xref: /openbmc/linux/fs/nfsd/nfs4callback.c (revision c1d3fb8a)
1 /*
2  *  Copyright (c) 2001 The Regents of the University of Michigan.
3  *  All rights reserved.
4  *
5  *  Kendrick Smith <kmsmith@umich.edu>
6  *  Andy Adamson <andros@umich.edu>
7  *
8  *  Redistribution and use in source and binary forms, with or without
9  *  modification, are permitted provided that the following conditions
10  *  are met:
11  *
12  *  1. Redistributions of source code must retain the above copyright
13  *     notice, this list of conditions and the following disclaimer.
14  *  2. Redistributions in binary form must reproduce the above copyright
15  *     notice, this list of conditions and the following disclaimer in the
16  *     documentation and/or other materials provided with the distribution.
17  *  3. Neither the name of the University nor the names of its
18  *     contributors may be used to endorse or promote products derived
19  *     from this software without specific prior written permission.
20  *
21  *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
22  *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
23  *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
24  *  DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25  *  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
26  *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
27  *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
28  *  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
29  *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
30  *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
31  *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32  */
33 
34 #include <linux/sunrpc/clnt.h>
35 #include <linux/sunrpc/xprt.h>
36 #include <linux/sunrpc/svc_xprt.h>
37 #include <linux/slab.h>
38 #include "nfsd.h"
39 #include "state.h"
40 #include "netns.h"
41 #include "xdr4cb.h"
42 #include "xdr4.h"
43 
44 #define NFSDDBG_FACILITY                NFSDDBG_PROC
45 
46 static void nfsd4_mark_cb_fault(struct nfs4_client *, int reason);
47 
48 #define NFSPROC4_CB_NULL 0
49 #define NFSPROC4_CB_COMPOUND 1
50 
51 /* Index of predefined Linux callback client operations */
52 
53 struct nfs4_cb_compound_hdr {
54 	/* args */
55 	u32		ident;	/* minorversion 0 only */
56 	u32		nops;
57 	__be32		*nops_p;
58 	u32		minorversion;
59 	/* res */
60 	int		status;
61 };
62 
63 static __be32 *xdr_encode_empty_array(__be32 *p)
64 {
65 	*p++ = xdr_zero;
66 	return p;
67 }
68 
69 /*
70  * Encode/decode NFSv4 CB basic data types
71  *
72  * Basic NFSv4 callback data types are defined in section 15 of RFC
73  * 3530: "Network File System (NFS) version 4 Protocol" and section
74  * 20 of RFC 5661: "Network File System (NFS) Version 4 Minor Version
75  * 1 Protocol"
76  */
77 
78 /*
79  *	nfs_cb_opnum4
80  *
81  *	enum nfs_cb_opnum4 {
82  *		OP_CB_GETATTR		= 3,
83  *		  ...
84  *	};
85  */
86 enum nfs_cb_opnum4 {
87 	OP_CB_GETATTR			= 3,
88 	OP_CB_RECALL			= 4,
89 	OP_CB_LAYOUTRECALL		= 5,
90 	OP_CB_NOTIFY			= 6,
91 	OP_CB_PUSH_DELEG		= 7,
92 	OP_CB_RECALL_ANY		= 8,
93 	OP_CB_RECALLABLE_OBJ_AVAIL	= 9,
94 	OP_CB_RECALL_SLOT		= 10,
95 	OP_CB_SEQUENCE			= 11,
96 	OP_CB_WANTS_CANCELLED		= 12,
97 	OP_CB_NOTIFY_LOCK		= 13,
98 	OP_CB_NOTIFY_DEVICEID		= 14,
99 	OP_CB_OFFLOAD			= 15,
100 	OP_CB_ILLEGAL			= 10044
101 };
102 
103 static void encode_nfs_cb_opnum4(struct xdr_stream *xdr, enum nfs_cb_opnum4 op)
104 {
105 	__be32 *p;
106 
107 	p = xdr_reserve_space(xdr, 4);
108 	*p = cpu_to_be32(op);
109 }
110 
111 /*
112  * nfs_fh4
113  *
114  *	typedef opaque nfs_fh4<NFS4_FHSIZE>;
115  */
116 static void encode_nfs_fh4(struct xdr_stream *xdr, const struct knfsd_fh *fh)
117 {
118 	u32 length = fh->fh_size;
119 	__be32 *p;
120 
121 	BUG_ON(length > NFS4_FHSIZE);
122 	p = xdr_reserve_space(xdr, 4 + length);
123 	xdr_encode_opaque(p, &fh->fh_base, length);
124 }
125 
126 /*
127  * stateid4
128  *
129  *	struct stateid4 {
130  *		uint32_t	seqid;
131  *		opaque		other[12];
132  *	};
133  */
134 static void encode_stateid4(struct xdr_stream *xdr, const stateid_t *sid)
135 {
136 	__be32 *p;
137 
138 	p = xdr_reserve_space(xdr, NFS4_STATEID_SIZE);
139 	*p++ = cpu_to_be32(sid->si_generation);
140 	xdr_encode_opaque_fixed(p, &sid->si_opaque, NFS4_STATEID_OTHER_SIZE);
141 }
142 
143 /*
144  * sessionid4
145  *
146  *	typedef opaque sessionid4[NFS4_SESSIONID_SIZE];
147  */
148 static void encode_sessionid4(struct xdr_stream *xdr,
149 			      const struct nfsd4_session *session)
150 {
151 	__be32 *p;
152 
153 	p = xdr_reserve_space(xdr, NFS4_MAX_SESSIONID_LEN);
154 	xdr_encode_opaque_fixed(p, session->se_sessionid.data,
155 					NFS4_MAX_SESSIONID_LEN);
156 }
157 
158 /*
159  * nfsstat4
160  */
161 static const struct {
162 	int stat;
163 	int errno;
164 } nfs_cb_errtbl[] = {
165 	{ NFS4_OK,		0		},
166 	{ NFS4ERR_PERM,		-EPERM		},
167 	{ NFS4ERR_NOENT,	-ENOENT		},
168 	{ NFS4ERR_IO,		-EIO		},
169 	{ NFS4ERR_NXIO,		-ENXIO		},
170 	{ NFS4ERR_ACCESS,	-EACCES		},
171 	{ NFS4ERR_EXIST,	-EEXIST		},
172 	{ NFS4ERR_XDEV,		-EXDEV		},
173 	{ NFS4ERR_NOTDIR,	-ENOTDIR	},
174 	{ NFS4ERR_ISDIR,	-EISDIR		},
175 	{ NFS4ERR_INVAL,	-EINVAL		},
176 	{ NFS4ERR_FBIG,		-EFBIG		},
177 	{ NFS4ERR_NOSPC,	-ENOSPC		},
178 	{ NFS4ERR_ROFS,		-EROFS		},
179 	{ NFS4ERR_MLINK,	-EMLINK		},
180 	{ NFS4ERR_NAMETOOLONG,	-ENAMETOOLONG	},
181 	{ NFS4ERR_NOTEMPTY,	-ENOTEMPTY	},
182 	{ NFS4ERR_DQUOT,	-EDQUOT		},
183 	{ NFS4ERR_STALE,	-ESTALE		},
184 	{ NFS4ERR_BADHANDLE,	-EBADHANDLE	},
185 	{ NFS4ERR_BAD_COOKIE,	-EBADCOOKIE	},
186 	{ NFS4ERR_NOTSUPP,	-ENOTSUPP	},
187 	{ NFS4ERR_TOOSMALL,	-ETOOSMALL	},
188 	{ NFS4ERR_SERVERFAULT,	-ESERVERFAULT	},
189 	{ NFS4ERR_BADTYPE,	-EBADTYPE	},
190 	{ NFS4ERR_LOCKED,	-EAGAIN		},
191 	{ NFS4ERR_RESOURCE,	-EREMOTEIO	},
192 	{ NFS4ERR_SYMLINK,	-ELOOP		},
193 	{ NFS4ERR_OP_ILLEGAL,	-EOPNOTSUPP	},
194 	{ NFS4ERR_DEADLOCK,	-EDEADLK	},
195 	{ -1,			-EIO		}
196 };
197 
198 /*
199  * If we cannot translate the error, the recovery routines should
200  * handle it.
