xref: /linux/fs/nfs/flexfilelayout/flexfilelayoutdev.c (revision ca55b2fef3a9373fcfc30f82fd26bc7fccbda732)
1 /*
2  * Device operations for the pnfs nfs4 file layout driver.
3  *
4  * Copyright (c) 2014, Primary Data, Inc. All rights reserved.
5  *
6  * Tao Peng <bergwolf@primarydata.com>
7  */
8 
9 #include <linux/nfs_fs.h>
10 #include <linux/vmalloc.h>
11 #include <linux/module.h>
12 #include <linux/sunrpc/addr.h>
13 
14 #include "../internal.h"
15 #include "../nfs4session.h"
16 #include "flexfilelayout.h"
17 
18 #define NFSDBG_FACILITY		NFSDBG_PNFS_LD
19 
20 static unsigned int dataserver_timeo = NFS4_DEF_DS_TIMEO;
21 static unsigned int dataserver_retrans = NFS4_DEF_DS_RETRANS;
22 
23 void nfs4_ff_layout_put_deviceid(struct nfs4_ff_layout_ds *mirror_ds)
24 {
25 	if (mirror_ds)
26 		nfs4_put_deviceid_node(&mirror_ds->id_node);
27 }
28 
29 void nfs4_ff_layout_free_deviceid(struct nfs4_ff_layout_ds *mirror_ds)
30 {
31 	nfs4_print_deviceid(&mirror_ds->id_node.deviceid);
32 	nfs4_pnfs_ds_put(mirror_ds->ds);
33 	kfree_rcu(mirror_ds, id_node.rcu);
34 }
35 
36 /* Decode opaque device data and construct new_ds using it */
37 struct nfs4_ff_layout_ds *
38 nfs4_ff_alloc_deviceid_node(struct nfs_server *server, struct pnfs_device *pdev,
39 			    gfp_t gfp_flags)
40 {
41 	struct xdr_stream stream;
42 	struct xdr_buf buf;
43 	struct page *scratch;
44 	struct list_head dsaddrs;
45 	struct nfs4_pnfs_ds_addr *da;
46 	struct nfs4_ff_layout_ds *new_ds = NULL;
47 	struct nfs4_ff_ds_version *ds_versions = NULL;
48 	u32 mp_count;
49 	u32 version_count;
50 	__be32 *p;
51 	int i, ret = -ENOMEM;
52 
53 	/* set up xdr stream */
54 	scratch = alloc_page(gfp_flags);
55 	if (!scratch)
56 		goto out_err;
57 
58 	new_ds = kzalloc(sizeof(struct nfs4_ff_layout_ds), gfp_flags);
59 	if (!new_ds)
60 		goto out_scratch;
61 
62 	nfs4_init_deviceid_node(&new_ds->id_node,
63 				server,
64 				&pdev->dev_id);
65 	INIT_LIST_HEAD(&dsaddrs);
66 
67 	xdr_init_decode_pages(&stream, &buf, pdev->pages, pdev->pglen);
68 	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
69 
70 	/* multipath count */
71 	p = xdr_inline_decode(&stream, 4);
72 	if (unlikely(!p))
73 		goto out_err_drain_dsaddrs;
74 	mp_count = be32_to_cpup(p);
75 	dprintk("%s: multipath ds count %d\n", __func__, mp_count);
76 
77 	for (i = 0; i < mp_count; i++) {
78 		/* multipath ds */
79 		da = nfs4_decode_mp_ds_addr(server->nfs_client->cl_net,
80 					    &stream, gfp_flags);
81 		if (da)
82 			list_add_tail(&da->da_node, &dsaddrs);
83 	}
84 	if (list_empty(&dsaddrs)) {
85 		dprintk("%s: no suitable DS addresses found\n",
86 			__func__);
87 		ret = -ENOMEDIUM;
88 		goto out_err_drain_dsaddrs;
89 	}
90 
91 	/* version count */
92 	p = xdr_inline_decode(&stream, 4);
93 	if (unlikely(!p))
94 		goto out_err_drain_dsaddrs;
95 	version_count = be32_to_cpup(p);
96 	dprintk("%s: version count %d\n", __func__, version_count);
97 
98 	ds_versions = kzalloc(version_count * sizeof(struct nfs4_ff_ds_version),
99 			      gfp_flags);
100 	if (!ds_versions)
101 		goto out_scratch;
102 
103 	for (i = 0; i < version_count; i++) {
104 		/* 20 = version(4) + minor_version(4) + rsize(4) + wsize(4) +
105 		 * tightly_coupled(4) */
