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_RETRANS;
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 ff_layout_mark_devid_invalid(struct pnfs_layout_segment *lseg,
187 		struct nfs4_deviceid_node *devid)
188 {
189 	nfs4_delete_deviceid(devid->ld, devid->nfs_client, &devid->deviceid);
190 	if (!ff_layout_has_available_ds(lseg))
191 		pnfs_error_mark_layout_for_return(lseg->pls_layout->plh_inode,
192 				lseg);
193 }
194 
195 static bool ff_layout_mirror_valid(struct pnfs_layout_segment *lseg,
196 				   struct nfs4_ff_layout_mirror *mirror,
197 				   bool create)
198 {
199 	if (mirror == NULL || IS_ERR(mirror->mirror_ds))
200 		goto outerr;
201 	if (mirror->mirror_ds == NULL) {
202 		if (create) {
203 			struct nfs4_deviceid_node *node;
204 			struct pnfs_layout_hdr *lh = lseg->pls_layout;
205 			struct nfs4_ff_layout_ds *mirror_ds = ERR_PTR(-ENODEV);
206 
207 			node = nfs4_find_get_deviceid(NFS_SERVER(lh->plh_inode),
208 					&mirror->devid, lh->plh_lc_cred,
209 					GFP_KERNEL);
210 			if (node)
211 				mirror_ds = FF_LAYOUT_MIRROR_DS(node);
212 
213 			/* check for race with another call to this function */
214 			if (cmpxchg(&mirror->mirror_ds, NULL, mirror_ds) &&
215 			    mirror_ds != ERR_PTR(-ENODEV))
216 				nfs4_put_deviceid_node(node);
217 		} else
218 			goto outerr;
219 	}
220 
221 	if (IS_ERR(mirror->mirror_ds))
222 		goto outerr;
223 
224 	if (mirror->mirror_ds->ds == NULL) {
225 		struct nfs4_deviceid_node *devid;
226 		devid = &mirror->mirror_ds->id_node;
227 		ff_layout_mark_devid_invalid(lseg, devid);
228 		return false;
229 	}
230 	return true;
231 outerr:
232 	pnfs_error_mark_layout_for_return(lseg->pls_layout->plh_inode, lseg);
233 	return false;
234 }
235 
236 static void extend_ds_error(struct nfs4_ff_layout_ds_err *err,
237 			    u64 offset, u64 length)
238 {
239 	u64 end;
240 
241 	end = max_t(u64, pnfs_end_offset(err->offset, err->length),
242 		    pnfs_end_offset(offset, length));
243 	err->offset = min_t(u64, err->offset, offset);
244 	err->length = end - err->offset;
245 }
246 
247 static int
248 ff_ds_error_match(const struct nfs4_ff_layout_ds_err *e1,
249 		const struct nfs4_ff_layout_ds_err *e2)
250 {
251 	int ret;
252 
253 	if (e1->opnum != e2->opnum)
254 		return e1->opnum < e2->opnum ? -1 : 1;
255 	if (e1->status != e2->status)
256 		return e1->status < e2->status ? -1 : 1;
257 	ret = memcmp(e1->stateid.data, e2->stateid.data,
258 			sizeof(e1->stateid.data));
259 	if (ret != 0)
260 		return ret;
261 	ret = memcmp(&e1->deviceid, &e2->deviceid, sizeof(e1->deviceid));
262 	if (ret != 0)
263 		return ret;
264 	if (pnfs_end_offset(e1->offset, e1->length) < e2->offset)
265 		return -1;
266 	if (e1->offset > pnfs_end_offset(e2->offset, e2->length))
267 		return 1;
268 	/* If ranges overlap or are contiguous, they are the same */
269 	return 0;
270 }
271 
272 static void
273 ff_layout_add_ds_error_locked(struct nfs4_flexfile_layout *flo,
274 			      struct nfs4_ff_layout_ds_err *dserr)
275 {
276 	struct nfs4_ff_layout_ds_err *err, *tmp;
277 	struct list_head *head = &flo->error_list;
278 	int match;
279 
280 	/* Do insertion sort w/ merges */
281 	list_for_each_entry_safe(err, tmp, &flo->error_list, list) {
282 		match = ff_ds_error_match(err, dserr);
283 		if (match < 0)
284 			continue;
285 		if (match > 0) {
286 			/* Add entry "dserr" _before_ entry "err" */
287 			head = &err->list;
288 			break;
289 		}
290 		/* Entries match, so merge "err" into "dserr" */
291 		extend_ds_error(dserr, err->offset, err->length);
292 		list_replace(&err->list, &dserr->list);
293 		kfree(err);
294 		return;
295 	}
296 
297 	list_add_tail(&dserr->list, head);
298 }
299 
300 int ff_layout_track_ds_error(struct nfs4_flexfile_layout *flo,