201  *
202  * Note: remaining NFSv4 error codes have values > 10000, so should
203  * not conflict with native Linux error codes.
204  */
205 static int nfs_cb_stat_to_errno(int status)
206 {
207 	int i;
208 
209 	for (i = 0; nfs_cb_errtbl[i].stat != -1; i++) {
210 		if (nfs_cb_errtbl[i].stat == status)
211 			return nfs_cb_errtbl[i].errno;
212 	}
213 
214 	dprintk("NFSD: Unrecognized NFS CB status value: %u\n", status);
215 	return -status;
216 }
217 
218 static int decode_cb_op_status(struct xdr_stream *xdr,
219 			       enum nfs_cb_opnum4 expected, int *status)
220 {
221 	__be32 *p;
222 	u32 op;
223 
224 	p = xdr_inline_decode(xdr, 4 + 4);
225 	if (unlikely(p == NULL))
226 		goto out_overflow;
227 	op = be32_to_cpup(p++);
228 	if (unlikely(op != expected))
229 		goto out_unexpected;
230 	*status = nfs_cb_stat_to_errno(be32_to_cpup(p));
231 	return 0;
232 out_overflow:
233 	return -EIO;
234 out_unexpected:
235 	dprintk("NFSD: Callback server returned operation %d but "
236 		"we issued a request for %d\n", op, expected);
237 	return -EIO;
238 }
239 
240 /*
241  * CB_COMPOUND4args
242  *
243  *	struct CB_COMPOUND4args {
244  *		utf8str_cs	tag;
245  *		uint32_t	minorversion;
246  *		uint32_t	callback_ident;
247  *		nfs_cb_argop4	argarray<>;
248  *	};
249 */
250 static void encode_cb_compound4args(struct xdr_stream *xdr,
251 				    struct nfs4_cb_compound_hdr *hdr)
252 {
253 	__be32 * p;
254 
255 	p = xdr_reserve_space(xdr, 4 + 4 + 4 + 4);
256 	p = xdr_encode_empty_array(p);		/* empty tag */
257 	*p++ = cpu_to_be32(hdr->minorversion);
258 	*p++ = cpu_to_be32(hdr->ident);
259 
260 	hdr->nops_p = p;
261 	*p = cpu_to_be32(hdr->nops);		/* argarray element count */
262 }
263 
264 /*
265  * Update argarray element count
266  */
267 static void encode_cb_nops(struct nfs4_cb_compound_hdr *hdr)
268 {
269 	BUG_ON(hdr->nops > NFS4_MAX_BACK_CHANNEL_OPS);
270 	*hdr->nops_p = cpu_to_be32(hdr->nops);
271 }
272 
273 /*
274  * CB_COMPOUND4res
275  *
276  *	struct CB_COMPOUND4res {
277  *		nfsstat4	status;
278  *		utf8str_cs	tag;
279  *		nfs_cb_resop4	resarray<>;
280  *	};
281  */
282 static int decode_cb_compound4res(struct xdr_stream *xdr,
283 				  struct nfs4_cb_compound_hdr *hdr)
284 {
285 	u32 length;
286 	__be32 *p;
287 
288 	p = xdr_inline_decode(xdr, 4 + 4);
289 	if (unlikely(p == NULL))
290 		goto out_overflow;
291 	hdr->status = be32_to_cpup(p++);
292 	/* Ignore the tag */
293 	length = be32_to_cpup(p++);
294 	p = xdr_inline_decode(xdr, length + 4);
295 	if (unlikely(p == NULL))
296 		goto out_overflow;
297 	p += XDR_QUADLEN(length);
298 	hdr->nops = be32_to_cpup(p);
299 	return 0;
300 out_overflow:
301 	return -EIO;
302 }
303 
304 /*
305  * CB_RECALL4args
306  *
307  *	struct CB_RECALL4args {
308  *		stateid4	stateid;
309  *		bool		truncate;
310  *		nfs_fh4		fh;
311  *	};
312  */
313 static void encode_cb_recall4args(struct xdr_stream *xdr,
314 				  const struct nfs4_delegation *dp,
315 				  struct nfs4_cb_compound_hdr *hdr)
316 {
317 	__be32 *p;
318 
319 	encode_nfs_cb_opnum4(xdr, OP_CB_RECALL);
320 	encode_stateid4(xdr, &dp->dl_stid.sc_stateid);
321 
322 	p = xdr_reserve_space(xdr, 4);
323 	*p++ = xdr_zero;			/* truncate */
324 
325 	encode_nfs_fh4(xdr, &dp->dl_stid.sc_file->fi_fhandle);
326 
327 	hdr->nops++;
328 }
329 
330 /*
331  * CB_SEQUENCE4args
332  *
333  *	struct CB_SEQUENCE4args {
334  *		sessionid4		csa_sessionid;
335  *		sequenceid4		csa_sequenceid;
336  *		slotid4			csa_slotid;
337  *		slotid4			csa_highest_slotid;
338  *		bool			csa_cachethis;
339  *		referring_call_list4	csa_referring_call_lists<>;
340  *	};
341  */
342 static void encode_cb_sequence4args(struct xdr_stream *xdr,
343 				    const struct nfsd4_callback *cb,
344 				    struct nfs4_cb_compound_hdr *hdr)
345 {
346 	struct nfsd4_session *session = cb->cb_clp->cl_cb_session;
347 	__be32 *p;
348 
349 	if (hdr->minorversion == 0)
350 		return;
351 
352 	encode_nfs_cb_opnum4(xdr, OP_CB_SEQUENCE);
353 	encode_sessionid4(xdr, session);
354 
355 	p = xdr_reserve_space(xdr, 4 + 4 + 4 + 4 + 4);
356 	*p++ = cpu_to_be32(session->se_cb_seq_nr);	/* csa_sequenceid */
357 	*p++ = xdr_zero;			/* csa_slotid */
358 	*p++ = xdr_zero;			/* csa_highest_slotid */
359 	*p++ = xdr_zero;			/* csa_cachethis */
360 	xdr_encode_empty_array(p);		/* csa_referring_call_lists */
361 
362 	hdr->nops++;
363 }
364 
365 /*
366  * CB_SEQUENCE4resok
367  *
368  *	struct CB_SEQUENCE4resok {
369  *		sessionid4	csr_sessionid;
370  *		sequenceid4	csr_sequenceid;
371  *		slotid4		csr_slotid;
372  *		slotid4		csr_highest_slotid;
373  *		slotid4		csr_target_highest_slotid;
374  *	};
375  *
376  *	union CB_SEQUENCE4res switch (nfsstat4 csr_status) {
377  *	case NFS4_OK:
378  *		CB_SEQUENCE4resok	csr_resok4;
379  *	default:
380  *		void;
381  *	};
382  *
383  * Our current back channel implmentation supports a single backchannel
384  * with a single slot.
