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Linux/net/sunrpc/xprt.c

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  1 /*
  2  *  linux/net/sunrpc/xprt.c
  3  *
  4  *  This is a generic RPC call interface supporting congestion avoidance,
  5  *  and asynchronous calls.
  6  *
  7  *  The interface works like this:
  8  *
  9  *  -   When a process places a call, it allocates a request slot if
 10  *      one is available. Otherwise, it sleeps on the backlog queue
 11  *      (xprt_reserve).
 12  *  -   Next, the caller puts together the RPC message, stuffs it into
 13  *      the request struct, and calls xprt_transmit().
 14  *  -   xprt_transmit sends the message and installs the caller on the
 15  *      transport's wait list. At the same time, if a reply is expected,
 16  *      it installs a timer that is run after the packet's timeout has
 17  *      expired.
 18  *  -   When a packet arrives, the data_ready handler walks the list of
 19  *      pending requests for that transport. If a matching XID is found, the
 20  *      caller is woken up, and the timer removed.
 21  *  -   When no reply arrives within the timeout interval, the timer is
 22  *      fired by the kernel and runs xprt_timer(). It either adjusts the
 23  *      timeout values (minor timeout) or wakes up the caller with a status
 24  *      of -ETIMEDOUT.
 25  *  -   When the caller receives a notification from RPC that a reply arrived,
 26  *      it should release the RPC slot, and process the reply.
 27  *      If the call timed out, it may choose to retry the operation by
 28  *      adjusting the initial timeout value, and simply calling rpc_call
 29  *      again.
 30  *
 31  *  Support for async RPC is done through a set of RPC-specific scheduling
 32  *  primitives that `transparently' work for processes as well as async
 33  *  tasks that rely on callbacks.
 34  *
 35  *  Copyright (C) 1995-1997, Olaf Kirch <okir@monad.swb.de>
 36  *
 37  *  Transport switch API copyright (C) 2005, Chuck Lever <cel@netapp.com>
 38  */
 39 
 40 #include <linux/module.h>
 41 
 42 #include <linux/types.h>
 43 #include <linux/interrupt.h>
 44 #include <linux/workqueue.h>
 45 #include <linux/net.h>
 46 #include <linux/ktime.h>
 47 
 48 #include <linux/sunrpc/clnt.h>
 49 #include <linux/sunrpc/metrics.h>
 50 #include <linux/sunrpc/bc_xprt.h>
 51 
 52 #include "sunrpc.h"
 53 
 54 /*
 55  * Local variables
 56  */
 57 
 58 #ifdef RPC_DEBUG
 59 # define RPCDBG_FACILITY        RPCDBG_XPRT
 60 #endif
 61 
 62 /*
 63  * Local functions
 64  */
 65 static void      xprt_init(struct rpc_xprt *xprt, struct net *net);
 66 static void     xprt_request_init(struct rpc_task *, struct rpc_xprt *);
 67 static void     xprt_connect_status(struct rpc_task *task);
 68 static int      __xprt_get_cong(struct rpc_xprt *, struct rpc_task *);
 69 static void      xprt_destroy(struct rpc_xprt *xprt);
 70 
 71 static DEFINE_SPINLOCK(xprt_list_lock);
 72 static LIST_HEAD(xprt_list);
 73 
 74 /*
 75  * The transport code maintains an estimate on the maximum number of out-
 76  * standing RPC requests, using a smoothed version of the congestion
 77  * avoidance implemented in 44BSD. This is basically the Van Jacobson
 78  * congestion algorithm: If a retransmit occurs, the congestion window is
 79  * halved; otherwise, it is incremented by 1/cwnd when
 80  *
 81  *      -       a reply is received and
 82  *      -       a full number of requests are outstanding and
 83  *      -       the congestion window hasn't been updated recently.
 84  */
 85 #define RPC_CWNDSHIFT           (8U)
 86 #define RPC_CWNDSCALE           (1U << RPC_CWNDSHIFT)
 87 #define RPC_INITCWND            RPC_CWNDSCALE
 88 #define RPC_MAXCWND(xprt)       ((xprt)->max_reqs << RPC_CWNDSHIFT)
 89 
 90 #define RPCXPRT_CONGESTED(xprt) ((xprt)->cong >= (xprt)->cwnd)
 91 
 92 /**
 93  * xprt_register_transport - register a transport implementation
 94  * @transport: transport to register
 95  *
 96  * If a transport implementation is loaded as a kernel module, it can
 97  * call this interface to make itself known to the RPC client.
 98  *
 99  * Returns:
100  * 0:           transport successfully registered
101  * -EEXIST:     transport already registered
102  * -EINVAL:     transport module being unloaded
103  */
104 int xprt_register_transport(struct xprt_class *transport)
105 {
106         struct xprt_class *t;
107         int result;
108 
109         result = -EEXIST;
110         spin_lock(&xprt_list_lock);
111         list_for_each_entry(t, &xprt_list, list) {
112                 /* don't register the same transport class twice */
113                 if (t->ident == transport->ident)
114                         goto out;
115         }
116 
117         list_add_tail(&transport->list, &xprt_list);
118         printk(KERN_INFO "RPC: Registered %s transport module.\n",
119                transport->name);
120         result = 0;
121 
122 out:
123         spin_unlock(&xprt_list_lock);
124         return result;
125 }
126 EXPORT_SYMBOL_GPL(xprt_register_transport);
127 
128 /**
129  * xprt_unregister_transport - unregister a transport implementation
130  * @transport: transport to unregister
131  *
132  * Returns:
133  * 0:           transport successfully unregistered
134  * -ENOENT:     transport never registered
135  */
136 int xprt_unregister_transport(struct xprt_class *transport)
137 {
138         struct xprt_class *t;
139         int result;
140 
141         result = 0;
142         spin_lock(&xprt_list_lock);
143         list_for_each_entry(t, &xprt_list, list) {
144                 if (t == transport) {
145                         printk(KERN_INFO
146                                 "RPC: Unregistered %s transport module.\n",
147                                 transport->name);
148                         list_del_init(&transport->list);
149                         goto out;
150                 }
151         }
152         result = -ENOENT;
153 
154 out:
155         spin_unlock(&xprt_list_lock);
156         return result;
157 }
158 EXPORT_SYMBOL_GPL(xprt_unregister_transport);
159 
160 /**
161  * xprt_load_transport - load a transport implementation
162  * @transport_name: transport to load
163  *
164  * Returns:
165  * 0:           transport successfully loaded
166  * -ENOENT:     transport module not available
167  */
168 int xprt_load_transport(const char *transport_name)
169 {
170         struct xprt_class *t;
171         int result;
172 
173         result = 0;
174         spin_lock(&xprt_list_lock);
175         list_for_each_entry(t, &xprt_list, list) {
176                 if (strcmp(t->name, transport_name) == 0) {
177                         spin_unlock(&xprt_list_lock);
178                         goto out;
179                 }
180         }
181         spin_unlock(&xprt_list_lock);
182         result = request_module("xprt%s", transport_name);
183 out:
184         return result;
185 }
186 EXPORT_SYMBOL_GPL(xprt_load_transport);
187 
188 /**
189  * xprt_reserve_xprt - serialize write access to transports
190  * @task: task that is requesting access to the transport
191  * @xprt: pointer to the target transport
192  *
193  * This prevents mixing the payload of separate requests, and prevents
194  * transport connects from colliding with writes.  No congestion control
195  * is provided.
