include/linux/sunrpc/svc.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * linux/include/linux/sunrpc/svc.h
   4  *
   5  * RPC server declarations.
   6  *
   7  * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
   8  */
   9
  10
  11 #ifndef SUNRPC_SVC_H
  12 #define SUNRPC_SVC_H
  13
  14 #include <linux/in.h>
  15 #include <linux/in6.h>
  16 #include <linux/sunrpc/types.h>
  17 #include <linux/sunrpc/xdr.h>
  18 #include <linux/sunrpc/auth.h>
  19 #include <linux/sunrpc/svcauth.h>
  20 #include <linux/lwq.h>
  21 #include <linux/wait.h>
  22 #include <linux/mm.h>
  23 #include <linux/pagevec.h>
  24 #include <linux/kthread.h>
  25
  26 /*
  27  *
  28  * RPC service thread pool.
  29  *
  30  * Pool of threads and temporary sockets.  Generally there is only
  31  * a single one of these per RPC service, but on NUMA machines those
  32  * services that can benefit from it (i.e. nfs but not lockd) will
  33  * have one pool per NUMA node.  This optimisation reduces cross-
  34  * node traffic on multi-node NUMA NFS servers.
  35  */
  36 struct svc_pool {
  37         unsigned int            sp_id;          /* pool id; also node id on NUMA */
  38         struct lwq              sp_xprts;       /* pending transports */
  39         unsigned int            sp_nrthreads;   /* # of threads in pool */
  40         struct list_head        sp_all_threads; /* all server threads */
  41         struct llist_head       sp_idle_threads; /* idle server threads */
  42
  43         /* statistics on pool operation */
  44         struct percpu_counter   sp_messages_arrived;
  45         struct percpu_counter   sp_sockets_queued;
  46         struct percpu_counter   sp_threads_woken;
  47
  48         unsigned long           sp_flags;
  49 } ____cacheline_aligned_in_smp;
  50
  51 /* bits for sp_flags */
  52 enum {
  53         SP_TASK_PENDING,        /* still work to do even if no xprt is queued */
  54         SP_NEED_VICTIM,         /* One thread needs to agree to exit */
  55         SP_VICTIM_REMAINS,      /* One thread needs to actually exit */
  56 };
  57
  58
  59 /*
  60  * RPC service.
  61  *
  62  * An RPC service is a ``daemon,'' possibly multithreaded, which
  63  * receives and processes incoming RPC messages.
  64  * It has one or more transport sockets associated with it, and maintains
  65  * a list of idle threads waiting for input.
  66  *
  67  * We currently do not support more than one RPC program per daemon.
  68  */
  69 struct svc_serv {
  70         struct svc_program *    sv_programs;    /* RPC programs */
  71         struct svc_stat *       sv_stats;       /* RPC statistics */
  72         spinlock_t              sv_lock;
  73         unsigned int            sv_nprogs;      /* Number of sv_programs */
  74         unsigned int            sv_nrthreads;   /* # of server threads */
  75         unsigned int            sv_maxconn;     /* max connections allowed or
  76                                                  * '0' causing max to be based
  77                                                  * on number of threads. */
  78
  79         unsigned int            sv_max_payload; /* datagram payload size */
  80         unsigned int            sv_max_mesg;    /* max_payload + 1 page for overheads */
  81         unsigned int            sv_xdrsize;     /* XDR buffer size */
  82         struct list_head        sv_permsocks;   /* all permanent sockets */
  83         struct list_head        sv_tempsocks;   /* all temporary sockets */
  84         int                     sv_tmpcnt;      /* count of temporary sockets */
  85         struct timer_list       sv_temptimer;   /* timer for aging temporary sockets */
  86
  87         char *                  sv_name;        /* service name */
  88
  89         unsigned int            sv_nrpools;     /* number of thread pools */
  90         bool                    sv_is_pooled;   /* is this a pooled service? */
  91         struct svc_pool *       sv_pools;       /* array of thread pools */
  92         int                     (*sv_threadfn)(void *data);
  93
  94 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
  95         struct lwq              sv_cb_list;     /* queue for callback requests
  96                                                  * that arrive over the same
  97                                                  * connection */
  98         bool                    sv_bc_enabled;  /* service uses backchannel */
  99 #endif /* CONFIG_SUNRPC_BACKCHANNEL */
 100 };
 101
 102 /* This is used by pool_stats to find and lock an svc */
 103 struct svc_info {
 104         struct svc_serv         *serv;
 105         struct mutex            *mutex;
 106 };
 107
 108 void svc_destroy(struct svc_serv **svcp);
 109
 110 /*
 111  * Maximum payload size supported by a kernel RPC server.
