root/fs/nfs/nfs4session.c

DEFINITIONS

1. nfs4_init_slot_table
2. nfs4_shrink_slot_table
3. nfs4_slot_tbl_drain_complete
4. nfs4_free_slot
5. nfs4_new_slot
6. nfs4_find_or_create_slot
7. nfs4_lock_slot
8. nfs4_try_to_lock_slot
9. nfs4_lookup_slot
10. nfs4_slot_get_seqid
11. nfs4_slot_seqid_in_use
12. nfs4_slot_wait_on_seqid
13. nfs4_alloc_slot
14. nfs4_grow_slot_table
15. nfs4_reset_slot_table
16. nfs4_realloc_slot_table
17. nfs4_release_slot_table
18. nfs4_shutdown_slot_table
19. nfs4_setup_slot_table
20. nfs41_assign_slot
21. __nfs41_wake_and_assign_slot
22. nfs41_wake_and_assign_slot
23. nfs41_try_wake_next_slot_table_entry
24. nfs41_wake_slot_table
25. nfs41_set_max_slotid_locked
26. nfs41_set_target_slotid_locked
27. nfs41_set_target_slotid
28. nfs41_set_server_slotid_locked
29. nfs41_derivative_target_slotid
30. nfs41_sign_s32
31. nfs41_same_sign_or_zero_s32
32. nfs41_is_outlier_target_slotid
33. nfs41_update_target_slotid
34. nfs4_release_session_slot_tables
35. nfs4_setup_session_slot_tables
36. nfs4_alloc_session
37. nfs4_destroy_session_slot_tables
38. nfs4_destroy_session
39. nfs41_check_session_ready
40. nfs4_init_session
41. nfs4_init_ds_session

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * fs/nfs/nfs4session.c
   4  *
   5  * Copyright (c) 2012 Trond Myklebust <Trond.Myklebust@netapp.com>
   6  *
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/errno.h>
  10 #include <linux/string.h>
  11 #include <linux/printk.h>
  12 #include <linux/slab.h>
  13 #include <linux/sunrpc/sched.h>
  14 #include <linux/sunrpc/bc_xprt.h>
  15 #include <linux/nfs.h>
  16 #include <linux/nfs4.h>
  17 #include <linux/nfs_fs.h>
  18 #include <linux/module.h>
  19 
  20 #include "nfs4_fs.h"
  21 #include "internal.h"
  22 #include "nfs4session.h"
  23 #include "callback.h"
  24 
  25 #define NFSDBG_FACILITY         NFSDBG_STATE
  26 
  27 static void nfs4_init_slot_table(struct nfs4_slot_table *tbl, const char *queue)
  28 {
  29         tbl->highest_used_slotid = NFS4_NO_SLOT;
  30         spin_lock_init(&tbl->slot_tbl_lock);
  31         rpc_init_priority_wait_queue(&tbl->slot_tbl_waitq, queue);
  32         init_waitqueue_head(&tbl->slot_waitq);
  33         init_completion(&tbl->complete);
  34 }
  35 
  36 /*
  37  * nfs4_shrink_slot_table - free retired slots from the slot table
  38  */
  39 static void nfs4_shrink_slot_table(struct nfs4_slot_table  *tbl, u32 newsize)
  40 {
  41         struct nfs4_slot **p;
  42         if (newsize >= tbl->max_slots)
  43                 return;
  44 
  45         p = &tbl->slots;
  46         while (newsize--)
  47                 p = &(*p)->next;
  48         while (*p) {
  49                 struct nfs4_slot *slot = *p;
  50 
  51                 *p = slot->next;
  52                 kfree(slot);
  53                 tbl->max_slots--;
  54         }
  55 }
  56 
  57 /**
  58  * nfs4_slot_tbl_drain_complete - wake waiters when drain is complete
  59  * @tbl: controlling slot table
  60  *
  61  */
  62 void nfs4_slot_tbl_drain_complete(struct nfs4_slot_table *tbl)
  63 {
  64         if (nfs4_slot_tbl_draining(tbl))
  65                 complete(&tbl->complete);
  66 }
  67 
  68 /*
  69  * nfs4_free_slot - free a slot and efficiently update slot table.