301 			     struct nfs4_ff_layout_mirror *mirror, u64 offset,
302 			     u64 length, int status, enum nfs_opnum4 opnum,
303 			     gfp_t gfp_flags)
304 {
305 	struct nfs4_ff_layout_ds_err *dserr;
306 
307 	if (status == 0)
308 		return 0;
309 
310 	if (mirror->mirror_ds == NULL)
311 		return -EINVAL;
312 
313 	dserr = kmalloc(sizeof(*dserr), gfp_flags);
314 	if (!dserr)
315 		return -ENOMEM;
316 
317 	INIT_LIST_HEAD(&dserr->list);
318 	dserr->offset = offset;
319 	dserr->length = length;
320 	dserr->status = status;
321 	dserr->opnum = opnum;
322 	nfs4_stateid_copy(&dserr->stateid, &mirror->stateid);
323 	memcpy(&dserr->deviceid, &mirror->mirror_ds->id_node.deviceid,
324 	       NFS4_DEVICEID4_SIZE);
325 
326 	spin_lock(&flo->generic_hdr.plh_inode->i_lock);
327 	ff_layout_add_ds_error_locked(flo, dserr);
328 	spin_unlock(&flo->generic_hdr.plh_inode->i_lock);
329 
330 	return 0;
331 }
332 
333 static struct rpc_cred *
334 ff_layout_get_mirror_cred(struct nfs4_ff_layout_mirror *mirror, u32 iomode)
335 {
336 	struct rpc_cred *cred, __rcu **pcred;
337 
338 	if (iomode == IOMODE_READ)
339 		pcred = &mirror->ro_cred;
340 	else
341 		pcred = &mirror->rw_cred;
342 
343 	rcu_read_lock();
344 	do {
345 		cred = rcu_dereference(*pcred);
346 		if (!cred)
347 			break;
348 
349 		cred = get_rpccred_rcu(cred);
350 	} while(!cred);
351 	rcu_read_unlock();
352 	return cred;
353 }
354 
355 struct nfs_fh *
356 nfs4_ff_layout_select_ds_fh(struct pnfs_layout_segment *lseg, u32 mirror_idx)
357 {
358 	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, mirror_idx);
359 	struct nfs_fh *fh = NULL;
360 
361 	if (!ff_layout_mirror_valid(lseg, mirror, false)) {
362 		pr_err_ratelimited("NFS: %s: No data server for mirror offset index %d\n",
363 			__func__, mirror_idx);
364 		goto out;
365 	}
366 
367 	/* FIXME: For now assume there is only 1 version available for the DS */
368 	fh = &mirror->fh_versions[0];
369 out:
370 	return fh;
371 }
372 
373 /**
374  * nfs4_ff_layout_prepare_ds - prepare a DS connection for an RPC call
375  * @lseg: the layout segment we're operating on
376  * @ds_idx: index of the DS to use
377  * @fail_return: return layout on connect failure?
378  *
379  * Try to prepare a DS connection to accept an RPC call. This involves
380  * selecting a mirror to use and connecting the client to it if it's not
381  * already connected.
382  *
383  * Since we only need a single functioning mirror to satisfy a read, we don't
384  * want to return the layout if there is one. For writes though, any down
385  * mirror should result in a LAYOUTRETURN. @fail_return is how we distinguish
386  * between the two cases.
387  *
388  * Returns a pointer to a connected DS object on success or NULL on failure.
389  */
390 struct nfs4_pnfs_ds *
391 nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx,
392 			  bool fail_return)
393 {
394 	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx);
395 	struct nfs4_pnfs_ds *ds = NULL;
396 	struct nfs4_deviceid_node *devid;
397 	struct inode *ino = lseg->pls_layout->plh_inode;
398 	struct nfs_server *s = NFS_SERVER(ino);
399 	unsigned int max_payload;
400 	int status;
401 
402 	if (!ff_layout_mirror_valid(lseg, mirror, true)) {
403 		pr_err_ratelimited("NFS: %s: No data server for offset index %d\n",
404 			__func__, ds_idx);
405 		goto out;
406 	}
407 
408 	devid = &mirror->mirror_ds->id_node;
409 	if (ff_layout_test_devid_unavailable(devid))
410 		goto out_fail;
411 
412 	ds = mirror->mirror_ds->ds;
413 	/* matching smp_wmb() in _nfs4_pnfs_v3/4_ds_connect */
414 	smp_rmb();
415 	if (ds->ds_clp)
416 		goto out;
417 
418 	/* FIXME: For now we assume the server sent only one version of NFS
419 	 * to use for the DS.