 112  * This is use to determine the max number of pages nfsd is
 113  * willing to return in a single READ operation.
 114  *
 115  * These happen to all be powers of 2, which is not strictly
 116  * necessary but helps enforce the real limitation, which is
 117  * that they should be multiples of PAGE_SIZE.
 118  *
 119  * For UDP transports, a block plus NFS,RPC, and UDP headers
 120  * has to fit into the IP datagram limit of 64K.  The largest
 121  * feasible number for all known page sizes is probably 48K,
 122  * but we choose 32K here.  This is the same as the historical
 123  * Linux limit; someone who cares more about NFS/UDP performance
 124  * can test a larger number.
 125  *
 126  * For TCP transports we have more freedom.  A size of 1MB is
 127  * chosen to match the client limit.  Other OSes are known to
 128  * have larger limits, but those numbers are probably beyond
 129  * the point of diminishing returns.
 130  */
 131 #define RPCSVC_MAXPAYLOAD       (1*1024*1024u)
 132 #define RPCSVC_MAXPAYLOAD_TCP   RPCSVC_MAXPAYLOAD
 133 #define RPCSVC_MAXPAYLOAD_UDP   (32*1024u)
 134
 135 extern u32 svc_max_payload(const struct svc_rqst *rqstp);
 136
 137 /*
 138  * RPC Requests and replies are stored in one or more pages.
 139  * We maintain an array of pages for each server thread.
 140  * Requests are copied into these pages as they arrive.  Remaining
 141  * pages are available to write the reply into.
 142  *
 143  * Pages are sent using ->sendmsg with MSG_SPLICE_PAGES so each server thread
 144  * needs to allocate more to replace those used in sending.  To help keep track
 145  * of these pages we have a receive list where all pages initialy live, and a
 146  * send list where pages are moved to when there are to be part of a reply.
 147  *
 148  * We use xdr_buf for holding responses as it fits well with NFS
 149  * read responses (that have a header, and some data pages, and possibly
 150  * a tail) and means we can share some client side routines.
 151  *
 152  * The xdr_buf.head kvec always points to the first page in the rq_*pages
 153  * list.  The xdr_buf.pages pointer points to the second page on that
 154  * list.  xdr_buf.tail points to the end of the first page.
 155  * This assumes that the non-page part of an rpc reply will fit
 156  * in a page - NFSd ensures this.  lockd also has no trouble.
 157  *
 158  * Each request/reply pair can have at most one "payload", plus two pages,
 159  * one for the request, and one for the reply.
 160  * We using ->sendfile to return read data, we might need one extra page
 161  * if the request is not page-aligned.  So add another '1'.
 162  */
 163 #define RPCSVC_MAXPAGES         ((RPCSVC_MAXPAYLOAD+PAGE_SIZE-1)/PAGE_SIZE \
 164                                 + 2 + 1)
 165
 166 /*
 167  * The context of a single thread, including the request currently being
 168  * processed.
 169  */
 170 struct svc_rqst {
 171         struct list_head        rq_all;         /* all threads list */
 172         struct llist_node       rq_idle;        /* On the idle list */
 173         struct rcu_head         rq_rcu_head;    /* for RCU deferred kfree */
 174         struct svc_xprt *       rq_xprt;        /* transport ptr */
 175
 176         struct sockaddr_storage rq_addr;        /* peer address */
 177         size_t                  rq_addrlen;
 178         struct sockaddr_storage rq_daddr;       /* dest addr of request
 179                                                  *  - reply from here */
 180         size_t                  rq_daddrlen;
 181
 182         struct svc_serv *       rq_server;      /* RPC service definition */
 183         struct svc_pool *       rq_pool;        /* thread pool */
 184         const struct svc_procedure *rq_procinfo;/* procedure info */
 185         struct auth_ops *       rq_authop;      /* authentication flavour */
 186         struct svc_cred         rq_cred;        /* auth info */
 187         void *                  rq_xprt_ctxt;   /* transport specific context ptr */
 188         struct svc_deferred_req*rq_deferred;    /* deferred request we are replaying */
 189
 190         struct xdr_buf          rq_arg;
 191         struct xdr_stream       rq_arg_stream;
 192         struct xdr_stream       rq_res_stream;
 193         struct page             *rq_scratch_page;
 194         struct xdr_buf          rq_res;
 195         struct page             *rq_pages[RPCSVC_MAXPAGES + 1];
 196         struct page *           *rq_respages;   /* points into rq_pages */
 197         struct page *           *rq_next_page; /* next reply page to use */
 198         struct page *           *rq_page_end;  /* one past the last page */
 199
 200         struct folio_batch      rq_fbatch;
 201         struct kvec             rq_vec[RPCSVC_MAXPAGES]; /* generally useful.. */
