xref: /linux/fs/nfs/flexfilelayout/flexfilelayoutdev.c (revision 55d0969c451159cff86949b38c39171cab962069)
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_page(&stream, scratch);
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_io_size(be32_to_cpup(p++),
117 						   server->nfs_client->cl_proto);
118 		ds_versions[i].wsize = nfs_io_size(be32_to_cpup(p++),
119 						   server->nfs_client->cl_proto);
120 		ds_versions[i].tightly_coupled = be32_to_cpup(p);
121 
122 		if (ds_versions[i].rsize > NFS_MAX_FILE_IO_SIZE)
123 			ds_versions[i].rsize = NFS_MAX_FILE_IO_SIZE;
124 		if (ds_versions[i].wsize > NFS_MAX_FILE_IO_SIZE)
125 			ds_versions[i].wsize = NFS_MAX_FILE_IO_SIZE;
126 
127 		/*
128 		 * check for valid major/minor combination.
129 		 * currently we support dataserver which talk:
130 		 *   v3, v4.0, v4.1, v4.2
131 		 */
132 		if (!((ds_versions[i].version == 3 && ds_versions[i].minor_version == 0) ||
133 			(ds_versions[i].version == 4 && ds_versions[i].minor_version < 3))) {
134 			dprintk("%s: [%d] unsupported ds version %d-%d\n", __func__,
135 				i, ds_versions[i].version,
136 				ds_versions[i].minor_version);
137 			ret = -EPROTONOSUPPORT;
138 			goto out_err_drain_dsaddrs;
139 		}
140 
141 		dprintk("%s: [%d] vers %u minor_ver %u rsize %u wsize %u coupled %d\n",
142 			__func__, i, ds_versions[i].version,
143 			ds_versions[i].minor_version,
144 			ds_versions[i].rsize,
145 			ds_versions[i].wsize,
146 			ds_versions[i].tightly_coupled);
147 	}
148 
149 	new_ds->ds_versions = ds_versions;
150 	new_ds->ds_versions_cnt = version_count;
151 
152 	new_ds->ds = nfs4_pnfs_ds_add(&dsaddrs, gfp_flags);
153 	if (!new_ds->ds)
154 		goto out_err_drain_dsaddrs;
155 
156 	/* If DS was already in cache, free ds addrs */
157 	while (!list_empty(&dsaddrs)) {
158 		da = list_first_entry(&dsaddrs,
159 				      struct nfs4_pnfs_ds_addr,
160 				      da_node);
161 		list_del_init(&da->da_node);
162 		kfree(da->da_remotestr);
163 		kfree(da);
164 	}
165 
166 	__free_page(scratch);
167 	return new_ds;
168 
169 out_err_drain_dsaddrs:
170 	while (!list_empty(&dsaddrs)) {
171 		da = list_first_entry(&dsaddrs, struct nfs4_pnfs_ds_addr,
172 				      da_node);
173 		list_del_init(&da->da_node);
174 		kfree(da->da_remotestr);
175 		kfree(da);
176 	}
177 
178 	kfree(ds_versions);
179 out_scratch:
180 	__free_page(scratch);
181 out_err:
182 	kfree(new_ds);
183 
184 	dprintk("%s ERROR: returning %d\n", __func__, ret);
185 	return NULL;
186 }
187 
188 static void extend_ds_error(struct nfs4_ff_layout_ds_err *err,
189 			    u64 offset, u64 length)
190 {
191 	u64 end;
192 
193 	end = max_t(u64, pnfs_end_offset(err->offset, err->length),
194 		    pnfs_end_offset(offset, length));
195 	err->offset = min_t(u64, err->offset, offset);
196 	err->length = end - err->offset;
197 }
198 
199 static int
200 ff_ds_error_match(const struct nfs4_ff_layout_ds_err *e1,
201 		const struct nfs4_ff_layout_ds_err *e2)
202 {
203 	int ret;
204 
205 	if (e1->opnum != e2->opnum)
206 		return e1->opnum < e2->opnum ? -1 : 1;
207 	if (e1->status != e2->status)