420 	 */
421 	status = nfs4_pnfs_ds_connect(s, ds, devid, dataserver_timeo,
422 			     dataserver_retrans,
423 			     mirror->mirror_ds->ds_versions[0].version,
424 			     mirror->mirror_ds->ds_versions[0].minor_version);
425 
426 	/* connect success, check rsize/wsize limit */
427 	if (!status) {
428 		max_payload =
429 			nfs_block_size(rpc_max_payload(ds->ds_clp->cl_rpcclient),
430 				       NULL);
431 		if (mirror->mirror_ds->ds_versions[0].rsize > max_payload)
432 			mirror->mirror_ds->ds_versions[0].rsize = max_payload;
433 		if (mirror->mirror_ds->ds_versions[0].wsize > max_payload)
434 			mirror->mirror_ds->ds_versions[0].wsize = max_payload;
435 		goto out;
436 	}
437 out_fail:
438 	ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout),
439 				 mirror, lseg->pls_range.offset,
440 				 lseg->pls_range.length, NFS4ERR_NXIO,
441 				 OP_ILLEGAL, GFP_NOIO);
442 	if (fail_return || !ff_layout_has_available_ds(lseg))
443 		pnfs_error_mark_layout_for_return(ino, lseg);
444 	ds = NULL;
445 out:
446 	return ds;
447 }
448 
449 struct rpc_cred *
450 ff_layout_get_ds_cred(struct pnfs_layout_segment *lseg, u32 ds_idx,
451 		      struct rpc_cred *mdscred)
452 {
453 	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx);
454 	struct rpc_cred *cred;
455 
456 	if (mirror) {
457 		cred = ff_layout_get_mirror_cred(mirror, lseg->pls_range.iomode);
458 		if (!cred)
459 			cred = get_rpccred(mdscred);
460 	} else {
461 		cred = get_rpccred(mdscred);
462 	}
463 	return cred;
464 }
465 
466 /**
467 * Find or create a DS rpc client with th MDS server rpc client auth flavor
468 * in the nfs_client cl_ds_clients list.
469 */
470 struct rpc_clnt *
471 nfs4_ff_find_or_create_ds_client(struct pnfs_layout_segment *lseg, u32 ds_idx,
472 				 struct nfs_client *ds_clp, struct inode *inode)
473 {
474 	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx);
475 
476 	switch (mirror->mirror_ds->ds_versions[0].version) {
477 	case 3:
478 		/* For NFSv3 DS, flavor is set when creating DS connections */
479 		return ds_clp->cl_rpcclient;
480 	case 4:
481 		return nfs4_find_or_create_ds_client(ds_clp, inode);
482 	default:
483 		BUG();
484 	}
485 }
486 
487 void ff_layout_free_ds_ioerr(struct list_head *head)
488 {
489 	struct nfs4_ff_layout_ds_err *err;
490 
491 	while (!list_empty(head)) {
492 		err = list_first_entry(head,
493 				struct nfs4_ff_layout_ds_err,
494 				list);
495 		list_del(&err->list);
496 		kfree(err);
497 	}
498 }
499 
500 /* called with inode i_lock held */
501 int ff_layout_encode_ds_ioerr(struct xdr_stream *xdr, const struct list_head *head)
502 {
503 	struct nfs4_ff_layout_ds_err *err;
504 	__be32 *p;
505 
506 	list_for_each_entry(err, head, list) {
507 		/* offset(8) + length(8) + stateid(NFS4_STATEID_SIZE)
508 		 * + array length + deviceid(NFS4_DEVICEID4_SIZE)
509 		 * + status(4) + opnum(4)
510 		 */
511 		p = xdr_reserve_space(xdr,
512 				28 + NFS4_STATEID_SIZE + NFS4_DEVICEID4_SIZE);
513 		if (unlikely(!p))
514 			return -ENOBUFS;
515 		p = xdr_encode_hyper(p, err->offset);
516 		p = xdr_encode_hyper(p, err->length);
517 		p = xdr_encode_opaque_fixed(p, &err->stateid,
518 					    NFS4_STATEID_SIZE);
519 		/* Encode 1 error */
520 		*p++ = cpu_to_be32(1);
521 		p = xdr_encode_opaque_fixed(p, &err->deviceid,
522 					    NFS4_DEVICEID4_SIZE);
523 		*p++ = cpu_to_be32(err->status);
524 		*p++ = cpu_to_be32(err->opnum);
525 		dprintk("%s: offset %llu length %llu status %d op %d\n",
526 			__func__, err->offset, err->length, err->status,
527 			err->opnum);
528 	}
529 
530 	return 0;
531 }
532 
533 static
534 unsigned int do_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
