flexfilelayoutdev.c

  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
 21static unsigned int dataserver_timeo = NFS_DEF_TCP_TIMEO;
 22static unsigned int dataserver_retrans;
 23
 24static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg);
 25
 26void 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
 32void 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 */
 41struct nfs4_ff_layout_ds *
 42nfs4_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 folio *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	struct net *net = server->nfs_client->cl_net;
 53	u32 mp_count;
 54	u32 version_count;
 55	__be32 *p;
 56	int i, ret = -ENOMEM;
 57
 58	/* set up xdr stream */
 59	scratch = folio_alloc(gfp_flags, 0);
 60	if (!scratch)
 61		goto out_err;
 62
 63	new_ds = kzalloc(sizeof(struct nfs4_ff_layout_ds), gfp_flags);
 64	if (!new_ds)
 65		goto out_scratch;
 66
 67	nfs4_init_deviceid_node(&new_ds->id_node,
 68				server,
 69				&pdev->dev_id);
 70	INIT_LIST_HEAD(&dsaddrs);
 71
 72	xdr_init_decode_pages(&stream, &buf, pdev->pages, pdev->pglen);
 73	xdr_set_scratch_folio(&stream, scratch);
 74
 75	/* multipath count */
 76	p = xdr_inline_decode(&stream, 4);
 77	if (unlikely(!p))
 78		goto out_err_drain_dsaddrs;
 79	mp_count = be32_to_cpup(p);
 80	dprintk("%s: multipath ds count %d\n", __func__, mp_count);
 81
 82	for (i = 0; i < mp_count; i++) {
 83		/* multipath ds */
 84		da = nfs4_decode_mp_ds_addr(net, &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_err_drain_dsaddrs;
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(net, &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	folio_put(scratch);
167	return new_ds;
168
169out_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);
179out_scratch:
180	folio_put(scratch);
181out_err:
182	kfree(new_ds);
183
184	dprintk("%s ERROR: returning %d\n", __func__, ret);
185	return NULL;
186}
187
188static 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
199static int
200ff_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
224static void
225ff_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
252int ff_layout_track_ds_error(struct nfs4_flexfile_layout *flo,
253			     struct nfs4_ff_layout_mirror *mirror,
254			     u32 dss_id, u64 offset, u64 length, int status,
255			     enum nfs_opnum4 opnum, 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->dss[dss_id].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->dss[dss_id].stateid);
275	memcpy(&dserr->deviceid, &mirror->dss[dss_id].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
284static const struct cred *
285ff_layout_get_mirror_cred(struct nfs4_ff_layout_mirror *mirror, u32 iomode, u32 dss_id)
286{
287	const struct cred *cred, __rcu **pcred;
288
289	if (iomode == IOMODE_READ)
290		pcred = &mirror->dss[dss_id].ro_cred;
291	else
292		pcred = &mirror->dss[dss_id].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
306struct nfs_fh *
307nfs4_ff_layout_select_ds_fh(struct nfs4_ff_layout_mirror *mirror, u32 dss_id)
308{
309	/* FIXME: For now assume there is only 1 version available for the DS */
310	return &mirror->dss[dss_id].fh_versions[0];
311}
312
313void
314nfs4_ff_layout_select_ds_stateid(const struct nfs4_ff_layout_mirror *mirror,
315				 u32 dss_id,
316				 nfs4_stateid *stateid)
317{
318	if (nfs4_ff_layout_ds_version(mirror, dss_id) == 4)
319		nfs4_stateid_copy(stateid, &mirror->dss[dss_id].stateid);
320}
321
322static bool
323ff_layout_init_mirror_ds(struct pnfs_layout_hdr *lo,
324			 struct nfs4_ff_layout_mirror *mirror,
325			 u32 dss_id)
326{
327	if (mirror == NULL)
328		goto outerr;
329	if (mirror->dss[dss_id].mirror_ds == NULL) {
330		struct nfs4_deviceid_node *node;
331		struct nfs4_ff_layout_ds *mirror_ds = ERR_PTR(-ENODEV);
332
333		node = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode),
334				&mirror->dss[dss_id].devid, lo->plh_lc_cred,
335				GFP_KERNEL);
336		if (node)
337			mirror_ds = FF_LAYOUT_MIRROR_DS(node);
338
339		/* check for race with another call to this function */
340		if (cmpxchg(&mirror->dss[dss_id].mirror_ds, NULL, mirror_ds) &&
341		    mirror_ds != ERR_PTR(-ENODEV))
342			nfs4_put_deviceid_node(node);
343	}
344
345	if (IS_ERR(mirror->dss[dss_id].mirror_ds))
346		goto outerr;
347
348	return true;
349outerr:
350	return false;
351}
352
353/**
354 * nfs4_ff_layout_prepare_ds - prepare a DS connection for an RPC call
355 * @lseg: the layout segment we're operating on
356 * @mirror: layout mirror describing the DS to use
357 * @dss_id: DS stripe id to select stripe to use
358 * @fail_return: return layout on connect failure?