208 		return e1->status < e2->status ? -1 : 1;
209 	ret = memcmp(e1->stateid.data, e2->stateid.data,
210 			sizeof(e1->stateid.data));
211 	if (ret != 0)
212 		return ret;
213 	ret = memcmp(&e1->deviceid, &e2->deviceid, sizeof(e1->deviceid));
214 	if (ret != 0)
215 		return ret;
216 	if (pnfs_end_offset(e1->offset, e1->length) < e2->offset)
217 		return -1;
218 	if (e1->offset > pnfs_end_offset(e2->offset, e2->length))
219 		return 1;
220 	/* If ranges overlap or are contiguous, they are the same */
221 	return 0;
222 }
223 
224 static void
225 ff_layout_add_ds_error_locked(struct nfs4_flexfile_layout *flo,
226 			      struct nfs4_ff_layout_ds_err *dserr)
227 {
228 	struct nfs4_ff_layout_ds_err *err, *tmp;
229 	struct list_head *head = &flo->error_list;
230 	int match;
231 
232 	/* Do insertion sort w/ merges */
233 	list_for_each_entry_safe(err, tmp, &flo->error_list, list) {
234 		match = ff_ds_error_match(err, dserr);
235 		if (match < 0)
236 			continue;
237 		if (match > 0) {
238 			/* Add entry "dserr" _before_ entry "err" */
239 			head = &err->list;
240 			break;
241 		}
242 		/* Entries match, so merge "err" into "dserr" */
243 		extend_ds_error(dserr, err->offset, err->length);
244 		list_replace(&err->list, &dserr->list);
245 		kfree(err);
246 		return;
247 	}
248 
249 	list_add_tail(&dserr->list, head);
250 }
251 
252 int ff_layout_track_ds_error(struct nfs4_flexfile_layout *flo,
253 			     struct nfs4_ff_layout_mirror *mirror, u64 offset,
254 			     u64 length, int status, enum nfs_opnum4 opnum,
255 			     gfp_t gfp_flags)
256 {
257 	struct nfs4_ff_layout_ds_err *dserr;
258 
259 	if (status == 0)
260 		return 0;
261 
262 	if (IS_ERR_OR_NULL(mirror->mirror_ds))
263 		return -EINVAL;
264 
265 	dserr = kmalloc(sizeof(*dserr), gfp_flags);
266 	if (!dserr)
267 		return -ENOMEM;
268 
269 	INIT_LIST_HEAD(&dserr->list);
270 	dserr->offset = offset;
271 	dserr->length = length;
272 	dserr->status = status;
273 	dserr->opnum = opnum;
274 	nfs4_stateid_copy(&dserr->stateid, &mirror->stateid);
275 	memcpy(&dserr->deviceid, &mirror->mirror_ds->id_node.deviceid,
276 	       NFS4_DEVICEID4_SIZE);
277 
278 	spin_lock(&flo->generic_hdr.plh_inode->i_lock);
279 	ff_layout_add_ds_error_locked(flo, dserr);
280 	spin_unlock(&flo->generic_hdr.plh_inode->i_lock);
281 	return 0;
282 }
283 
284 static const struct cred *
285 ff_layout_get_mirror_cred(struct nfs4_ff_layout_mirror *mirror, u32 iomode)
286 {
287 	const struct cred *cred, __rcu **pcred;
288 
289 	if (iomode == IOMODE_READ)
290 		pcred = &mirror->ro_cred;
291 	else
292 		pcred = &mirror->rw_cred;
293 
294 	rcu_read_lock();
295 	do {
296 		cred = rcu_dereference(*pcred);
297 		if (!cred)
298 			break;
299 
300 		cred = get_cred_rcu(cred);
301 	} while(!cred);
302 	rcu_read_unlock();
303 	return cred;
304 }
305 
306 struct nfs_fh *
307 nfs4_ff_layout_select_ds_fh(struct nfs4_ff_layout_mirror *mirror)
308 {
309 	/* FIXME: For now assume there is only 1 version available for the DS */
310 	return &mirror->fh_versions[0];
311 }
312 
313 void