385  */
386 static int decode_cb_sequence4resok(struct xdr_stream *xdr,
387 				    struct nfsd4_callback *cb)
388 {
389 	struct nfsd4_session *session = cb->cb_clp->cl_cb_session;
390 	int status = -ESERVERFAULT;
391 	__be32 *p;
392 	u32 dummy;
393 
394 	/*
395 	 * If the server returns different values for sessionID, slotID or
396 	 * sequence number, the server is looney tunes.
397 	 */
398 	p = xdr_inline_decode(xdr, NFS4_MAX_SESSIONID_LEN + 4 + 4 + 4 + 4);
399 	if (unlikely(p == NULL))
400 		goto out_overflow;
401 
402 	if (memcmp(p, session->se_sessionid.data, NFS4_MAX_SESSIONID_LEN)) {
403 		dprintk("NFS: %s Invalid session id\n", __func__);
404 		goto out;
405 	}
406 	p += XDR_QUADLEN(NFS4_MAX_SESSIONID_LEN);
407 
408 	dummy = be32_to_cpup(p++);
409 	if (dummy != session->se_cb_seq_nr) {
410 		dprintk("NFS: %s Invalid sequence number\n", __func__);
411 		goto out;
412 	}
413 
414 	dummy = be32_to_cpup(p++);
415 	if (dummy != 0) {
416 		dprintk("NFS: %s Invalid slotid\n", __func__);
417 		goto out;
418 	}
419 
420 	/*
421 	 * FIXME: process highest slotid and target highest slotid
422 	 */
423 	status = 0;
424 out:
425 	cb->cb_seq_status = status;
426 	return status;
427 out_overflow:
428 	status = -EIO;
429 	goto out;
430 }
431 
432 static int decode_cb_sequence4res(struct xdr_stream *xdr,
433 				  struct nfsd4_callback *cb)
434 {
435 	int status;
436 
437 	if (cb->cb_clp->cl_minorversion == 0)
438 		return 0;
439 
440 	status = decode_cb_op_status(xdr, OP_CB_SEQUENCE, &cb->cb_seq_status);
441 	if (unlikely(status || cb->cb_seq_status))
442 		return status;
443 
444 	return decode_cb_sequence4resok(xdr, cb);
445 }
446 
447 /*
448  * NFSv4.0 and NFSv4.1 XDR encode functions
449  *
450  * NFSv4.0 callback argument types are defined in section 15 of RFC
451  * 3530: "Network File System (NFS) version 4 Protocol" and section 20
452  * of RFC 5661:  "Network File System (NFS) Version 4 Minor Version 1
453  * Protocol".
454  */
455 
456 /*
457  * NB: Without this zero space reservation, callbacks over krb5p fail
458  */
459 static void nfs4_xdr_enc_cb_null(struct rpc_rqst *req, struct xdr_stream *xdr,
460 				 const void *__unused)
461 {
462 	xdr_reserve_space(xdr, 0);
463 }
464 
465 /*
466  * 20.2. Operation 4: CB_RECALL - Recall a Delegation
467  */
468 static void nfs4_xdr_enc_cb_recall(struct rpc_rqst *req, struct xdr_stream *xdr,
469 				   const void *data)
470 {
471 	const struct nfsd4_callback *cb = data;
472 	const struct nfs4_delegation *dp = cb_to_delegation(cb);
473 	struct nfs4_cb_compound_hdr hdr = {
474 		.ident = cb->cb_clp->cl_cb_ident,
475 		.minorversion = cb->cb_clp->cl_minorversion,
476 	};
477 
478 	encode_cb_compound4args(xdr, &hdr);
479 	encode_cb_sequence4args(xdr, cb, &hdr);
480 	encode_cb_recall4args(xdr, dp, &hdr);
481 	encode_cb_nops(&hdr);
482 }
483 
484 
485 /*
486  * NFSv4.0 and NFSv4.1 XDR decode functions
487  *
488  * NFSv4.0 callback result types are defined in section 15 of RFC
489  * 3530: "Network File System (NFS) version 4 Protocol" and section 20
490  * of RFC 5661:  "Network File System (NFS) Version 4 Minor Version 1
491  * Protocol".