106 		p = xdr_inline_decode(&stream, 20);
107 		if (unlikely(!p))
108 			goto out_err_drain_dsaddrs;
109 		ds_versions[i].version = be32_to_cpup(p++);
110 		ds_versions[i].minor_version = be32_to_cpup(p++);
111 		ds_versions[i].rsize = nfs_block_size(be32_to_cpup(p++), NULL);
112 		ds_versions[i].wsize = nfs_block_size(be32_to_cpup(p++), NULL);
113 		ds_versions[i].tightly_coupled = be32_to_cpup(p);
114 
115 		if (ds_versions[i].rsize > NFS_MAX_FILE_IO_SIZE)
116 			ds_versions[i].rsize = NFS_MAX_FILE_IO_SIZE;
117 		if (ds_versions[i].wsize > NFS_MAX_FILE_IO_SIZE)
118 			ds_versions[i].wsize = NFS_MAX_FILE_IO_SIZE;
119 
120 		if (ds_versions[i].version != 3 || ds_versions[i].minor_version != 0) {
121 			dprintk("%s: [%d] unsupported ds version %d-%d\n", __func__,
122 				i, ds_versions[i].version,
123 				ds_versions[i].minor_version);
124 			ret = -EPROTONOSUPPORT;
125 			goto out_err_drain_dsaddrs;
126 		}
127 
128 		dprintk("%s: [%d] vers %u minor_ver %u rsize %u wsize %u coupled %d\n",
129 			__func__, i, ds_versions[i].version,
130 			ds_versions[i].minor_version,
131 			ds_versions[i].rsize,
132 			ds_versions[i].wsize,
133 			ds_versions[i].tightly_coupled);
134 	}
135 
136 	new_ds->ds_versions = ds_versions;
137 	new_ds->ds_versions_cnt = version_count;
138 
139 	new_ds->ds = nfs4_pnfs_ds_add(&dsaddrs, gfp_flags);
140 	if (!new_ds->ds)
141 		goto out_err_drain_dsaddrs;
142 
143 	/* If DS was already in cache, free ds addrs */
144 	while (!list_empty(&dsaddrs)) {
145 		da = list_first_entry(&dsaddrs,
146 				      struct nfs4_pnfs_ds_addr,
147 				      da_node);
148 		list_del_init(&da->da_node);
149 		kfree(da->da_remotestr);
150 		kfree(da);
151 	}
152 
153 	__free_page(scratch);
154 	return new_ds;
155 
156 out_err_drain_dsaddrs:
157 	while (!list_empty(&dsaddrs)) {
158 		da = list_first_entry(&dsaddrs, struct nfs4_pnfs_ds_addr,
159 				      da_node);
160 		list_del_init(&da->da_node);
161 		kfree(da->da_remotestr);
162 		kfree(da);
163 	}
164 
165 	kfree(ds_versions);
166 out_scratch:
167 	__free_page(scratch);
168 out_err:
169 	kfree(new_ds);
170 
171 	dprintk("%s ERROR: returning %d\n", __func__, ret);
172 	return NULL;
173 }
174 
175 static void ff_layout_mark_devid_invalid(struct pnfs_layout_segment *lseg,
176 		struct nfs4_deviceid_node *devid)
177 {
178 	nfs4_mark_deviceid_unavailable(devid);
179 	if (!ff_layout_has_available_ds(lseg))
180 		pnfs_error_mark_layout_for_return(lseg->pls_layout->plh_inode,
181 				lseg);
182 }
183 
184 static bool ff_layout_mirror_valid(struct pnfs_layout_segment *lseg,
185 		struct nfs4_ff_layout_mirror *mirror)
186 {
187 	if (mirror == NULL || mirror->mirror_ds == NULL) {
188 		pnfs_error_mark_layout_for_return(lseg->pls_layout->plh_inode,
189 					lseg);
190 		return false;
191 	}
192 	if (mirror->mirror_ds->ds == NULL) {
193 		struct nfs4_deviceid_node *devid;
194 		devid = &mirror->mirror_ds->id_node;
195 		ff_layout_mark_devid_invalid(lseg, devid);
196 		return false;
197 	}
198 	return true;
199 }
200 
201 static u64
202 end_offset(u64 start, u64 len)
203 {
204 	u64 end;
205 
206 	end = start + len;
207 	return end >= start ? end : NFS4_MAX_UINT64;
208 }
209 
