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TOMOYO Linux Cross Reference
Linux/fs/nfs/nfs4session.c

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

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