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 bool __xprt_lock_write_func(struct rpc_task *task, void *data)
 296 {
 297         struct rpc_xprt *xprt = data;
 298         struct rpc_rqst *req;
 299
 300         req = task->tk_rqstp;
 301         xprt->snd_task = task;
 302         if (req) {
 303                 req->rq_bytes_sent = 0;
 304                 req->rq_ntrans++;
 305         }
 306         return true;
 307 }
 308
 309 static void __xprt_lock_write_next(struct rpc_xprt *xprt)
 310 {
 311         if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
 312                 return;
 313
 314         if (rpc_wake_up_first(&xprt->sending, __xprt_lock_write_func, xprt))
 315                 return;
 316         xprt_clear_locked(xprt);
 317 }
 318
 319 static bool __xprt_lock_write_cong_func(struct rpc_task *task, void *data)
 320 {
 321         struct rpc_xprt *xprt = data;
 322         struct rpc_rqst *req;
 323
 324         req = task->tk_rqstp;
 325         if (req == NULL) {
 326                 xprt->snd_task = task;
 327                 return true;
 328         }
 329         if (__xprt_get_cong(xprt, task)) {
 330                 xprt->snd_task = task;
 331                 req->rq_bytes_sent = 0;
 332                 req->rq_ntrans++;
 333                 return true;
 334         }
 335         return false;
 336 }
 337
 338 static void __xprt_lock_write_next_cong(struct rpc_xprt *xprt)
 339 {
 340         if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
 341                 return;
 342         if (RPCXPRT_CONGESTED(xprt))
 343                 goto out_unlock;
 344         if (rpc_wake_up_first(&xprt->sending, __xprt_lock_write_cong_func, xprt))
 345                 return;
 346 out_unlock:
 347         xprt_clear_locked(xprt);
 348 }
 349
 350 /**
 351  * xprt_release_xprt - allow other requests to use a transport
 352  * @xprt: transport with other tasks potentially waiting
 353  * @task: task that is releasing access to the transport
 354  *
 355  * Note that "task" can be NULL.  No congestion control is provided.
 356  */
 357 void xprt_release_xprt(struct rpc_xprt *xprt, struct rpc_task *task)
 358 {
 359         if (xprt->snd_task == task) {
 360                 xprt_clear_locked(xprt);
 361                 __xprt_lock_write_next(xprt);
 362         }
 363 }
 364 EXPORT_SYMBOL_GPL(xprt_release_xprt);
 365
 366 /**
 367  * xprt_release_xprt_cong - allow other requests to use a transport
 368  * @xprt: transport with other tasks potentially waiting
 369  * @task: task that is releasing access to the transport
 370  *
 371  * Note that "task" can be NULL.  Another task is awoken to use the
 372  * transport if the transport's congestion window allows it.
 373  */
 374 void xprt_release_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task)
 375 {
 376         if (xprt->snd_task == task) {
 377                 xprt_clear_locked(xprt);
 378                 __xprt_lock_write_next_cong(xprt);
 379         }
 380 }
 381 EXPORT_SYMBOL_GPL(xprt_release_xprt_cong);
 382
 383 static inline void xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *task)
 384 {
 385         spin_lock_bh(&xprt->transport_lock);
 386         xprt->ops->release_xprt(xprt, task);
 387         spin_unlock_bh(&xprt->transport_lock);
 388 }
 389
 390 /*
 391  * Van Jacobson congestion avoidance. Check if the congestion window
 392  * overflowed. Put the task to sleep if this is the case.
 393  */
 394 static int
 395 __xprt_get_cong(struct rpc_xprt *xprt, struct rpc_task *task)
 396 {
 397         struct rpc_rqst *req = task->tk_rqstp;
 398
 399         if (req->rq_cong)
 400                 return 1;
 401         dprintk("RPC: %5u xprt_cwnd_limited cong = %lu cwnd = %lu\n",
 402                         task->tk_pid, xprt->cong, xprt->cwnd);
 403         if (RPCXPRT_CONGESTED(xprt))
 404                 return 0;
 405         req->rq_cong = 1;
 406         xprt->cong += RPC_CWNDSCALE;
 407         return 1;
 408 }
 409
 410 /*
 411  * Adjust the congestion window, and wake up the next task
 412  * that has been sleeping due to congestion
 413  */
 414 static void
 415 __xprt_put_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
 416 {
 417         if (!req->rq_cong)
 418                 return;
 419         req->rq_cong = 0;
 420         xprt->cong -= RPC_CWNDSCALE;
 421         __xprt_lock_write_next_cong(xprt);
 422 }
 423
 424 /**
 425  * xprt_release_rqst_cong - housekeeping when request is complete
 426  * @task: RPC request that recently completed
 427  *
 428  * Useful for transports that require congestion control.