314 nfs4_ff_layout_select_ds_stateid(const struct nfs4_ff_layout_mirror *mirror,
315 		nfs4_stateid *stateid)
316 {
317 	if (nfs4_ff_layout_ds_version(mirror) == 4)
318 		nfs4_stateid_copy(stateid, &mirror->stateid);
319 }
320 
321 static bool
322 ff_layout_init_mirror_ds(struct pnfs_layout_hdr *lo,
323 			 struct nfs4_ff_layout_mirror *mirror)
324 {
325 	if (mirror == NULL)
326 		goto outerr;
327 	if (mirror->mirror_ds == NULL) {
328 		struct nfs4_deviceid_node *node;
329 		struct nfs4_ff_layout_ds *mirror_ds = ERR_PTR(-ENODEV);
330 
331 		node = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode),
332 				&mirror->devid, lo->plh_lc_cred,
333 				GFP_KERNEL);
334 		if (node)
335 			mirror_ds = FF_LAYOUT_MIRROR_DS(node);
336 
337 		/* check for race with another call to this function */
338 		if (cmpxchg(&mirror->mirror_ds, NULL, mirror_ds) &&
339 		    mirror_ds != ERR_PTR(-ENODEV))
340 			nfs4_put_deviceid_node(node);
341 	}
342 
343 	if (IS_ERR(mirror->mirror_ds))
344 		goto outerr;
345 
346 	return true;
347 outerr:
348 	return false;
349 }
350 
351 /**
352  * nfs4_ff_layout_prepare_ds - prepare a DS connection for an RPC call
353  * @lseg: the layout segment we're operating on
354  * @mirror: layout mirror describing the DS to use
355  * @fail_return: return layout on connect failure?
356  *
357  * Try to prepare a DS connection to accept an RPC call. This involves
358  * selecting a mirror to use and connecting the client to it if it's not
359  * already connected.
360  *
361  * Since we only need a single functioning mirror to satisfy a read, we don't
362  * want to return the layout if there is one. For writes though, any down
363  * mirror should result in a LAYOUTRETURN. @fail_return is how we distinguish
364  * between the two cases.
365  *
366  * Returns a pointer to a connected DS object on success or NULL on failure.
367  */
368 struct nfs4_pnfs_ds *
369 nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg,
370 			  struct nfs4_ff_layout_mirror *mirror,
371 			  bool fail_return)
372 {
373 	struct nfs4_pnfs_ds *ds = NULL;
374 	struct inode *ino = lseg->pls_layout->plh_inode;
375 	struct nfs_server *s = NFS_SERVER(ino);
376 	unsigned int max_payload;
377 	int status;
378 
379 	if (!ff_layout_init_mirror_ds(lseg->pls_layout, mirror))
380 		goto noconnect;
381 
382 	ds = mirror->mirror_ds->ds;
383 	if (READ_ONCE(ds->ds_clp))
384 		goto out;
385 	/* matching smp_wmb() in _nfs4_pnfs_v3/4_ds_connect */
386 	smp_rmb();
387 
388 	/* FIXME: For now we assume the server sent only one version of NFS
389 	 * to use for the DS.
390 	 */
391 	status = nfs4_pnfs_ds_connect(s, ds, &mirror->mirror_ds->id_node,
392 			     dataserver_timeo, dataserver_retrans,
393 			     mirror->mirror_ds->ds_versions[0].version,
394 			     mirror->mirror_ds->ds_versions[0].minor_version);
395 
396 	/* connect success, check rsize/wsize limit */
397 	if (!status) {
398 		/*
399 		 * ds_clp is put in destroy_ds().
400 		 * keep ds_clp even if DS is local, so that if local IO cannot
401 		 * proceed somehow, we can fall back to NFS whenever we want.