210 static void extend_ds_error(struct nfs4_ff_layout_ds_err *err,
211 			    u64 offset, u64 length)
212 {
213 	u64 end;
214 
215 	end = max_t(u64, end_offset(err->offset, err->length),
216 		    end_offset(offset, length));
217 	err->offset = min_t(u64, err->offset, offset);
218 	err->length = end - err->offset;
219 }
220 
221 static bool ds_error_can_merge(struct nfs4_ff_layout_ds_err *err,  u64 offset,
222 			       u64 length, int status, enum nfs_opnum4 opnum,
223 			       nfs4_stateid *stateid,
224 			       struct nfs4_deviceid *deviceid)
225 {
226 	return err->status == status && err->opnum == opnum &&
227 	       nfs4_stateid_match(&err->stateid, stateid) &&
228 	       !memcmp(&err->deviceid, deviceid, sizeof(*deviceid)) &&
229 	       end_offset(err->offset, err->length) >= offset &&
230 	       err->offset <= end_offset(offset, length);
231 }
232 
233 static bool merge_ds_error(struct nfs4_ff_layout_ds_err *old,
234 			   struct nfs4_ff_layout_ds_err *new)
235 {
236 	if (!ds_error_can_merge(old, new->offset, new->length, new->status,
237 				new->opnum, &new->stateid, &new->deviceid))
238 		return false;
239 
240 	extend_ds_error(old, new->offset, new->length);
241 	return true;
242 }
243 
244 static bool
245 ff_layout_add_ds_error_locked(struct nfs4_flexfile_layout *flo,
246 			      struct nfs4_ff_layout_ds_err *dserr)
247 {
248 	struct nfs4_ff_layout_ds_err *err;
249 
250 	list_for_each_entry(err, &flo->error_list, list) {
251 		if (merge_ds_error(err, dserr)) {
252 			return true;
253 		}
254 	}
255 
256 	list_add(&dserr->list, &flo->error_list);
257 	return false;
258 }
259 
260 static bool
261 ff_layout_update_ds_error(struct nfs4_flexfile_layout *flo, u64 offset,
262 			  u64 length, int status, enum nfs_opnum4 opnum,
263 			  nfs4_stateid *stateid, struct nfs4_deviceid *deviceid)
264 {
265 	bool found = false;
266 	struct nfs4_ff_layout_ds_err *err;
267 
268 	list_for_each_entry(err, &flo->error_list, list) {
269 		if (ds_error_can_merge(err, offset, length, status, opnum,
270 				       stateid, deviceid)) {
271 			found = true;
272 			extend_ds_error(err, offset, length);
273 			break;
274 		}
275 	}
276 
277 	return found;
278 }
279 
280 int ff_layout_track_ds_error(struct nfs4_flexfile_layout *flo,
281 			     struct nfs4_ff_layout_mirror *mirror, u64 offset,
282 			     u64 length, int status, enum nfs_opnum4 opnum,
283 			     gfp_t gfp_flags)
284 {
285 	struct nfs4_ff_layout_ds_err *dserr;
286 	bool needfree;
287 
288 	if (status == 0)
289 		return 0;
290 
291 	if (mirror->mirror_ds == NULL)
292 		return -EINVAL;
293 
294 	spin_lock(&flo->generic_hdr.plh_inode->i_lock);
295 	if (ff_layout_update_ds_error(flo, offset, length, status, opnum,
296 				      &mirror->stateid,
297 				      &mirror->mirror_ds->id_node.deviceid)) {
298 		spin_unlock(&flo->generic_hdr.plh_inode->i_lock);
299 		return 0;
300 	}
301 	spin_unlock(&flo->generic_hdr.plh_inode->i_lock);
302 	dserr = kmalloc(sizeof(*dserr), gfp_flags);
303 	if (!dserr)
304 		return -ENOMEM;
305 
306 	INIT_LIST_HEAD(&dserr->list);
307 	dserr->offset = offset;
308 	dserr->length = length;
309 	dserr->status = status;
310 	dserr->opnum = opnum;