 202         struct bio_vec          rq_bvec[RPCSVC_MAXPAGES];
 203
 204         __be32                  rq_xid;         /* transmission id */
 205         u32                     rq_prog;        /* program number */
 206         u32                     rq_vers;        /* program version */
 207         u32                     rq_proc;        /* procedure number */
 208         u32                     rq_prot;        /* IP protocol */
 209         int                     rq_cachetype;   /* catering to nfsd */
 210         unsigned long           rq_flags;       /* flags field */
 211         ktime_t                 rq_qtime;       /* enqueue time */
 212
 213         void *                  rq_argp;        /* decoded arguments */
 214         void *                  rq_resp;        /* xdr'd results */
 215         __be32                  *rq_accept_statp;
 216         void *                  rq_auth_data;   /* flavor-specific data */
 217         __be32                  rq_auth_stat;   /* authentication status */
 218         int                     rq_auth_slack;  /* extra space xdr code
 219                                                  * should leave in head
 220                                                  * for krb5i, krb5p.
 221                                                  */
 222         int                     rq_reserved;    /* space on socket outq
 223                                                  * reserved for this request
 224                                                  */
 225         ktime_t                 rq_stime;       /* start time */
 226
 227         struct cache_req        rq_chandle;     /* handle passed to caches for
 228                                                  * request delaying
 229                                                  */
 230         /* Catering to nfsd */
 231         struct auth_domain *    rq_client;      /* RPC peer info */
 232         struct auth_domain *    rq_gssclient;   /* "gss/"-style peer info */
 233         struct task_struct      *rq_task;       /* service thread */
 234         struct net              *rq_bc_net;     /* pointer to backchannel's
 235                                                  * net namespace
 236                                                  */
 237
 238         int                     rq_err;         /* Thread sets this to inidicate
 239                                                  * initialisation success.
 240                                                  */
 241
 242         unsigned long   bc_to_initval;
 243         unsigned int    bc_to_retries;
 244         void **                 rq_lease_breaker; /* The v4 client breaking a lease */
 245         unsigned int            rq_status_counter; /* RPC processing counter */
 246 };
 247
 248 /* bits for rq_flags */
 249 enum {
 250         RQ_SECURE,              /* secure port */
 251         RQ_LOCAL,               /* local request */
 252         RQ_USEDEFERRAL,         /* use deferral */
 253         RQ_DROPME,              /* drop current reply */
 254         RQ_VICTIM,              /* Have agreed to shut down */
 255         RQ_DATA,                /* request has data */
 256 };
 257
 258 #define SVC_NET(rqst) (rqst->rq_xprt ? rqst->rq_xprt->xpt_net : rqst->rq_bc_net)
 259
 260 /*
 261  * Rigorous type checking on sockaddr type conversions
 262  */
 263 static inline struct sockaddr_in *svc_addr_in(const struct svc_rqst *rqst)
 264 {
 265         return (struct sockaddr_in *) &rqst->rq_addr;
 266 }
 267
 268 static inline struct sockaddr_in6 *svc_addr_in6(const struct svc_rqst *rqst)
 269 {
 270         return (struct sockaddr_in6 *) &rqst->rq_addr;
 271 }
 272
 273 static inline struct sockaddr *svc_addr(const struct svc_rqst *rqst)
 274 {
 275         return (struct sockaddr *) &rqst->rq_addr;
 276 }
 277
 278 static inline struct sockaddr_in *svc_daddr_in(const struct svc_rqst *rqst)
 279 {
 280         return (struct sockaddr_in *) &rqst->rq_daddr;
 281 }
 282
 283 static inline struct sockaddr_in6 *svc_daddr_in6(const struct svc_rqst *rqst)
 284 {
 285         return (struct sockaddr_in6 *) &rqst->rq_daddr;
 286 }
 287
 288 static inline struct sockaddr *svc_daddr(const struct svc_rqst *rqst)
 289 {
 290         return (struct sockaddr *) &rqst->rq_daddr;
 291 }
 292
 293 /**
 294  * svc_thread_should_stop - check if this thread should stop
 295  * @rqstp: the thread that might need to stop
 296  *
 297  * To stop an svc thread, the pool flags SP_NEED_VICTIM and SP_VICTIM_REMAINS
 298  * are set.  The first thread which sees SP_NEED_VICTIM clears it, becoming
 299  * the victim using this function.  It should then promptly call
 300  * svc_exit_thread() to complete the process, clearing SP_VICTIM_REMAINS
 301  * so the task waiting for a thread to exit can wake and continue.