492  */
493 
494 static int nfs4_xdr_dec_cb_null(struct rpc_rqst *req, struct xdr_stream *xdr,
495 				void *__unused)
496 {
497 	return 0;
498 }
499 
500 /*
501  * 20.2. Operation 4: CB_RECALL - Recall a Delegation
502  */
503 static int nfs4_xdr_dec_cb_recall(struct rpc_rqst *rqstp,
504 				  struct xdr_stream *xdr,
505 				  void *data)
506 {
507 	struct nfsd4_callback *cb = data;
508 	struct nfs4_cb_compound_hdr hdr;
509 	int status;
510 
511 	status = decode_cb_compound4res(xdr, &hdr);
512 	if (unlikely(status))
513 		return status;
514 
515 	status = decode_cb_sequence4res(xdr, cb);
516 	if (unlikely(status || cb->cb_seq_status))
517 		return status;
518 
519 	return decode_cb_op_status(xdr, OP_CB_RECALL, &cb->cb_status);
520 }
521 
522 #ifdef CONFIG_NFSD_PNFS
523 /*
524  * CB_LAYOUTRECALL4args
525  *
526  *	struct layoutrecall_file4 {
527  *		nfs_fh4         lor_fh;
528  *		offset4         lor_offset;
529  *		length4         lor_length;
530  *		stateid4        lor_stateid;
531  *	};
532  *
533  *	union layoutrecall4 switch(layoutrecall_type4 lor_recalltype) {
534  *	case LAYOUTRECALL4_FILE:
535  *		layoutrecall_file4 lor_layout;
536  *	case LAYOUTRECALL4_FSID:
537  *		fsid4              lor_fsid;
538  *	case LAYOUTRECALL4_ALL:
539  *		void;
540  *	};
541  *
542  *	struct CB_LAYOUTRECALL4args {
543  *		layouttype4             clora_type;
544  *		layoutiomode4           clora_iomode;
545  *		bool                    clora_changed;
546  *		layoutrecall4           clora_recall;
547  *	};
548  */
549 static void encode_cb_layout4args(struct xdr_stream *xdr,
550 				  const struct nfs4_layout_stateid *ls,
551 				  struct nfs4_cb_compound_hdr *hdr)
552 {
553 	__be32 *p;
554 
555 	BUG_ON(hdr->minorversion == 0);
556 
557 	p = xdr_reserve_space(xdr, 5 * 4);
558 	*p++ = cpu_to_be32(OP_CB_LAYOUTRECALL);
559 	*p++ = cpu_to_be32(ls->ls_layout_type);
560 	*p++ = cpu_to_be32(IOMODE_ANY);
561 	*p++ = cpu_to_be32(1);
562 	*p = cpu_to_be32(RETURN_FILE);
563 
564 	encode_nfs_fh4(xdr, &ls->ls_stid.sc_file->fi_fhandle);
565 
566 	p = xdr_reserve_space(xdr, 2 * 8);
567 	p = xdr_encode_hyper(p, 0);
568 	xdr_encode_hyper(p, NFS4_MAX_UINT64);
569 
570 	encode_stateid4(xdr, &ls->ls_recall_sid);
571 
572 	hdr->nops++;
573 }
574 
575 static void nfs4_xdr_enc_cb_layout(struct rpc_rqst *req,
576 				   struct xdr_stream *xdr,
577 				   const void *data)
578 {
579 	const struct nfsd4_callback *cb = data;
580 	const struct nfs4_layout_stateid *ls =
581 		container_of(cb, struct nfs4_layout_stateid, ls_recall);
582 	struct nfs4_cb_compound_hdr hdr = {
583 		.ident = 0,
584 		.minorversion = cb->cb_clp->cl_minorversion,
585 	};
586 
587 	encode_cb_compound4args(xdr, &hdr);
588 	encode_cb_sequence4args(xdr, cb, &hdr);
589 	encode_cb_layout4args(xdr, ls, &hdr);
590 	encode_cb_nops(&hdr);
591 }
592 
593 static int nfs4_xdr_dec_cb_layout(struct rpc_rqst *rqstp,
594 				  struct xdr_stream *xdr,
595 				  void *data)
596 {
597 	struct nfsd4_callback *cb = data;
598 	struct nfs4_cb_compound_hdr hdr;
599 	int status;
600 
601 	status = decode_cb_compound4res(xdr, &hdr);
602 	if (unlikely(status))
603 		return status;
604 
605 	status = decode_cb_sequence4res(xdr, cb);
606 	if (unlikely(status || cb->cb_seq_status))
607 		return status;
608 
609 	return decode_cb_op_status(xdr, OP_CB_LAYOUTRECALL, &cb->cb_status);
610 }
611 #endif /* CONFIG_NFSD_PNFS */
612 
613 static void encode_stateowner(struct xdr_stream *xdr, struct nfs4_stateowner *so)
614 {
615 	__be32	*p;
616 
617 	p = xdr_reserve_space(xdr, 8 + 4 + so->so_owner.len);
618 	p = xdr_encode_opaque_fixed(p, &so->so_client->cl_clientid, 8);
619 	xdr_encode_opaque(p, so->so_owner.data, so->so_owner.len);
620 }
621 
622 static void nfs4_xdr_enc_cb_notify_lock(struct rpc_rqst *req,
623 					struct xdr_stream *xdr,
624 					const void *data)
625 {
626 	const struct nfsd4_callback *cb = data;
627 	const struct nfsd4_blocked_lock *nbl =
628 		container_of(cb, struct nfsd4_blocked_lock, nbl_cb);
629 	struct nfs4_lockowner *lo = (struct nfs4_lockowner *)nbl->nbl_lock.fl_owner;
630 	struct nfs4_cb_compound_hdr hdr = {
631 		.ident = 0,
632 		.minorversion = cb->cb_clp->cl_minorversion,
633 	};
634 
635 	__be32 *p;
636 
637 	BUG_ON(hdr.minorversion == 0);
638 
639 	encode_cb_compound4args(xdr, &hdr);
640 	encode_cb_sequence4args(xdr, cb, &hdr);
641 
642 	p = xdr_reserve_space(xdr, 4);
643 	*p = cpu_to_be32(OP_CB_NOTIFY_LOCK);
644 	encode_nfs_fh4(xdr, &nbl->nbl_fh);
645 	encode_stateowner(xdr, &lo->lo_owner);
646 	hdr.nops++;
647 
648 	encode_cb_nops(&hdr);
649 }
650 
651 static int nfs4_xdr_dec_cb_notify_lock(struct rpc_rqst *rqstp,
652 					struct xdr_stream *xdr,
653 					void *data)
654 {
655 	struct nfsd4_callback *cb = data;
656 	struct nfs4_cb_compound_hdr hdr;
657 	int status;
658 
659 	status = decode_cb_compound4res(xdr, &hdr);
660 	if (unlikely(status))
661 		return status;
662 
663 	status = decode_cb_sequence4res(xdr, cb);
664 	if (unlikely(status || cb->cb_seq_status))
665 		return status;
666 
667 	return decode_cb_op_status(xdr, OP_CB_NOTIFY_LOCK, &cb->cb_status);
668 }
669 
670 /*
671  * struct write_response4 {
672  *	stateid4	wr_callback_id<1>;
673  *	length4		wr_count;
674  *	stable_how4	wr_committed;
675  *	verifier4	wr_writeverf;
676  * };
677  * union offload_info4 switch (nfsstat4 coa_status) {
678  *	case NFS4_OK:
679  *		write_response4	coa_resok4;
680  *	default:
681  *	length4		coa_bytes_copied;
682  * };
683  * struct CB_OFFLOAD4args {
