xref: /linux/net/sunrpc/svc.c (revision b454cc6636d254fbf6049b73e9560aee76fb04a3)
1 /*
2  * linux/net/sunrpc/svc.c
3  *
4  * High-level RPC service routines
5  *
6  * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
7  *
8  * Multiple threads pools and NUMAisation
9  * Copyright (c) 2006 Silicon Graphics, Inc.
10  * by Greg Banks <gnb@melbourne.sgi.com>
11  */
12 
13 #include <linux/linkage.h>
14 #include <linux/sched.h>
15 #include <linux/errno.h>
16 #include <linux/net.h>
17 #include <linux/in.h>
18 #include <linux/mm.h>
19 #include <linux/interrupt.h>
20 #include <linux/module.h>
21 
22 #include <linux/sunrpc/types.h>
23 #include <linux/sunrpc/xdr.h>
24 #include <linux/sunrpc/stats.h>
25 #include <linux/sunrpc/svcsock.h>
26 #include <linux/sunrpc/clnt.h>
27 
28 #define RPCDBG_FACILITY	RPCDBG_SVCDSP
29 
30 /*
31  * Mode for mapping cpus to pools.
32  */
33 enum {
34 	SVC_POOL_NONE = -1,	/* uninitialised, choose one of the others */
35 	SVC_POOL_GLOBAL,	/* no mapping, just a single global pool
36 				 * (legacy & UP mode) */
37 	SVC_POOL_PERCPU,	/* one pool per cpu */
38 	SVC_POOL_PERNODE	/* one pool per numa node */
39 };
40 
41 /*
42  * Structure for mapping cpus to pools and vice versa.
43  * Setup once during sunrpc initialisation.
44  */
45 static struct svc_pool_map {
46 	int mode;			/* Note: int not enum to avoid
47 					 * warnings about "enumeration value
48 					 * not handled in switch" */
49 	unsigned int npools;
50 	unsigned int *pool_to;		/* maps pool id to cpu or node */
51 	unsigned int *to_pool;		/* maps cpu or node to pool id */
52 } svc_pool_map = {
53 	.mode = SVC_POOL_NONE
54 };
55 
56 
57 /*
58  * Detect best pool mapping mode heuristically,
59  * according to the machine's topology.
60  */
61 static int
62 svc_pool_map_choose_mode(void)
63 {
64 	unsigned int node;
65 
66 	if (num_online_nodes() > 1) {
67 		/*
68 		 * Actually have multiple NUMA nodes,
69 		 * so split pools on NUMA node boundaries
70 		 */
71 		return SVC_POOL_PERNODE;
72 	}
73 
74 	node = any_online_node(node_online_map);
75 	if (nr_cpus_node(node) > 2) {
76 		/*
77 		 * Non-trivial SMP, or CONFIG_NUMA on
78 		 * non-NUMA hardware, e.g. with a generic
79 		 * x86_64 kernel on Xeons.  In this case we
80 		 * want to divide the pools on cpu boundaries.
81 		 */
82 		return SVC_POOL_PERCPU;
83 	}
84 
85 	/* default: one global pool */
86 	return SVC_POOL_GLOBAL;
87 }
88 
89 /*
90  * Allocate the to_pool[] and pool_to[] arrays.
91  * Returns 0 on success or an errno.
92  */
93 static int
94 svc_pool_map_alloc_arrays(struct svc_pool_map *m, unsigned int maxpools)
95 {
96 	m->to_pool = kcalloc(maxpools, sizeof(unsigned int), GFP_KERNEL);
97 	if (!m->to_pool)
98 		goto fail;
99 	m->pool_to = kcalloc(maxpools, sizeof(unsigned int), GFP_KERNEL);
100 	if (!m->pool_to)
101 		goto fail_free;
102 
103 	return 0;
104 
105 fail_free:
106 	kfree(m->to_pool);
107 fail:
108 	return -ENOMEM;
109 }
110 
111 /*
112  * Initialise the pool map for SVC_POOL_PERCPU mode.
113  * Returns number of pools or <0 on error.
