_call_sync(clnt, &msg, RPC_TASK_SOFT);
 	}
 out_put_cred:
 	/*
 	 * Success or failure, now we're either waiting for lease expiration
 	 * or deleg_return.
 	 */
 	nfs4_lock_state();
 	put_nfs4_client(clp);
 	nfs4_put_delegation(dp);
 	nfs4_unlock_state();
 	return;
 }
	/*
	* linux/fs/nfsd/nfs4callback.c
	*
	* Copyright (c) 2001 The Regents of the University of Michigan.
	* All rights reserved.
	*
	* Kendrick Smith <kmsmith@umich.edu>
	* Andy Adamson <andros@umich.edu>
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	*
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. Neither the name of the University nor the names of its
	* contributors may be used to endorse or promote products derived
	* from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
	* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
	* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
	* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
	* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
	* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include <linux/module.h>
	#include <linux/list.h>
	#include <linux/inet.h>
	#include <linux/errno.h>
	#include <linux/delay.h>
	#include <linux/sched.h>
	#include <linux/kthread.h>
	#include <linux/sunrpc/xdr.h>
	#include <linux/sunrpc/svc.h>
	#include <linux/sunrpc/clnt.h>
	#include <linux/nfsd/nfsd.h>
	#include <linux/nfsd/state.h>
	#include <linux/sunrpc/sched.h>
	#include <linux/nfs4.h>

	#define NFSDDBG_FACILITY NFSDDBG_PROC

	#define NFSPROC4_CB_NULL 0
	#define NFSPROC4_CB_COMPOUND 1

	/* Index of predefined Linux callback client operations */

	enum {
	NFSPROC4_CLNT_CB_NULL = 0,
	NFSPROC4_CLNT_CB_RECALL,
	};

	enum nfs_cb_opnum4 {
	OP_CB_RECALL = 4,
	};

	#define NFS4_MAXTAGLEN 20

	#define NFS4_enc_cb_null_sz 0
	#define NFS4_dec_cb_null_sz 0
	#define cb_compound_enc_hdr_sz 4
	#define cb_compound_dec_hdr_sz (3 + (NFS4_MAXTAGLEN >> 2))
	#define op_enc_sz 1
	#define op_dec_sz 2
	#define enc_nfs4_fh_sz (1 + (NFS4_FHSIZE >> 2))
	#define enc_stateid_sz (NFS4_STATEID_SIZE >> 2)
	#define NFS4_enc_cb_recall_sz (cb_compound_enc_hdr_sz + \
	1 + enc_stateid_sz + \
	enc_nfs4_fh_sz)

	#define NFS4_dec_cb_recall_sz (cb_compound_dec_hdr_sz + \
	op_dec_sz)

	/*
	* Generic encode routines from fs/nfs/nfs4xdr.c
	*/
	static inline __be32 *
	xdr_writemem(__be32 p, const void ptr, int nbytes)
	{
	int tmp = XDR_QUADLEN(nbytes);
	if (!tmp)
	return p;
	p[tmp-1] = 0;
	memcpy(p, ptr, nbytes);
	return p + tmp;
	}

	#define WRITE32(n) *p++ = htonl(n)
	#define WRITEMEM(ptr,nbytes) do { \
	p = xdr_writemem(p, ptr, nbytes); \
	} while (0)
	#define RESERVE_SPACE(nbytes) do { \
	p = xdr_reserve_space(xdr, nbytes); \
	if (!p) dprintk("NFSD: RESERVE_SPACE(%d) failed in function %s\n", (int) (nbytes), __func__); \
	BUG_ON(!p); \
	} while (0)

	/*
	* Generic decode routines from fs/nfs/nfs4xdr.c
	*/
	#define DECODE_TAIL \
	status = 0; \
	out: \
	return status; \
	xdr_error: \
	dprintk("NFSD: xdr error! (%s:%d)\n", __FILE__, __LINE__); \
	status = -EIO; \
	goto out