535 				      const struct pnfs_layout_range *range,
536 				      struct list_head *head,
537 				      unsigned int maxnum)
538 {
539 	struct nfs4_flexfile_layout *flo = FF_LAYOUT_FROM_HDR(lo);
540 	struct inode *inode = lo->plh_inode;
541 	struct nfs4_ff_layout_ds_err *err, *n;
542 	unsigned int ret = 0;
543 
544 	spin_lock(&inode->i_lock);
545 	list_for_each_entry_safe(err, n, &flo->error_list, list) {
546 		if (!pnfs_is_range_intersecting(err->offset,
547 				pnfs_end_offset(err->offset, err->length),
548 				range->offset,
549 				pnfs_end_offset(range->offset, range->length)))
550 			continue;
551 		if (!maxnum)
552 			break;
553 		list_move(&err->list, head);
554 		maxnum--;
555 		ret++;
556 	}
557 	spin_unlock(&inode->i_lock);
558 	return ret;
559 }
560 
561 unsigned int ff_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
562 				      const struct pnfs_layout_range *range,
563 				      struct list_head *head,
564 				      unsigned int maxnum)
565 {
566 	unsigned int ret;
567 
568 	ret = do_layout_fetch_ds_ioerr(lo, range, head, maxnum);
569 	/* If we're over the max, discard all remaining entries */
570 	if (ret == maxnum) {
571 		LIST_HEAD(discard);
572 		do_layout_fetch_ds_ioerr(lo, range, &discard, -1);
573 		ff_layout_free_ds_ioerr(&discard);
574 	}
575 	return ret;
576 }
577 
578 static bool ff_read_layout_has_available_ds(struct pnfs_layout_segment *lseg)
579 {
580 	struct nfs4_ff_layout_mirror *mirror;
581 	struct nfs4_deviceid_node *devid;
582 	u32 idx;
583 
584 	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
585 		mirror = FF_LAYOUT_COMP(lseg, idx);
586 		if (mirror) {
587 			if (!mirror->mirror_ds)
588 				return true;
589 			if (IS_ERR(mirror->mirror_ds))
590 				continue;
591 			devid = &mirror->mirror_ds->id_node;
592 			if (!ff_layout_test_devid_unavailable(devid))
593 				return true;
594 		}
595 	}
596 
597 	return false;
598 }
599 
600 static bool ff_rw_layout_has_available_ds(struct pnfs_layout_segment *lseg)
601 {
602 	struct nfs4_ff_layout_mirror *mirror;
603 	struct nfs4_deviceid_node *devid;
604 	u32 idx;
605 
606 	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
607 		mirror = FF_LAYOUT_COMP(lseg, idx);
608 		if (!mirror || IS_ERR(mirror->mirror_ds))
609 			return false;
610 		if (!mirror->mirror_ds)
611 			continue;
612 		devid = &mirror->mirror_ds->id_node;
613 		if (ff_layout_test_devid_unavailable(devid))
614 			return false;
615 	}
616 
617 	return FF_LAYOUT_MIRROR_COUNT(lseg) != 0;
618 }
619 
620 static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg)
621 {
622 	if (lseg->pls_range.iomode == IOMODE_READ)
623 		return  ff_read_layout_has_available_ds(lseg);
624 	/* Note: RW layout needs all mirrors available */
625 	return ff_rw_layout_has_available_ds(lseg);
626 }
627 
628 bool ff_layout_avoid_mds_available_ds(struct pnfs_layout_segment *lseg)
629 {
630 	return ff_layout_no_fallback_to_mds(lseg) ||
631 	       ff_layout_has_available_ds(lseg);
632 }
633 
634 bool ff_layout_avoid_read_on_rw(struct pnfs_layout_segment *lseg)
635 {
636 	return lseg->pls_range.iomode == IOMODE_RW &&
637 	       ff_layout_no_read_on_rw(lseg);
638 }
639 
640 module_param(dataserver_retrans, uint, 0644);
641 MODULE_PARM_DESC(dataserver_retrans, "The  number of times the NFSv4.1 client "
642 			"retries a request before it attempts further "
643 			" recovery  action.");
644 module_param(dataserver_timeo, uint, 0644);
645 MODULE_PARM_DESC(dataserver_timeo, "The time (in tenths of a second) the "
646 			"NFSv4.1  client  waits for a response from a "
647 			" data server before it retries an NFS request.");
648