196  */
197 int xprt_reserve_xprt(struct rpc_xprt *xprt, struct rpc_task *task)
198 {
199         struct rpc_rqst *req = task->tk_rqstp;
200         int priority;
201 
202         if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
203                 if (task == xprt->snd_task)
204                         return 1;
205                 goto out_sleep;
206         }
207         xprt->snd_task = task;
208         if (req != NULL) {
209                 req->rq_bytes_sent = 0;
210                 req->rq_ntrans++;
211         }
212 
213         return 1;
214 
215 out_sleep:
216         dprintk("RPC: %5u failed to lock transport %p\n",
217                         task->tk_pid, xprt);
218         task->tk_timeout = 0;
219         task->tk_status = -EAGAIN;
220         if (req == NULL)
221                 priority = RPC_PRIORITY_LOW;
222         else if (!req->rq_ntrans)
223                 priority = RPC_PRIORITY_NORMAL;
224         else
225                 priority = RPC_PRIORITY_HIGH;
226         rpc_sleep_on_priority(&xprt->sending, task, NULL, priority);
227         return 0;
228 }
229 EXPORT_SYMBOL_GPL(xprt_reserve_xprt);
230 
231 static void xprt_clear_locked(struct rpc_xprt *xprt)
232 {
233         xprt->snd_task = NULL;
234         if (!test_bit(XPRT_CLOSE_WAIT, &xprt->state)) {
235                 smp_mb__before_clear_bit();
236                 clear_bit(XPRT_LOCKED, &xprt->state);
237                 smp_mb__after_clear_bit();
238         } else
239                 queue_work(rpciod_workqueue, &xprt->task_cleanup);
240 }
241 
242 /*
243  * xprt_reserve_xprt_cong - serialize write access to transports
244  * @task: task that is requesting access to the transport
245  *
246  * Same as xprt_reserve_xprt, but Van Jacobson congestion control is
247  * integrated into the decision of whether a request is allowed to be
248  * woken up and given access to the transport.
249  */
250 int xprt_reserve_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task)
251 {
252         struct rpc_rqst *req = task->tk_rqstp;
253         int priority;
254 
255         if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
256                 if (task == xprt->snd_task)
257                         return 1;
258                 goto out_sleep;
259         }
260         if (req == NULL) {
261                 xprt->snd_task = task;
262                 return 1;
263         }
264         if (__xprt_get_cong(xprt, task)) {
265                 xprt->snd_task = task;
266                 req->rq_bytes_sent = 0;
267                 req->rq_ntrans++;
268                 return 1;
269         }
270         xprt_clear_locked(xprt);
271 out_sleep:
272         dprintk("RPC: %5u failed to lock transport %p\n", task->tk_pid, xprt);
273         task->tk_timeout = 0;
274         task->tk_status = -EAGAIN;
275         if (req == NULL)
276                 priority = RPC_PRIORITY_LOW;
277         else if (!req->rq_ntrans)
278                 priority = RPC_PRIORITY_NORMAL;
279         else
280                 priority = RPC_PRIORITY_HIGH;
281         rpc_sleep_on_priority(&xprt->sending, task, NULL, priority);
282         return 0;
283 }
284 EXPORT_SYMBOL_GPL(xprt_reserve_xprt_cong);
285 
286 static inline int xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
287 {
288         int retval;
289 
290         spin_lock_bh(&xprt->transport_lock);
291         retval = xprt->ops->reserve_xprt(xprt, task);
292         spin_unlock_bh(&xprt->transport_lock);
293         return retval;
294 }
295 
296 static bool __xprt_lock_write_func(struct rpc_task *task, void *data)
297 {
298         struct rpc_xprt *xprt = data;
299         struct rpc_rqst *req;
300 
301         req = task->tk_rqstp;
302         xprt->snd_task = task;
303         if (req) {
304                 req->rq_bytes_sent = 0;
305                 req->rq_ntrans++;
306         }
307         return true;
308 }
309 
310 static void __xprt_lock_write_next(struct rpc_xprt *xprt)
311 {
312         if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
313                 return;
314 
315         if (rpc_wake_up_first(&xprt->sending, __xprt_lock_write_func, xprt))
316                 return;
317         xprt_clear_locked(xprt);
318 }
319 
320 static bool __xprt_lock_write_cong_func(struct rpc_task *task, void *data)
321 {
322         struct rpc_xprt *xprt = data;
323         struct rpc_rqst *req;
324 
325         req = task->tk_rqstp;
326         if (req == NULL) {
327                 xprt->snd_task = task;
328                 return true;
329         }
330         if (__xprt_get_cong(xprt, task)) {
331                 xprt->snd_task = task;
332                 req->rq_bytes_sent = 0;
333                 req->rq_ntrans++;
334                 return true;
335         }
336         return false;
337 }
338 
339 static void __xprt_lock_write_next_cong(struct rpc_xprt *xprt)
340 {
341         if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
342                 return;
343         if (RPCXPRT_CONGESTED(xprt))
344                 goto out_unlock;
345         if (rpc_wake_up_first(&xprt->sending, __xprt_lock_write_cong_func, xprt))
346                 return;
347 out_unlock:
348         xprt_clear_locked(xprt);
349 }
350 
351 /**
352  * xprt_release_xprt - allow other requests to use a transport
353  * @xprt: transport with other tasks potentially waiting
354  * @task: task that is releasing access to the transport
355  *
356  * Note that "task" can be NULL.  No congestion control is provided.
357  */
358 void xprt_release_xprt(struct rpc_xprt *xprt, struct rpc_task *task)
359 {
360         if (xprt->snd_task == task) {
361                 xprt_clear_locked(xprt);
362                 __xprt_lock_write_next(xprt);
363         }
364 }
365 EXPORT_SYMBOL_GPL(xprt_release_xprt);
366 
367 /**
368  * xprt_release_xprt_cong - allow other requests to use a transport
369  * @xprt: transport with other tasks potentially waiting
370  * @task: task that is releasing access to the transport
371  *
372  * Note that "task" can be NULL.  Another task is awoken to use the
373  * transport if the transport's congestion window allows it.
