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