311 	nfs4_stateid_copy(&dserr->stateid, &mirror->stateid);
312 	memcpy(&dserr->deviceid, &mirror->mirror_ds->id_node.deviceid,
313 	       NFS4_DEVICEID4_SIZE);
314 
315 	spin_lock(&flo->generic_hdr.plh_inode->i_lock);
316 	needfree = ff_layout_add_ds_error_locked(flo, dserr);
317 	spin_unlock(&flo->generic_hdr.plh_inode->i_lock);
318 	if (needfree)
319 		kfree(dserr);
320 
321 	return 0;
322 }
323 
324 /* currently we only support AUTH_NONE and AUTH_SYS */
325 static rpc_authflavor_t
326 nfs4_ff_layout_choose_authflavor(struct nfs4_ff_layout_mirror *mirror)
327 {
328 	if (mirror->uid == (u32)-1)
329 		return RPC_AUTH_NULL;
330 	return RPC_AUTH_UNIX;
331 }
332 
333 /* fetch cred for NFSv3 DS */
334 static int ff_layout_update_mirror_cred(struct nfs4_ff_layout_mirror *mirror,
335 				      struct nfs4_pnfs_ds *ds)
336 {
337 	if (ds->ds_clp && !mirror->cred &&
338 	    mirror->mirror_ds->ds_versions[0].version == 3) {
339 		struct rpc_auth *auth = ds->ds_clp->cl_rpcclient->cl_auth;
340 		struct rpc_cred *cred;
341 		struct auth_cred acred = {
342 			.uid = make_kuid(&init_user_ns, mirror->uid),
343 			.gid = make_kgid(&init_user_ns, mirror->gid),
344 		};
345 
346 		/* AUTH_NULL ignores acred */
347 		cred = auth->au_ops->lookup_cred(auth, &acred, 0);
348 		if (IS_ERR(cred)) {
349 			dprintk("%s: lookup_cred failed with %ld\n",
350 				__func__, PTR_ERR(cred));
351 			return PTR_ERR(cred);
352 		} else {
353 			if (cmpxchg(&mirror->cred, NULL, cred))
354 				put_rpccred(cred);
355 		}
356 	}
357 	return 0;
358 }
359 
360 struct nfs_fh *
361 nfs4_ff_layout_select_ds_fh(struct pnfs_layout_segment *lseg, u32 mirror_idx)
362 {
363 	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, mirror_idx);
364 	struct nfs_fh *fh = NULL;
365 
366 	if (!ff_layout_mirror_valid(lseg, mirror)) {
367 		pr_err_ratelimited("NFS: %s: No data server for mirror offset index %d\n",
368 			__func__, mirror_idx);
369 		goto out;
370 	}
371 
372 	/* FIXME: For now assume there is only 1 version available for the DS */
373 	fh = &mirror->fh_versions[0];
374 out:
375 	return fh;
376 }
377 
378 /* Upon return, either ds is connected, or ds is NULL */
379 struct nfs4_pnfs_ds *
380 nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx,
381 			  bool fail_return)
382 {
383 	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx);
384 	struct nfs4_pnfs_ds *ds = NULL;
385 	struct nfs4_deviceid_node *devid;
386 	struct inode *ino = lseg->pls_layout->plh_inode;
387 	struct nfs_server *s = NFS_SERVER(ino);
388 	unsigned int max_payload;
389 	rpc_authflavor_t flavor;
390 
391 	if (!ff_layout_mirror_valid(lseg, mirror)) {
392 		pr_err_ratelimited("NFS: %s: No data server for offset index %d\n",
393 			__func__, ds_idx);
394 		goto out;
395 	}
396 
397 	devid = &mirror->mirror_ds->id_node;
398 	if (ff_layout_test_devid_unavailable(devid))
399 		goto out;
400 
401 	ds = mirror->mirror_ds->ds;
402 	/* matching smp_wmb() in _nfs4_pnfs_v3/4_ds_connect */
403 	smp_rmb();
404 	if (ds->ds_clp)
405 		goto out_update_creds;
406 
407 	flavor = nfs4_ff_layout_choose_authflavor(mirror);
408 
409 	/* FIXME: For now we assume the server sent only one version of NFS
410 	 * to use for the DS.