359 *
360 * Try to prepare a DS connection to accept an RPC call. This involves
361 * selecting a mirror to use and connecting the client to it if it's not
362 * already connected.
363 *
364 * Since we only need a single functioning mirror to satisfy a read, we don't
365 * want to return the layout if there is one. For writes though, any down
366 * mirror should result in a LAYOUTRETURN. @fail_return is how we distinguish
367 * between the two cases.
368 *
369 * Returns a pointer to a connected DS object on success or NULL on failure.
370 */
371struct nfs4_pnfs_ds *
372nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg,
373			  struct nfs4_ff_layout_mirror *mirror,
374			  u32 dss_id,
375			  bool fail_return)
376{
377	struct nfs4_pnfs_ds *ds;
378	struct inode *ino = lseg->pls_layout->plh_inode;
379	struct nfs_server *s = NFS_SERVER(ino);
380	unsigned int max_payload;
381	int status = -EAGAIN;
382
383	if (!ff_layout_init_mirror_ds(lseg->pls_layout, mirror, dss_id))
384		goto noconnect;
385
386	ds = mirror->dss[dss_id].mirror_ds->ds;
387	if (READ_ONCE(ds->ds_clp))
388		goto out;
389	/* matching smp_wmb() in _nfs4_pnfs_v3/4_ds_connect */
390	smp_rmb();
391
392	/* FIXME: For now we assume the server sent only one version of NFS
393	 * to use for the DS.
394	 */
395	status = nfs4_pnfs_ds_connect(s, ds, &mirror->dss[dss_id].mirror_ds->id_node,
396			     dataserver_timeo, dataserver_retrans,
397			     mirror->dss[dss_id].mirror_ds->ds_versions[0].version,
398			     mirror->dss[dss_id].mirror_ds->ds_versions[0].minor_version);
399
400	/* connect success, check rsize/wsize limit */
401	if (!status) {
402		/*
403		 * ds_clp is put in destroy_ds().
404		 * keep ds_clp even if DS is local, so that if local IO cannot
405		 * proceed somehow, we can fall back to NFS whenever we want.