 302  *
 303  * Return values:
 304  *   %true: caller should invoke svc_exit_thread()
 305  *   %false: caller should do nothing
 306  */
 307 static inline bool svc_thread_should_stop(struct svc_rqst *rqstp)
 308 {
 309         if (test_and_clear_bit(SP_NEED_VICTIM, &rqstp->rq_pool->sp_flags))
 310                 set_bit(RQ_VICTIM, &rqstp->rq_flags);
 311
 312         return test_bit(RQ_VICTIM, &rqstp->rq_flags);
 313 }
 314
 315 /**
 316  * svc_thread_init_status - report whether thread has initialised successfully
 317  * @rqstp: the thread in question
 318  * @err: errno code
 319  *
 320  * After performing any initialisation that could fail, and before starting
 321  * normal work, each sunrpc svc_thread must call svc_thread_init_status()
 322  * with an appropriate error, or zero.
 323  *
 324  * If zero is passed, the thread is ready and must continue until
 325  * svc_thread_should_stop() returns true.  If a non-zero error is passed
 326  * the call will not return - the thread will exit.
 327  */
 328 static inline void svc_thread_init_status(struct svc_rqst *rqstp, int err)
 329 {
 330         rqstp->rq_err = err;
 331         /* memory barrier ensures assignment to error above is visible before
 332          * waitqueue_active() test below completes.
 333          */
 334         smp_mb();
 335         wake_up_var(&rqstp->rq_err);
 336         if (err)
 337                 kthread_exit(1);
 338 }
 339
 340 struct svc_deferred_req {
 341         u32                     prot;   /* protocol (UDP or TCP) */
 342         struct svc_xprt         *xprt;
 343         struct sockaddr_storage addr;   /* where reply must go */
 344         size_t                  addrlen;
 345         struct sockaddr_storage daddr;  /* where reply must come from */
 346         size_t                  daddrlen;
 347         void                    *xprt_ctxt;
 348         struct cache_deferred_req handle;
 349         int                     argslen;
 350         __be32                  args[];
 351 };
 352
 353 struct svc_process_info {
 354         union {
 355                 int  (*dispatch)(struct svc_rqst *rqstp);
 356                 struct {
 357                         unsigned int lovers;
 358                         unsigned int hivers;
 359                 } mismatch;
 360         };
 361 };
 362
 363 /*
 364  * RPC program - an array of these can use the same transport endpoint
 365  */
 366 struct svc_program {
 367         u32                     pg_prog;        /* program number */
 368         unsigned int            pg_lovers;      /* lowest version */
 369         unsigned int            pg_hivers;      /* highest version */
 370         unsigned int            pg_nvers;       /* number of versions */
 371         const struct svc_version **pg_vers;     /* version array */
 372         char *                  pg_name;        /* service name */
 373         char *                  pg_class;       /* class name: services sharing authentication */
 374         enum svc_auth_status    (*pg_authenticate)(struct svc_rqst *rqstp);
 375         __be32                  (*pg_init_request)(struct svc_rqst *,
 376                                                    const struct svc_program *,
 377                                                    struct svc_process_info *);
 378         int                     (*pg_rpcbind_set)(struct net *net,
 379                                                   const struct svc_program *,
 380                                                   u32 version, int family,
 381                                                   unsigned short proto,
 382                                                   unsigned short port);
 383 };
 384
 385 /*
 386  * RPC program version
 387  */
 388 struct svc_version {
 389         u32                     vs_vers;        /* version number */
 390         u32                     vs_nproc;       /* number of procedures */
 391         const struct svc_procedure *vs_proc;    /* per-procedure info */
 392         unsigned long __percpu  *vs_count;      /* call counts */
 393         u32                     vs_xdrsize;     /* xdrsize needed for this version */
 394
 395         /* Don't register with rpcbind */
 396         bool                    vs_hidden;
 397
 398         /* Don't care if the rpcbind registration fails */
 399         bool                    vs_rpcb_optnl;
 400
 401         /* Need xprt with congestion control */
 402         bool                    vs_need_cong_ctrl;
 403
 404         /* Dispatch function */
 405         int                     (*vs_dispatch)(struct svc_rqst *rqstp);
 406 };
 407
 408 /*
 409  * RPC procedure info
 410  */
 411 struct svc_procedure {
 412         /* process the request: */
 413         __be32                  (*pc_func)(struct svc_rqst *);
 414         /* XDR decode args: */
 415         bool                    (*pc_decode)(struct svc_rqst *rqstp,
 416                                              struct xdr_stream *xdr);
 417         /* XDR encode result: */
 418         bool                    (*pc_encode)(struct svc_rqst *rqstp,
 419                                              struct xdr_stream *xdr);
 420         /* XDR free result: */
 421         void                    (*pc_release)(struct svc_rqst *);
 422         unsigned int            pc_argsize;     /* argument struct size */
 423         unsigned int            pc_argzero;     /* how much of argument to clear */
 424         unsigned int            pc_ressize;     /* result struct size */
 425         unsigned int            pc_cachetype;   /* cache info (NFS) */
 426         unsigned int            pc_xdrressize;  /* maximum size of XDR reply */
 427         const char *            pc_name;        /* for display */
 428 };
 429
 430 /*
 431  * Function prototypes.