374  */
375 void xprt_release_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task)
376 {
377         if (xprt->snd_task == task) {
378                 xprt_clear_locked(xprt);
379                 __xprt_lock_write_next_cong(xprt);
380         }
381 }
382 EXPORT_SYMBOL_GPL(xprt_release_xprt_cong);
383 
384 static inline void xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *task)
385 {
386         spin_lock_bh(&xprt->transport_lock);
387         xprt->ops->release_xprt(xprt, task);
388         spin_unlock_bh(&xprt->transport_lock);
389 }
390 
391 /*
392  * Van Jacobson congestion avoidance. Check if the congestion window
393  * overflowed. Put the task to sleep if this is the case.
394  */
395 static int
396 __xprt_get_cong(struct rpc_xprt *xprt, struct rpc_task *task)
397 {
398         struct rpc_rqst *req = task->tk_rqstp;
399 
400         if (req->rq_cong)
401                 return 1;
402         dprintk("RPC: %5u xprt_cwnd_limited cong = %lu cwnd = %lu\n",
403                         task->tk_pid, xprt->cong, xprt->cwnd);
404         if (RPCXPRT_CONGESTED(xprt))
405                 return 0;
406         req->rq_cong = 1;
407         xprt->cong += RPC_CWNDSCALE;
408         return 1;
409 }
410 
411 /*
412  * Adjust the congestion window, and wake up the next task
413  * that has been sleeping due to congestion
414  */
415 static void
416 __xprt_put_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
417 {
418         if (!req->rq_cong)
419                 return;
420         req->rq_cong = 0;
421         xprt->cong -= RPC_CWNDSCALE;
422         __xprt_lock_write_next_cong(xprt);
423 }
424 
425 /**
426  * xprt_release_rqst_cong - housekeeping when request is complete
427  * @task: RPC request that recently completed
428  *
429  * Useful for transports that require congestion control.
430  */
431 void xprt_release_rqst_cong(struct rpc_task *task)
432 {
433         struct rpc_rqst *req = task->tk_rqstp;
434 
435         __xprt_put_cong(req->rq_xprt, req);
436 }
437 EXPORT_SYMBOL_GPL(xprt_release_rqst_cong);
438 
439 /**
440  * xprt_adjust_cwnd - adjust transport congestion window
441  * @xprt: pointer to xprt
442  * @task: recently completed RPC request used to adjust window
443  * @result: result code of completed RPC request
444  *
445  * We use a time-smoothed congestion estimator to avoid heavy oscillation.
446  */
447 void xprt_adjust_cwnd(struct rpc_xprt *xprt, struct rpc_task *task, int result)
448 {
449         struct rpc_rqst *req = task->tk_rqstp;
450         unsigned long cwnd = xprt->cwnd;
451 
452         if (result >= 0 && cwnd <= xprt->cong) {
453                 /* The (cwnd >> 1) term makes sure
454                  * the result gets rounded properly. */
455                 cwnd += (RPC_CWNDSCALE * RPC_CWNDSCALE + (cwnd >> 1)) / cwnd;
456                 if (cwnd > RPC_MAXCWND(xprt))
457                         cwnd = RPC_MAXCWND(xprt);
458                 __xprt_lock_write_next_cong(xprt);
459         } else if (result == -ETIMEDOUT) {
460                 cwnd >>= 1;
461                 if (cwnd < RPC_CWNDSCALE)
462                         cwnd = RPC_CWNDSCALE;
463         }
464         dprintk("RPC:       cong %ld, cwnd was %ld, now %ld\n",
465                         xprt->cong, xprt->cwnd, cwnd);
466         xprt->cwnd = cwnd;
467         __xprt_put_cong(xprt, req);
468 }
469 EXPORT_SYMBOL_GPL(xprt_adjust_cwnd);
470 
471 /**
472  * xprt_wake_pending_tasks - wake all tasks on a transport's pending queue
473  * @xprt: transport with waiting tasks
474  * @status: result code to plant in each task before waking it
475  *
476  */
477 void xprt_wake_pending_tasks(struct rpc_xprt *xprt, int status)
478 {
479         if (status < 0)
480                 rpc_wake_up_status(&xprt->pending, status);
481         else
482                 rpc_wake_up(&xprt->pending);
483 }
484 EXPORT_SYMBOL_GPL(xprt_wake_pending_tasks);
485 
486 /**
487  * xprt_wait_for_buffer_space - wait for transport output buffer to clear
488  * @task: task to be put to sleep
489  * @action: function pointer to be executed after wait
490  *
491  * Note that we only set the timer for the case of RPC_IS_SOFT(), since
492  * we don't in general want to force a socket disconnection due to
493  * an incomplete RPC call transmission.
494  */
495 void xprt_wait_for_buffer_space(struct rpc_task *task, rpc_action action)
496 {
497         struct rpc_rqst *req = task->tk_rqstp;
498         struct rpc_xprt *xprt = req->rq_xprt;
499 
500         task->tk_timeout = RPC_IS_SOFT(task) ? req->rq_timeout : 0;
501         rpc_sleep_on(&xprt->pending, task, action);
502 }
503 EXPORT_SYMBOL_GPL(xprt_wait_for_buffer_space);
504 
505 /**
506  * xprt_write_space - wake the task waiting for transport output buffer space
507  * @xprt: transport with waiting tasks
508  *
509  * Can be called in a soft IRQ context, so xprt_write_space never sleeps.
510  */
511 void xprt_write_space(struct rpc_xprt *xprt)
512 {
513         spin_lock_bh(&xprt->transport_lock);
514         if (xprt->snd_task) {
515                 dprintk("RPC:       write space: waking waiting task on "
516                                 "xprt %p\n", xprt);
517                 rpc_wake_up_queued_task(&xprt->pending, xprt->snd_task);
518         }
519         spin_unlock_bh(&xprt->transport_lock);
520 }
521 EXPORT_SYMBOL_GPL(xprt_write_space);
522 
523 /**
524  * xprt_set_retrans_timeout_def - set a request's retransmit timeout
525  * @task: task whose timeout is to be set
526  *
527  * Set a request's retransmit timeout based on the transport's
528  * default timeout parameters.  Used by transports that don't adjust
529  * the retransmit timeout based on round-trip time estimation.
530  */
531 void xprt_set_retrans_timeout_def(struct rpc_task *task)
532 {
533         task->tk_timeout = task->tk_rqstp->rq_timeout;
534 }
535 EXPORT_SYMBOL_GPL(xprt_set_retrans_timeout_def);
536 
537 /**
538  * xprt_set_retrans_timeout_rtt - set a request's retransmit timeout
539  * @task: task whose timeout is to be set
540  *
541  * Set a request's retransmit timeout using the RTT estimator.