114  */
115 static int
116 svc_pool_map_init_percpu(struct svc_pool_map *m)
117 {
118 	unsigned int maxpools = highest_possible_processor_id()+1;
119 	unsigned int pidx = 0;
120 	unsigned int cpu;
121 	int err;
122 
123 	err = svc_pool_map_alloc_arrays(m, maxpools);
124 	if (err)
125 		return err;
126 
127 	for_each_online_cpu(cpu) {
128 		BUG_ON(pidx > maxpools);
129 		m->to_pool[cpu] = pidx;
130 		m->pool_to[pidx] = cpu;
131 		pidx++;
132 	}
133 	/* cpus brought online later all get mapped to pool0, sorry */
134 
135 	return pidx;
136 };
137 
138 
139 /*
140  * Initialise the pool map for SVC_POOL_PERNODE mode.
141  * Returns number of pools or <0 on error.
142  */
143 static int
144 svc_pool_map_init_pernode(struct svc_pool_map *m)
145 {
146 	unsigned int maxpools = highest_possible_node_id()+1;
147 	unsigned int pidx = 0;
148 	unsigned int node;
149 	int err;
150 
151 	err = svc_pool_map_alloc_arrays(m, maxpools);
152 	if (err)
153 		return err;
154 
155 	for_each_node_with_cpus(node) {
156 		/* some architectures (e.g. SN2) have cpuless nodes */
157 		BUG_ON(pidx > maxpools);
158 		m->to_pool[node] = pidx;
159 		m->pool_to[pidx] = node;
160 		pidx++;
161 	}
162 	/* nodes brought online later all get mapped to pool0, sorry */
163 
164 	return pidx;
165 }
166 
167 
168 /*
169  * Build the global map of cpus to pools and vice versa.
170  */
171 static unsigned int
172 svc_pool_map_init(void)
173 {
174 	struct svc_pool_map *m = &svc_pool_map;
175 	int npools = -1;
176 
177 	if (m->mode != SVC_POOL_NONE)
178 		return m->npools;
179 
180 	m->mode = svc_pool_map_choose_mode();
181 
182 	switch (m->mode) {
183 	case SVC_POOL_PERCPU:
184 		npools = svc_pool_map_init_percpu(m);
185 		break;
186 	case SVC_POOL_PERNODE:
187 		npools = svc_pool_map_init_pernode(m);
188 		break;
189 	}
190 
191 	if (npools < 0) {
192 		/* default, or memory allocation failure */
193 		npools = 1;
194 		m->mode = SVC_POOL_GLOBAL;
195 	}
196 	m->npools = npools;
197 
198 	return m->npools;
199 }
200 
201 /*
202  * Set the current thread's cpus_allowed mask so that it
203  * will only run on cpus in the given pool.
204  *
205  * Returns 1 and fills in oldmask iff a cpumask was applied.
206  */
207 static inline int
208 svc_pool_map_set_cpumask(unsigned int pidx, cpumask_t *oldmask)
209 {
210 	struct svc_pool_map *m = &svc_pool_map;
211 	unsigned int node; /* or cpu */
212 
213 	/*
214 	 * The caller checks for sv_nrpools > 1, which
215 	 * implies that we've been initialized and the
216 	 * map mode is not NONE.
217 	 */
218 	BUG_ON(m->mode == SVC_POOL_NONE);
219 
220 	switch (m->mode)
221 	{
222 	default:
223 		return 0;
224 	case SVC_POOL_PERCPU:
225 		node = m->pool_to[pidx];
226 		*oldmask = current->cpus_allowed;
227 		set_cpus_allowed(current, cpumask_of_cpu(node));
228 		return 1;
229 	case SVC_POOL_PERNODE:
230 		node = m->pool_to[pidx];
231 		*oldmask = current->cpus_allowed;
232 		set_cpus_allowed(current, node_to_cpumask(node));
233 		return 1;
234 	}
235 }
236 
237 /*
238  * Use the mapping mode to choose a pool for a given CPU.
239  * Used when enqueueing an incoming RPC.  Always returns
240  * a non-NULL pool pointer.
241  */
242 struct svc_pool *
243 svc_pool_for_cpu(struct svc_serv *serv, int cpu)
244 {
245 	struct svc_pool_map *m = &svc_pool_map;
246 	unsigned int pidx = 0;
247 
248 	/*
249 	 * SVC_POOL_NONE happens in a pure client when
250 	 * lockd is brought up, so silently treat it the
251 	 * same as SVC_POOL_GLOBAL.
