1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Device operations for the pnfs nfs4 file layout driver.
4  *
5  * Copyright (c) 2014, Primary Data, Inc. All rights reserved.
6  *
7  * Tao Peng <bergwolf@primarydata.com>
8  */
9 
10 #include <linux/nfs_fs.h>
11 #include <linux/vmalloc.h>
12 #include <linux/module.h>
13 #include <linux/sunrpc/addr.h>
14 
15 #include "../internal.h"
16 #include "../nfs4session.h"
17 #include "flexfilelayout.h"
18 
19 #define NFSDBG_FACILITY		NFSDBG_PNFS_LD
20 
21 static unsigned int dataserver_timeo = NFS_DEF_TCP_TIMEO;
22 static unsigned int dataserver_retrans;
23 
24 static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg);
25 
26 void nfs4_ff_layout_put_deviceid(struct nfs4_ff_layout_ds *mirror_ds)
27 {
28 	if (!IS_ERR_OR_NULL(mirror_ds))
29 		nfs4_put_deviceid_node(&mirror_ds->id_node);
30 }
31 
32 void nfs4_ff_layout_free_deviceid(struct nfs4_ff_layout_ds *mirror_ds)
33 {
34 	nfs4_print_deviceid(&mirror_ds->id_node.deviceid);
35 	nfs4_pnfs_ds_put(mirror_ds->ds);
36 	kfree(mirror_ds->ds_versions);
37 	kfree_rcu(mirror_ds, id_node.rcu);
38 }
39 
40 /* Decode opaque device data and construct new_ds using it */
41 struct nfs4_ff_layout_ds *
42 nfs4_ff_alloc_deviceid_node(struct nfs_server *server, struct pnfs_device *pdev,
43 			    gfp_t gfp_flags)
44 {
45 	struct xdr_stream stream;
46 	struct xdr_buf buf;
47 	struct page *scratch;
48 	struct list_head dsaddrs;
49 	struct nfs4_pnfs_ds_addr *da;
50 	struct nfs4_ff_layout_ds *new_ds = NULL;
51 	struct nfs4_ff_ds_version *ds_versions = NULL;
52 	u32 mp_count;
53 	u32 version_count;
54 	__be32 *p;
55 	int i, ret = -ENOMEM;
56 
57 	/* set up xdr stream */
58 	scratch = alloc_page(gfp_flags);
59 	if (!scratch)
60 		goto out_err;
61 
62 	new_ds = kzalloc(sizeof(struct nfs4_ff_layout_ds), gfp_flags);
63 	if (!new_ds)
64 		goto out_scratch;
65 
66 	nfs4_init_deviceid_node(&new_ds->id_node,
67 				server,
68 				&pdev->dev_id);
69 	INIT_LIST_HEAD(&dsaddrs);
70 
71 	xdr_init_decode_pages(&stream, &buf, pdev->pages, pdev->pglen);
72 	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
73 
74 	/* multipath count */
75 	p = xdr_inline_decode(&stream, 4);
76 	if (unlikely(!p))
77 		goto out_err_drain_dsaddrs;
78 	mp_count = be32_to_cpup(p);
79 	dprintk("%s: multipath ds count %d\n", __func__, mp_count);
80 
81 	for (i = 0; i < mp_count; i++) {
82 		/* multipath ds */
83 		da = nfs4_decode_mp_ds_addr(server->nfs_client->cl_net,
84 					    &stream, gfp_flags);
85 		if (da)
86 			list_add_tail(&da->da_node, &dsaddrs);
87 	}
88 	if (list_empty(&dsaddrs)) {
89 		dprintk("%s: no suitable DS addresses found\n",
90 			__func__);
91 		ret = -ENOMEDIUM;
92 		goto out_err_drain_dsaddrs;
93 	}
94 
95 	/* version count */
96 	p = xdr_inline_decode(&stream, 4);
97 	if (unlikely(!p))
98 		goto out_err_drain_dsaddrs;
99 	version_count = be32_to_cpup(p);
100 	dprintk("%s: version count %d\n", __func__, version_count);
101 
102 	ds_versions = kcalloc(version_count,