  70  *
  71  * freeing a slot is trivially done by clearing its respective bit
  72  * in the bitmap.
  73  * If the freed slotid equals highest_used_slotid we want to update it
  74  * so that the server would be able to size down the slot table if needed,
  75  * otherwise we know that the highest_used_slotid is still in use.
  76  * When updating highest_used_slotid there may be "holes" in the bitmap
  77  * so we need to scan down from highest_used_slotid to 0 looking for the now
  78  * highest slotid in use.
  79  * If none found, highest_used_slotid is set to NFS4_NO_SLOT.
  80  *
  81  * Must be called while holding tbl->slot_tbl_lock
  82  */
  83 void nfs4_free_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot)
  84 {
  85         u32 slotid = slot->slot_nr;
  86 
  87         /* clear used bit in bitmap */
  88         __clear_bit(slotid, tbl->used_slots);
  89 
  90         /* update highest_used_slotid when it is freed */
  91         if (slotid == tbl->highest_used_slotid) {
  92                 u32 new_max = find_last_bit(tbl->used_slots, slotid);
  93                 if (new_max < slotid)
  94                         tbl->highest_used_slotid = new_max;
  95                 else {
  96                         tbl->highest_used_slotid = NFS4_NO_SLOT;
  97                         nfs4_slot_tbl_drain_complete(tbl);
  98                 }
  99         }
 100         dprintk("%s: slotid %u highest_used_slotid %u\n", __func__,
 101                 slotid, tbl->highest_used_slotid);
 102 }
 103 
 104 static struct nfs4_slot *nfs4_new_slot(struct nfs4_slot_table  *tbl,
 105                 u32 slotid, u32 seq_init, gfp_t gfp_mask)
 106 {
 107         struct nfs4_slot *slot;
 108 
 109         slot = kzalloc(sizeof(*slot), gfp_mask);
 110         if (slot) {
 111                 slot->table = tbl;
 112                 slot->slot_nr = slotid;
 113                 slot->seq_nr = seq_init;
 114                 slot->seq_nr_highest_sent = seq_init;
 115                 slot->seq_nr_last_acked = seq_init - 1;
 116         }
 117         return slot;
 118 }
 119 
 120 static struct nfs4_slot *nfs4_find_or_create_slot(struct nfs4_slot_table  *tbl,
 121                 u32 slotid, u32 seq_init, gfp_t gfp_mask)
 122 {
 123         struct nfs4_slot **p, *slot;
 124 
 125         p = &tbl->slots;
 126         for (;;) {
 127                 if (*p == NULL) {
 128                         *p = nfs4_new_slot(tbl, tbl->max_slots,
 129                                         seq_init, gfp_mask);
 130                         if (*p == NULL)
 131                                 break;
 132                         tbl->max_slots++;
 133                 }
 134                 slot = *p;
 135                 if (slot->slot_nr == slotid)
 136                         return slot;
 137                 p = &slot->next;
 138         }
 139         return ERR_PTR(-ENOMEM);
 140 }
 141 
 142 static void nfs4_lock_slot(struct nfs4_slot_table *tbl,
 143                 struct nfs4_slot *slot)
 144 {
 145         u32 slotid = slot->slot_nr;
 146 
 147         __set_bit(slotid, tbl->used_slots);
 148         if (slotid > tbl->highest_used_slotid ||
 149             tbl->highest_used_slotid == NFS4_NO_SLOT)
 150                 tbl->highest_used_slotid = slotid;
 151         slot->generation = tbl->generation;
 152 }
 153 
 154 /*
 155  * nfs4_try_to_lock_slot - Given a slot try to allocate it
 156  *
 157  * Note: must be called with the slot_tbl_lock held.
 158  */
 159 bool nfs4_try_to_lock_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot)
 160 {
 161         if (nfs4_test_locked_slot(tbl, slot->slot_nr))
 162                 return false;
 163         nfs4_lock_slot(tbl, slot);
 164         return true;
 165 }
 166 
 167 /*
 168  * nfs4_lookup_slot - Find a slot but don't allocate it
 169  *
 170  * Note: must be called with the slot_tbl_lock held.