684  *	nfs_fh4		coa_fh;
685  *	stateid4	coa_stateid;
686  *	offload_info4	coa_offload_info;
687  * };
688  */
689 static void encode_offload_info4(struct xdr_stream *xdr,
690 				 __be32 nfserr,
691 				 const struct nfsd4_copy *cp)
692 {
693 	__be32 *p;
694 
695 	p = xdr_reserve_space(xdr, 4);
696 	*p++ = nfserr;
697 	if (!nfserr) {
698 		p = xdr_reserve_space(xdr, 4 + 8 + 4 + NFS4_VERIFIER_SIZE);
699 		p = xdr_encode_empty_array(p);
700 		p = xdr_encode_hyper(p, cp->cp_res.wr_bytes_written);
701 		*p++ = cpu_to_be32(cp->cp_res.wr_stable_how);
702 		p = xdr_encode_opaque_fixed(p, cp->cp_res.wr_verifier.data,
703 					    NFS4_VERIFIER_SIZE);
704 	} else {
705 		p = xdr_reserve_space(xdr, 8);
706 		/* We always return success if bytes were written */
707 		p = xdr_encode_hyper(p, 0);
708 	}
709 }
710 
711 static void encode_cb_offload4args(struct xdr_stream *xdr,
712 				   __be32 nfserr,
713 				   const struct knfsd_fh *fh,
714 				   const struct nfsd4_copy *cp,
715 				   struct nfs4_cb_compound_hdr *hdr)
716 {
717 	__be32 *p;
718 
719 	p = xdr_reserve_space(xdr, 4);
720 	*p++ = cpu_to_be32(OP_CB_OFFLOAD);
721 	encode_nfs_fh4(xdr, fh);
722 	encode_stateid4(xdr, &cp->cp_res.cb_stateid);
723 	encode_offload_info4(xdr, nfserr, cp);
724 
725 	hdr->nops++;
726 }
727 
728 static void nfs4_xdr_enc_cb_offload(struct rpc_rqst *req,
729 				    struct xdr_stream *xdr,
730 				    const void *data)
731 {
732 	const struct nfsd4_callback *cb = data;
733 	const struct nfsd4_copy *cp =
734 		container_of(cb, struct nfsd4_copy, cp_cb);
735 	struct nfs4_cb_compound_hdr hdr = {
736 		.ident = 0,
737 		.minorversion = cb->cb_clp->cl_minorversion,
738 	};
739 
740 	encode_cb_compound4args(xdr, &hdr);
741 	encode_cb_sequence4args(xdr, cb, &hdr);
742 	encode_cb_offload4args(xdr, cp->nfserr, &cp->fh, cp, &hdr);
743 	encode_cb_nops(&hdr);
744 }
745 
746 static int nfs4_xdr_dec_cb_offload(struct rpc_rqst *rqstp,
747 				   struct xdr_stream *xdr,
748 				   void *data)
749 {
750 	struct nfsd4_callback *cb = data;
751 	struct nfs4_cb_compound_hdr hdr;
752 	int status;
753 
754 	status = decode_cb_compound4res(xdr, &hdr);
755 	if (unlikely(status))
756 		return status;
757 
758 	status = decode_cb_sequence4res(xdr, cb);
759 	if (unlikely(status || cb->cb_seq_status))
760 		return status;
761 
762 	return decode_cb_op_status(xdr, OP_CB_OFFLOAD, &cb->cb_status);
763 }
764 /*
765  * RPC procedure tables
766  */
767 #define PROC(proc, call, argtype, restype)				\
768 [NFSPROC4_CLNT_##proc] = {						\
769 	.p_proc    = NFSPROC4_CB_##call,				\
770 	.p_encode  = nfs4_xdr_enc_##argtype,		\
771 	.p_decode  = nfs4_xdr_dec_##restype,				\
772 	.p_arglen  = NFS4_enc_##argtype##_sz,				\
773 	.p_replen  = NFS4_dec_##restype##_sz,				\
774 	.p_statidx = NFSPROC4_CB_##call,				\
775 	.p_name    = #proc,						\
776 }
777 
778 static const struct rpc_procinfo nfs4_cb_procedures[] = {
779 	PROC(CB_NULL,	NULL,		cb_null,	cb_null),
780 	PROC(CB_RECALL,	COMPOUND,	cb_recall,	cb_recall),
781 #ifdef CONFIG_NFSD_PNFS
782 	PROC(CB_LAYOUT,	COMPOUND,	cb_layout,	cb_layout),
783 #endif
784 	PROC(CB_NOTIFY_LOCK,	COMPOUND,	cb_notify_lock,	cb_notify_lock),
785 	PROC(CB_OFFLOAD,	COMPOUND,	cb_offload,	cb_offload),
786 };
787 
788 static unsigned int nfs4_cb_counts[ARRAY_SIZE(nfs4_cb_procedures)];
789 static const struct rpc_version nfs_cb_version4 = {
790 /*
791  * Note on the callback rpc program version number: despite language in rfc
792  * 5661 section 18.36.3 requiring servers to use 4 in this field, the
793  * official xdr descriptions for both 4.0 and 4.1 specify version 1, and
794  * in practice that appears to be what implementations use.  The section
795  * 18.36.3 language is expected to be fixed in an erratum.
796  */
797 	.number			= 1,
798 	.nrprocs		= ARRAY_SIZE(nfs4_cb_procedures),
799 	.procs			= nfs4_cb_procedures,
800 	.counts			= nfs4_cb_counts,
801 };
802 
803 static const struct rpc_version *nfs_cb_version[2] = {
804 	[1] = &nfs_cb_version4,
805 };
806 
807 static const struct rpc_program cb_program;
808 
809 static struct rpc_stat cb_stats = {
810 	.program		= &cb_program
811 };
812 
813 #define NFS4_CALLBACK 0x40000000
814 static const struct rpc_program cb_program = {
815 	.name			= "nfs4_cb",
816 	.number			= NFS4_CALLBACK,
817 	.nrvers			= ARRAY_SIZE(nfs_cb_version),
818 	.version		= nfs_cb_version,
819 	.stats			= &cb_stats,
820 	.pipe_dir_name		= "nfsd4_cb",
821 };
822 
823 static int max_cb_time(struct net *net)
824 {
825 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
826 	return max(nn->nfsd4_lease/10, (time_t)1) * HZ;
827 }
828 
829 static struct workqueue_struct *callback_wq;
830 
831 static bool nfsd4_queue_cb(struct nfsd4_callback *cb)
832 {
833 	return queue_work(callback_wq, &cb->cb_work);
834 }
835 
836 static void nfsd41_cb_inflight_begin(struct nfs4_client *clp)
837 {
838 	atomic_inc(&clp->cl_cb_inflight);
839 }
840 
841 static void nfsd41_cb_inflight_end(struct nfs4_client *clp)
842 {
843 
844 	if (atomic_dec_and_test(&clp->cl_cb_inflight))
845 		wake_up_var(&clp->cl_cb_inflight);
846 }
847 
848 static void nfsd41_cb_inflight_wait_complete(struct nfs4_client *clp)
849 {
850 	wait_var_event(&clp->cl_cb_inflight,
851 			!atomic_read(&clp->cl_cb_inflight));
852 }
853 
854 static const struct cred *get_backchannel_cred(struct nfs4_client *clp, struct rpc_clnt *client, struct nfsd4_session *ses)
855 {
856 	if (clp->cl_minorversion == 0) {
857 		client->cl_principal = clp->cl_cred.cr_targ_princ ?