542  */
543 void xprt_set_retrans_timeout_rtt(struct rpc_task *task)
544 {
545         int timer = task->tk_msg.rpc_proc->p_timer;
546         struct rpc_clnt *clnt = task->tk_client;
547         struct rpc_rtt *rtt = clnt->cl_rtt;
548         struct rpc_rqst *req = task->tk_rqstp;
549         unsigned long max_timeout = clnt->cl_timeout->to_maxval;
550 
551         task->tk_timeout = rpc_calc_rto(rtt, timer);
552         task->tk_timeout <<= rpc_ntimeo(rtt, timer) + req->rq_retries;
553         if (task->tk_timeout > max_timeout || task->tk_timeout == 0)
554                 task->tk_timeout = max_timeout;
555 }
556 EXPORT_SYMBOL_GPL(xprt_set_retrans_timeout_rtt);
557 
558 static void xprt_reset_majortimeo(struct rpc_rqst *req)
559 {
560         const struct rpc_timeout *to = req->rq_task->tk_client->cl_timeout;
561 
562         req->rq_majortimeo = req->rq_timeout;
563         if (to->to_exponential)
564                 req->rq_majortimeo <<= to->to_retries;
565         else
566                 req->rq_majortimeo += to->to_increment * to->to_retries;
567         if (req->rq_majortimeo > to->to_maxval || req->rq_majortimeo == 0)
568                 req->rq_majortimeo = to->to_maxval;
569         req->rq_majortimeo += jiffies;
570 }
571 
572 /**
573  * xprt_adjust_timeout - adjust timeout values for next retransmit
574  * @req: RPC request containing parameters to use for the adjustment
575  *
576  */
577 int xprt_adjust_timeout(struct rpc_rqst *req)
578 {
579         struct rpc_xprt *xprt = req->rq_xprt;
580         const struct rpc_timeout *to = req->rq_task->tk_client->cl_timeout;
581         int status = 0;
582 
583         if (time_before(jiffies, req->rq_majortimeo)) {
584                 if (to->to_exponential)
585                         req->rq_timeout <<= 1;
586                 else
587                         req->rq_timeout += to->to_increment;
588                 if (to->to_maxval && req->rq_timeout >= to->to_maxval)
589                         req->rq_timeout = to->to_maxval;
590                 req->rq_retries++;
591         } else {
592                 req->rq_timeout = to->to_initval;
593                 req->rq_retries = 0;
594                 xprt_reset_majortimeo(req);
595                 /* Reset the RTT counters == "slow start" */
596                 spin_lock_bh(&xprt->transport_lock);
597                 rpc_init_rtt(req->rq_task->tk_client->cl_rtt, to->to_initval);
598                 spin_unlock_bh(&xprt->transport_lock);
599                 status = -ETIMEDOUT;
600         }
601 
602         if (req->rq_timeout == 0) {
603                 printk(KERN_WARNING "xprt_adjust_timeout: rq_timeout = 0!\n");
604                 req->rq_timeout = 5 * HZ;
605         }
606         return status;
607 }
608 
609 static void xprt_autoclose(struct work_struct *work)
610 {
611         struct rpc_xprt *xprt =
612                 container_of(work, struct rpc_xprt, task_cleanup);
613 
614         xprt->ops->close(xprt);
615         clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
616         xprt_release_write(xprt, NULL);
617 }
618 
619 /**
620  * xprt_disconnect_done - mark a transport as disconnected
621  * @xprt: transport to flag for disconnect
622  *
623  */
624 void xprt_disconnect_done(struct rpc_xprt *xprt)
625 {
626         dprintk("RPC:       disconnected transport %p\n", xprt);
627         spin_lock_bh(&xprt->transport_lock);
628         xprt_clear_connected(xprt);
629         xprt_wake_pending_tasks(xprt, -EAGAIN);
630         spin_unlock_bh(&xprt->transport_lock);
631 }
632 EXPORT_SYMBOL_GPL(xprt_disconnect_done);
633 
634 /**
635  * xprt_force_disconnect - force a transport to disconnect
636  * @xprt: transport to disconnect
637  *
638  */
639 void xprt_force_disconnect(struct rpc_xprt *xprt)
640 {
641         /* Don't race with the test_bit() in xprt_clear_locked() */
642         spin_lock_bh(&xprt->transport_lock);
643         set_bit(XPRT_CLOSE_WAIT, &xprt->state);
644         /* Try to schedule an autoclose RPC call */
645         if (test_and_set_bit(XPRT_LOCKED, &xprt->state) == 0)
646                 queue_work(rpciod_workqueue, &xprt->task_cleanup);
647         xprt_wake_pending_tasks(xprt, -EAGAIN);
648         spin_unlock_bh(&xprt->transport_lock);
649 }
650 
651 /**
652  * xprt_conditional_disconnect - force a transport to disconnect
653  * @xprt: transport to disconnect
654  * @cookie: 'connection cookie'
655  *
656  * This attempts to break the connection if and only if 'cookie' matches
657  * the current transport 'connection cookie'. It ensures that we don't
658  * try to break the connection more than once when we need to retransmit
659  * a batch of RPC requests.