 429  */
 430 void xprt_release_rqst_cong(struct rpc_task *task)
 431 {
 432         __xprt_put_cong(task->tk_xprt, task->tk_rqstp);
 433 }
 434 EXPORT_SYMBOL_GPL(xprt_release_rqst_cong);
 435
 436 /**
 437  * xprt_adjust_cwnd - adjust transport congestion window
 438  * @task: recently completed RPC request used to adjust window
 439  * @result: result code of completed RPC request
 440  *
 441  * We use a time-smoothed congestion estimator to avoid heavy oscillation.
 442  */
 443 void xprt_adjust_cwnd(struct rpc_task *task, int result)
 444 {
 445         struct rpc_rqst *req = task->tk_rqstp;
 446         struct rpc_xprt *xprt = task->tk_xprt;
 447         unsigned long cwnd = xprt->cwnd;
 448
 449         if (result >= 0 && cwnd <= xprt->cong) {
 450                 /* The (cwnd >> 1) term makes sure
 451                  * the result gets rounded properly. */
 452                 cwnd += (RPC_CWNDSCALE * RPC_CWNDSCALE + (cwnd >> 1)) / cwnd;
 453                 if (cwnd > RPC_MAXCWND(xprt))
 454                         cwnd = RPC_MAXCWND(xprt);
 455                 __xprt_lock_write_next_cong(xprt);
 456         } else if (result == -ETIMEDOUT) {
 457                 cwnd >>= 1;
 458                 if (cwnd < RPC_CWNDSCALE)
 459                         cwnd = RPC_CWNDSCALE;
 460         }
 461         dprintk("RPC:       cong %ld, cwnd was %ld, now %ld\n",
 462                         xprt->cong, xprt->cwnd, cwnd);
 463         xprt->cwnd = cwnd;
 464         __xprt_put_cong(xprt, req);
 465 }
 466 EXPORT_SYMBOL_GPL(xprt_adjust_cwnd);
 467
 468 /**
 469  * xprt_wake_pending_tasks - wake all tasks on a transport's pending queue
 470  * @xprt: transport with waiting tasks
 471  * @status: result code to plant in each task before waking it
 472  *
 473  */
 474 void xprt_wake_pending_tasks(struct rpc_xprt *xprt, int status)
 475 {
 476         if (status < 0)
 477                 rpc_wake_up_status(&xprt->pending, status);
 478         else
 479                 rpc_wake_up(&xprt->pending);
 480 }
 481 EXPORT_SYMBOL_GPL(xprt_wake_pending_tasks);
 482
 483 /**
 484  * xprt_wait_for_buffer_space - wait for transport output buffer to clear
 485  * @task: task to be put to sleep
 486  * @action: function pointer to be executed after wait
 487  */
 488 void xprt_wait_for_buffer_space(struct rpc_task *task, rpc_action action)
 489 {
 490         struct rpc_rqst *req = task->tk_rqstp;
 491         struct rpc_xprt *xprt = req->rq_xprt;
 492
 493         task->tk_timeout = req->rq_timeout;
 494         rpc_sleep_on(&xprt->pending, task, action);
 495 }
 496 EXPORT_SYMBOL_GPL(xprt_wait_for_buffer_space);
 497
 498 /**
 499  * xprt_write_space - wake the task waiting for transport output buffer space
 500  * @xprt: transport with waiting tasks
 501  *
 502  * Can be called in a soft IRQ context, so xprt_write_space never sleeps.
 503  */
 504 void xprt_write_space(struct rpc_xprt *xprt)
 505 {
 506         if (unlikely(xprt->shutdown))
 507                 return;
 508
 509         spin_lock_bh(&xprt->transport_lock);
 510         if (xprt->snd_task) {
 511                 dprintk("RPC:       write space: waking waiting task on "
 512                                 "xprt %p\n", xprt);
 513                 rpc_wake_up_queued_task(&xprt->pending, xprt->snd_task);
 514         }
 515         spin_unlock_bh(&xprt->transport_lock);
 516 }
 517 EXPORT_SYMBOL_GPL(xprt_write_space);
 518
 519 /**
 520  * xprt_set_retrans_timeout_def - set a request's retransmit timeout
 521  * @task: task whose timeout is to be set
 522  *
 523  * Set a request's retransmit timeout based on the transport's
 524  * default timeout parameters.  Used by transports that don't adjust
 525  * the retransmit timeout based on round-trip time estimation.
 526  */
 527 void xprt_set_retrans_timeout_def(struct rpc_task *task)
 528 {
 529         task->tk_timeout = task->tk_rqstp->rq_timeout;
 530 }
 531 EXPORT_SYMBOL_GPL(xprt_set_retrans_timeout_def);
 532
 533 /*
 534  * xprt_set_retrans_timeout_rtt - set a request's retransmit timeout
 535  * @task: task whose timeout is to be set
 536  *
 537  * Set a request's retransmit timeout using the RTT estimator.