858 			clp->cl_cred.cr_targ_princ : "nfs";
859 
860 		return get_cred(rpc_machine_cred());
861 	} else {
862 		struct cred *kcred;
863 
864 		kcred = prepare_kernel_cred(NULL);
865 		if (!kcred)
866 			return NULL;
867 
868 		kcred->uid = ses->se_cb_sec.uid;
869 		kcred->gid = ses->se_cb_sec.gid;
870 		return kcred;
871 	}
872 }
873 
874 static int setup_callback_client(struct nfs4_client *clp, struct nfs4_cb_conn *conn, struct nfsd4_session *ses)
875 {
876 	int maxtime = max_cb_time(clp->net);
877 	struct rpc_timeout	timeparms = {
878 		.to_initval	= maxtime,
879 		.to_retries	= 0,
880 		.to_maxval	= maxtime,
881 	};
882 	struct rpc_create_args args = {
883 		.net		= clp->net,
884 		.address	= (struct sockaddr *) &conn->cb_addr,
885 		.addrsize	= conn->cb_addrlen,
886 		.saddress	= (struct sockaddr *) &conn->cb_saddr,
887 		.timeout	= &timeparms,
888 		.program	= &cb_program,
889 		.version	= 1,
890 		.flags		= (RPC_CLNT_CREATE_NOPING | RPC_CLNT_CREATE_QUIET),
891 		.cred		= current_cred(),
892 	};
893 	struct rpc_clnt *client;
894 	const struct cred *cred;
895 
896 	if (clp->cl_minorversion == 0) {
897 		if (!clp->cl_cred.cr_principal &&
898 				(clp->cl_cred.cr_flavor >= RPC_AUTH_GSS_KRB5))
899 			return -EINVAL;
900 		args.client_name = clp->cl_cred.cr_principal;
901 		args.prognumber	= conn->cb_prog;
902 		args.protocol = XPRT_TRANSPORT_TCP;
903 		args.authflavor = clp->cl_cred.cr_flavor;
904 		clp->cl_cb_ident = conn->cb_ident;
905 	} else {
906 		if (!conn->cb_xprt)
907 			return -EINVAL;
908 		clp->cl_cb_conn.cb_xprt = conn->cb_xprt;
909 		clp->cl_cb_session = ses;
910 		args.bc_xprt = conn->cb_xprt;
911 		args.prognumber = clp->cl_cb_session->se_cb_prog;
912 		args.protocol = conn->cb_xprt->xpt_class->xcl_ident |
913 				XPRT_TRANSPORT_BC;
914 		args.authflavor = ses->se_cb_sec.flavor;
915 	}
916 	/* Create RPC client */
917 	client = rpc_create(&args);
918 	if (IS_ERR(client)) {
919 		dprintk("NFSD: couldn't create callback client: %ld\n",
920 			PTR_ERR(client));
921 		return PTR_ERR(client);
922 	}
923 	cred = get_backchannel_cred(clp, client, ses);
924 	if (!cred) {
925 		rpc_shutdown_client(client);
926 		return -ENOMEM;
927 	}
928 	clp->cl_cb_client = client;
929 	clp->cl_cb_cred = cred;
930 	return 0;
931 }
932 
933 static void warn_no_callback_path(struct nfs4_client *clp, int reason)
934 {
935 	dprintk("NFSD: warning: no callback path to client %.*s: error %d\n",
936 		(int)clp->cl_name.len, clp->cl_name.data, reason);
937 }
938 
939 static void nfsd4_mark_cb_down(struct nfs4_client *clp, int reason)
940 {
941 	if (test_bit(NFSD4_CLIENT_CB_UPDATE, &clp->cl_flags))
942 		return;
943 	clp->cl_cb_state = NFSD4_CB_DOWN;
944 	warn_no_callback_path(clp, reason);
945 }
946 
947 static void nfsd4_mark_cb_fault(struct nfs4_client *clp, int reason)
948 {
949 	if (test_bit(NFSD4_CLIENT_CB_UPDATE, &clp->cl_flags))
950 		return;
951 	clp->cl_cb_state = NFSD4_CB_FAULT;
952 	warn_no_callback_path(clp, reason);
953 }
954 
955 static void nfsd4_cb_probe_done(struct rpc_task *task, void *calldata)
956 {
957 	struct nfs4_client *clp = container_of(calldata, struct nfs4_client, cl_cb_null);
958 
959 	if (task->tk_status)
960 		nfsd4_mark_cb_down(clp, task->tk_status);
961 	else
962 		clp->cl_cb_state = NFSD4_CB_UP;
963 }
964 
965 static void nfsd4_cb_probe_release(void *calldata)
966 {
967 	struct nfs4_client *clp = container_of(calldata, struct nfs4_client, cl_cb_null);
968 
969 	nfsd41_cb_inflight_end(clp);
970 
971 }
972 
973 static const struct rpc_call_ops nfsd4_cb_probe_ops = {
974 	/* XXX: release method to ensure we set the cb channel down if
975 	 * necessary on early failure? */
976 	.rpc_call_done = nfsd4_cb_probe_done,
977 	.rpc_release = nfsd4_cb_probe_release,
978 };
979 
980 /*
981  * Poke the callback thread to process any updates to the callback
982  * parameters, and send a null probe.
983  */
984 void nfsd4_probe_callback(struct nfs4_client *clp)
985 {
986 	clp->cl_cb_state = NFSD4_CB_UNKNOWN;
987 	set_bit(NFSD4_CLIENT_CB_UPDATE, &clp->cl_flags);
988 	nfsd4_run_cb(&clp->cl_cb_null);
989 }
990 
991 void nfsd4_probe_callback_sync(struct nfs4_client *clp)
992 {
993 	nfsd4_probe_callback(clp);
994 	flush_workqueue(callback_wq);
995 }
996 
997 void nfsd4_change_callback(struct nfs4_client *clp, struct nfs4_cb_conn *conn)
998 {
999 	clp->cl_cb_state = NFSD4_CB_UNKNOWN;
1000 	spin_lock(&clp->cl_lock);
1001 	memcpy(&clp->cl_cb_conn, conn, sizeof(struct nfs4_cb_conn));
1002 	spin_unlock(&clp->cl_lock);
1003 }
1004 
1005 /*
1006  * There's currently a single callback channel slot.
1007  * If the slot is available, then mark it busy.  Otherwise, set the
1008  * thread for sleeping on the callback RPC wait queue.