 171  */
 172 struct nfs4_slot *nfs4_lookup_slot(struct nfs4_slot_table *tbl, u32 slotid)
 173 {
 174         if (slotid <= tbl->max_slotid)
 175                 return nfs4_find_or_create_slot(tbl, slotid, 0, GFP_NOWAIT);
 176         return ERR_PTR(-E2BIG);
 177 }
 178 
 179 static int nfs4_slot_get_seqid(struct nfs4_slot_table  *tbl, u32 slotid,
 180                 u32 *seq_nr)
 181         __must_hold(&tbl->slot_tbl_lock)
 182 {
 183         struct nfs4_slot *slot;
 184         int ret;
 185 
 186         slot = nfs4_lookup_slot(tbl, slotid);
 187         ret = PTR_ERR_OR_ZERO(slot);
 188         if (!ret)
 189                 *seq_nr = slot->seq_nr;
 190 
 191         return ret;
 192 }
 193 
 194 /*
 195  * nfs4_slot_seqid_in_use - test if a slot sequence id is still in use
 196  *
 197  * Given a slot table, slot id and sequence number, determine if the
 198  * RPC call in question is still in flight. This function is mainly
 199  * intended for use by the callback channel.
 200  */
 201 static bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl,
 202                 u32 slotid, u32 seq_nr)
 203 {
 204         u32 cur_seq = 0;
 205         bool ret = false;
 206 
 207         spin_lock(&tbl->slot_tbl_lock);
 208         if (nfs4_slot_get_seqid(tbl, slotid, &cur_seq) == 0 &&
 209             cur_seq == seq_nr && test_bit(slotid, tbl->used_slots))
 210                 ret = true;
 211         spin_unlock(&tbl->slot_tbl_lock);
 212         return ret;
 213 }
 214 
 215 /*
 216  * nfs4_slot_wait_on_seqid - wait until a slot sequence id is complete
 217  *
 218  * Given a slot table, slot id and sequence number, wait until the
 219  * corresponding RPC call completes. This function is mainly
 220  * intended for use by the callback channel.
 221  */
 222 int nfs4_slot_wait_on_seqid(struct nfs4_slot_table *tbl,
 223                 u32 slotid, u32 seq_nr,
 224                 unsigned long timeout)
 225 {
 226         if (wait_event_timeout(tbl->slot_waitq,
 227                         !nfs4_slot_seqid_in_use(tbl, slotid, seq_nr),
 228                         timeout) == 0)
 229                 return -ETIMEDOUT;
 230         return 0;
 231 }
 232 
 233 /*
 234  * nfs4_alloc_slot - efficiently look for a free slot
 235  *
 236  * nfs4_alloc_slot looks for an unset bit in the used_slots bitmap.
 237  * If found, we mark the slot as used, update the highest_used_slotid,
 238  * and respectively set up the sequence operation args.
 239  *
 240  * Note: must be called with under the slot_tbl_lock.