406		 */
407		nfs_local_probe_async(ds->ds_clp);
408		max_payload =
409			nfs_block_size(rpc_max_payload(ds->ds_clp->cl_rpcclient),
410				       NULL);
411		if (mirror->dss[dss_id].mirror_ds->ds_versions[0].rsize > max_payload)
412			mirror->dss[dss_id].mirror_ds->ds_versions[0].rsize = max_payload;
413		if (mirror->dss[dss_id].mirror_ds->ds_versions[0].wsize > max_payload)
414			mirror->dss[dss_id].mirror_ds->ds_versions[0].wsize = max_payload;
415		goto out;
416	}
417noconnect:
418	ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout),
419				 mirror, dss_id, lseg->pls_range.offset,
420				 lseg->pls_range.length, NFS4ERR_NXIO,
421				 OP_ILLEGAL, GFP_NOIO);
422	ff_layout_send_layouterror(lseg);
423	if (fail_return || !ff_layout_has_available_ds(lseg))
424		pnfs_error_mark_layout_for_return(ino, lseg);
425	ds = ERR_PTR(status);
426out:
427	return ds;
428}
429
430const struct cred *
431ff_layout_get_ds_cred(struct nfs4_ff_layout_mirror *mirror,
432		      const struct pnfs_layout_range *range,
433		      const struct cred *mdscred,
434		      u32 dss_id)
435{
436	const struct cred *cred;
437
438	if (mirror && !mirror->dss[dss_id].mirror_ds->ds_versions[0].tightly_coupled) {
439		cred = ff_layout_get_mirror_cred(mirror, range->iomode, dss_id);
440		if (!cred)
441			cred = get_cred(mdscred);
442	} else {
443		cred = get_cred(mdscred);
444	}
445	return cred;
446}
447
448/**
449 * nfs4_ff_find_or_create_ds_client - Find or create a DS rpc client
450 * @mirror: pointer to the mirror
451 * @ds_clp: nfs_client for the DS
452 * @inode: pointer to inode
453 * @dss_id: DS stripe id
454 *
455 * Find or create a DS rpc client with th MDS server rpc client auth flavor
456 * in the nfs_client cl_ds_clients list.
457 */
458struct rpc_clnt *
459nfs4_ff_find_or_create_ds_client(struct nfs4_ff_layout_mirror *mirror,
460				 struct nfs_client *ds_clp, struct inode *inode,
461				 u32 dss_id)
462{
463	switch (mirror->dss[dss_id].mirror_ds->ds_versions[0].version) {
464	case 3:
465		/* For NFSv3 DS, flavor is set when creating DS connections */
466		return ds_clp->cl_rpcclient;
467	case 4:
468		return nfs4_find_or_create_ds_client(ds_clp, inode);
469	default:
470		BUG();
471	}
472}
473
474void ff_layout_free_ds_ioerr(struct list_head *head)
475{
476	struct nfs4_ff_layout_ds_err *err;
477
478	while (!list_empty(head)) {
479		err = list_first_entry(head,
480				struct nfs4_ff_layout_ds_err,
481				list);
482		list_del(&err->list);
483		kfree(err);
484	}
485}
486
487/* called with inode i_lock held */
488int ff_layout_encode_ds_ioerr(struct xdr_stream *xdr, const struct list_head *head)
489{
490	struct nfs4_ff_layout_ds_err *err;
491	__be32 *p;
492
493	list_for_each_entry(err, head, list) {
494		/* offset(8) + length(8) + stateid(NFS4_STATEID_SIZE)
495		 * + array length + deviceid(NFS4_DEVICEID4_SIZE)
496		 * + status(4) + opnum(4)
497		 */
498		p = xdr_reserve_space(xdr,
499				28 + NFS4_STATEID_SIZE + NFS4_DEVICEID4_SIZE);
500		if (unlikely(!p))
501			return -ENOBUFS;
502		p = xdr_encode_hyper(p, err->offset);
503		p = xdr_encode_hyper(p, err->length);
504		p = xdr_encode_opaque_fixed(p, &err->stateid,
505					    NFS4_STATEID_SIZE);
506		/* Encode 1 error */
507		*p++ = cpu_to_be32(1);
508		p = xdr_encode_opaque_fixed(p, &err->deviceid,
509					    NFS4_DEVICEID4_SIZE);
510		*p++ = cpu_to_be32(err->status);
511		*p++ = cpu_to_be32(err->opnum);
512		dprintk("%s: offset %llu length %llu status %d op %d\n",
513			__func__, err->offset, err->length, err->status,
514			err->opnum);
515	}
516
517	return 0;
518}
519
520static
521unsigned int do_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
522				      const struct pnfs_layout_range *range,