660  *
661  */
662 void xprt_conditional_disconnect(struct rpc_xprt *xprt, unsigned int cookie)
663 {
664         /* Don't race with the test_bit() in xprt_clear_locked() */
665         spin_lock_bh(&xprt->transport_lock);
666         if (cookie != xprt->connect_cookie)
667                 goto out;
668         if (test_bit(XPRT_CLOSING, &xprt->state) || !xprt_connected(xprt))
669                 goto out;
670         set_bit(XPRT_CLOSE_WAIT, &xprt->state);
671         /* Try to schedule an autoclose RPC call */
672         if (test_and_set_bit(XPRT_LOCKED, &xprt->state) == 0)
673                 queue_work(rpciod_workqueue, &xprt->task_cleanup);
674         xprt_wake_pending_tasks(xprt, -EAGAIN);
675 out:
676         spin_unlock_bh(&xprt->transport_lock);
677 }
678 
679 static void
680 xprt_init_autodisconnect(unsigned long data)
681 {
682         struct rpc_xprt *xprt = (struct rpc_xprt *)data;
683 
684         spin_lock(&xprt->transport_lock);
685         if (!list_empty(&xprt->recv))
686                 goto out_abort;
687         if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
688                 goto out_abort;
689         spin_unlock(&xprt->transport_lock);
690         set_bit(XPRT_CONNECTION_CLOSE, &xprt->state);
691         queue_work(rpciod_workqueue, &xprt->task_cleanup);
692         return;
693 out_abort:
694         spin_unlock(&xprt->transport_lock);
695 }
696 
697 /**
698  * xprt_connect - schedule a transport connect operation
699  * @task: RPC task that is requesting the connect
700  *
701  */
702 void xprt_connect(struct rpc_task *task)
703 {
704         struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;
705 
706         dprintk("RPC: %5u xprt_connect xprt %p %s connected\n", task->tk_pid,
707                         xprt, (xprt_connected(xprt) ? "is" : "is not"));
708 
709         if (!xprt_bound(xprt)) {
710                 task->tk_status = -EAGAIN;
711                 return;
712         }
713         if (!xprt_lock_write(xprt, task))
714                 return;
715 
716         if (test_and_clear_bit(XPRT_CLOSE_WAIT, &xprt->state))
717                 xprt->ops->close(xprt);
718 
719         if (xprt_connected(xprt))
720                 xprt_release_write(xprt, task);
721         else {
722                 task->tk_rqstp->rq_bytes_sent = 0;
723                 task->tk_timeout = task->tk_rqstp->rq_timeout;
724                 rpc_sleep_on(&xprt->pending, task, xprt_connect_status);
725 
726                 if (test_bit(XPRT_CLOSING, &xprt->state))
727                         return;
728                 if (xprt_test_and_set_connecting(xprt))
729                         return;
730                 xprt->stat.connect_start = jiffies;
731                 xprt->ops->connect(xprt, task);
732         }
733 }
734 
735 static void xprt_connect_status(struct rpc_task *task)
736 {
737         struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;
738 
739         if (task->tk_status == 0) {
740                 xprt->stat.connect_count++;
741                 xprt->stat.connect_time += (long)jiffies - xprt->stat.connect_start;
742                 dprintk("RPC: %5u xprt_connect_status: connection established\n",
743                                 task->tk_pid);
744                 return;
745         }
746 
747         switch (task->tk_status) {
748         case -ECONNREFUSED:
749         case -ECONNRESET:
750         case -ECONNABORTED:
751         case -ENETUNREACH:
752         case -EHOSTUNREACH:
753         case -EPIPE:
754         case -EAGAIN:
755                 dprintk("RPC: %5u xprt_connect_status: retrying\n", task->tk_pid);
756                 break;
757         case -ETIMEDOUT:
758                 dprintk("RPC: %5u xprt_connect_status: connect attempt timed "
759                                 "out\n", task->tk_pid);
760                 break;
761         default:
762                 dprintk("RPC: %5u xprt_connect_status: error %d connecting to "
763                                 "server %s\n", task->tk_pid, -task->tk_status,
764                                 xprt->servername);
765                 xprt_release_write(xprt, task);
766                 task->tk_status = -EIO;
767         }
768 }
769 
770 /**
771  * xprt_lookup_rqst - find an RPC request corresponding to an XID
772  * @xprt: transport on which the original request was transmitted
773  * @xid: RPC XID of incoming reply
774  *
775  */
776 struct rpc_rqst *xprt_lookup_rqst(struct rpc_xprt *xprt, __be32 xid)
777 {
778         struct rpc_rqst *entry;
779 
780         list_for_each_entry(entry, &xprt->recv, rq_list)
781                 if (entry->rq_xid == xid)
782                         return entry;
783 
784         dprintk("RPC:       xprt_lookup_rqst did not find xid %08x\n",
785                         ntohl(xid));
786         xprt->stat.bad_xids++;
787         return NULL;
788 }
789 EXPORT_SYMBOL_GPL(xprt_lookup_rqst);
790 
791 static void xprt_update_rtt(struct rpc_task *task)
792 {
793         struct rpc_rqst *req = task->tk_rqstp;
794         struct rpc_rtt *rtt = task->tk_client->cl_rtt;
795         unsigned int timer = task->tk_msg.rpc_proc->p_timer;
796         long m = usecs_to_jiffies(ktime_to_us(req->rq_rtt));
797 
798         if (timer) {
799                 if (req->rq_ntrans == 1)
800                         rpc_update_rtt(rtt, timer, m);
801                 rpc_set_timeo(rtt, timer, req->rq_ntrans - 1);
802         }
803 }
804 
805 /**
806  * xprt_complete_rqst - called when reply processing is complete
807  * @task: RPC request that recently completed
808  * @copied: actual number of bytes received from the transport
809  *
810  * Caller holds transport lock.
811  */
812 void xprt_complete_rqst(struct rpc_task *task, int copied)
813 {
814         struct rpc_rqst *req = task->tk_rqstp;
815         struct rpc_xprt *xprt = req->rq_xprt;
816 
817         dprintk("RPC: %5u xid %08x complete (%d bytes received)\n",
818                         task->tk_pid, ntohl(req->rq_xid), copied);
819 
820         xprt->stat.recvs++;
821         req->rq_rtt = ktime_sub(ktime_get(), req->rq_xtime);
822         if (xprt->ops->timer != NULL)
823                 xprt_update_rtt(task);
824 
825         list_del_init(&req->rq_list);
826         req->rq_private_buf.len = copied;
827         /* Ensure all writes are done before we update */
828         /* req->rq_reply_bytes_recvd */
829         smp_wmb();
830         req->rq_reply_bytes_recvd = copied;
831         rpc_wake_up_queued_task(&xprt->pending, task);
832 }
833 EXPORT_SYMBOL_GPL(xprt_complete_rqst);
834 
835 static void xprt_timer(struct rpc_task *task)
836 {
837         struct rpc_rqst *req = task->tk_rqstp;
838         struct rpc_xprt *xprt = req->rq_xprt;
839 
840         if (task->tk_status != -ETIMEDOUT)
841                 return;
842         dprintk("RPC: %5u xprt_timer\n", task->tk_pid);
843 
844         spin_lock_bh(&xprt->transport_lock);
845         if (!req->rq_reply_bytes_recvd) {
846                 if (xprt->ops->timer)
847                         xprt->ops->timer(xprt, task);
848         } else
849                 task->tk_status = 0;
850         spin_unlock_bh(&xprt->transport_lock);
851 }
852 
853 static inline int xprt_has_timer(struct rpc_xprt *xprt)
854 {
855         return xprt->idle_timeout != 0;
856 }
857 
858 /**
859  * xprt_prepare_transmit - reserve the transport before sending a request
860  * @task: RPC task about to send a request
861  *
862  */
863 int xprt_prepare_transmit(struct rpc_task *task)
864 {
865         struct rpc_rqst *req = task->tk_rqstp;
866         struct rpc_xprt *xprt = req->rq_xprt;
867         int err = 0;
868 
869         dprintk("RPC: %5u xprt_prepare_transmit\n", task->tk_pid);
870 
871         spin_lock_bh(&xprt->transport_lock);
872         if (req->rq_reply_bytes_recvd && !req->rq_bytes_sent) {
873                 err = req->rq_reply_bytes_recvd;
874                 goto out_unlock;
875         }
876         if (!xprt->ops->reserve_xprt(xprt, task))
877                 err = -EAGAIN;
878 out_unlock:
879         spin_unlock_bh(&xprt->transport_lock);
880         return err;
881 }
882 
883 void xprt_end_transmit(struct rpc_task *task)
884 {
885         xprt_release_write(task->tk_rqstp->rq_xprt, task);
886 }
887 
888 /**
889  * xprt_transmit - send an RPC request on a transport
890  * @task: controlling RPC task
891  *
892  * We have to copy the iovec because sendmsg fiddles with its contents.