 241  */
 242 struct nfs4_slot *nfs4_alloc_slot(struct nfs4_slot_table *tbl)
 243 {
 244         struct nfs4_slot *ret = ERR_PTR(-EBUSY);
 245         u32 slotid;
 246 
 247         dprintk("--> %s used_slots=%04lx highest_used=%u max_slots=%u\n",
 248                 __func__, tbl->used_slots[0], tbl->highest_used_slotid,
 249                 tbl->max_slotid + 1);
 250         slotid = find_first_zero_bit(tbl->used_slots, tbl->max_slotid + 1);
 251         if (slotid <= tbl->max_slotid) {
 252                 ret = nfs4_find_or_create_slot(tbl, slotid, 1, GFP_NOWAIT);
 253                 if (!IS_ERR(ret))
 254                         nfs4_lock_slot(tbl, ret);
 255         }
 256         dprintk("<-- %s used_slots=%04lx highest_used=%u slotid=%u\n",
 257                 __func__, tbl->used_slots[0], tbl->highest_used_slotid,
 258                 !IS_ERR(ret) ? ret->slot_nr : NFS4_NO_SLOT);
 259         return ret;
 260 }
 261 
 262 static int nfs4_grow_slot_table(struct nfs4_slot_table *tbl,
 263                  u32 max_reqs, u32 ivalue)
 264 {
 265         if (max_reqs <= tbl->max_slots)
 266                 return 0;
 267         if (!IS_ERR(nfs4_find_or_create_slot(tbl, max_reqs - 1, ivalue, GFP_NOFS)))
 268                 return 0;
 269         return -ENOMEM;
 270 }
 271 
 272 static void nfs4_reset_slot_table(struct nfs4_slot_table *tbl,
 273                 u32 server_highest_slotid,
 274                 u32 ivalue)
 275 {
 276         struct nfs4_slot **p;
 277 
 278         nfs4_shrink_slot_table(tbl, server_highest_slotid + 1);
 279         p = &tbl->slots;
 280         while (*p) {
 281                 (*p)->seq_nr = ivalue;
 282                 (*p)->seq_nr_highest_sent = ivalue;
 283                 (*p)->seq_nr_last_acked = ivalue - 1;
 284                 p = &(*p)->next;
 285         }
 286         tbl->highest_used_slotid = NFS4_NO_SLOT;
 287         tbl->target_highest_slotid = server_highest_slotid;
 288         tbl->server_highest_slotid = server_highest_slotid;
 289         tbl->d_target_highest_slotid = 0;
 290         tbl->d2_target_highest_slotid = 0;
 291         tbl->max_slotid = server_highest_slotid;
 292 }
 293 
 294 /*
 295  * (re)Initialise a slot table
 296  */
 297 static int nfs4_realloc_slot_table(struct nfs4_slot_table *tbl,
 298                 u32 max_reqs, u32 ivalue)
 299 {
 300         int ret;
 301 
 302         dprintk("--> %s: max_reqs=%u, tbl->max_slots %u\n", __func__,
 303                 max_reqs, tbl->max_slots);
 304 
 305         if (max_reqs > NFS4_MAX_SLOT_TABLE)
 306                 max_reqs = NFS4_MAX_SLOT_TABLE;
 307 
 308         ret = nfs4_grow_slot_table(tbl, max_reqs, ivalue);
 309         if (ret)
 310                 goto out;
 311 
 312         spin_lock(&tbl->slot_tbl_lock);
 313         nfs4_reset_slot_table(tbl, max_reqs - 1, ivalue);
 314         spin_unlock(&tbl->slot_tbl_lock);
 315 
 316         dprintk("%s: tbl=%p slots=%p max_slots=%u\n", __func__,
 317                 tbl, tbl->slots, tbl->max_slots);
 318 out:
 319         dprintk("<-- %s: return %d\n", __func__, ret);
 320         return ret;
 321 }
 322 
 323 /*
 324  * nfs4_release_slot_table - release all slot table entries
 325  */
 326 static void nfs4_release_slot_table(struct nfs4_slot_table *tbl)
 327 {
 328         nfs4_shrink_slot_table(tbl, 0);
 329 }
 330 
 331 /**
 332  * nfs4_shutdown_slot_table - release resources attached to a slot table
 333  * @tbl: slot table to shut down
 334  *
 335  */
 336 void nfs4_shutdown_slot_table(struct nfs4_slot_table *tbl)
 337 {
 338         nfs4_release_slot_table(tbl);
 339         rpc_destroy_wait_queue(&tbl->slot_tbl_waitq);
 340 }
 341 
 342 /**
 343  * nfs4_setup_slot_table - prepare a stand-alone slot table for use
 344  * @tbl: slot table to set up
 345  * @max_reqs: maximum number of requests allowed
 346  * @queue: name to give RPC wait queue
 347  *
 348  * Returns zero on success, or a negative errno.