 538  */
 539 void xprt_set_retrans_timeout_rtt(struct rpc_task *task)
 540 {
 541         int timer = task->tk_msg.rpc_proc->p_timer;
 542         struct rpc_clnt *clnt = task->tk_client;
 543         struct rpc_rtt *rtt = clnt->cl_rtt;
 544         struct rpc_rqst *req = task->tk_rqstp;
 545         unsigned long max_timeout = clnt->cl_timeout->to_maxval;
 546
 547         task->tk_timeout = rpc_calc_rto(rtt, timer);
 548         task->tk_timeout <<= rpc_ntimeo(rtt, timer) + req->rq_retries;
 549         if (task->tk_timeout > max_timeout || task->tk_timeout == 0)
 550                 task->tk_timeout = max_timeout;
 551 }
 552 EXPORT_SYMBOL_GPL(xprt_set_retrans_timeout_rtt);
 553
 554 static void xprt_reset_majortimeo(struct rpc_rqst *req)
 555 {
 556         const struct rpc_timeout *to = req->rq_task->tk_client->cl_timeout;
 557
 558         req->rq_majortimeo = req->rq_timeout;
 559         if (to->to_exponential)
 560                 req->rq_majortimeo <<= to->to_retries;
 561         else
 562                 req->rq_majortimeo += to->to_increment * to->to_retries;
 563         if (req->rq_majortimeo > to->to_maxval || req->rq_majortimeo == 0)
 564                 req->rq_majortimeo = to->to_maxval;
 565         req->rq_majortimeo += jiffies;
 566 }
 567
 568 /**
 569  * xprt_adjust_timeout - adjust timeout values for next retransmit
 570  * @req: RPC request containing parameters to use for the adjustment
 571  *
 572  */
 573 int xprt_adjust_timeout(struct rpc_rqst *req)
 574 {
 575         struct rpc_xprt *xprt = req->rq_xprt;
 576         const struct rpc_timeout *to = req->rq_task->tk_client->cl_timeout;
 577         int status = 0;
 578
 579         if (time_before(jiffies, req->rq_majortimeo)) {
 580                 if (to->to_exponential)
 581                         req->rq_timeout <<= 1;
 582                 else
 583                         req->rq_timeout += to->to_increment;
 584                 if (to->to_maxval && req->rq_timeout >= to->to_maxval)
 585                         req->rq_timeout = to->to_maxval;
 586                 req->rq_retries++;
 587         } else {
 588                 req->rq_timeout = to->to_initval;
 589                 req->rq_retries = 0;
 590                 xprt_reset_majortimeo(req);
 591                 /* Reset the RTT counters == "slow start" */
 592                 spin_lock_bh(&xprt->transport_lock);
 593                 rpc_init_rtt(req->rq_task->tk_client->cl_rtt, to->to_initval);
 594                 spin_unlock_bh(&xprt->transport_lock);
 595                 status = -ETIMEDOUT;
 596         }
 597
 598         if (req->rq_timeout == 0) {
 599                 printk(KERN_WARNING "xprt_adjust_timeout: rq_timeout = 0!\n");
 600                 req->rq_timeout = 5 * HZ;
 601         }
 602         return status;
 603 }
 604
 605 static void xprt_autoclose(struct work_struct *work)
 606 {
 607         struct rpc_xprt *xprt =
 608                 container_of(work, struct rpc_xprt, task_cleanup);
 609
 610         xprt->ops->close(xprt);
 611         clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
 612         xprt_release_write(xprt, NULL);
 613 }
 614
 615 /**
 616  * xprt_disconnect_done - mark a transport as disconnected
 617  * @xprt: transport to flag for disconnect
 618  *
 619  */
 620 void xprt_disconnect_done(struct rpc_xprt *xprt)
 621 {
 622         dprintk("RPC:       disconnected transport %p\n", xprt);
 623         spin_lock_bh(&xprt->transport_lock);
 624         xprt_clear_connected(xprt);
 625         xprt_wake_pending_tasks(xprt, -EAGAIN);
 626         spin_unlock_bh(&xprt->transport_lock);
 627 }
 628 EXPORT_SYMBOL_GPL(xprt_disconnect_done);
 629
 630 /**
 631  * xprt_force_disconnect - force a transport to disconnect
 632  * @xprt: transport to disconnect
 633  *
 634  */
 635 void xprt_force_disconnect(struct rpc_xprt *xprt)
 636 {
 637         /* Don't race with the test_bit() in xprt_clear_locked() */
 638         spin_lock_bh(&xprt->transport_lock);
 639         set_bit(XPRT_CLOSE_WAIT, &xprt->state);
 640         /* Try to schedule an autoclose RPC call */
 641         if (test_and_set_bit(XPRT_LOCKED, &xprt->state) == 0)
 642                 queue_work(rpciod_workqueue, &xprt->task_cleanup);
 643         xprt_wake_pending_tasks(xprt, -EAGAIN);
 644         spin_unlock_bh(&xprt->transport_lock);
 645 }
 646
 647 /**
 648  * xprt_conditional_disconnect - force a transport to disconnect
 649  * @xprt: transport to disconnect
 650  * @cookie: 'connection cookie'
 651  *
 652  * This attempts to break the connection if and only if 'cookie' matches
 653  * the current transport 'connection cookie'. It ensures that we don't
 654  * try to break the connection more than once when we need to retransmit
 655  * a batch of RPC requests.