893  */
894 void xprt_transmit(struct rpc_task *task)
895 {
896         struct rpc_rqst *req = task->tk_rqstp;
897         struct rpc_xprt *xprt = req->rq_xprt;
898         int status, numreqs;
899 
900         dprintk("RPC: %5u xprt_transmit(%u)\n", task->tk_pid, req->rq_slen);
901 
902         if (!req->rq_reply_bytes_recvd) {
903                 if (list_empty(&req->rq_list) && rpc_reply_expected(task)) {
904                         /*
905                          * Add to the list only if we're expecting a reply
906                          */
907                         spin_lock_bh(&xprt->transport_lock);
908                         /* Update the softirq receive buffer */
909                         memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
910                                         sizeof(req->rq_private_buf));
911                         /* Add request to the receive list */
912                         list_add_tail(&req->rq_list, &xprt->recv);
913                         spin_unlock_bh(&xprt->transport_lock);
914                         xprt_reset_majortimeo(req);
915                         /* Turn off autodisconnect */
916                         del_singleshot_timer_sync(&xprt->timer);
917                 }
918         } else if (!req->rq_bytes_sent)
919                 return;
920 
921         req->rq_connect_cookie = xprt->connect_cookie;
922         req->rq_xtime = ktime_get();
923         status = xprt->ops->send_request(task);
924         if (status != 0) {
925                 task->tk_status = status;
926                 return;
927         }
928 
929         dprintk("RPC: %5u xmit complete\n", task->tk_pid);
930         task->tk_flags |= RPC_TASK_SENT;
931         spin_lock_bh(&xprt->transport_lock);
932 
933         xprt->ops->set_retrans_timeout(task);
934 
935         numreqs = atomic_read(&xprt->num_reqs);
936         if (numreqs > xprt->stat.max_slots)
937                 xprt->stat.max_slots = numreqs;
938         xprt->stat.sends++;
939         xprt->stat.req_u += xprt->stat.sends - xprt->stat.recvs;
940         xprt->stat.bklog_u += xprt->backlog.qlen;
941         xprt->stat.sending_u += xprt->sending.qlen;
942         xprt->stat.pending_u += xprt->pending.qlen;
943 
944         /* Don't race with disconnect */
945         if (!xprt_connected(xprt))
946                 task->tk_status = -ENOTCONN;
947         else if (!req->rq_reply_bytes_recvd && rpc_reply_expected(task)) {
948                 /*
949                  * Sleep on the pending queue since
950                  * we're expecting a reply.
951                  */
952                 rpc_sleep_on(&xprt->pending, task, xprt_timer);
953         }
954         spin_unlock_bh(&xprt->transport_lock);
955 }
956 
957 static void xprt_add_backlog(struct rpc_xprt *xprt, struct rpc_task *task)
958 {
959         set_bit(XPRT_CONGESTED, &xprt->state);
960         rpc_sleep_on(&xprt->backlog, task, NULL);
961 }
962 
963 static void xprt_wake_up_backlog(struct rpc_xprt *xprt)
964 {
965         if (rpc_wake_up_next(&xprt->backlog) == NULL)
966                 clear_bit(XPRT_CONGESTED, &xprt->state);
967 }
968 
969 static bool xprt_throttle_congested(struct rpc_xprt *xprt, struct rpc_task *task)
970 {
971         bool ret = false;
972 
973         if (!test_bit(XPRT_CONGESTED, &xprt->state))
974                 goto out;
975         spin_lock(&xprt->reserve_lock);
976         if (test_bit(XPRT_CONGESTED, &xprt->state)) {
977                 rpc_sleep_on(&xprt->backlog, task, NULL);
978                 ret = true;
979         }
980         spin_unlock(&xprt->reserve_lock);
981 out:
982         return ret;
983 }
984 
985 static struct rpc_rqst *xprt_dynamic_alloc_slot(struct rpc_xprt *xprt, gfp_t gfp_flags)
986 {
987         struct rpc_rqst *req = ERR_PTR(-EAGAIN);
988 
989         if (!atomic_add_unless(&xprt->num_reqs, 1, xprt->max_reqs))
990                 goto out;
991         req = kzalloc(sizeof(struct rpc_rqst), gfp_flags);
992         if (req != NULL)
993                 goto out;
994         atomic_dec(&xprt->num_reqs);
995         req = ERR_PTR(-ENOMEM);
996 out:
997         return req;
998 }
999 
1000 static bool xprt_dynamic_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
1001 {
1002         if (atomic_add_unless(&xprt->num_reqs, -1, xprt->min_reqs)) {
1003                 kfree(req);
1004                 return true;
1005         }
1006         return false;
1007 }
1008 
1009 void xprt_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task)
1010 {
1011         struct rpc_rqst *req;
1012 
1013         spin_lock(&xprt->reserve_lock);
1014         if (!list_empty(&xprt->free)) {
1015                 req = list_entry(xprt->free.next, struct rpc_rqst, rq_list);
1016                 list_del(&req->rq_list);
1017                 goto out_init_req;
1018         }
1019         req = xprt_dynamic_alloc_slot(xprt, GFP_NOWAIT|__GFP_NOWARN);
1020         if (!IS_ERR(req))
1021                 goto out_init_req;
1022         switch (PTR_ERR(req)) {
1023         case -ENOMEM:
1024                 dprintk("RPC:       dynamic allocation of request slot "
1025                                 "failed! Retrying\n");
1026                 task->tk_status = -ENOMEM;
1027                 break;
1028         case -EAGAIN:
1029                 xprt_add_backlog(xprt, task);
1030                 dprintk("RPC:       waiting for request slot\n");
1031         default:
1032                 task->tk_status = -EAGAIN;
1033         }
1034         spin_unlock(&xprt->reserve_lock);
1035         return;
1036 out_init_req:
1037         task->tk_status = 0;
1038         task->tk_rqstp = req;
1039         xprt_request_init(task, xprt);
1040         spin_unlock(&xprt->reserve_lock);
1041 }
1042 EXPORT_SYMBOL_GPL(xprt_alloc_slot);
1043 
1044 void xprt_lock_and_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task)
1045 {
1046         /* Note: grabbing the xprt_lock_write() ensures that we throttle
1047          * new slot allocation if the transport is congested (i.e. when
1048          * reconnecting a stream transport or when out of socket write
1049          * buffer space).