 349  */
 350 int nfs4_setup_slot_table(struct nfs4_slot_table *tbl, unsigned int max_reqs,
 351                 const char *queue)
 352 {
 353         nfs4_init_slot_table(tbl, queue);
 354         return nfs4_realloc_slot_table(tbl, max_reqs, 0);
 355 }
 356 
 357 static bool nfs41_assign_slot(struct rpc_task *task, void *pslot)
 358 {
 359         struct nfs4_sequence_args *args = task->tk_msg.rpc_argp;
 360         struct nfs4_sequence_res *res = task->tk_msg.rpc_resp;
 361         struct nfs4_slot *slot = pslot;
 362         struct nfs4_slot_table *tbl = slot->table;
 363 
 364         if (nfs4_slot_tbl_draining(tbl) && !args->sa_privileged)
 365                 return false;
 366         slot->generation = tbl->generation;
 367         args->sa_slot = slot;
 368         res->sr_timestamp = jiffies;
 369         res->sr_slot = slot;
 370         res->sr_status_flags = 0;
 371         res->sr_status = 1;
 372         return true;
 373 }
 374 
 375 static bool __nfs41_wake_and_assign_slot(struct nfs4_slot_table *tbl,
 376                 struct nfs4_slot *slot)
 377 {
 378         if (rpc_wake_up_first(&tbl->slot_tbl_waitq, nfs41_assign_slot, slot))
 379                 return true;
 380         return false;
 381 }
 382 
 383 bool nfs41_wake_and_assign_slot(struct nfs4_slot_table *tbl,
 384                 struct nfs4_slot *slot)
 385 {
 386         if (slot->slot_nr > tbl->max_slotid)
 387                 return false;
 388         return __nfs41_wake_and_assign_slot(tbl, slot);
 389 }
 390 
 391 static bool nfs41_try_wake_next_slot_table_entry(struct nfs4_slot_table *tbl)
 392 {
 393         struct nfs4_slot *slot = nfs4_alloc_slot(tbl);
 394         if (!IS_ERR(slot)) {
 395                 bool ret = __nfs41_wake_and_assign_slot(tbl, slot);
 396                 if (ret)
 397                         return ret;
 398                 nfs4_free_slot(tbl, slot);
 399         }
 400         return false;
 401 }
 402 
 403 void nfs41_wake_slot_table(struct nfs4_slot_table *tbl)
 404 {
 405         for (;;) {
 406                 if (!nfs41_try_wake_next_slot_table_entry(tbl))
 407                         break;
 408         }
 409 }
 410 
 411 #if defined(CONFIG_NFS_V4_1)
 412 
 413 static void nfs41_set_max_slotid_locked(struct nfs4_slot_table *tbl,
 414                 u32 target_highest_slotid)
 415 {
 416         u32 max_slotid;
 417 
 418         max_slotid = min(NFS4_MAX_SLOT_TABLE - 1, target_highest_slotid);
 419         if (max_slotid > tbl->server_highest_slotid)
 420                 max_slotid = tbl->server_highest_slotid;
 421         if (max_slotid > tbl->target_highest_slotid)
 422                 max_slotid = tbl->target_highest_slotid;
 423         tbl->max_slotid = max_slotid;
 424         nfs41_wake_slot_table(tbl);
 425 }
 426 
 427 /* Update the client's idea of target_highest_slotid */
 428 static void nfs41_set_target_slotid_locked(struct nfs4_slot_table *tbl,
 429                 u32 target_highest_slotid)
 430 {
 431         if (tbl->target_highest_slotid == target_highest_slotid)
 432                 return;
 433         tbl->target_highest_slotid = target_highest_slotid;
 434         tbl->generation++;
 435 }
 436 
 437 void nfs41_set_target_slotid(struct nfs4_slot_table *tbl,
 438                 u32 target_highest_slotid)
 439 {
 440         spin_lock(&tbl->slot_tbl_lock);
 441         nfs41_set_target_slotid_locked(tbl, target_highest_slotid);
 442         tbl->d_target_highest_slotid = 0;
 443         tbl->d2_target_highest_slotid = 0;
 444         nfs41_set_max_slotid_locked(tbl, target_highest_slotid);
 445         spin_unlock(&tbl->slot_tbl_lock);
 446 }
 447 
 448 static void nfs41_set_server_slotid_locked(struct nfs4_slot_table *tbl,
 449                 u32 highest_slotid)