 656  *
 657  */
 658 void xprt_conditional_disconnect(struct rpc_xprt *xprt, unsigned int cookie)
 659 {
 660         /* Don't race with the test_bit() in xprt_clear_locked() */
 661         spin_lock_bh(&xprt->transport_lock);
 662         if (cookie != xprt->connect_cookie)
 663                 goto out;
 664         if (test_bit(XPRT_CLOSING, &xprt->state) || !xprt_connected(xprt))
 665                 goto out;
 666         set_bit(XPRT_CLOSE_WAIT, &xprt->state);
 667         /* Try to schedule an autoclose RPC call */
 668         if (test_and_set_bit(XPRT_LOCKED, &xprt->state) == 0)
 669                 queue_work(rpciod_workqueue, &xprt->task_cleanup);
 670         xprt_wake_pending_tasks(xprt, -EAGAIN);
 671 out:
 672         spin_unlock_bh(&xprt->transport_lock);
 673 }
 674
 675 static void
 676 xprt_init_autodisconnect(unsigned long data)
 677 {
 678         struct rpc_xprt *xprt = (struct rpc_xprt *)data;
 679
 680         spin_lock(&xprt->transport_lock);
 681         if (!list_empty(&xprt->recv) || xprt->shutdown)
 682                 goto out_abort;
 683         if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
 684                 goto out_abort;
 685         spin_unlock(&xprt->transport_lock);
 686         set_bit(XPRT_CONNECTION_CLOSE, &xprt->state);
 687         queue_work(rpciod_workqueue, &xprt->task_cleanup);
 688         return;
 689 out_abort:
 690         spin_unlock(&xprt->transport_lock);
 691 }
 692
 693 /**
 694  * xprt_connect - schedule a transport connect operation
 695  * @task: RPC task that is requesting the connect
 696  *
 697  */
 698 void xprt_connect(struct rpc_task *task)
 699 {
 700         struct rpc_xprt *xprt = task->tk_xprt;
 701
 702         dprintk("RPC: %5u xprt_connect xprt %p %s connected\n", task->tk_pid,
 703                         xprt, (xprt_connected(xprt) ? "is" : "is not"));
 704
 705         if (!xprt_bound(xprt)) {
 706                 task->tk_status = -EAGAIN;
 707                 return;
 708         }
 709         if (!xprt_lock_write(xprt, task))
 710                 return;
 711
 712         if (test_and_clear_bit(XPRT_CLOSE_WAIT, &xprt->state))
 713                 xprt->ops->close(xprt);
 714
 715         if (xprt_connected(xprt))
 716                 xprt_release_write(xprt, task);
 717         else {
 718                 if (task->tk_rqstp)
 719                         task->tk_rqstp->rq_bytes_sent = 0;
 720
 721                 task->tk_timeout = task->tk_rqstp->rq_timeout;
 722                 rpc_sleep_on(&xprt->pending, task, xprt_connect_status);
 723
 724                 if (test_bit(XPRT_CLOSING, &xprt->state))
 725                         return;
 726                 if (xprt_test_and_set_connecting(xprt))
 727                         return;
 728                 xprt->stat.connect_start = jiffies;
 729                 xprt->ops->connect(task);
 730         }
 731 }
 732
 733 static void xprt_connect_status(struct rpc_task *task)
 734 {
 735         struct rpc_xprt *xprt = task->tk_xprt;
 736
 737         if (task->tk_status == 0) {
 738                 xprt->stat.connect_count++;
 739                 xprt->stat.connect_time += (long)jiffies - xprt->stat.connect_start;
 740                 dprintk("RPC: %5u xprt_connect_status: connection established\n",
 741                                 task->tk_pid);
 742                 return;
 743         }
 744
 745         switch (task->tk_status) {
 746         case -EAGAIN:
 747                 dprintk("RPC: %5u xprt_connect_status: retrying\n", task->tk_pid);
 748                 break;
 749         case -ETIMEDOUT:
 750                 dprintk("RPC: %5u xprt_connect_status: connect attempt timed "
 751                                 "out\n", task->tk_pid);
 752                 break;
 753         default:
 754                 dprintk("RPC: %5u xprt_connect_status: error %d connecting to "
 755                                 "server %s\n", task->tk_pid, -task->tk_status,
 756                                 task->tk_client->cl_server);
 757                 xprt_release_write(xprt, task);
 758                 task->tk_status = -EIO;
 759         }
 760 }
 761
 762 /**
 763  * xprt_lookup_rqst - find an RPC request corresponding to an XID
 764  * @xprt: transport on which the original request was transmitted
 765  * @xid: RPC XID of incoming reply
 766  *
 767  */
 768 struct rpc_rqst *xprt_lookup_rqst(struct rpc_xprt *xprt, __be32 xid)
 769 {
 770         struct rpc_rqst *entry;
 771
 772         list_for_each_entry(entry, &xprt->recv, rq_list)
 773                 if (entry->rq_xid == xid)
 774                         return entry;
 775
 776         dprintk("RPC:       xprt_lookup_rqst did not find xid %08x\n",
 777                         ntohl(xid));
 778         xprt->stat.bad_xids++;
 779         return NULL;
 780 }
 781 EXPORT_SYMBOL_GPL(xprt_lookup_rqst);
 782
 783 static void xprt_update_rtt(struct rpc_task *task)
 784 {
 785         struct rpc_rqst *req = task->tk_rqstp;
 786         struct rpc_rtt *rtt = task->tk_client->cl_rtt;
 787         unsigned timer = task->tk_msg.rpc_proc->p_timer;
 788         long m = usecs_to_jiffies(ktime_to_us(req->rq_rtt));
 789
 790         if (timer) {
 791                 if (req->rq_ntrans == 1)
 792                         rpc_update_rtt(rtt, timer, m);
 793                 rpc_set_timeo(rtt, timer, req->rq_ntrans - 1);
 794         }
 795 }
 796
 797 /**
 798  * xprt_complete_rqst - called when reply processing is complete
 799  * @task: RPC request that recently completed
 800  * @copied: actual number of bytes received from the transport
 801  *
 802  * Caller holds transport lock.