402 		 */
403 		nfs_local_probe(ds->ds_clp);
404 		max_payload =
405 			nfs_block_size(rpc_max_payload(ds->ds_clp->cl_rpcclient),
406 				       NULL);
407 		if (mirror->mirror_ds->ds_versions[0].rsize > max_payload)
408 			mirror->mirror_ds->ds_versions[0].rsize = max_payload;
409 		if (mirror->mirror_ds->ds_versions[0].wsize > max_payload)
410 			mirror->mirror_ds->ds_versions[0].wsize = max_payload;
411 		goto out;
412 	}
413 noconnect:
414 	ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout),
415 				 mirror, lseg->pls_range.offset,
416 				 lseg->pls_range.length, NFS4ERR_NXIO,
417 				 OP_ILLEGAL, GFP_NOIO);
418 	ff_layout_send_layouterror(lseg);
419 	if (fail_return || !ff_layout_has_available_ds(lseg))
420 		pnfs_error_mark_layout_for_return(ino, lseg);
421 	ds = NULL;
422 out:
423 	return ds;
424 }
425 
426 const struct cred *
427 ff_layout_get_ds_cred(struct nfs4_ff_layout_mirror *mirror,
428 		      const struct pnfs_layout_range *range,
429 		      const struct cred *mdscred)
430 {
431 	const struct cred *cred;
432 
433 	if (mirror && !mirror->mirror_ds->ds_versions[0].tightly_coupled) {
434 		cred = ff_layout_get_mirror_cred(mirror, range->iomode);
435 		if (!cred)
436 			cred = get_cred(mdscred);
437 	} else {
438 		cred = get_cred(mdscred);
439 	}
440 	return cred;
441 }
442 
443 /**
444  * nfs4_ff_find_or_create_ds_client - Find or create a DS rpc client
445  * @mirror: pointer to the mirror
446  * @ds_clp: nfs_client for the DS
447  * @inode: pointer to inode
448  *
449  * Find or create a DS rpc client with th MDS server rpc client auth flavor
450  * in the nfs_client cl_ds_clients list.
451  */
452 struct rpc_clnt *
453 nfs4_ff_find_or_create_ds_client(struct nfs4_ff_layout_mirror *mirror,
454 				 struct nfs_client *ds_clp, struct inode *inode)
455 {
456 	switch (mirror->mirror_ds->ds_versions[0].version) {
457 	case 3:
458 		/* For NFSv3 DS, flavor is set when creating DS connections */
459 		return ds_clp->cl_rpcclient;
460 	case 4:
461 		return nfs4_find_or_create_ds_client(ds_clp, inode);
462 	default:
463 		BUG();
464 	}
465 }
466 
467 void ff_layout_free_ds_ioerr(struct list_head *head)
468 {
469 	struct nfs4_ff_layout_ds_err *err;
470 
471 	while (!list_empty(head)) {
472 		err = list_first_entry(head,
473 				struct nfs4_ff_layout_ds_err,
474 				list);
475 		list_del(&err->list);
476 		kfree(err);
477 	}
478 }
479 
480 /* called with inode i_lock held */
481 int ff_layout_encode_ds_ioerr(struct xdr_stream *xdr, const struct list_head *head)
482 {
483 	struct nfs4_ff_layout_ds_err *err;
484 	__be32 *p;
485 
486 	list_for_each_entry(err, head, list) {
487 		/* offset(8) + length(8) + stateid(NFS4_STATEID_SIZE)
488 		 * + array length + deviceid(NFS4_DEVICEID4_SIZE)
489 		 * + status(4) + opnum(4)
490 		 */
491 		p = xdr_reserve_space(xdr,
492 				28 + NFS4_STATEID_SIZE + NFS4_DEVICEID4_SIZE);
493 		if (unlikely(!p))
494 			return -ENOBUFS;
495 		p = xdr_encode_hyper(p, err->offset);
496 		p = xdr_encode_hyper(p, err->length);
497 		p = xdr_encode_opaque_fixed(p, &err->stateid,
498 					    NFS4_STATEID_SIZE);
499 		/* Encode 1 error */
500 		*p++ = cpu_to_be32(1);
501 		p = xdr_encode_opaque_fixed(p, &err->deviceid,
502 					    NFS4_DEVICEID4_SIZE);
503 		*p++ = cpu_to_be32(err->status);
504 		*p++ = cpu_to_be32(err->opnum);
505 		dprintk("%s: offset %llu length %llu status %d op %d\n",
506 			__func__, err->offset, err->length, err->status,
507 			err->opnum);
508 	}
509 
510 	return 0;
511 }
512 
513 static
514 unsigned int do_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