 450 {
 451         if (tbl->server_highest_slotid == highest_slotid)
 452                 return;
 453         if (tbl->highest_used_slotid > highest_slotid)
 454                 return;
 455         /* Deallocate slots */
 456         nfs4_shrink_slot_table(tbl, highest_slotid + 1);
 457         tbl->server_highest_slotid = highest_slotid;
 458 }
 459 
 460 static s32 nfs41_derivative_target_slotid(s32 s1, s32 s2)
 461 {
 462         s1 -= s2;
 463         if (s1 == 0)
 464                 return 0;
 465         if (s1 < 0)
 466                 return (s1 - 1) >> 1;
 467         return (s1 + 1) >> 1;
 468 }
 469 
 470 static int nfs41_sign_s32(s32 s1)
 471 {
 472         if (s1 > 0)
 473                 return 1;
 474         if (s1 < 0)
 475                 return -1;
 476         return 0;
 477 }
 478 
 479 static bool nfs41_same_sign_or_zero_s32(s32 s1, s32 s2)
 480 {
 481         if (!s1 || !s2)
 482                 return true;
 483         return nfs41_sign_s32(s1) == nfs41_sign_s32(s2);
 484 }
 485 
 486 /* Try to eliminate outliers by checking for sharp changes in the
 487  * derivatives and second derivatives
 488  */
 489 static bool nfs41_is_outlier_target_slotid(struct nfs4_slot_table *tbl,
 490                 u32 new_target)
 491 {
 492         s32 d_target, d2_target;
 493         bool ret = true;
 494 
 495         d_target = nfs41_derivative_target_slotid(new_target,
 496                         tbl->target_highest_slotid);
 497         d2_target = nfs41_derivative_target_slotid(d_target,
 498                         tbl->d_target_highest_slotid);
 499         /* Is first derivative same sign? */
 500         if (nfs41_same_sign_or_zero_s32(d_target, tbl->d_target_highest_slotid))
 501                 ret = false;
 502         /* Is second derivative same sign? */
 503         if (nfs41_same_sign_or_zero_s32(d2_target, tbl->d2_target_highest_slotid))
 504                 ret = false;
 505         tbl->d_target_highest_slotid = d_target;
 506         tbl->d2_target_highest_slotid = d2_target;
 507         return ret;
 508 }
 509 
 510 void nfs41_update_target_slotid(struct nfs4_slot_table *tbl,
 511                 struct nfs4_slot *slot,
 512                 struct nfs4_sequence_res *res)
 513 {
 514         spin_lock(&tbl->slot_tbl_lock);
 515         if (!nfs41_is_outlier_target_slotid(tbl, res->sr_target_highest_slotid))
 516                 nfs41_set_target_slotid_locked(tbl, res->sr_target_highest_slotid);
 517         if (tbl->generation == slot->generation)
 518                 nfs41_set_server_slotid_locked(tbl, res->sr_highest_slotid);
 519         nfs41_set_max_slotid_locked(tbl, res->sr_target_highest_slotid);
 520         spin_unlock(&tbl->slot_tbl_lock);
 521 }
 522 
 523 static void nfs4_release_session_slot_tables(struct nfs4_session *session)
 524 {
 525         nfs4_release_slot_table(&session->fc_slot_table);
 526         nfs4_release_slot_table(&session->bc_slot_table);
 527 }
 528 
 529 /*
 530  * Initialize or reset the forechannel and backchannel tables
 531  */
 532 int nfs4_setup_session_slot_tables(struct nfs4_session *ses)
 533 {
 534         struct nfs4_slot_table *tbl;
 535         int status;
 536 
 537         dprintk("--> %s\n", __func__);
 538         /* Fore channel */
 539         tbl = &ses->fc_slot_table;
 540         tbl->session = ses;
 541         status = nfs4_realloc_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
 542         if (status || !(ses->flags & SESSION4_BACK_CHAN)) /* -ENOMEM */
 543                 return status;
 544         /* Back channel */
 545         tbl = &ses->bc_slot_table;
 546         tbl->session = ses;
 547         status = nfs4_realloc_slot_table(tbl, ses->bc_attrs.max_reqs, 0);