 803  */
 804 void xprt_complete_rqst(struct rpc_task *task, int copied)
 805 {
 806         struct rpc_rqst *req = task->tk_rqstp;
 807         struct rpc_xprt *xprt = req->rq_xprt;
 808
 809         dprintk("RPC: %5u xid %08x complete (%d bytes received)\n",
 810                         task->tk_pid, ntohl(req->rq_xid), copied);
 811
 812         xprt->stat.recvs++;
 813         req->rq_rtt = ktime_sub(ktime_get(), req->rq_xtime);
 814         if (xprt->ops->timer != NULL)
 815                 xprt_update_rtt(task);
 816
 817         list_del_init(&req->rq_list);
 818         req->rq_private_buf.len = copied;
 819         /* Ensure all writes are done before we update */
 820         /* req->rq_reply_bytes_recvd */
 821         smp_wmb();
 822         req->rq_reply_bytes_recvd = copied;
 823         rpc_wake_up_queued_task(&xprt->pending, task);
 824 }
 825 EXPORT_SYMBOL_GPL(xprt_complete_rqst);
 826
 827 static void xprt_timer(struct rpc_task *task)
 828 {
 829         struct rpc_rqst *req = task->tk_rqstp;
 830         struct rpc_xprt *xprt = req->rq_xprt;
 831
 832         if (task->tk_status != -ETIMEDOUT)
 833                 return;
 834         dprintk("RPC: %5u xprt_timer\n", task->tk_pid);
 835
 836         spin_lock_bh(&xprt->transport_lock);
 837         if (!req->rq_reply_bytes_recvd) {
 838                 if (xprt->ops->timer)
 839                         xprt->ops->timer(task);
 840         } else
 841                 task->tk_status = 0;
 842         spin_unlock_bh(&xprt->transport_lock);
 843 }
 844
 845 static inline int xprt_has_timer(struct rpc_xprt *xprt)
 846 {
 847         return xprt->idle_timeout != 0;
 848 }
 849
 850 /**
 851  * xprt_prepare_transmit - reserve the transport before sending a request
 852  * @task: RPC task about to send a request
 853  *
 854  */
 855 int xprt_prepare_transmit(struct rpc_task *task)
 856 {
 857         struct rpc_rqst *req = task->tk_rqstp;
 858         struct rpc_xprt *xprt = req->rq_xprt;
 859         int err = 0;
 860
 861         dprintk("RPC: %5u xprt_prepare_transmit\n", task->tk_pid);
 862
 863         spin_lock_bh(&xprt->transport_lock);
 864         if (req->rq_reply_bytes_recvd && !req->rq_bytes_sent) {
 865                 err = req->rq_reply_bytes_recvd;
 866                 goto out_unlock;
 867         }
 868         if (!xprt->ops->reserve_xprt(xprt, task))
 869                 err = -EAGAIN;
 870 out_unlock:
 871         spin_unlock_bh(&xprt->transport_lock);
 872         return err;
 873 }
 874
 875 void xprt_end_transmit(struct rpc_task *task)
 876 {
 877         xprt_release_write(task->tk_rqstp->rq_xprt, task);
 878 }
 879
 880 /**
 881  * xprt_transmit - send an RPC request on a transport
 882  * @task: controlling RPC task
 883  *
 884  * We have to copy the iovec because sendmsg fiddles with its contents.