1009  */
1010 static bool nfsd41_cb_get_slot(struct nfsd4_callback *cb, struct rpc_task *task)
1011 {
1012 	struct nfs4_client *clp = cb->cb_clp;
1013 
1014 	if (!cb->cb_holds_slot &&
1015 	    test_and_set_bit(0, &clp->cl_cb_slot_busy) != 0) {
1016 		rpc_sleep_on(&clp->cl_cb_waitq, task, NULL);
1017 		/* Race breaker */
1018 		if (test_and_set_bit(0, &clp->cl_cb_slot_busy) != 0) {
1019 			dprintk("%s slot is busy\n", __func__);
1020 			return false;
1021 		}
1022 		rpc_wake_up_queued_task(&clp->cl_cb_waitq, task);
1023 	}
1024 	cb->cb_holds_slot = true;
1025 	return true;
1026 }
1027 
1028 static void nfsd41_cb_release_slot(struct nfsd4_callback *cb)
1029 {
1030 	struct nfs4_client *clp = cb->cb_clp;
1031 
1032 	if (cb->cb_holds_slot) {
1033 		cb->cb_holds_slot = false;
1034 		clear_bit(0, &clp->cl_cb_slot_busy);
1035 		rpc_wake_up_next(&clp->cl_cb_waitq);
1036 	}
1037 }
1038 
1039 static void nfsd41_destroy_cb(struct nfsd4_callback *cb)
1040 {
1041 	struct nfs4_client *clp = cb->cb_clp;
1042 
1043 	nfsd41_cb_release_slot(cb);
1044 	if (cb->cb_ops && cb->cb_ops->release)
1045 		cb->cb_ops->release(cb);
1046 	nfsd41_cb_inflight_end(clp);
1047 }
1048 
1049 /*
1050  * TODO: cb_sequence should support referring call lists, cachethis, multiple
1051  * slots, and mark callback channel down on communication errors.
1052  */
1053 static void nfsd4_cb_prepare(struct rpc_task *task, void *calldata)
1054 {
1055 	struct nfsd4_callback *cb = calldata;
1056 	struct nfs4_client *clp = cb->cb_clp;
1057 	u32 minorversion = clp->cl_minorversion;
1058 
1059 	/*
1060 	 * cb_seq_status is only set in decode_cb_sequence4res,
1061 	 * and so will remain 1 if an rpc level failure occurs.
1062 	 */
1063 	cb->cb_seq_status = 1;
1064 	cb->cb_status = 0;
1065 	if (minorversion && !nfsd41_cb_get_slot(cb, task))
1066 		return;
1067 	rpc_call_start(task);
1068 }
1069 
1070 static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback *cb)
1071 {
1072 	struct nfs4_client *clp = cb->cb_clp;
1073 	struct nfsd4_session *session = clp->cl_cb_session;
1074 	bool ret = true;
1075 
1076 	if (!clp->cl_minorversion) {
1077 		/*
1078 		 * If the backchannel connection was shut down while this
1079 		 * task was queued, we need to resubmit it after setting up
1080 		 * a new backchannel connection.
1081 		 *
1082 		 * Note that if we lost our callback connection permanently
1083 		 * the submission code will error out, so we don't need to
1084 		 * handle that case here.
1085 		 */
1086 		if (RPC_SIGNALLED(task))
1087 			goto need_restart;
1088 
1089 		return true;
1090 	}
1091 
1092 	if (!cb->cb_holds_slot)
1093 		goto need_restart;
1094 
1095 	switch (cb->cb_seq_status) {
1096 	case 0:
1097 		/*
1098 		 * No need for lock, access serialized in nfsd4_cb_prepare
1099 		 *
1100 		 * RFC5661 20.9.3
1101 		 * If CB_SEQUENCE returns an error, then the state of the slot
1102 		 * (sequence ID, cached reply) MUST NOT change.
1103 		 */
1104 		++session->se_cb_seq_nr;
1105 		break;
1106 	case -ESERVERFAULT:
1107 		++session->se_cb_seq_nr;
1108 		/* Fall through */
1109 	case 1:
1110 	case -NFS4ERR_BADSESSION:
1111 		nfsd4_mark_cb_fault(cb->cb_clp, cb->cb_seq_status);
1112 		ret = false;
1113 		break;
1114 	case -NFS4ERR_DELAY:
1115 		if (!rpc_restart_call(task))
1116 			goto out;
1117 
1118 		rpc_delay(task, 2 * HZ);
1119 		return false;
1120 	case -NFS4ERR_BADSLOT:
1121 		goto retry_nowait;
1122 	case -NFS4ERR_SEQ_MISORDERED:
1123 		if (session->se_cb_seq_nr != 1) {
1124 			session->se_cb_seq_nr = 1;
1125 			goto retry_nowait;
1126 		}
1127 		break;
1128 	default:
1129 		nfsd4_mark_cb_fault(cb->cb_clp, cb->cb_seq_status);
1130 		dprintk("%s: unprocessed error %d\n", __func__,
1131 			cb->cb_seq_status);
1132 	}
1133 
1134 	nfsd41_cb_release_slot(cb);
1135 	dprintk("%s: freed slot, new seqid=%d\n", __func__,
1136 		clp->cl_cb_session->se_cb_seq_nr);
1137 
1138 	if (RPC_SIGNALLED(task))
1139 		goto need_restart;
1140 out:
1141 	return ret;
1142 retry_nowait:
1143 	if (rpc_restart_call_prepare(task))
1144 		ret = false;
1145 	goto out;
1146 need_restart:
1147 	if (!test_bit(NFSD4_CLIENT_CB_KILL, &clp->cl_flags)) {
1148 		task->tk_status = 0;
1149 		cb->cb_need_restart = true;
1150 	}
1151 	return false;
1152 }
1153 
1154 static void nfsd4_cb_done(struct rpc_task *task, void *calldata)
1155 {
1156 	struct nfsd4_callback *cb = calldata;
1157 	struct nfs4_client *clp = cb->cb_clp;
1158 
1159 	dprintk("%s: minorversion=%d\n", __func__,
1160 		clp->cl_minorversion);
1161 
1162 	if (!nfsd4_cb_sequence_done(task, cb))
1163 		return;
1164 
1165 	if (cb->cb_status) {
1166 		WARN_ON_ONCE(task->tk_status);
1167 		task->tk_status = cb->cb_status;
1168 	}
1169 
1170 	switch (cb->cb_ops->done(cb, task)) {
1171 	case 0:
1172 		task->tk_status = 0;
1173 		rpc_restart_call_prepare(task);
1174 		return;
1175 	case 1:
1176 		switch (task->tk_status) {
1177 		case -EIO:
1178 		case -ETIMEDOUT:
1179 			nfsd4_mark_cb_down(clp, task->tk_status);
1180 		}
1181 		break;
1182 	default:
1183 		BUG();
1184 	}
1185 }
1186 
1187 static void nfsd4_cb_release(void *calldata)
1188 {
1189 	struct nfsd4_callback *cb = calldata;
1190 
1191 	if (cb->cb_need_restart)
1192 		nfsd4_queue_cb(cb);
1193 	else
1194 		nfsd41_destroy_cb(cb);
1195 
1196 }
1197 
1198 static const struct rpc_call_ops nfsd4_cb_ops = {
1199 	.rpc_call_prepare = nfsd4_cb_prepare,
1200 	.rpc_call_done = nfsd4_cb_done,
1201 	.rpc_release = nfsd4_cb_release,
1202 };
1203 
1204 int nfsd4_create_callback_queue(void)
1205 {
1206 	callback_wq = alloc_ordered_workqueue("nfsd4_callbacks", 0);
1207 	if (!callback_wq)
1208 		return -ENOMEM;
1209 	return 0;
1210 }
1211 
1212 void nfsd4_destroy_callback_queue(void)
1213 {
1214 	destroy_workqueue(callback_wq);
1215 }
1216 
1217 /* must be called under the state lock */
1218 void nfsd4_shutdown_callback(struct nfs4_client *clp)
1219 {
1220 	set_bit(NFSD4_CLIENT_CB_KILL, &clp->cl_flags);
1221 	/*
1222 	 * Note this won't actually result in a null callback;
1223 	 * instead, nfsd4_run_cb_null() will detect the killed
1224 	 * client, destroy the rpc client, and stop:
1225 	 */
1226 	nfsd4_run_cb(&clp->cl_cb_null);
1227 	flush_workqueue(callback_wq);
1228 	nfsd41_cb_inflight_wait_complete(clp);
1229 }
1230 
1231 /* requires cl_lock: */
1232 static struct nfsd4_conn * __nfsd4_find_backchannel(struct nfs4_client *clp)
1233 {
1234 	struct nfsd4_session *s;
1235 	struct nfsd4_conn *c;
1236 
1237 	list_for_each_entry(s, &clp->cl_sessions, se_perclnt) {
1238 		list_for_each_entry(c, &s->se_conns, cn_persession) {
1239 			if (c->cn_flags & NFS4_CDFC4_BACK)
1240 				return c;
1241 		}
1242 	}
1243 	return NULL;
1244 }
1245 
1246 /*
1247  * Note there isn't a lot of locking in this code; instead we depend on
1248  * the fact that it is run from the callback_wq, which won't run two
1249  * work items at once.  So, for example, callback_wq handles all access
1250  * of cl_cb_client and all calls to rpc_create or rpc_shutdown_client.