 548         if (status && tbl->slots == NULL)
 549                 /* Fore and back channel share a connection so get
 550                  * both slot tables or neither */
 551                 nfs4_release_session_slot_tables(ses);
 552         return status;
 553 }
 554 
 555 struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp)
 556 {
 557         struct nfs4_session *session;
 558 
 559         session = kzalloc(sizeof(struct nfs4_session), GFP_NOFS);
 560         if (!session)
 561                 return NULL;
 562 
 563         nfs4_init_slot_table(&session->fc_slot_table, "ForeChannel Slot table");
 564         nfs4_init_slot_table(&session->bc_slot_table, "BackChannel Slot table");
 565         session->session_state = 1<<NFS4_SESSION_INITING;
 566 
 567         session->clp = clp;
 568         return session;
 569 }
 570 
 571 static void nfs4_destroy_session_slot_tables(struct nfs4_session *session)
 572 {
 573         nfs4_shutdown_slot_table(&session->fc_slot_table);
 574         nfs4_shutdown_slot_table(&session->bc_slot_table);
 575 }
 576 
 577 void nfs4_destroy_session(struct nfs4_session *session)
 578 {
 579         struct rpc_xprt *xprt;
 580         const struct cred *cred;
 581 
 582         cred = nfs4_get_clid_cred(session->clp);
 583         nfs4_proc_destroy_session(session, cred);
 584         put_cred(cred);
 585 
 586         rcu_read_lock();
 587         xprt = rcu_dereference(session->clp->cl_rpcclient->cl_xprt);
 588         rcu_read_unlock();
 589         dprintk("%s Destroy backchannel for xprt %p\n",
 590                 __func__, xprt);
 591         xprt_destroy_backchannel(xprt, NFS41_BC_MIN_CALLBACKS);
 592         nfs4_destroy_session_slot_tables(session);
 593         kfree(session);
 594 }
 595 
 596 /*
 597  * With sessions, the client is not marked ready until after a
 598  * successful EXCHANGE_ID and CREATE_SESSION.
 599  *
 600  * Map errors cl_cons_state errors to EPROTONOSUPPORT to indicate
 601  * other versions of NFS can be tried.
 602  */
 603 static int nfs41_check_session_ready(struct nfs_client *clp)
 604 {
 605         int ret;
 606         
 607         if (clp->cl_cons_state == NFS_CS_SESSION_INITING) {
 608                 ret = nfs4_client_recover_expired_lease(clp);
 609                 if (ret)
 610                         return ret;
 611         }
 612         if (clp->cl_cons_state < NFS_CS_READY)
 613                 return -EPROTONOSUPPORT;
 614         smp_rmb();
 615         return 0;
 616 }
 617 
 618 int nfs4_init_session(struct nfs_client *clp)
 619 {
 620         if (!nfs4_has_session(clp))
 621                 return 0;
 622 
 623         clear_bit(NFS4_SESSION_INITING, &clp->cl_session->session_state);
 624         return nfs41_check_session_ready(clp);
 625 }
 626 
 627 int nfs4_init_ds_session(struct nfs_client *clp, unsigned long lease_time)
 628 {
 629         struct nfs4_session *session = clp->cl_session;
 630         int ret;
 631 
 632         spin_lock(&clp->cl_lock);
 633         if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
 634                 /*
 635                  * Do not set NFS_CS_CHECK_LEASE_TIME instead set the
 636                  * DS lease to be equal to the MDS lease.
 637                  */
 638                 clp->cl_lease_time = lease_time;
 639                 clp->cl_last_renewal = jiffies;
 640         }
 641         spin_unlock(&clp->cl_lock);
 642 
 643         ret = nfs41_check_session_ready(clp);
 644         if (ret)
 645                 return ret;
 646         /* Test for the DS role */
 647         if (!is_ds_client(clp))
 648                 return -ENODEV;
 649         return 0;
 650 }
 651 EXPORT_SYMBOL_GPL(nfs4_init_ds_session);
 652 
 653 #endif  /* defined(CONFIG_NFS_V4_1) */