	#define READ32(x) (x) = ntohl(*p++)
	#define READ64(x) do { \
	(x) = (u64)ntohl(*p++) << 32; \
	(x) \|= ntohl(*p++); \
	} while (0)
	#define READTIME(x) do { \
	p++; \
	(x.tv_sec) = ntohl(*p++); \
	(x.tv_nsec) = ntohl(*p++); \
	} while (0)
	#define READ_BUF(nbytes) do { \
	p = xdr_inline_decode(xdr, nbytes); \
	if (!p) { \
	dprintk("NFSD: %s: reply buffer overflowed in line %d.\n", \
	__func__, __LINE__); \
	return -EIO; \
	} \
	} while (0)

	struct nfs4_cb_compound_hdr {
	int status;
	u32 ident;
	u32 nops;
	u32 taglen;
	char * tag;
	};

	static struct {
	int stat;
	int errno;
	} nfs_cb_errtbl[] = {
	{ NFS4_OK, 0 },
	{ NFS4ERR_PERM, EPERM },
	{ NFS4ERR_NOENT, ENOENT },
	{ NFS4ERR_IO, EIO },
	{ NFS4ERR_NXIO, ENXIO },
	{ NFS4ERR_ACCESS, EACCES },
	{ NFS4ERR_EXIST, EEXIST },
	{ NFS4ERR_XDEV, EXDEV },
	{ NFS4ERR_NOTDIR, ENOTDIR },
	{ NFS4ERR_ISDIR, EISDIR },
	{ NFS4ERR_INVAL, EINVAL },
	{ NFS4ERR_FBIG, EFBIG },
	{ NFS4ERR_NOSPC, ENOSPC },
	{ NFS4ERR_ROFS, EROFS },
	{ NFS4ERR_MLINK, EMLINK },
	{ NFS4ERR_NAMETOOLONG, ENAMETOOLONG },
	{ NFS4ERR_NOTEMPTY, ENOTEMPTY },
	{ NFS4ERR_DQUOT, EDQUOT },
	{ NFS4ERR_STALE, ESTALE },
	{ NFS4ERR_BADHANDLE, EBADHANDLE },
	{ NFS4ERR_BAD_COOKIE, EBADCOOKIE },
	{ NFS4ERR_NOTSUPP, ENOTSUPP },
	{ NFS4ERR_TOOSMALL, ETOOSMALL },
	{ NFS4ERR_SERVERFAULT, ESERVERFAULT },
	{ NFS4ERR_BADTYPE, EBADTYPE },
	{ NFS4ERR_LOCKED, EAGAIN },
	{ NFS4ERR_RESOURCE, EREMOTEIO },
	{ NFS4ERR_SYMLINK, ELOOP },
	{ NFS4ERR_OP_ILLEGAL, EOPNOTSUPP },
	{ NFS4ERR_DEADLOCK, EDEADLK },
	{ -1, EIO }
	};

	static int
	nfs_cb_stat_to_errno(int stat)
	{
	int i;
	for (i = 0; nfs_cb_errtbl[i].stat != -1; i++) {
	if (nfs_cb_errtbl[i].stat == stat)
	return nfs_cb_errtbl[i].errno;
	}
	/* If we cannot translate the error, the recovery routines should
	* handle it.
	* Note: remaining NFSv4 error codes have values > 10000, so should
	* not conflict with native Linux error codes.
	*/
	return stat;
	}

	/*
	* XDR encode
	*/

	static int
	encode_cb_compound_hdr(struct xdr_stream xdr, struct nfs4_cb_compound_hdr hdr)
	{
	__be32 * p;

	RESERVE_SPACE(16);
	WRITE32(0); /* tag length is always 0 */
	WRITE32(NFS4_MINOR_VERSION);
	WRITE32(hdr->ident);
	WRITE32(hdr->nops);
	return 0;
	}

	static int
	encode_cb_recall(struct xdr_stream xdr, struct nfs4_cb_recall cb_rec)
	{
	__be32 *p;
	int len = cb_rec->cbr_fh.fh_size;