411 	 */
412 	nfs4_pnfs_ds_connect(s, ds, devid, dataserver_timeo,
413 			     dataserver_retrans,
414 			     mirror->mirror_ds->ds_versions[0].version,
415 			     mirror->mirror_ds->ds_versions[0].minor_version,
416 			     flavor);
417 
418 	/* connect success, check rsize/wsize limit */
419 	if (ds->ds_clp) {
420 		max_payload =
421 			nfs_block_size(rpc_max_payload(ds->ds_clp->cl_rpcclient),
422 				       NULL);
423 		if (mirror->mirror_ds->ds_versions[0].rsize > max_payload)
424 			mirror->mirror_ds->ds_versions[0].rsize = max_payload;
425 		if (mirror->mirror_ds->ds_versions[0].wsize > max_payload)
426 			mirror->mirror_ds->ds_versions[0].wsize = max_payload;
427 	} else {
428 		ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout),
429 					 mirror, lseg->pls_range.offset,
430 					 lseg->pls_range.length, NFS4ERR_NXIO,
431 					 OP_ILLEGAL, GFP_NOIO);
432 		if (fail_return) {
433 			pnfs_error_mark_layout_for_return(ino, lseg);
434 			if (ff_layout_has_available_ds(lseg))
435 				pnfs_set_retry_layoutget(lseg->pls_layout);
436 			else
437 				pnfs_clear_retry_layoutget(lseg->pls_layout);
438 
439 		} else {
440 			if (ff_layout_has_available_ds(lseg))
441 				set_bit(NFS_LAYOUT_RETURN_BEFORE_CLOSE,
442 					&lseg->pls_layout->plh_flags);
443 			else {
444 				pnfs_error_mark_layout_for_return(ino, lseg);
445 				pnfs_clear_retry_layoutget(lseg->pls_layout);
446 			}
447 		}
448 	}
449 out_update_creds:
450 	if (ff_layout_update_mirror_cred(mirror, ds))
451 		ds = NULL;
452 out:
453 	return ds;
454 }
455 
456 struct rpc_cred *
457 ff_layout_get_ds_cred(struct pnfs_layout_segment *lseg, u32 ds_idx,
458 		      struct rpc_cred *mdscred)
459 {
460 	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx);
461 	struct rpc_cred *cred = ERR_PTR(-EINVAL);
462 
463 	if (!nfs4_ff_layout_prepare_ds(lseg, ds_idx, true))
464 		goto out;
465 
466 	if (mirror && mirror->cred)
467 		cred = mirror->cred;
468 	else
469 		cred = mdscred;
470 out:
471 	return cred;
472 }
473 
474 /**
475 * Find or create a DS rpc client with th MDS server rpc client auth flavor
476 * in the nfs_client cl_ds_clients list.