103 			      sizeof(struct nfs4_ff_ds_version),
104 			      gfp_flags);
105 	if (!ds_versions)
106 		goto out_scratch;
107 
108 	for (i = 0; i < version_count; i++) {
109 		/* 20 = version(4) + minor_version(4) + rsize(4) + wsize(4) +
110 		 * tightly_coupled(4) */
111 		p = xdr_inline_decode(&stream, 20);
112 		if (unlikely(!p))
113 			goto out_err_drain_dsaddrs;
114 		ds_versions[i].version = be32_to_cpup(p++);
115 		ds_versions[i].minor_version = be32_to_cpup(p++);
116 		ds_versions[i].rsize = nfs_block_size(be32_to_cpup(p++), NULL);
117 		ds_versions[i].wsize = nfs_block_size(be32_to_cpup(p++), NULL);
118 		ds_versions[i].tightly_coupled = be32_to_cpup(p);
119 
120 		if (ds_versions[i].rsize > NFS_MAX_FILE_IO_SIZE)
121 			ds_versions[i].rsize = NFS_MAX_FILE_IO_SIZE;
122 		if (ds_versions[i].wsize > NFS_MAX_FILE_IO_SIZE)
123 			ds_versions[i].wsize = NFS_MAX_FILE_IO_SIZE;
124 
125 		/*
126 		 * check for valid major/minor combination.
127 		 * currently we support dataserver which talk:
128 		 *   v3, v4.0, v4.1, v4.2
129 		 */
130 		if (!((ds_versions[i].version == 3 && ds_versions[i].minor_version == 0) ||
131 			(ds_versions[i].version == 4 && ds_versions[i].minor_version < 3))) {
132 			dprintk("%s: [%d] unsupported ds version %d-%d\n", __func__,
133 				i, ds_versions[i].version,
134 				ds_versions[i].minor_version);
135 			ret = -EPROTONOSUPPORT;
136 			goto out_err_drain_dsaddrs;
137 		}
138 
139 		dprintk("%s: [%d] vers %u minor_ver %u rsize %u wsize %u coupled %d\n",
140 			__func__, i, ds_versions[i].version,
141 			ds_versions[i].minor_version,
142 			ds_versions[i].rsize,
143 			ds_versions[i].wsize,
144 			ds_versions[i].tightly_coupled);
145 	}
146 
147 	new_ds->ds_versions = ds_versions;
148 	new_ds->ds_versions_cnt = version_count;
149 
150 	new_ds->ds = nfs4_pnfs_ds_add(&dsaddrs, gfp_flags);
151 	if (!new_ds->ds)
152 		goto out_err_drain_dsaddrs;
153 
154 	/* If DS was already in cache, free ds addrs */
155 	while (!list_empty(&dsaddrs)) {
156 		da = list_first_entry(&dsaddrs,
157 				      struct nfs4_pnfs_ds_addr,
158 				      da_node);
159 		list_del_init(&da->da_node);
160 		kfree(da->da_remotestr);
161 		kfree(da);
162 	}
163 
164 	__free_page(scratch);
165 	return new_ds;
166 
167 out_err_drain_dsaddrs:
168 	while (!list_empty(&dsaddrs)) {
169 		da = list_first_entry(&dsaddrs, struct nfs4_pnfs_ds_addr,
170 				      da_node);
171 		list_del_init(&da->da_node);
172 		kfree(da->da_remotestr);
173 		kfree(da);
174 	}
175 
176 	kfree(ds_versions);
177 out_scratch:
178 	__free_page(scratch);
179 out_err:
180 	kfree(new_ds);
181 
182 	dprintk("%s ERROR: returning %d\n", __func__, ret);
183 	return NULL;
184 }
185 
186 static void extend_ds_error(struct nfs4_ff_layout_ds_err *err,
187 			    u64 offset, u64 length)
188 {
189 	u64 end;
190 
191 	end = max_t(u64, pnfs_end_offset(err->offset, err->length),
192 		    pnfs_end_offset(offset, length));
193 	err->offset = min_t(u64, err->offset, offset);