252 	 */
253 
254 	switch (m->mode) {
255 	case SVC_POOL_PERCPU:
256 		pidx = m->to_pool[cpu];
257 		break;
258 	case SVC_POOL_PERNODE:
259 		pidx = m->to_pool[cpu_to_node(cpu)];
260 		break;
261 	}
262 	return &serv->sv_pools[pidx % serv->sv_nrpools];
263 }
264 
265 
266 /*
267  * Create an RPC service
268  */
269 static struct svc_serv *
270 __svc_create(struct svc_program *prog, unsigned int bufsize, int npools,
271 	   void (*shutdown)(struct svc_serv *serv))
272 {
273 	struct svc_serv	*serv;
274 	int vers;
275 	unsigned int xdrsize;
276 	unsigned int i;
277 
278 	if (!(serv = kzalloc(sizeof(*serv), GFP_KERNEL)))
279 		return NULL;
280 	serv->sv_name      = prog->pg_name;
281 	serv->sv_program   = prog;
282 	serv->sv_nrthreads = 1;
283 	serv->sv_stats     = prog->pg_stats;
284 	if (bufsize > RPCSVC_MAXPAYLOAD)
285 		bufsize = RPCSVC_MAXPAYLOAD;
286 	serv->sv_max_payload = bufsize? bufsize : 4096;
287 	serv->sv_max_mesg  = roundup(serv->sv_max_payload + PAGE_SIZE, PAGE_SIZE);
288 	serv->sv_shutdown  = shutdown;
289 	xdrsize = 0;
290 	while (prog) {
291 		prog->pg_lovers = prog->pg_nvers-1;
292 		for (vers=0; vers<prog->pg_nvers ; vers++)
293 			if (prog->pg_vers[vers]) {
294 				prog->pg_hivers = vers;
295 				if (prog->pg_lovers > vers)
296 					prog->pg_lovers = vers;
297 				if (prog->pg_vers[vers]->vs_xdrsize > xdrsize)
298 					xdrsize = prog->pg_vers[vers]->vs_xdrsize;
299 			}
300 		prog = prog->pg_next;
301 	}
302 	serv->sv_xdrsize   = xdrsize;
303 	INIT_LIST_HEAD(&serv->sv_tempsocks);
304 	INIT_LIST_HEAD(&serv->sv_permsocks);
305 	init_timer(&serv->sv_temptimer);
306 	spin_lock_init(&serv->sv_lock);
307 
308 	serv->sv_nrpools = npools;
309 	serv->sv_pools =
310 		kcalloc(serv->sv_nrpools, sizeof(struct svc_pool),
311 			GFP_KERNEL);
312 	if (!serv->sv_pools) {
313 		kfree(serv);
314 		return NULL;
315 	}
316 
317 	for (i = 0; i < serv->sv_nrpools; i++) {
318 		struct svc_pool *pool = &serv->sv_pools[i];
319 
320 		dprintk("initialising pool %u for %s\n",
321 				i, serv->sv_name);
322 
323 		pool->sp_id = i;
324 		INIT_LIST_HEAD(&pool->sp_threads);
325 		INIT_LIST_HEAD(&pool->sp_sockets);
326 		INIT_LIST_HEAD(&pool->sp_all_threads);
327 		spin_lock_init(&pool->sp_lock);
328 	}
329 
330 
331 	/* Remove any stale portmap registrations */
332 	svc_register(serv, 0, 0);
333 
334 	return serv;
335 }
336 
337 struct svc_serv *
338 svc_create(struct svc_program *prog, unsigned int bufsize,
339 		void (*shutdown)(struct svc_serv *serv))
340 {
341 	return __svc_create(prog, bufsize, /*npools*/1, shutdown);
342 }
343 
344 struct svc_serv *
345 svc_create_pooled(struct svc_program *prog, unsigned int bufsize,
346 		void (*shutdown)(struct svc_serv *serv),
347 		  svc_thread_fn func, int sig, struct module *mod)
348 {
349 	struct svc_serv *serv;
350 	unsigned int npools = svc_pool_map_init();
351 
352 	serv = __svc_create(prog, bufsize, npools, shutdown);
353 
354 	if (serv != NULL) {
355 		serv->sv_function = func;
356 		serv->sv_kill_signal = sig;
357 		serv->sv_module = mod;
358 	}
359 
360 	return serv;
361 }
362 
363 /*
364  * Destroy an RPC service.  Should be called with the BKL held
365  */
366 void
367 svc_destroy(struct svc_serv *serv)
368 {
369 	struct svc_sock	*svsk;
370 
371 	dprintk("RPC: svc_destroy(%s, %d)\n",
372 				serv->sv_program->pg_name,