477 */
478 struct rpc_clnt *
479 nfs4_ff_find_or_create_ds_client(struct pnfs_layout_segment *lseg, u32 ds_idx,
480 				 struct nfs_client *ds_clp, struct inode *inode)
481 {
482 	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx);
483 
484 	switch (mirror->mirror_ds->ds_versions[0].version) {
485 	case 3:
486 		/* For NFSv3 DS, flavor is set when creating DS connections */
487 		return ds_clp->cl_rpcclient;
488 	case 4:
489 		return nfs4_find_or_create_ds_client(ds_clp, inode);
490 	default:
491 		BUG();
492 	}
493 }
494 
495 static bool is_range_intersecting(u64 offset1, u64 length1,
496 				  u64 offset2, u64 length2)
497 {
498 	u64 end1 = end_offset(offset1, length1);
499 	u64 end2 = end_offset(offset2, length2);
500 
501 	return (end1 == NFS4_MAX_UINT64 || end1 > offset2) &&
502 	       (end2 == NFS4_MAX_UINT64 || end2 > offset1);
503 }
504 
505 /* called with inode i_lock held */
506 int ff_layout_encode_ds_ioerr(struct nfs4_flexfile_layout *flo,
507 			      struct xdr_stream *xdr, int *count,
508 			      const struct pnfs_layout_range *range)
509 {
510 	struct nfs4_ff_layout_ds_err *err, *n;
511 	__be32 *p;
512 
513 	list_for_each_entry_safe(err, n, &flo->error_list, list) {
514 		if (!is_range_intersecting(err->offset, err->length,
515 					   range->offset, range->length))
516 			continue;
517 		/* offset(8) + length(8) + stateid(NFS4_STATEID_SIZE)
518 		 * + array length + deviceid(NFS4_DEVICEID4_SIZE)
519 		 * + status(4) + opnum(4)
520 		 */
521 		p = xdr_reserve_space(xdr,
522 				28 + NFS4_STATEID_SIZE + NFS4_DEVICEID4_SIZE);
523 		if (unlikely(!p))
524 			return -ENOBUFS;
525 		p = xdr_encode_hyper(p, err->offset);
526 		p = xdr_encode_hyper(p, err->length);
527 		p = xdr_encode_opaque_fixed(p, &err->stateid,
528 					    NFS4_STATEID_SIZE);
529 		/* Encode 1 error */
530 		*p++ = cpu_to_be32(1);
531 		p = xdr_encode_opaque_fixed(p, &err->deviceid,
532 					    NFS4_DEVICEID4_SIZE);
533 		*p++ = cpu_to_be32(err->status);
534 		*p++ = cpu_to_be32(err->opnum);
535 		*count += 1;
536 		list_del(&err->list);
537 		dprintk("%s: offset %llu length %llu status %d op %d count %d\n",
538 			__func__, err->offset, err->length, err->status,
539 			err->opnum, *count);
540 		kfree(err);
541 	}
542 
543 	return 0;
544 }
545 
546 static bool ff_read_layout_has_available_ds(struct pnfs_layout_segment *lseg)
547 {
548 	struct nfs4_ff_layout_mirror *mirror;
549 	struct nfs4_deviceid_node *devid;
550 	u32 idx;
551 
552 	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
553 		mirror = FF_LAYOUT_COMP(lseg, idx);
554 		if (mirror && mirror->mirror_ds) {
555 			devid = &mirror->mirror_ds->id_node;
556 			if (!ff_layout_test_devid_unavailable(devid))
557 				return true;
558 		}
559 	}
560 
561 	return false;
562 }
563 
564 static bool ff_rw_layout_has_available_ds(struct pnfs_layout_segment *lseg)
565 {
566 	struct nfs4_ff_layout_mirror *mirror;
567 	struct nfs4_deviceid_node *devid;
568 	u32 idx;
569 
570 	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
571 		mirror = FF_LAYOUT_COMP(lseg, idx);
572 		if (!mirror || !mirror->mirror_ds)
573 			return false;
574 		devid = &mirror->mirror_ds->id_node;
575 		if (ff_layout_test_devid_unavailable(devid))
576 			return false;
577 	}
578 
579 	return FF_LAYOUT_MIRROR_COUNT(lseg) != 0;
580 }
581 
582 bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg)
583 {
584 	if (lseg->pls_range.iomode == IOMODE_READ)
585 		return  ff_read_layout_has_available_ds(lseg);
586 	/* Note: RW layout needs all mirrors available */
587 	return ff_rw_layout_has_available_ds(lseg);
588 }
589 
590 module_param(dataserver_retrans, uint, 0644);
591 MODULE_PARM_DESC(dataserver_retrans, "The  number of times the NFSv4.1 client "
592 			"retries a request before it attempts further "
593 			" recovery  action.");
594 module_param(dataserver_timeo, uint, 0644);
595 MODULE_PARM_DESC(dataserver_timeo, "The time (in tenths of a second) the "
596 			"NFSv4.1  client  waits for a response from a "
597 			" data server before it retries an NFS request.");
598