194 	err->length = end - err->offset;
195 }
196 
197 static int
198 ff_ds_error_match(const struct nfs4_ff_layout_ds_err *e1,
199 		const struct nfs4_ff_layout_ds_err *e2)
200 {
201 	int ret;
202 
203 	if (e1->opnum != e2->opnum)
204 		return e1->opnum < e2->opnum ? -1 : 1;
205 	if (e1->status != e2->status)
206 		return e1->status < e2->status ? -1 : 1;
207 	ret = memcmp(e1->stateid.data, e2->stateid.data,
208 			sizeof(e1->stateid.data));
209 	if (ret != 0)
210 		return ret;
211 	ret = memcmp(&e1->deviceid, &e2->deviceid, sizeof(e1->deviceid));
212 	if (ret != 0)
213 		return ret;
214 	if (pnfs_end_offset(e1->offset, e1->length) < e2->offset)
215 		return -1;
216 	if (e1->offset > pnfs_end_offset(e2->offset, e2->length))
217 		return 1;
218 	/* If ranges overlap or are contiguous, they are the same */
219 	return 0;
220 }
221 
222 static void
223 ff_layout_add_ds_error_locked(struct nfs4_flexfile_layout *flo,
224 			      struct nfs4_ff_layout_ds_err *dserr)
225 {
226 	struct nfs4_ff_layout_ds_err *err, *tmp;
227 	struct list_head *head = &flo->error_list;
228 	int match;
229 
230 	/* Do insertion sort w/ merges */
231 	list_for_each_entry_safe(err, tmp, &flo->error_list, list) {
232 		match = ff_ds_error_match(err, dserr);
233 		if (match < 0)
234 			continue;
235 		if (match > 0) {
236 			/* Add entry "dserr" _before_ entry "err" */
237 			head = &err->list;
238 			break;
239 		}
240 		/* Entries match, so merge "err" into "dserr" */
241 		extend_ds_error(dserr, err->offset, err->length);
242 		list_replace(&err->list, &dserr->list);
243 		kfree(err);
244 		return;
245 	}
246 
247 	list_add_tail(&dserr->list, head);
248 }
249 
250 int ff_layout_track_ds_error(struct nfs4_flexfile_layout *flo,
251 			     struct nfs4_ff_layout_mirror *mirror, u64 offset,
252 			     u64 length, int status, enum nfs_opnum4 opnum,
253 			     gfp_t gfp_flags)
254 {
255 	struct nfs4_ff_layout_ds_err *dserr;
256 
257 	if (status == 0)
258 		return 0;
259 
260 	if (IS_ERR_OR_NULL(mirror->mirror_ds))
261 		return -EINVAL;
262 
263 	dserr = kmalloc(sizeof(*dserr), gfp_flags);
264 	if (!dserr)
265 		return -ENOMEM;
266 
267 	INIT_LIST_HEAD(&dserr->list);
268 	dserr->offset = offset;
269 	dserr->length = length;
270 	dserr->status = status;
271 	dserr->opnum = opnum;
272 	nfs4_stateid_copy(&dserr->stateid, &mirror->stateid);
273 	memcpy(&dserr->deviceid, &mirror->mirror_ds->id_node.deviceid,
274 	       NFS4_DEVICEID4_SIZE);
275 
276 	spin_lock(&flo->generic_hdr.plh_inode->i_lock);
277 	ff_layout_add_ds_error_locked(flo, dserr);
278 	spin_unlock(&flo->generic_hdr.plh_inode->i_lock);
279 	return 0;
280 }
281 
282 static const struct cred *
283 ff_layout_get_mirror_cred(struct nfs4_ff_layout_mirror *mirror, u32 iomode)
284 {
285 	const struct cred *cred, __rcu **pcred;
286 
287 	if (iomode == IOMODE_READ)
288 		pcred = &mirror->ro_cred;
289 	else
290 		pcred = &mirror->rw_cred;
291 
292 	rcu_read_lock();
293 	do {