1251  */
1252 static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
1253 {
1254 	struct nfs4_cb_conn conn;
1255 	struct nfs4_client *clp = cb->cb_clp;
1256 	struct nfsd4_session *ses = NULL;
1257 	struct nfsd4_conn *c;
1258 	int err;
1259 
1260 	/*
1261 	 * This is either an update, or the client dying; in either case,
1262 	 * kill the old client:
1263 	 */
1264 	if (clp->cl_cb_client) {
1265 		rpc_shutdown_client(clp->cl_cb_client);
1266 		clp->cl_cb_client = NULL;
1267 		put_cred(clp->cl_cb_cred);
1268 		clp->cl_cb_cred = NULL;
1269 	}
1270 	if (clp->cl_cb_conn.cb_xprt) {
1271 		svc_xprt_put(clp->cl_cb_conn.cb_xprt);
1272 		clp->cl_cb_conn.cb_xprt = NULL;
1273 	}
1274 	if (test_bit(NFSD4_CLIENT_CB_KILL, &clp->cl_flags))
1275 		return;
1276 	spin_lock(&clp->cl_lock);
1277 	/*
1278 	 * Only serialized callback code is allowed to clear these
1279 	 * flags; main nfsd code can only set them:
1280 	 */
1281 	BUG_ON(!(clp->cl_flags & NFSD4_CLIENT_CB_FLAG_MASK));
1282 	clear_bit(NFSD4_CLIENT_CB_UPDATE, &clp->cl_flags);
1283 	memcpy(&conn, &cb->cb_clp->cl_cb_conn, sizeof(struct nfs4_cb_conn));
1284 	c = __nfsd4_find_backchannel(clp);
1285 	if (c) {
1286 		svc_xprt_get(c->cn_xprt);
1287 		conn.cb_xprt = c->cn_xprt;
1288 		ses = c->cn_session;
1289 	}
1290 	spin_unlock(&clp->cl_lock);
1291 
1292 	err = setup_callback_client(clp, &conn, ses);
1293 	if (err) {
1294 		nfsd4_mark_cb_down(clp, err);
1295 		return;
1296 	}
1297 }
1298 
1299 static void
1300 nfsd4_run_cb_work(struct work_struct *work)
1301 {
1302 	struct nfsd4_callback *cb =
1303 		container_of(work, struct nfsd4_callback, cb_work);
1304 	struct nfs4_client *clp = cb->cb_clp;
1305 	struct rpc_clnt *clnt;
1306 
1307 	if (cb->cb_need_restart) {
1308 		cb->cb_need_restart = false;
1309 	} else {
1310 		if (cb->cb_ops && cb->cb_ops->prepare)
1311 			cb->cb_ops->prepare(cb);
1312 	}
1313 
1314 	if (clp->cl_flags & NFSD4_CLIENT_CB_FLAG_MASK)
1315 		nfsd4_process_cb_update(cb);
1316 
1317 	clnt = clp->cl_cb_client;
1318 	if (!clnt) {
1319 		/* Callback channel broken, or client killed; give up: */
1320 		nfsd41_destroy_cb(cb);
1321 		return;
1322 	}
1323 
1324 	/*
1325 	 * Don't send probe messages for 4.1 or later.
1326 	 */
1327 	if (!cb->cb_ops && clp->cl_minorversion) {
1328 		clp->cl_cb_state = NFSD4_CB_UP;
1329 		nfsd41_destroy_cb(cb);
1330 		return;
1331 	}
1332 
1333 	cb->cb_msg.rpc_cred = clp->cl_cb_cred;
1334 	rpc_call_async(clnt, &cb->cb_msg, RPC_TASK_SOFT | RPC_TASK_SOFTCONN,
1335 			cb->cb_ops ? &nfsd4_cb_ops : &nfsd4_cb_probe_ops, cb);
1336 }
1337 
1338 void nfsd4_init_cb(struct nfsd4_callback *cb, struct nfs4_client *clp,
1339 		const struct nfsd4_callback_ops *ops, enum nfsd4_cb_op op)
1340 {
1341 	cb->cb_clp = clp;
1342 	cb->cb_msg.rpc_proc = &nfs4_cb_procedures[op];
1343 	cb->cb_msg.rpc_argp = cb;
1344 	cb->cb_msg.rpc_resp = cb;
1345 	cb->cb_ops = ops;
1346 	INIT_WORK(&cb->cb_work, nfsd4_run_cb_work);
1347 	cb->cb_seq_status = 1;
1348 	cb->cb_status = 0;
1349 	cb->cb_need_restart = false;
1350 	cb->cb_holds_slot = false;
1351 }
1352 
1353 void nfsd4_run_cb(struct nfsd4_callback *cb)
1354 {
1355 	struct nfs4_client *clp = cb->cb_clp;
1356 
1357 	nfsd41_cb_inflight_begin(clp);
1358 	if (!nfsd4_queue_cb(cb))
1359 		nfsd41_cb_inflight_end(clp);
1360 }
1361