	RESERVE_SPACE(12+sizeof(cb_rec->cbr_stateid) + len);
	WRITE32(OP_CB_RECALL);
	WRITE32(cb_rec->cbr_stateid.si_generation);
	WRITEMEM(&cb_rec->cbr_stateid.si_opaque, sizeof(stateid_opaque_t));
	WRITE32(cb_rec->cbr_trunc);
	WRITE32(len);
	WRITEMEM(&cb_rec->cbr_fh.fh_base, len);
	return 0;
	}

	static int
	nfs4_xdr_enc_cb_null(struct rpc_rqst req, __be32 p)
	{
	struct xdr_stream xdrs, *xdr = &xdrs;

	xdr_init_encode(&xdrs, &req->rq_snd_buf, p);
	RESERVE_SPACE(0);
	return 0;
	}

	static int
	nfs4_xdr_enc_cb_recall(struct rpc_rqst req, __be32 p, struct nfs4_cb_recall *args)
	{
	struct xdr_stream xdr;
	struct nfs4_cb_compound_hdr hdr = {
	.ident = args->cbr_ident,
	.nops = 1,
	};

	xdr_init_encode(&xdr, &req->rq_snd_buf, p);
	encode_cb_compound_hdr(&xdr, &hdr);
	return (encode_cb_recall(&xdr, args));
	}


	static int
	decode_cb_compound_hdr(struct xdr_stream xdr, struct nfs4_cb_compound_hdr hdr){
	__be32 *p;

	READ_BUF(8);
	READ32(hdr->status);
	READ32(hdr->taglen);
	READ_BUF(hdr->taglen + 4);
	hdr->tag = (char *)p;
	p += XDR_QUADLEN(hdr->taglen);
	READ32(hdr->nops);
	return 0;
	}

	static int
	decode_cb_op_hdr(struct xdr_stream *xdr, enum nfs_opnum4 expected)
	{
	__be32 *p;
	u32 op;
	int32_t nfserr;

	READ_BUF(8);
	READ32(op);
	if (op != expected) {
	dprintk("NFSD: decode_cb_op_hdr: Callback server returned "
	" operation %d but we issued a request for %d\n",
	op, expected);
	return -EIO;
	}
	READ32(nfserr);
	if (nfserr != NFS_OK)
	return -nfs_cb_stat_to_errno(nfserr);
	return 0;
	}

	static int
	nfs4_xdr_dec_cb_null(struct rpc_rqst req, __be32 p)
	{
	return 0;
	}

	static int
	nfs4_xdr_dec_cb_recall(struct rpc_rqst rqstp, __be32 p)
	{
	struct xdr_stream xdr;
	struct nfs4_cb_compound_hdr hdr;
	int status;

	xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, p);
	status = decode_cb_compound_hdr(&xdr, &hdr);
	if (status)
	goto out;
	status = decode_cb_op_hdr(&xdr, OP_CB_RECALL);
	out:
	return status;
	}

	/*
	* RPC procedure tables
	*/
	#define PROC(proc, call, argtype, restype) \
	[NFSPROC4_CLNT_##proc] = { \
	.p_proc = NFSPROC4_CB_##call, \
	.p_encode = (kxdrproc_t) nfs4_xdr_##argtype, \
	.p_decode = (kxdrproc_t) nfs4_xdr_##restype, \
	.p_arglen = NFS4_##argtype##_sz, \
	.p_replen = NFS4_##restype##_sz, \
	.p_statidx = NFSPROC4_CB_##call, \
	.p_name = #proc, \
	}

	static struct rpc_procinfo nfs4_cb_procedures[] = {
	PROC(CB_NULL, NULL, enc_cb_null, dec_cb_null),
	PROC(CB_RECALL, COMPOUND, enc_cb_recall, dec_cb_recall),
	};

	static struct rpc_version nfs_cb_version4 = {
	.number = 1,
	.nrprocs = ARRAY_SIZE(nfs4_cb_procedures),
	.procs = nfs4_cb_procedures
	};

	static struct rpc_version * nfs_cb_version[] = {
	NULL,
	&nfs_cb_version4,
	};

	static struct rpc_program cb_program;

	static struct rpc_stat cb_stats = {
	.program = &cb_program
	};

	#define NFS4_CALLBACK 0x40000000
	static struct rpc_program cb_program = {
	.name = "nfs4_cb",
	.number = NFS4_CALLBACK,
	.nrvers = ARRAY_SIZE(nfs_cb_version),
	.version = nfs_cb_version,
	.stats = &cb_stats,
	.pipe_dir_name = "/nfsd4_cb",
	};