294 		cred = rcu_dereference(*pcred);
295 		if (!cred)
296 			break;
297 
298 		cred = get_cred_rcu(cred);
299 	} while(!cred);
300 	rcu_read_unlock();
301 	return cred;
302 }
303 
304 struct nfs_fh *
305 nfs4_ff_layout_select_ds_fh(struct nfs4_ff_layout_mirror *mirror)
306 {
307 	/* FIXME: For now assume there is only 1 version available for the DS */
308 	return &mirror->fh_versions[0];
309 }
310 
311 void
312 nfs4_ff_layout_select_ds_stateid(const struct nfs4_ff_layout_mirror *mirror,
313 		nfs4_stateid *stateid)
314 {
315 	if (nfs4_ff_layout_ds_version(mirror) == 4)
316 		nfs4_stateid_copy(stateid, &mirror->stateid);
317 }
318 
319 static bool
320 ff_layout_init_mirror_ds(struct pnfs_layout_hdr *lo,
321 			 struct nfs4_ff_layout_mirror *mirror)
322 {
323 	if (mirror == NULL)
324 		goto outerr;
325 	if (mirror->mirror_ds == NULL) {
326 		struct nfs4_deviceid_node *node;
327 		struct nfs4_ff_layout_ds *mirror_ds = ERR_PTR(-ENODEV);
328 
329 		node = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode),
330 				&mirror->devid, lo->plh_lc_cred,
331 				GFP_KERNEL);
332 		if (node)
333 			mirror_ds = FF_LAYOUT_MIRROR_DS(node);
334 
335 		/* check for race with another call to this function */
336 		if (cmpxchg(&mirror->mirror_ds, NULL, mirror_ds) &&
337 		    mirror_ds != ERR_PTR(-ENODEV))
338 			nfs4_put_deviceid_node(node);
339 	}
340 
341 	if (IS_ERR(mirror->mirror_ds))
342 		goto outerr;
343 
344 	return true;
345 outerr:
346 	return false;
347 }
348 
349 /**
350  * nfs4_ff_layout_prepare_ds - prepare a DS connection for an RPC call
351  * @lseg: the layout segment we're operating on
352  * @mirror: layout mirror describing the DS to use
353  * @fail_return: return layout on connect failure?
354  *
355  * Try to prepare a DS connection to accept an RPC call. This involves
356  * selecting a mirror to use and connecting the client to it if it's not
357  * already connected.
358  *
359  * Since we only need a single functioning mirror to satisfy a read, we don't
360  * want to return the layout if there is one. For writes though, any down
361  * mirror should result in a LAYOUTRETURN. @fail_return is how we distinguish
362  * between the two cases.
363  *
364  * Returns a pointer to a connected DS object on success or NULL on failure.
365  */
366 struct nfs4_pnfs_ds *
367 nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg,
368 			  struct nfs4_ff_layout_mirror *mirror,
369 			  bool fail_return)
370 {
371 	struct nfs4_pnfs_ds *ds = NULL;
372 	struct inode *ino = lseg->pls_layout->plh_inode;
373 	struct nfs_server *s = NFS_SERVER(ino);
374 	unsigned int max_payload;
375 	int status;
376 
377 	if (!ff_layout_init_mirror_ds(lseg->pls_layout, mirror))
378 		goto noconnect;
379 
380 	ds = mirror->mirror_ds->ds;
381 	/* matching smp_wmb() in _nfs4_pnfs_v3/4_ds_connect */
382 	smp_rmb();
383 	if (ds->ds_clp)
384 		goto out;
385 
386 	/* FIXME: For now we assume the server sent only one version of NFS
387 	 * to use for the DS.