1050          */
1051         if (xprt_lock_write(xprt, task)) {
1052                 xprt_alloc_slot(xprt, task);
1053                 xprt_release_write(xprt, task);
1054         }
1055 }
1056 EXPORT_SYMBOL_GPL(xprt_lock_and_alloc_slot);
1057 
1058 static void xprt_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
1059 {
1060         spin_lock(&xprt->reserve_lock);
1061         if (!xprt_dynamic_free_slot(xprt, req)) {
1062                 memset(req, 0, sizeof(*req));   /* mark unused */
1063                 list_add(&req->rq_list, &xprt->free);
1064         }
1065         xprt_wake_up_backlog(xprt);
1066         spin_unlock(&xprt->reserve_lock);
1067 }
1068 
1069 static void xprt_free_all_slots(struct rpc_xprt *xprt)
1070 {
1071         struct rpc_rqst *req;
1072         while (!list_empty(&xprt->free)) {
1073                 req = list_first_entry(&xprt->free, struct rpc_rqst, rq_list);
1074                 list_del(&req->rq_list);
1075                 kfree(req);
1076         }
1077 }
1078 
1079 struct rpc_xprt *xprt_alloc(struct net *net, size_t size,
1080                 unsigned int num_prealloc,
1081                 unsigned int max_alloc)
1082 {
1083         struct rpc_xprt *xprt;
1084         struct rpc_rqst *req;
1085         int i;
1086 
1087         xprt = kzalloc(size, GFP_KERNEL);
1088         if (xprt == NULL)
1089                 goto out;
1090 
1091         xprt_init(xprt, net);
1092 
1093         for (i = 0; i < num_prealloc; i++) {
1094                 req = kzalloc(sizeof(struct rpc_rqst), GFP_KERNEL);
1095                 if (!req)
1096                         break;
1097                 list_add(&req->rq_list, &xprt->free);
1098         }
1099         if (i < num_prealloc)
1100                 goto out_free;
1101         if (max_alloc > num_prealloc)
1102                 xprt->max_reqs = max_alloc;
1103         else
1104                 xprt->max_reqs = num_prealloc;
1105         xprt->min_reqs = num_prealloc;
1106         atomic_set(&xprt->num_reqs, num_prealloc);
1107 
1108         return xprt;
1109 
1110 out_free:
1111         xprt_free(xprt);
1112 out:
1113         return NULL;
1114 }
1115 EXPORT_SYMBOL_GPL(xprt_alloc);
1116 
1117 void xprt_free(struct rpc_xprt *xprt)
1118 {
1119         put_net(xprt->xprt_net);
1120         xprt_free_all_slots(xprt);
1121         kfree(xprt);
1122 }
1123 EXPORT_SYMBOL_GPL(xprt_free);
1124 
1125 /**
1126  * xprt_reserve - allocate an RPC request slot
1127  * @task: RPC task requesting a slot allocation
1128  *
1129  * If the transport is marked as being congested, or if no more
1130  * slots are available, place the task on the transport's
1131  * backlog queue.
1132  */
1133 void xprt_reserve(struct rpc_task *task)
1134 {
1135         struct rpc_xprt *xprt;
1136 
1137         task->tk_status = 0;
1138         if (task->tk_rqstp != NULL)
1139                 return;
1140 
1141         task->tk_timeout = 0;
1142         task->tk_status = -EAGAIN;
1143         rcu_read_lock();
1144         xprt = rcu_dereference(task->tk_client->cl_xprt);
1145         if (!xprt_throttle_congested(xprt, task))
1146                 xprt->ops->alloc_slot(xprt, task);
1147         rcu_read_unlock();
1148 }
1149 
1150 /**
1151  * xprt_retry_reserve - allocate an RPC request slot
1152  * @task: RPC task requesting a slot allocation
1153  *
1154  * If no more slots are available, place the task on the transport's
1155  * backlog queue.
1156  * Note that the only difference with xprt_reserve is that we now
1157  * ignore the value of the XPRT_CONGESTED flag.
1158  */
1159 void xprt_retry_reserve(struct rpc_task *task)
1160 {
1161         struct rpc_xprt *xprt;
1162 
1163         task->tk_status = 0;
1164         if (task->tk_rqstp != NULL)
1165                 return;
1166 
1167         task->tk_timeout = 0;
1168         task->tk_status = -EAGAIN;
1169         rcu_read_lock();
1170         xprt = rcu_dereference(task->tk_client->cl_xprt);
1171         xprt->ops->alloc_slot(xprt, task);
1172         rcu_read_unlock();
1173 }
1174 
1175 static inline __be32 xprt_alloc_xid(struct rpc_xprt *xprt)
1176 {
1177         return (__force __be32)xprt->xid++;
1178 }
1179 
1180 static inline void xprt_init_xid(struct rpc_xprt *xprt)
1181 {
1182         xprt->xid = net_random();
1183 }
1184 
1185 static void xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt)
1186 {
1187         struct rpc_rqst *req = task->tk_rqstp;
1188 
1189         INIT_LIST_HEAD(&req->rq_list);
1190         req->rq_timeout = task->tk_client->cl_timeout->to_initval;
1191         req->rq_task    = task;
1192         req->rq_xprt    = xprt;
1193         req->rq_buffer  = NULL;
1194         req->rq_xid     = xprt_alloc_xid(xprt);
1195         req->rq_release_snd_buf = NULL;
1196         xprt_reset_majortimeo(req);
1197         dprintk("RPC: %5u reserved req %p xid %08x\n", task->tk_pid,
1198                         req, ntohl(req->rq_xid));
1199 }
1200 
1201 /**
1202  * xprt_release - release an RPC request slot
1203  * @task: task which is finished with the slot
1204  *
1205  */
1206 void xprt_release(struct rpc_task *task)
1207 {
1208         struct rpc_xprt *xprt;
1209         struct rpc_rqst *req = task->tk_rqstp;
1210 
1211         if (req == NULL) {
1212                 if (task->tk_client) {
1213                         rcu_read_lock();
1214                         xprt = rcu_dereference(task->tk_client->cl_xprt);
1215                         if (xprt->snd_task == task)
1216                                 xprt_release_write(xprt, task);
1217                         rcu_read_unlock();
1218                 }
1219                 return;
1220         }
1221 
1222         xprt = req->rq_xprt;
1223         if (task->tk_ops->rpc_count_stats != NULL)
