fs/nfs/flexfilelayout/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
  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_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.");