net/sunrpc/xprt.c

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