515 				      const struct pnfs_layout_range *range,
516 				      struct list_head *head,
517 				      unsigned int maxnum)
518 {
519 	struct nfs4_flexfile_layout *flo = FF_LAYOUT_FROM_HDR(lo);
520 	struct inode *inode = lo->plh_inode;
521 	struct nfs4_ff_layout_ds_err *err, *n;
522 	unsigned int ret = 0;
523 
524 	spin_lock(&inode->i_lock);
525 	list_for_each_entry_safe(err, n, &flo->error_list, list) {
526 		if (!pnfs_is_range_intersecting(err->offset,
527 				pnfs_end_offset(err->offset, err->length),
528 				range->offset,
529 				pnfs_end_offset(range->offset, range->length)))
530 			continue;
531 		if (!maxnum)
532 			break;
533 		list_move(&err->list, head);
534 		maxnum--;
535 		ret++;
536 	}
537 	spin_unlock(&inode->i_lock);
538 	return ret;
539 }
540 
541 unsigned int ff_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
542 				      const struct pnfs_layout_range *range,
543 				      struct list_head *head,
544 				      unsigned int maxnum)
545 {
546 	unsigned int ret;
547 
548 	ret = do_layout_fetch_ds_ioerr(lo, range, head, maxnum);
549 	/* If we're over the max, discard all remaining entries */
550 	if (ret == maxnum) {
551 		LIST_HEAD(discard);
552 		do_layout_fetch_ds_ioerr(lo, range, &discard, -1);
553 		ff_layout_free_ds_ioerr(&discard);
554 	}
555 	return ret;
556 }
557 
558 static bool ff_read_layout_has_available_ds(struct pnfs_layout_segment *lseg)
559 {
560 	struct nfs4_ff_layout_mirror *mirror;
561 	struct nfs4_deviceid_node *devid;
562 	u32 idx;
563 
564 	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
565 		mirror = FF_LAYOUT_COMP(lseg, idx);
566 		if (mirror) {
567 			if (!mirror->mirror_ds)
568 				return true;
569 			if (IS_ERR(mirror->mirror_ds))
570 				continue;
571 			devid = &mirror->mirror_ds->id_node;
572 			if (!nfs4_test_deviceid_unavailable(devid))
573 				return true;
574 		}
575 	}
576 
577 	return false;
578 }
579 
580 static bool ff_rw_layout_has_available_ds(struct pnfs_layout_segment *lseg)
581 {
582 	struct nfs4_ff_layout_mirror *mirror;
583 	struct nfs4_deviceid_node *devid;
584 	u32 idx;
585 
586 	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
587 		mirror = FF_LAYOUT_COMP(lseg, idx);
588 		if (!mirror || IS_ERR(mirror->mirror_ds))
589 			return false;
590 		if (!mirror->mirror_ds)
591 			continue;
592 		devid = &mirror->mirror_ds->id_node;
593 		if (nfs4_test_deviceid_unavailable(devid))
594 			return false;
595 	}
596 
597 	return FF_LAYOUT_MIRROR_COUNT(lseg) != 0;
598 }
599 
600 static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg)
601 {
602 	if (lseg->pls_range.iomode == IOMODE_READ)
603 		return  ff_read_layout_has_available_ds(lseg);
604 	/* Note: RW layout needs all mirrors available */
605 	return ff_rw_layout_has_available_ds(lseg);
606 }
607 
608 bool ff_layout_avoid_mds_available_ds(struct pnfs_layout_segment *lseg)
609 {
610 	return ff_layout_no_fallback_to_mds(lseg) ||
611 	       ff_layout_has_available_ds(lseg);
612 }
613 
614 bool ff_layout_avoid_read_on_rw(struct pnfs_layout_segment *lseg)
615 {
616 	return lseg->pls_range.iomode == IOMODE_RW &&
617 	       ff_layout_no_read_on_rw(lseg);
618 }
619 
620 module_param(dataserver_retrans, uint, 0644);
621 MODULE_PARM_DESC(dataserver_retrans, "The  number of times the NFSv4.1 client "
622 			"retries a request before it attempts further "
623 			" recovery  action.");
624 module_param(dataserver_timeo, uint, 0644);
625 MODULE_PARM_DESC(dataserver_timeo, "The time (in tenths of a second) the "
626 			"NFSv4.1  client  waits for a response from a "
627 			" data server before it retries an NFS request.");
628