373 				serv->sv_nrthreads);
374 
375 	if (serv->sv_nrthreads) {
376 		if (--(serv->sv_nrthreads) != 0) {
377 			svc_sock_update_bufs(serv);
378 			return;
379 		}
380 	} else
381 		printk("svc_destroy: no threads for serv=%p!\n", serv);
382 
383 	del_timer_sync(&serv->sv_temptimer);
384 
385 	while (!list_empty(&serv->sv_tempsocks)) {
386 		svsk = list_entry(serv->sv_tempsocks.next,
387 				  struct svc_sock,
388 				  sk_list);
389 		svc_delete_socket(svsk);
390 	}
391 	if (serv->sv_shutdown)
392 		serv->sv_shutdown(serv);
393 
394 	while (!list_empty(&serv->sv_permsocks)) {
395 		svsk = list_entry(serv->sv_permsocks.next,
396 				  struct svc_sock,
397 				  sk_list);
398 		svc_delete_socket(svsk);
399 	}
400 
401 	cache_clean_deferred(serv);
402 
403 	/* Unregister service with the portmapper */
404 	svc_register(serv, 0, 0);
405 	kfree(serv->sv_pools);
406 	kfree(serv);
407 }
408 
409 /*
410  * Allocate an RPC server's buffer space.
411  * We allocate pages and place them in rq_argpages.
412  */
413 static int
414 svc_init_buffer(struct svc_rqst *rqstp, unsigned int size)
415 {
416 	int pages;
417 	int arghi;
418 
419 	pages = size / PAGE_SIZE + 1; /* extra page as we hold both request and reply.
420 				       * We assume one is at most one page
421 				       */
422 	arghi = 0;
423 	BUG_ON(pages > RPCSVC_MAXPAGES);
424 	while (pages) {
425 		struct page *p = alloc_page(GFP_KERNEL);
426 		if (!p)
427 			break;
428 		rqstp->rq_pages[arghi++] = p;
429 		pages--;
430 	}
431 	return ! pages;
432 }
433 
434 /*
435  * Release an RPC server buffer
436  */
437 static void
438 svc_release_buffer(struct svc_rqst *rqstp)
439 {
440 	int i;
441 	for (i=0; i<ARRAY_SIZE(rqstp->rq_pages); i++)
442 		if (rqstp->rq_pages[i])
443 			put_page(rqstp->rq_pages[i]);
444 }
445 
446 /*
447  * Create a thread in the given pool.  Caller must hold BKL.
448  * On a NUMA or SMP machine, with a multi-pool serv, the thread
449  * will be restricted to run on the cpus belonging to the pool.
450  */
451 static int
452 __svc_create_thread(svc_thread_fn func, struct svc_serv *serv,
453 		    struct svc_pool *pool)
454 {
455 	struct svc_rqst	*rqstp;
456 	int		error = -ENOMEM;
457 	int		have_oldmask = 0;
458 	cpumask_t	oldmask;
459 
460 	rqstp = kzalloc(sizeof(*rqstp), GFP_KERNEL);
461 	if (!rqstp)
462 		goto out;
463 
464 	init_waitqueue_head(&rqstp->rq_wait);
465 
466 	if (!(rqstp->rq_argp = kmalloc(serv->sv_xdrsize, GFP_KERNEL))
467 	 || !(rqstp->rq_resp = kmalloc(serv->sv_xdrsize, GFP_KERNEL))
468 	 || !svc_init_buffer(rqstp, serv->sv_max_mesg))
469 		goto out_thread;
470 
471 	serv->sv_nrthreads++;
472 	spin_lock_bh(&pool->sp_lock);
473 	pool->sp_nrthreads++;
474 	list_add(&rqstp->rq_all, &pool->sp_all_threads);
475 	spin_unlock_bh(&pool->sp_lock);
476 	rqstp->rq_server = serv;
477 	rqstp->rq_pool = pool;
478 
479 	if (serv->sv_nrpools > 1)
480 		have_oldmask = svc_pool_map_set_cpumask(pool->sp_id, &oldmask);
481 
482 	error = kernel_thread((int (*)(void *)) func, rqstp, 0);
483 
484 	if (have_oldmask)
485 		set_cpus_allowed(current, oldmask);
486 
487 	if (error < 0)
488 		goto out_thread;
489 	svc_sock_update_bufs(serv);
490 	error = 0;
491 out:
492 	return error;
493 
494 out_thread:
495 	svc_exit_thread(rqstp);
496 	goto out;
497 }
498 
499 /*
500  * Create a thread in the default pool.  Caller must hold BKL.