 885  */
 886 void xprt_transmit(struct rpc_task *task)
 887 {
 888         struct rpc_rqst *req = task->tk_rqstp;
 889         struct rpc_xprt *xprt = req->rq_xprt;
 890         int status;
 891
 892         dprintk("RPC: %5u xprt_transmit(%u)\n", task->tk_pid, req->rq_slen);
 893
 894         if (!req->rq_reply_bytes_recvd) {
 895                 if (list_empty(&req->rq_list) && rpc_reply_expected(task)) {
 896                         /*
 897                          * Add to the list only if we're expecting a reply
 898                          */
 899                         spin_lock_bh(&xprt->transport_lock);
 900                         /* Update the softirq receive buffer */
 901                         memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
 902                                         sizeof(req->rq_private_buf));
 903                         /* Add request to the receive list */
 904                         list_add_tail(&req->rq_list, &xprt->recv);
 905                         spin_unlock_bh(&xprt->transport_lock);
 906                         xprt_reset_majortimeo(req);
 907                         /* Turn off autodisconnect */
 908                         del_singleshot_timer_sync(&xprt->timer);
 909                 }
 910         } else if (!req->rq_bytes_sent)
 911                 return;
 912
 913         req->rq_connect_cookie = xprt->connect_cookie;
 914         req->rq_xtime = ktime_get();
 915         status = xprt->ops->send_request(task);
 916         if (status != 0) {
 917                 task->tk_status = status;
 918                 return;
 919         }
 920
 921         dprintk("RPC: %5u xmit complete\n", task->tk_pid);
 922         task->tk_flags |= RPC_TASK_SENT;
 923         spin_lock_bh(&xprt->transport_lock);
 924
 925         xprt->ops->set_retrans_timeout(task);
 926
 927         xprt->stat.sends++;
 928         xprt->stat.req_u += xprt->stat.sends - xprt->stat.recvs;
 929         xprt->stat.bklog_u += xprt->backlog.qlen;
 930
 931         /* Don't race with disconnect */
 932         if (!xprt_connected(xprt))
 933                 task->tk_status = -ENOTCONN;
 934         else if (!req->rq_reply_bytes_recvd && rpc_reply_expected(task)) {
 935                 /*
 936                  * Sleep on the pending queue since
 937                  * we're expecting a reply.
 938                  */
 939                 rpc_sleep_on(&xprt->pending, task, xprt_timer);
 940         }
 941         spin_unlock_bh(&xprt->transport_lock);
 942 }
 943
 944 static struct rpc_rqst *xprt_dynamic_alloc_slot(struct rpc_xprt *xprt, gfp_t gfp_flags)
 945 {
 946         struct rpc_rqst *req = ERR_PTR(-EAGAIN);
 947
 948         if (!atomic_add_unless(&xprt->num_reqs, 1, xprt->max_reqs))
 949                 goto out;
 950         req = kzalloc(sizeof(struct rpc_rqst), gfp_flags);
 951         if (req != NULL)
 952                 goto out;
 953         atomic_dec(&xprt->num_reqs);
 954         req = ERR_PTR(-ENOMEM);
 955 out:
 956         return req;
 957 }
 958
 959 static bool xprt_dynamic_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
 960 {
 961         if (atomic_add_unless(&xprt->num_reqs, -1, xprt->min_reqs)) {
 962                 kfree(req);
 963                 return true;
 964         }
 965         return false;
 966 }
 967
 968 static void xprt_alloc_slot(struct rpc_task *task)
 969 {
 970         struct rpc_xprt *xprt = task->tk_xprt;
 971         struct rpc_rqst *req;
 972
 973         if (!list_empty(&xprt->free)) {
 974                 req = list_entry(xprt->free.next, struct rpc_rqst, rq_list);
 975                 list_del(&req->rq_list);
 976                 goto out_init_req;
 977         }
 978         req = xprt_dynamic_alloc_slot(xprt, GFP_NOWAIT);
 979         if (!IS_ERR(req))
 980                 goto out_init_req;
 981         switch (PTR_ERR(req)) {
 982         case -ENOMEM:
 983                 rpc_delay(task, HZ >> 2);
 984                 dprintk("RPC:       dynamic allocation of request slot "
 985                                 "failed! Retrying\n");
 986                 break;
 987         case -EAGAIN:
 988                 rpc_sleep_on(&xprt->backlog, task, NULL);
 989                 dprintk("RPC:       waiting for request slot\n");
 990         }
 991         task->tk_status = -EAGAIN;
 992         return;
 993 out_init_req:
 994         task->tk_status = 0;
 995         task->tk_rqstp = req;
 996         xprt_request_init(task, xprt);
 997 }
 998
 999 static void xprt_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
1000 {
1001         spin_lock(&xprt->reserve_lock);