	/* Reference counting, callback cleanup, etc., all look racy as heck.
	* And why is cb_set an atomic? */

	static int do_probe_callback(void *data)
	{
	struct nfs4_client *clp = data;
	struct sockaddr_in addr;
	struct nfs4_callback *cb = &clp->cl_callback;
	struct rpc_timeout timeparms = {
	.to_initval = (NFSD_LEASE_TIME/4) * HZ,
	.to_retries = 5,
	.to_maxval = (NFSD_LEASE_TIME/2) * HZ,
	.to_exponential = 1,
	};
	struct rpc_create_args args = {
	.protocol = IPPROTO_TCP,
	.address = (struct sockaddr *)&addr,
	.addrsize = sizeof(addr),
	.timeout = &timeparms,
	.program = &cb_program,
	.prognumber = cb->cb_prog,
	.version = nfs_cb_version[1]->number,
	.authflavor = clp->cl_flavor,
	.flags = (RPC_CLNT_CREATE_NOPING \| RPC_CLNT_CREATE_QUIET),
	.client_name = clp->cl_principal,
	};
	struct rpc_message msg = {
	.rpc_proc = &nfs4_cb_procedures[NFSPROC4_CLNT_CB_NULL],
	.rpc_argp = clp,
	};
	struct rpc_clnt *client;
	int status;

	if (!clp->cl_principal && (clp->cl_flavor >= RPC_AUTH_GSS_KRB5)) {
	status = nfserr_cb_path_down;
	goto out_err;
	}

	/* Initialize address */
	memset(&addr, 0, sizeof(addr));
	addr.sin_family = AF_INET;
	addr.sin_port = htons(cb->cb_port);
	addr.sin_addr.s_addr = htonl(cb->cb_addr);

	/* Create RPC client */
	client = rpc_create(&args);
	if (IS_ERR(client)) {
	dprintk("NFSD: couldn't create callback client\n");
	status = PTR_ERR(client);
	goto out_err;
	}

	status = rpc_call_sync(client, &msg, RPC_TASK_SOFT);

	if (status)
	goto out_release_client;

	cb->cb_client = client;
	atomic_set(&cb->cb_set, 1);
	put_nfs4_client(clp);
	return 0;
	out_release_client:
	rpc_shutdown_client(client);
	out_err:
	dprintk("NFSD: warning: no callback path to client %.*s\n",
	(int)clp->cl_name.len, clp->cl_name.data);
	put_nfs4_client(clp);
	return status;
	}

	/*
	* Set up the callback client and put a NFSPROC4_CB_NULL on the wire...
	*/
	void
	nfsd4_probe_callback(struct nfs4_client *clp)
	{
	struct task_struct *t;

	BUG_ON(atomic_read(&clp->cl_callback.cb_set));

	/* the task holds a reference to the nfs4_client struct */
	atomic_inc(&clp->cl_count);

	t = kthread_run(do_probe_callback, clp, "nfs4_cb_probe");

	if (IS_ERR(t))
	atomic_dec(&clp->cl_count);

	return;
	}

	/*
	* called with dp->dl_count inc'ed.
	*/
	void
	nfsd4_cb_recall(struct nfs4_delegation *dp)
	{
	struct nfs4_client *clp = dp->dl_client;
	struct rpc_clnt *clnt = clp->cl_callback.cb_client;
	struct nfs4_cb_recall *cbr = &dp->dl_recall;
	struct rpc_message msg = {
	.rpc_proc = &nfs4_cb_procedures[NFSPROC4_CLNT_CB_RECALL],
	.rpc_argp = cbr,
	};
	int retries = 1;
	int status = 0;

	cbr->cbr_trunc = 0; /* XXX need to implement truncate optimization */
	cbr->cbr_dp = dp;

	status = rpc_call_sync(clnt, &msg, RPC_TASK_SOFT);
	while (retries--) {
	switch (status) {
	case -EIO:
	/* Network partition? */
	atomic_set(&clp->cl_callback.cb_set, 0);
	case -EBADHANDLE:
	case -NFS4ERR_BAD_STATEID:
	/* Race: client probably got cb_recall
	* before open reply granting delegation */
	break;
	default:
	goto out_put_cred;
	}
	ssleep(2);
	status = rpc_call_sync(clnt, &msg, RPC_TASK_SOFT);
	}
	out_put_cred:
	/*
	* Success or failure, now we're either waiting for lease expiration
	* or deleg_return.
	*/
	nfs4_lock_state();
	put_nfs4_client(clp);
	nfs4_put_delegation(dp);
	nfs4_unlock_state();
	return;
	}