501  */
502 int
503 svc_create_thread(svc_thread_fn func, struct svc_serv *serv)
504 {
505 	return __svc_create_thread(func, serv, &serv->sv_pools[0]);
506 }
507 
508 /*
509  * Choose a pool in which to create a new thread, for svc_set_num_threads
510  */
511 static inline struct svc_pool *
512 choose_pool(struct svc_serv *serv, struct svc_pool *pool, unsigned int *state)
513 {
514 	if (pool != NULL)
515 		return pool;
516 
517  	return &serv->sv_pools[(*state)++ % serv->sv_nrpools];
518 }
519 
520 /*
521  * Choose a thread to kill, for svc_set_num_threads
522  */
523 static inline struct task_struct *
524 choose_victim(struct svc_serv *serv, struct svc_pool *pool, unsigned int *state)
525 {
526 	unsigned int i;
527 	struct task_struct *task = NULL;
528 
529 	if (pool != NULL) {
530 		spin_lock_bh(&pool->sp_lock);
531 	} else {
532 		/* choose a pool in round-robin fashion */
533  		for (i = 0; i < serv->sv_nrpools; i++) {
534  			pool = &serv->sv_pools[--(*state) % serv->sv_nrpools];
535 			spin_lock_bh(&pool->sp_lock);
536  			if (!list_empty(&pool->sp_all_threads))
537  				goto found_pool;
538 			spin_unlock_bh(&pool->sp_lock);
539  		}
540 		return NULL;
541 	}
542 
543 found_pool:
544 	if (!list_empty(&pool->sp_all_threads)) {
545 		struct svc_rqst *rqstp;
546 
547 		/*
548 		 * Remove from the pool->sp_all_threads list
549 		 * so we don't try to kill it again.
550 		 */
551 		rqstp = list_entry(pool->sp_all_threads.next, struct svc_rqst, rq_all);
552 		list_del_init(&rqstp->rq_all);
553 		task = rqstp->rq_task;
554     	}
555 	spin_unlock_bh(&pool->sp_lock);
556 
557 	return task;
558 }
559 
560 /*
561  * Create or destroy enough new threads to make the number
562  * of threads the given number.  If `pool' is non-NULL, applies
563  * only to threads in that pool, otherwise round-robins between
564  * all pools.  Must be called with a svc_get() reference and
565  * the BKL held.
566  *
567  * Destroying threads relies on the service threads filling in
568  * rqstp->rq_task, which only the nfs ones do.  Assumes the serv
569  * has been created using svc_create_pooled().
570  *
571  * Based on code that used to be in nfsd_svc() but tweaked
572  * to be pool-aware.
573  */
574 int
575 svc_set_num_threads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
576 {
577 	struct task_struct *victim;
578 	int error = 0;
579 	unsigned int state = serv->sv_nrthreads-1;
580 
581 	if (pool == NULL) {
582 		/* The -1 assumes caller has done a svc_get() */
583 		nrservs -= (serv->sv_nrthreads-1);
584 	} else {
585 		spin_lock_bh(&pool->sp_lock);
586 		nrservs -= pool->sp_nrthreads;
587 		spin_unlock_bh(&pool->sp_lock);
588 	}
589 
590 	/* create new threads */
591 	while (nrservs > 0) {
592 		nrservs--;
593 		__module_get(serv->sv_module);
594 		error = __svc_create_thread(serv->sv_function, serv,
595 					    choose_pool(serv, pool, &state));
596 		if (error < 0) {
597 			module_put(serv->sv_module);
598 			break;
599 		}
600 	}
601 	/* destroy old threads */
602 	while (nrservs < 0 &&
603 	       (victim = choose_victim(serv, pool, &state)) != NULL) {
604 		send_sig(serv->sv_kill_signal, victim, 1);
605 		nrservs++;
606 	}
607 
608 	return error;
609 }
610 
611 /*
612  * Called from a server thread as it's exiting.  Caller must hold BKL.