1002         if (!xprt_dynamic_free_slot(xprt, req)) {
1003                 memset(req, 0, sizeof(*req));   /* mark unused */
1004                 list_add(&req->rq_list, &xprt->free);
1005         }
1006         rpc_wake_up_next(&xprt->backlog);
1007         spin_unlock(&xprt->reserve_lock);
1008 }
1009
1010 static void xprt_free_all_slots(struct rpc_xprt *xprt)
1011 {
1012         struct rpc_rqst *req;
1013         while (!list_empty(&xprt->free)) {
1014                 req = list_first_entry(&xprt->free, struct rpc_rqst, rq_list);
1015                 list_del(&req->rq_list);
1016                 kfree(req);
1017         }
1018 }
1019
1020 struct rpc_xprt *xprt_alloc(struct net *net, size_t size,
1021                 unsigned int num_prealloc,
1022                 unsigned int max_alloc)
1023 {
1024         struct rpc_xprt *xprt;
1025         struct rpc_rqst *req;
1026         int i;
1027
1028         xprt = kzalloc(size, GFP_KERNEL);
1029         if (xprt == NULL)
1030                 goto out;
1031
1032         xprt_init(xprt, net);
1033
1034         for (i = 0; i < num_prealloc; i++) {
1035                 req = kzalloc(sizeof(struct rpc_rqst), GFP_KERNEL);
1036                 if (!req)
1037                         break;
1038                 list_add(&req->rq_list, &xprt->free);
1039         }
1040         if (i < num_prealloc)
1041                 goto out_free;
1042         if (max_alloc > num_prealloc)
1043                 xprt->max_reqs = max_alloc;
1044         else
1045                 xprt->max_reqs = num_prealloc;
1046         xprt->min_reqs = num_prealloc;
1047         atomic_set(&xprt->num_reqs, num_prealloc);
1048
1049         return xprt;
1050
1051 out_free:
1052         xprt_free(xprt);
1053 out:
1054         return NULL;
1055 }
1056 EXPORT_SYMBOL_GPL(xprt_alloc);
1057
1058 void xprt_free(struct rpc_xprt *xprt)
1059 {
1060         put_net(xprt->xprt_net);
1061         xprt_free_all_slots(xprt);
1062         kfree(xprt);
1063 }
1064 EXPORT_SYMBOL_GPL(xprt_free);
1065
1066 /**
1067  * xprt_reserve - allocate an RPC request slot
1068  * @task: RPC task requesting a slot allocation
1069  *
1070  * If no more slots are available, place the task on the transport's
1071  * backlog queue.
1072  */
1073 void xprt_reserve(struct rpc_task *task)
1074 {
1075         struct rpc_xprt *xprt = task->tk_xprt;
1076
1077         task->tk_status = 0;
1078         if (task->tk_rqstp != NULL)
1079                 return;
1080
1081         /* Note: grabbing the xprt_lock_write() here is not strictly needed,
1082          * but ensures that we throttle new slot allocation if the transport
1083          * is congested (e.g. if reconnecting or if we're out of socket
1084          * write buffer space).
1085          */
1086         task->tk_timeout = 0;
1087         task->tk_status = -EAGAIN;
1088         if (!xprt_lock_write(xprt, task))
1089                 return;
1090
1091         spin_lock(&xprt->reserve_lock);
1092         xprt_alloc_slot(task);
1093         spin_unlock(&xprt->reserve_lock);
1094         xprt_release_write(xprt, task);
1095 }
1096
1097 static inline __be32 xprt_alloc_xid(struct rpc_xprt *xprt)
1098 {
1099         return (__force __be32)xprt->xid++;
1100 }
1101
1102 static inline void xprt_init_xid(struct rpc_xprt *xprt)
1103 {
1104         xprt->xid = net_random();
1105 }
1106
1107 static void xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt)
1108 {
1109         struct rpc_rqst *req = task->tk_rqstp;
1110
1111         INIT_LIST_HEAD(&req->rq_list);
1112         req->rq_timeout = task->tk_client->cl_timeout->to_initval;
1113         req->rq_task    = task;
1114         req->rq_xprt    = xprt;
1115         req->rq_buffer  = NULL;
1116         req->rq_xid     = xprt_alloc_xid(xprt);
1117         req->rq_release_snd_buf = NULL;
1118         xprt_reset_majortimeo(req);
1119         dprintk("RPC: %5u reserved req %p xid %08x\n", task->tk_pid,
1120                         req, ntohl(req->rq_xid));
1121 }
1122
1123 /**
1124  * xprt_release - release an RPC request slot
1125  * @task: task which is finished with the slot
1126  *
1127  */
1128 void xprt_release(struct rpc_task *task)
1129 {
1130         struct rpc_xprt *xprt;
1131         struct rpc_rqst *req;
1132
1133         if (!(req = task->tk_rqstp))
1134                 return;
1135
1136         xprt = req->rq_xprt;
1137         rpc_count_iostats(task);
1138         spin_lock_bh(&xprt->transport_lock);
1139         xprt->ops->release_xprt(xprt, task);
1140         if (xprt->ops->release_request)
1141                 xprt->ops->release_request(task);
1142         if (!list_empty(&req->rq_list))
1143                 list_del(&req->rq_list);