 432  */
 433 int sunrpc_set_pool_mode(const char *val);
 434 int sunrpc_get_pool_mode(char *val, size_t size);
 435 void svc_rpcb_cleanup(struct svc_serv *serv, struct net *net);
 436 int svc_bind(struct svc_serv *serv, struct net *net);
 437 struct svc_serv *svc_create(struct svc_program *, unsigned int,
 438                             int (*threadfn)(void *data));
 439 bool               svc_rqst_replace_page(struct svc_rqst *rqstp,
 440                                          struct page *page);
 441 void               svc_rqst_release_pages(struct svc_rqst *rqstp);
 442 void               svc_exit_thread(struct svc_rqst *);
 443 struct svc_serv *  svc_create_pooled(struct svc_program *prog,
 444                                      unsigned int nprog,
 445                                      struct svc_stat *stats,
 446                                      unsigned int bufsize,
 447                                      int (*threadfn)(void *data));
 448 int                svc_set_num_threads(struct svc_serv *, struct svc_pool *, int);
 449 int                svc_pool_stats_open(struct svc_info *si, struct file *file);
 450 void               svc_process(struct svc_rqst *rqstp);
 451 void               svc_process_bc(struct rpc_rqst *req, struct svc_rqst *rqstp);
 452 int                svc_register(const struct svc_serv *, struct net *, const int,
 453                                 const unsigned short, const unsigned short);
 454
 455 void               svc_wake_up(struct svc_serv *);
 456 void               svc_reserve(struct svc_rqst *rqstp, int space);
 457 void               svc_pool_wake_idle_thread(struct svc_pool *pool);
 458 struct svc_pool   *svc_pool_for_cpu(struct svc_serv *serv);
 459 char *             svc_print_addr(struct svc_rqst *, char *, size_t);
 460 const char *       svc_proc_name(const struct svc_rqst *rqstp);
 461 int                svc_encode_result_payload(struct svc_rqst *rqstp,
 462                                              unsigned int offset,
 463                                              unsigned int length);
 464 unsigned int       svc_fill_write_vector(struct svc_rqst *rqstp,
 465                                          struct xdr_buf *payload);
 466 char              *svc_fill_symlink_pathname(struct svc_rqst *rqstp,
 467                                              struct kvec *first, void *p,
 468                                              size_t total);
 469 __be32             svc_generic_init_request(struct svc_rqst *rqstp,
 470                                             const struct svc_program *progp,
 471                                             struct svc_process_info *procinfo);
 472 int                svc_generic_rpcbind_set(struct net *net,
 473                                            const struct svc_program *progp,
 474                                            u32 version, int family,
 475                                            unsigned short proto,
 476                                            unsigned short port);
 477
 478 #define RPC_MAX_ADDRBUFLEN      (63U)
 479
 480 /*
 481  * When we want to reduce the size of the reserved space in the response
 482  * buffer, we need to take into account the size of any checksum data that
 483  * may be at the end of the packet. This is difficult to determine exactly
 484  * for all cases without actually generating the checksum, so we just use a
 485  * static value.