613  */
614 void
615 svc_exit_thread(struct svc_rqst *rqstp)
616 {
617 	struct svc_serv	*serv = rqstp->rq_server;
618 	struct svc_pool	*pool = rqstp->rq_pool;
619 
620 	svc_release_buffer(rqstp);
621 	kfree(rqstp->rq_resp);
622 	kfree(rqstp->rq_argp);
623 	kfree(rqstp->rq_auth_data);
624 
625 	spin_lock_bh(&pool->sp_lock);
626 	pool->sp_nrthreads--;
627 	list_del(&rqstp->rq_all);
628 	spin_unlock_bh(&pool->sp_lock);
629 
630 	kfree(rqstp);
631 
632 	/* Release the server */
633 	if (serv)
634 		svc_destroy(serv);
635 }
636 
637 /*
638  * Register an RPC service with the local portmapper.
639  * To unregister a service, call this routine with
640  * proto and port == 0.
641  */
642 int
643 svc_register(struct svc_serv *serv, int proto, unsigned short port)
644 {
645 	struct svc_program	*progp;
646 	unsigned long		flags;
647 	int			i, error = 0, dummy;
648 
649 	if (!port)
650 		clear_thread_flag(TIF_SIGPENDING);
651 
652 	for (progp = serv->sv_program; progp; progp = progp->pg_next) {
653 		for (i = 0; i < progp->pg_nvers; i++) {
654 			if (progp->pg_vers[i] == NULL)
655 				continue;
656 
657 			dprintk("RPC: svc_register(%s, %s, %d, %d)%s\n",
658 					progp->pg_name,
659 					proto == IPPROTO_UDP?  "udp" : "tcp",
660 					port,
661 					i,
662 					progp->pg_vers[i]->vs_hidden?
663 						" (but not telling portmap)" : "");
664 
665 			if (progp->pg_vers[i]->vs_hidden)
666 				continue;
667 
668 			error = rpc_register(progp->pg_prog, i, proto, port, &dummy);
669 			if (error < 0)
670 				break;
671 			if (port && !dummy) {
672 				error = -EACCES;
673 				break;
674 			}
675 		}
676 	}
677 
678 	if (!port) {
679 		spin_lock_irqsave(&current->sighand->siglock, flags);
680 		recalc_sigpending();
681 		spin_unlock_irqrestore(&current->sighand->siglock, flags);
682 	}
683 
684 	return error;
685 }
686 
687 /*
688  * Process the RPC request.
689  */
690 int
691 svc_process(struct svc_rqst *rqstp)
692 {
693 	struct svc_program	*progp;
694 	struct svc_version	*versp = NULL;	/* compiler food */
695 	struct svc_procedure	*procp = NULL;
696 	struct kvec *		argv = &rqstp->rq_arg.head[0];
697 	struct kvec *		resv = &rqstp->rq_res.head[0];
698 	struct svc_serv		*serv = rqstp->rq_server;
699 	kxdrproc_t		xdr;
700 	__be32			*statp;
701 	u32			dir, prog, vers, proc;
702 	__be32			auth_stat, rpc_stat;
703 	int			auth_res;
704 	__be32			*reply_statp;
705 
706 	rpc_stat = rpc_success;
707 
708 	if (argv->iov_len < 6*4)
709 		goto err_short_len;
710 
711 	/* setup response xdr_buf.
712 	 * Initially it has just one page
713 	 */
714 	rqstp->rq_resused = 1;
715 	resv->iov_base = page_address(rqstp->rq_respages[0]);
716 	resv->iov_len = 0;
717 	rqstp->rq_res.pages = rqstp->rq_respages + 1;
718 	rqstp->rq_res.len = 0;
719 	rqstp->rq_res.page_base = 0;
720 	rqstp->rq_res.page_len = 0;
721 	rqstp->rq_res.buflen = PAGE_SIZE;
722 	rqstp->rq_res.tail[0].iov_base = NULL;
723 	rqstp->rq_res.tail[0].iov_len = 0;
724 	/* Will be turned off only in gss privacy case: */
725 	rqstp->rq_sendfile_ok = 1;
726 	/* tcp needs a space for the record length... */
727 	if (rqstp->rq_prot == IPPROTO_TCP)
728 		svc_putnl(resv, 0);
729 
730 	rqstp->rq_xid = svc_getu32(argv);
731 	svc_putu32(resv, rqstp->rq_xid);
732 
733 	dir  = svc_getnl(argv);
734 	vers = svc_getnl(argv);
735 
736 	/* First words of reply: */
737 	svc_putnl(resv, 1);		/* REPLY */
738 
739 	if (dir != 0)		/* direction != CALL */
740 		goto err_bad_dir;
741 	if (vers != 2)		/* RPC version number */
742 		goto err_bad_rpc;
743 
744 	/* Save position in case we later decide to reject: */
745 	reply_statp = resv->iov_base + resv->iov_len;
746 
747 	svc_putnl(resv, 0);		/* ACCEPT */
748 
749 	rqstp->rq_prog = prog = svc_getnl(argv);	/* program number */
750 	rqstp->rq_vers = vers = svc_getnl(argv);	/* version number */
751 	rqstp->rq_proc = proc = svc_getnl(argv);	/* procedure number */
752 
753 	progp = serv->sv_program;
754 
755 	for (progp = serv->sv_program; progp; progp = progp->pg_next)
756 		if (prog == progp->pg_prog)
757 			break;
758 
759 	/*
760 	 * Decode auth data, and add verifier to reply buffer.