523				      struct list_head *head,
524				      unsigned int maxnum)
525{
526	struct nfs4_flexfile_layout *flo = FF_LAYOUT_FROM_HDR(lo);
527	struct inode *inode = lo->plh_inode;
528	struct nfs4_ff_layout_ds_err *err, *n;
529	unsigned int ret = 0;
530
531	spin_lock(&inode->i_lock);
532	list_for_each_entry_safe(err, n, &flo->error_list, list) {
533		if (!pnfs_is_range_intersecting(err->offset,
534				pnfs_end_offset(err->offset, err->length),
535				range->offset,
536				pnfs_end_offset(range->offset, range->length)))
537			continue;
538		if (!maxnum)
539			break;
540		list_move(&err->list, head);
541		maxnum--;
542		ret++;
543	}
544	spin_unlock(&inode->i_lock);
545	return ret;
546}
547
548unsigned int ff_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
549				      const struct pnfs_layout_range *range,
550				      struct list_head *head,
551				      unsigned int maxnum)
552{
553	unsigned int ret;
554
555	ret = do_layout_fetch_ds_ioerr(lo, range, head, maxnum);
556	/* If we're over the max, discard all remaining entries */
557	if (ret == maxnum) {
558		LIST_HEAD(discard);
559		do_layout_fetch_ds_ioerr(lo, range, &discard, -1);
560		ff_layout_free_ds_ioerr(&discard);
561	}
562	return ret;
563}
564
565static bool ff_read_layout_has_available_ds(struct pnfs_layout_segment *lseg)
566{
567	struct nfs4_ff_layout_mirror *mirror;
568	struct nfs4_deviceid_node *devid;
569	u32 idx, dss_id;
570
571	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
572		mirror = FF_LAYOUT_COMP(lseg, idx);
573		if (!mirror)
574			continue;
575		for (dss_id = 0; dss_id < mirror->dss_count; dss_id++) {
576			if (!mirror->dss[dss_id].mirror_ds)
577				return true;
578			if (IS_ERR(mirror->dss[dss_id].mirror_ds))
579				continue;
580			devid = &mirror->dss[dss_id].mirror_ds->id_node;
581			if (!nfs4_test_deviceid_unavailable(devid))
582				return true;
583		}
584	}
585
586	return false;
587}
588
589static bool ff_rw_layout_has_available_ds(struct pnfs_layout_segment *lseg)
590{
591	struct nfs4_ff_layout_mirror *mirror;
592	struct nfs4_deviceid_node *devid;
593	u32 idx, dss_id;
594
595	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
596		mirror = FF_LAYOUT_COMP(lseg, idx);
597		if (!mirror)
598			return false;
599		for (dss_id = 0; dss_id < mirror->dss_count; dss_id++) {
600			if (IS_ERR(mirror->dss[dss_id].mirror_ds))
601				return false;
602			if (!mirror->dss[dss_id].mirror_ds)
603				continue;
604			devid = &mirror->dss[dss_id].mirror_ds->id_node;
605			if (nfs4_test_deviceid_unavailable(devid))
606				return false;
607		}
608	}
609
610	return FF_LAYOUT_MIRROR_COUNT(lseg) != 0;
611}
612
613static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg)
614{
615	if (lseg->pls_range.iomode == IOMODE_READ)
616		return  ff_read_layout_has_available_ds(lseg);
617	/* Note: RW layout needs all mirrors available */
618	return ff_rw_layout_has_available_ds(lseg);
619}
620
621bool ff_layout_avoid_mds_available_ds(struct pnfs_layout_segment *lseg)
622{
623	return ff_layout_no_fallback_to_mds(lseg) ||
624	       ff_layout_has_available_ds(lseg);
625}
626
627bool ff_layout_avoid_read_on_rw(struct pnfs_layout_segment *lseg)
628{
629	return lseg->pls_range.iomode == IOMODE_RW &&
630	       ff_layout_no_read_on_rw(lseg);
631}
632
633module_param(dataserver_retrans, uint, 0644);
634MODULE_PARM_DESC(dataserver_retrans, "The  number of times the NFSv4.1 client "
635			"retries a request before it attempts further "
636			" recovery  action.");
637module_param(dataserver_timeo, uint, 0644);
638MODULE_PARM_DESC(dataserver_timeo, "The time (in tenths of a second) the "
639			"NFSv4.1  client  waits for a response from a "
640			" data server before it retries an NFS request.");