 486  */
 487 static inline void svc_reserve_auth(struct svc_rqst *rqstp, int space)
 488 {
 489         svc_reserve(rqstp, space + rqstp->rq_auth_slack);
 490 }
 491
 492 /**
 493  * svcxdr_init_decode - Prepare an xdr_stream for Call decoding
 494  * @rqstp: controlling server RPC transaction context
 495  *
 496  */
 497 static inline void svcxdr_init_decode(struct svc_rqst *rqstp)
 498 {
 499         struct xdr_stream *xdr = &rqstp->rq_arg_stream;
 500         struct xdr_buf *buf = &rqstp->rq_arg;
 501         struct kvec *argv = buf->head;
 502
 503         WARN_ON(buf->len != buf->head->iov_len + buf->page_len + buf->tail->iov_len);
 504         buf->len = buf->head->iov_len + buf->page_len + buf->tail->iov_len;
 505
 506         xdr_init_decode(xdr, buf, argv->iov_base, NULL);
 507         xdr_set_scratch_page(xdr, rqstp->rq_scratch_page);
 508 }
 509
 510 /**
 511  * svcxdr_init_encode - Prepare an xdr_stream for svc Reply encoding
 512  * @rqstp: controlling server RPC transaction context
 513  *
 514  */
 515 static inline void svcxdr_init_encode(struct svc_rqst *rqstp)
 516 {
 517         struct xdr_stream *xdr = &rqstp->rq_res_stream;
 518         struct xdr_buf *buf = &rqstp->rq_res;
 519         struct kvec *resv = buf->head;
 520
 521         xdr_reset_scratch_buffer(xdr);
 522
 523         xdr->buf = buf;
 524         xdr->iov = resv;
 525         xdr->p   = resv->iov_base + resv->iov_len;
 526         xdr->end = resv->iov_base + PAGE_SIZE;
 527         buf->len = resv->iov_len;
 528         xdr->page_ptr = buf->pages - 1;
 529         buf->buflen = PAGE_SIZE * (rqstp->rq_page_end - buf->pages);
 530         xdr->rqst = NULL;
 531 }
 532
 533 /**
 534  * svcxdr_encode_opaque_pages - Insert pages into an xdr_stream
 535  * @xdr: xdr_stream to be updated
 536  * @pages: array of pages to insert
 537  * @base: starting offset of first data byte in @pages
 538  * @len: number of data bytes in @pages to insert
 539  *
 540  * After the @pages are added, the tail iovec is instantiated pointing
 541  * to end of the head buffer, and the stream is set up to encode
 542  * subsequent items into the tail.
 543  */
 544 static inline void svcxdr_encode_opaque_pages(struct svc_rqst *rqstp,
 545                                               struct xdr_stream *xdr,
 546                                               struct page **pages,
 547                                               unsigned int base,
 548                                               unsigned int len)
 549 {
 550         xdr_write_pages(xdr, pages, base, len);
 551         xdr->page_ptr = rqstp->rq_next_page - 1;
 552 }
 553
 554 /**
 555  * svcxdr_set_auth_slack -
 556  * @rqstp: RPC transaction
 557  * @slack: buffer space to reserve for the transaction's security flavor
 558  *
 559  * Set the request's slack space requirement, and set aside that much
 560  * space in the rqstp's rq_res.head for use when the auth wraps the Reply.
 561  */
 562 static inline void svcxdr_set_auth_slack(struct svc_rqst *rqstp, int slack)
 563 {
 564         struct xdr_stream *xdr = &rqstp->rq_res_stream;
 565         struct xdr_buf *buf = &rqstp->rq_res;
 566         struct kvec *resv = buf->head;
 567
 568         rqstp->rq_auth_slack = slack;
 569
 570         xdr->end -= XDR_QUADLEN(slack);
 571         buf->buflen -= rqstp->rq_auth_slack;
 572
 573         WARN_ON(xdr->iov != resv);
 574         WARN_ON(xdr->p > xdr->end);
 575 }
 576
 577 /**
 578  * svcxdr_set_accept_stat - Reserve space for the accept_stat field
 579  * @rqstp: RPC transaction context
 580  *
 581  * Return values:
 582  *   %true: Success
 583  *   %false: No response buffer space was available
 584  */
 585 static inline bool svcxdr_set_accept_stat(struct svc_rqst *rqstp)
 586 {
 587         struct xdr_stream *xdr = &rqstp->rq_res_stream;
 588
 589         rqstp->rq_accept_statp = xdr_reserve_space(xdr, XDR_UNIT);
 590         if (unlikely(!rqstp->rq_accept_statp))
 591                 return false;
 592         *rqstp->rq_accept_statp = rpc_success;
 593         return true;
 594 }
 595
 596 #endif /* SUNRPC_SVC_H */