761 	 * We do this before anything else in order to get a decent
762 	 * auth verifier.
763 	 */
764 	auth_res = svc_authenticate(rqstp, &auth_stat);
765 	/* Also give the program a chance to reject this call: */
766 	if (auth_res == SVC_OK && progp) {
767 		auth_stat = rpc_autherr_badcred;
768 		auth_res = progp->pg_authenticate(rqstp);
769 	}
770 	switch (auth_res) {
771 	case SVC_OK:
772 		break;
773 	case SVC_GARBAGE:
774 		rpc_stat = rpc_garbage_args;
775 		goto err_bad;
776 	case SVC_SYSERR:
777 		rpc_stat = rpc_system_err;
778 		goto err_bad;
779 	case SVC_DENIED:
780 		goto err_bad_auth;
781 	case SVC_DROP:
782 		goto dropit;
783 	case SVC_COMPLETE:
784 		goto sendit;
785 	}
786 
787 	if (progp == NULL)
788 		goto err_bad_prog;
789 
790 	if (vers >= progp->pg_nvers ||
791 	  !(versp = progp->pg_vers[vers]))
792 		goto err_bad_vers;
793 
794 	procp = versp->vs_proc + proc;
795 	if (proc >= versp->vs_nproc || !procp->pc_func)
796 		goto err_bad_proc;
797 	rqstp->rq_server   = serv;
798 	rqstp->rq_procinfo = procp;
799 
800 	/* Syntactic check complete */
801 	serv->sv_stats->rpccnt++;
802 
803 	/* Build the reply header. */
804 	statp = resv->iov_base +resv->iov_len;
805 	svc_putnl(resv, RPC_SUCCESS);
806 
807 	/* Bump per-procedure stats counter */
808 	procp->pc_count++;
809 
810 	/* Initialize storage for argp and resp */
811 	memset(rqstp->rq_argp, 0, procp->pc_argsize);
812 	memset(rqstp->rq_resp, 0, procp->pc_ressize);
813 
814 	/* un-reserve some of the out-queue now that we have a
815 	 * better idea of reply size
816 	 */
817 	if (procp->pc_xdrressize)
818 		svc_reserve(rqstp, procp->pc_xdrressize<<2);
819 
820 	/* Call the function that processes the request. */
821 	if (!versp->vs_dispatch) {
822 		/* Decode arguments */
823 		xdr = procp->pc_decode;
824 		if (xdr && !xdr(rqstp, argv->iov_base, rqstp->rq_argp))
825 			goto err_garbage;
826 
827 		*statp = procp->pc_func(rqstp, rqstp->rq_argp, rqstp->rq_resp);
828 
829 		/* Encode reply */
830 		if (*statp == rpc_drop_reply) {
831 			if (procp->pc_release)
832 				procp->pc_release(rqstp, NULL, rqstp->rq_resp);
833 			goto dropit;
834 		}
835 		if (*statp == rpc_success && (xdr = procp->pc_encode)
836 		 && !xdr(rqstp, resv->iov_base+resv->iov_len, rqstp->rq_resp)) {
837 			dprintk("svc: failed to encode reply\n");
838 			/* serv->sv_stats->rpcsystemerr++; */
839 			*statp = rpc_system_err;
840 		}
841 	} else {
842 		dprintk("svc: calling dispatcher\n");
843 		if (!versp->vs_dispatch(rqstp, statp)) {
844 			/* Release reply info */
845 			if (procp->pc_release)
846 				procp->pc_release(rqstp, NULL, rqstp->rq_resp);
847 			goto dropit;
848 		}
849 	}
850 
851 	/* Check RPC status result */
852 	if (*statp != rpc_success)
853 		resv->iov_len = ((void*)statp)  - resv->iov_base + 4;