1144         xprt->last_used = jiffies;
1145         if (list_empty(&xprt->recv) && xprt_has_timer(xprt))
1146                 mod_timer(&xprt->timer,
1147                                 xprt->last_used + xprt->idle_timeout);
1148         spin_unlock_bh(&xprt->transport_lock);
1149         if (req->rq_buffer)
1150                 xprt->ops->buf_free(req->rq_buffer);
1151         if (req->rq_cred != NULL)
1152                 put_rpccred(req->rq_cred);
1153         task->tk_rqstp = NULL;
1154         if (req->rq_release_snd_buf)
1155                 req->rq_release_snd_buf(req);
1156
1157         dprintk("RPC: %5u release request %p\n", task->tk_pid, req);
1158         if (likely(!bc_prealloc(req)))
1159                 xprt_free_slot(xprt, req);
1160         else
1161                 xprt_free_bc_request(req);
1162 }
1163
1164 static void xprt_init(struct rpc_xprt *xprt, struct net *net)
1165 {
1166         atomic_set(&xprt->count, 1);
1167
1168         spin_lock_init(&xprt->transport_lock);
1169         spin_lock_init(&xprt->reserve_lock);
1170
1171         INIT_LIST_HEAD(&xprt->free);
1172         INIT_LIST_HEAD(&xprt->recv);
1173 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
1174         spin_lock_init(&xprt->bc_pa_lock);
1175         INIT_LIST_HEAD(&xprt->bc_pa_list);
1176 #endif /* CONFIG_SUNRPC_BACKCHANNEL */
1177
1178         xprt->last_used = jiffies;
1179         xprt->cwnd = RPC_INITCWND;
1180         xprt->bind_index = 0;
1181
1182         rpc_init_wait_queue(&xprt->binding, "xprt_binding");
1183         rpc_init_wait_queue(&xprt->pending, "xprt_pending");
1184         rpc_init_priority_wait_queue(&xprt->sending, "xprt_sending");
1185         rpc_init_priority_wait_queue(&xprt->backlog, "xprt_backlog");
1186
1187         xprt_init_xid(xprt);
1188
1189         xprt->xprt_net = get_net(net);
1190 }
1191
1192 /**
1193  * xprt_create_transport - create an RPC transport
1194  * @args: rpc transport creation arguments
1195  *
1196  */
1197 struct rpc_xprt *xprt_create_transport(struct xprt_create *args)
1198 {
1199         struct rpc_xprt *xprt;
1200         struct xprt_class *t;
1201
1202         spin_lock(&xprt_list_lock);
1203         list_for_each_entry(t, &xprt_list, list) {
1204                 if (t->ident == args->ident) {
1205                         spin_unlock(&xprt_list_lock);
1206                         goto found;
1207                 }
1208         }
1209         spin_unlock(&xprt_list_lock);
1210         printk(KERN_ERR "RPC: transport (%d) not supported\n", args->ident);
1211         return ERR_PTR(-EIO);
1212
1213 found:
1214         xprt = t->setup(args);
1215         if (IS_ERR(xprt)) {
1216                 dprintk("RPC:       xprt_create_transport: failed, %ld\n",
1217                                 -PTR_ERR(xprt));
1218                 goto out;
1219         }
1220         INIT_WORK(&xprt->task_cleanup, xprt_autoclose);
1221         if (xprt_has_timer(xprt))
1222                 setup_timer(&xprt->timer, xprt_init_autodisconnect,
1223                             (unsigned long)xprt);
1224         else
1225                 init_timer(&xprt->timer);
1226         dprintk("RPC:       created transport %p with %u slots\n", xprt,
1227                         xprt->max_reqs);
1228 out:
1229         return xprt;
1230 }
1231
1232 /**
1233  * xprt_destroy - destroy an RPC transport, killing off all requests.
1234  * @xprt: transport to destroy
1235  *
1236  */
1237 static void xprt_destroy(struct rpc_xprt *xprt)
1238 {
1239         dprintk("RPC:       destroying transport %p\n", xprt);
1240         xprt->shutdown = 1;
1241         del_timer_sync(&xprt->timer);
1242
1243         rpc_destroy_wait_queue(&xprt->binding);
1244         rpc_destroy_wait_queue(&xprt->pending);
1245         rpc_destroy_wait_queue(&xprt->sending);
1246         rpc_destroy_wait_queue(&xprt->backlog);
1247         cancel_work_sync(&xprt->task_cleanup);
1248         /*
1249          * Tear down transport state and free the rpc_xprt
1250          */
1251         xprt->ops->destroy(xprt);
1252 }
1253
1254 /**
1255  * xprt_put - release a reference to an RPC transport.
1256  * @xprt: pointer to the transport
1257  *
1258  */
1259 void xprt_put(struct rpc_xprt *xprt)
1260 {
1261         if (atomic_dec_and_test(&xprt->count))
1262                 xprt_destroy(xprt);
1263 }
1264
1265 /**
1266  * xprt_get - return a reference to an RPC transport.
1267  * @xprt: pointer to the transport
1268  *
1269  */
1270 struct rpc_xprt *xprt_get(struct rpc_xprt *xprt)
1271 {
1272         if (atomic_inc_not_zero(&xprt->count))
1273                 return xprt;
1274         return NULL;
1275 }