388 	 */
389 	status = nfs4_pnfs_ds_connect(s, ds, &mirror->mirror_ds->id_node,
390 			     dataserver_timeo, dataserver_retrans,
391 			     mirror->mirror_ds->ds_versions[0].version,
392 			     mirror->mirror_ds->ds_versions[0].minor_version);
393 
394 	/* connect success, check rsize/wsize limit */
395 	if (!status) {
396 		max_payload =
397 			nfs_block_size(rpc_max_payload(ds->ds_clp->cl_rpcclient),
398 				       NULL);
399 		if (mirror->mirror_ds->ds_versions[0].rsize > max_payload)
400 			mirror->mirror_ds->ds_versions[0].rsize = max_payload;
401 		if (mirror->mirror_ds->ds_versions[0].wsize > max_payload)
402 			mirror->mirror_ds->ds_versions[0].wsize = max_payload;
403 		goto out;
404 	}
405 noconnect:
406 	ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout),
407 				 mirror, lseg->pls_range.offset,
408 				 lseg->pls_range.length, NFS4ERR_NXIO,
409 				 OP_ILLEGAL, GFP_NOIO);
410 	ff_layout_send_layouterror(lseg);
411 	if (fail_return || !ff_layout_has_available_ds(lseg))
412 		pnfs_error_mark_layout_for_return(ino, lseg);
413 	ds = NULL;
414 out:
415 	return ds;
416 }
417 
418 const struct cred *
419 ff_layout_get_ds_cred(struct nfs4_ff_layout_mirror *mirror,
420 		      const struct pnfs_layout_range *range,
421 		      const struct cred *mdscred)
422 {
423 	const struct cred *cred;
424 
425 	if (mirror && !mirror->mirror_ds->ds_versions[0].tightly_coupled) {
426 		cred = ff_layout_get_mirror_cred(mirror, range->iomode);
427 		if (!cred)
428 			cred = get_cred(mdscred);
429 	} else {
430 		cred = get_cred(mdscred);
431 	}
432 	return cred;
433 }
434 
435 /**
436  * nfs4_ff_find_or_create_ds_client - Find or create a DS rpc client
437  * @mirror: pointer to the mirror
438  * @ds_clp: nfs_client for the DS
439  * @inode: pointer to inode
440  *
441  * Find or create a DS rpc client with th MDS server rpc client auth flavor
442  * in the nfs_client cl_ds_clients list.
443  */
444 struct rpc_clnt *
445 nfs4_ff_find_or_create_ds_client(struct nfs4_ff_layout_mirror *mirror,
446 				 struct nfs_client *ds_clp, struct inode *inode)
447 {
448 	switch (mirror->mirror_ds->ds_versions[0].version) {
449 	case 3:
450 		/* For NFSv3 DS, flavor is set when creating DS connections */
451 		return ds_clp->cl_rpcclient;
452 	case 4:
453 		return nfs4_find_or_create_ds_client(ds_clp, inode);
454 	default:
455 		BUG();
456 	}
457 }
458 
459 void ff_layout_free_ds_ioerr(struct list_head *head)
460 {
461 	struct nfs4_ff_layout_ds_err *err;
462 
463 	while (!list_empty(head)) {
464 		err = list_first_entry(head,
465 				struct nfs4_ff_layout_ds_err,
466 				list);
467 		list_del(&err->list);
468 		kfree(err);
469 	}
470 }
471 
472 /* called with inode i_lock held */
473 int ff_layout_encode_ds_ioerr(struct xdr_stream *xdr, const struct list_head *head)
474 {
475 	struct nfs4_ff_layout_ds_err *err;
476 	__be32 *p;
477 
478 	list_for_each_entry(err, head, list) {
479 		/* offset(8) + length(8) + stateid(NFS4_STATEID_SIZE)
480 		 * + array length + deviceid(NFS4_DEVICEID4_SIZE)
481 		 * + status(4) + opnum(4)
482 		 */
483 		p = xdr_reserve_space(xdr,
484 				28 + NFS4_STATEID_SIZE + NFS4_DEVICEID4_SIZE);
485 		if (unlikely(!p))
486 			return -ENOBUFS;
487 		p = xdr_encode_hyper(p, err->offset);
488 		p = xdr_encode_hyper(p, err->length);
489 		p = xdr_encode_opaque_fixed(p, &err->stateid,
490 					    NFS4_STATEID_SIZE);
491 		/* Encode 1 error */
492 		*p++ = cpu_to_be32(1);
493 		p = xdr_encode_opaque_fixed(p, &err->deviceid,
494 					    NFS4_DEVICEID4_SIZE);
495 		*p++ = cpu_to_be32(err->status);
496 		*p++ = cpu_to_be32(err->opnum);
497 		dprintk("%s: offset %llu length %llu status %d op %d\n",
498 			__func__, err->offset, err->length, err->status,
499 			err->opnum);