854 
855 	/* Release reply info */
856 	if (procp->pc_release)
857 		procp->pc_release(rqstp, NULL, rqstp->rq_resp);
858 
859 	if (procp->pc_encode == NULL)
860 		goto dropit;
861 
862  sendit:
863 	if (svc_authorise(rqstp))
864 		goto dropit;
865 	return svc_send(rqstp);
866 
867  dropit:
868 	svc_authorise(rqstp);	/* doesn't hurt to call this twice */
869 	dprintk("svc: svc_process dropit\n");
870 	svc_drop(rqstp);
871 	return 0;
872 
873 err_short_len:
874 	if (net_ratelimit())
875 		printk("svc: short len %Zd, dropping request\n", argv->iov_len);
876 
877 	goto dropit;			/* drop request */
878 
879 err_bad_dir:
880 	if (net_ratelimit())
881 		printk("svc: bad direction %d, dropping request\n", dir);
882 
883 	serv->sv_stats->rpcbadfmt++;
884 	goto dropit;			/* drop request */
885 
886 err_bad_rpc:
887 	serv->sv_stats->rpcbadfmt++;
888 	svc_putnl(resv, 1);	/* REJECT */
889 	svc_putnl(resv, 0);	/* RPC_MISMATCH */
890 	svc_putnl(resv, 2);	/* Only RPCv2 supported */
891 	svc_putnl(resv, 2);
892 	goto sendit;
893 
894 err_bad_auth:
895 	dprintk("svc: authentication failed (%d)\n", ntohl(auth_stat));
896 	serv->sv_stats->rpcbadauth++;
897 	/* Restore write pointer to location of accept status: */
898 	xdr_ressize_check(rqstp, reply_statp);
899 	svc_putnl(resv, 1);	/* REJECT */
900 	svc_putnl(resv, 1);	/* AUTH_ERROR */
901 	svc_putnl(resv, ntohl(auth_stat));	/* status */
902 	goto sendit;
903 
904 err_bad_prog:
905 	dprintk("svc: unknown program %d\n", prog);
906 	serv->sv_stats->rpcbadfmt++;
907 	svc_putnl(resv, RPC_PROG_UNAVAIL);
908 	goto sendit;
909 
910 err_bad_vers:
911 	if (net_ratelimit())
912 		printk("svc: unknown version (%d for prog %d, %s)\n",
913 		       vers, prog, progp->pg_name);
914 
915 	serv->sv_stats->rpcbadfmt++;
916 	svc_putnl(resv, RPC_PROG_MISMATCH);
917 	svc_putnl(resv, progp->pg_lovers);
918 	svc_putnl(resv, progp->pg_hivers);
919 	goto sendit;
920 
921 err_bad_proc:
922 	if (net_ratelimit())
923 		printk("svc: unknown procedure (%d)\n", proc);
924 
925 	serv->sv_stats->rpcbadfmt++;
926 	svc_putnl(resv, RPC_PROC_UNAVAIL);
927 	goto sendit;
928 
929 err_garbage:
930 	if (net_ratelimit())
931 		printk("svc: failed to decode args\n");
932 
933 	rpc_stat = rpc_garbage_args;
934 err_bad:
935 	serv->sv_stats->rpcbadfmt++;
936 	svc_putnl(resv, ntohl(rpc_stat));
937 	goto sendit;
938 }
939 
940 /*
941  * Return (transport-specific) limit on the rpc payload.
942  */
943 u32 svc_max_payload(const struct svc_rqst *rqstp)
944 {
945 	int max = RPCSVC_MAXPAYLOAD_TCP;
946 
947 	if (rqstp->rq_sock->sk_sock->type == SOCK_DGRAM)
948 		max = RPCSVC_MAXPAYLOAD_UDP;
949 	if (rqstp->rq_server->sv_max_payload < max)
950 		max = rqstp->rq_server->sv_max_payload;
951 	return max;
952 }
953 EXPORT_SYMBOL_GPL(svc_max_payload);
954