1224                 task->tk_ops->rpc_count_stats(task, task->tk_calldata);
1225         else if (task->tk_client)
1226                 rpc_count_iostats(task, task->tk_client->cl_metrics);
1227         spin_lock_bh(&xprt->transport_lock);
1228         xprt->ops->release_xprt(xprt, task);
1229         if (xprt->ops->release_request)
1230                 xprt->ops->release_request(task);
1231         if (!list_empty(&req->rq_list))
1232                 list_del(&req->rq_list);
1233         xprt->last_used = jiffies;
1234         if (list_empty(&xprt->recv) && xprt_has_timer(xprt))
1235                 mod_timer(&xprt->timer,
1236                                 xprt->last_used + xprt->idle_timeout);
1237         spin_unlock_bh(&xprt->transport_lock);
1238         if (req->rq_buffer)
1239                 xprt->ops->buf_free(req->rq_buffer);
1240         if (req->rq_cred != NULL)
1241                 put_rpccred(req->rq_cred);
1242         task->tk_rqstp = NULL;
1243         if (req->rq_release_snd_buf)
1244                 req->rq_release_snd_buf(req);
1245 
1246         dprintk("RPC: %5u release request %p\n", task->tk_pid, req);
1247         if (likely(!bc_prealloc(req)))
1248                 xprt_free_slot(xprt, req);
1249         else
1250                 xprt_free_bc_request(req);
1251 }
1252 
1253 static void xprt_init(struct rpc_xprt *xprt, struct net *net)
1254 {
1255         atomic_set(&xprt->count, 1);
1256 
1257         spin_lock_init(&xprt->transport_lock);
1258         spin_lock_init(&xprt->reserve_lock);
1259 
1260         INIT_LIST_HEAD(&xprt->free);
1261         INIT_LIST_HEAD(&xprt->recv);
1262 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
1263         spin_lock_init(&xprt->bc_pa_lock);
1264         INIT_LIST_HEAD(&xprt->bc_pa_list);
1265 #endif /* CONFIG_SUNRPC_BACKCHANNEL */
1266 
1267         xprt->last_used = jiffies;
1268         xprt->cwnd = RPC_INITCWND;
1269         xprt->bind_index = 0;
1270 
1271         rpc_init_wait_queue(&xprt->binding, "xprt_binding");
1272         rpc_init_wait_queue(&xprt->pending, "xprt_pending");
1273         rpc_init_priority_wait_queue(&xprt->sending, "xprt_sending");
1274         rpc_init_priority_wait_queue(&xprt->backlog, "xprt_backlog");
1275 
1276         xprt_init_xid(xprt);
1277 
1278         xprt->xprt_net = get_net(net);
1279 }
1280 
1281 /**
1282  * xprt_create_transport - create an RPC transport
1283  * @args: rpc transport creation arguments
1284  *
1285  */
1286 struct rpc_xprt *xprt_create_transport(struct xprt_create *args)
1287 {
1288         struct rpc_xprt *xprt;
1289         struct xprt_class *t;
1290 
1291         spin_lock(&xprt_list_lock);
1292         list_for_each_entry(t, &xprt_list, list) {
1293                 if (t->ident == args->ident) {
1294                         spin_unlock(&xprt_list_lock);
1295                         goto found;
1296                 }
1297         }
1298         spin_unlock(&xprt_list_lock);
1299         dprintk("RPC: transport (%d) not supported\n", args->ident);
1300         return ERR_PTR(-EIO);
1301 
1302 found:
1303         xprt = t->setup(args);
1304         if (IS_ERR(xprt)) {
1305                 dprintk("RPC:       xprt_create_transport: failed, %ld\n",
1306                                 -PTR_ERR(xprt));
1307                 goto out;
1308         }
1309         if (args->flags & XPRT_CREATE_NO_IDLE_TIMEOUT)
1310                 xprt->idle_timeout = 0;
1311         INIT_WORK(&xprt->task_cleanup, xprt_autoclose);
1312         if (xprt_has_timer(xprt))
1313                 setup_timer(&xprt->timer, xprt_init_autodisconnect,
1314                             (unsigned long)xprt);
1315         else
1316                 init_timer(&xprt->timer);
1317 
1318         if (strlen(args->servername) > RPC_MAXNETNAMELEN) {
1319                 xprt_destroy(xprt);
1320                 return ERR_PTR(-EINVAL);
1321         }
1322         xprt->servername = kstrdup(args->servername, GFP_KERNEL);
1323         if (xprt->servername == NULL) {
1324                 xprt_destroy(xprt);
1325                 return ERR_PTR(-ENOMEM);
1326         }
1327 
1328         dprintk("RPC:       created transport %p with %u slots\n", xprt,
1329                         xprt->max_reqs);
1330 out:
1331         return xprt;
1332 }
1333 
1334 /**
1335  * xprt_destroy - destroy an RPC transport, killing off all requests.
1336  * @xprt: transport to destroy
1337  *
1338  */
1339 static void xprt_destroy(struct rpc_xprt *xprt)
1340 {
1341         dprintk("RPC:       destroying transport %p\n", xprt);
1342         del_timer_sync(&xprt->timer);
1343 
1344         rpc_destroy_wait_queue(&xprt->binding);
1345         rpc_destroy_wait_queue(&xprt->pending);
1346         rpc_destroy_wait_queue(&xprt->sending);
1347         rpc_destroy_wait_queue(&xprt->backlog);
1348         cancel_work_sync(&xprt->task_cleanup);
1349         kfree(xprt->servername);
1350         /*
1351          * Tear down transport state and free the rpc_xprt
1352          */
1353         xprt->ops->destroy(xprt);
1354 }
1355 
1356 /**
1357  * xprt_put - release a reference to an RPC transport.
1358  * @xprt: pointer to the transport
1359  *
1360  */
1361 void xprt_put(struct rpc_xprt *xprt)
1362 {
1363         if (atomic_dec_and_test(&xprt->count))
1364                 xprt_destroy(xprt);
1365 }
1366 
1367 /**
1368  * xprt_get - return a reference to an RPC transport.
1369  * @xprt: pointer to the transport
1370  *
1371  */
1372 struct rpc_xprt *xprt_get(struct rpc_xprt *xprt)
1373 {
1374         if (atomic_inc_not_zero(&xprt->count))
1375                 return xprt;
1376         return NULL;
1377 }
1378 

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