500 	}
501 
502 	return 0;
503 }
504 
505 static
506 unsigned int do_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
507 				      const struct pnfs_layout_range *range,
508 				      struct list_head *head,
509 				      unsigned int maxnum)
510 {
511 	struct nfs4_flexfile_layout *flo = FF_LAYOUT_FROM_HDR(lo);
512 	struct inode *inode = lo->plh_inode;
513 	struct nfs4_ff_layout_ds_err *err, *n;
514 	unsigned int ret = 0;
515 
516 	spin_lock(&inode->i_lock);
517 	list_for_each_entry_safe(err, n, &flo->error_list, list) {
518 		if (!pnfs_is_range_intersecting(err->offset,
519 				pnfs_end_offset(err->offset, err->length),
520 				range->offset,
521 				pnfs_end_offset(range->offset, range->length)))
522 			continue;
523 		if (!maxnum)
524 			break;
525 		list_move(&err->list, head);
526 		maxnum--;
527 		ret++;
528 	}
529 	spin_unlock(&inode->i_lock);
530 	return ret;
531 }
532 
533 unsigned int ff_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
534 				      const struct pnfs_layout_range *range,
535 				      struct list_head *head,
536 				      unsigned int maxnum)
537 {
538 	unsigned int ret;
539 
540 	ret = do_layout_fetch_ds_ioerr(lo, range, head, maxnum);
541 	/* If we're over the max, discard all remaining entries */
542 	if (ret == maxnum) {
543 		LIST_HEAD(discard);
544 		do_layout_fetch_ds_ioerr(lo, range, &discard, -1);
545 		ff_layout_free_ds_ioerr(&discard);
546 	}
547 	return ret;
548 }
549 
550 static bool ff_read_layout_has_available_ds(struct pnfs_layout_segment *lseg)
551 {
552 	struct nfs4_ff_layout_mirror *mirror;
553 	struct nfs4_deviceid_node *devid;
554 	u32 idx;
555 
556 	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
557 		mirror = FF_LAYOUT_COMP(lseg, idx);
558 		if (mirror) {
559 			if (!mirror->mirror_ds)
560 				return true;
561 			if (IS_ERR(mirror->mirror_ds))
562 				continue;
563 			devid = &mirror->mirror_ds->id_node;
564 			if (!nfs4_test_deviceid_unavailable(devid))
565 				return true;
566 		}
567 	}
568 
569 	return false;
570 }
571 
572 static bool ff_rw_layout_has_available_ds(struct pnfs_layout_segment *lseg)
573 {
574 	struct nfs4_ff_layout_mirror *mirror;
575 	struct nfs4_deviceid_node *devid;
576 	u32 idx;
577 
578 	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
579 		mirror = FF_LAYOUT_COMP(lseg, idx);
580 		if (!mirror || IS_ERR(mirror->mirror_ds))
581 			return false;
582 		if (!mirror->mirror_ds)
583 			continue;
584 		devid = &mirror->mirror_ds->id_node;
585 		if (nfs4_test_deviceid_unavailable(devid))
586 			return false;
587 	}
588 
589 	return FF_LAYOUT_MIRROR_COUNT(lseg) != 0;
590 }
591 
592 static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg)
593 {
594 	if (lseg->pls_range.iomode == IOMODE_READ)
595 		return  ff_read_layout_has_available_ds(lseg);
596 	/* Note: RW layout needs all mirrors available */
597 	return ff_rw_layout_has_available_ds(lseg);
598 }
599 
600 bool ff_layout_avoid_mds_available_ds(struct pnfs_layout_segment *lseg)
601 {
602 	return ff_layout_no_fallback_to_mds(lseg) ||
603 	       ff_layout_has_available_ds(lseg);
604 }
605 
606 bool ff_layout_avoid_read_on_rw(struct pnfs_layout_segment *lseg)
607 {
608 	return lseg->pls_range.iomode == IOMODE_RW &&
609 	       ff_layout_no_read_on_rw(lseg);
610 }
611 
612 module_param(dataserver_retrans, uint, 0644);
613 MODULE_PARM_DESC(dataserver_retrans, "The  number of times the NFSv4.1 client "
614 			"retries a request before it attempts further "
615 			" recovery  action.");
616 module_param(dataserver_timeo, uint, 0644);
617 MODULE_PARM_DESC(dataserver_timeo, "The time (in tenths of a second) the "
618 			"NFSv4.1  client  waits for a response from a "
619 			" data server before it retries an NFS request.");
620