summaryrefslogtreecommitdiff
path: root/net/sunrpc/xprtmultipath.c
blob: 5f4845d1e922ffc1d7fb3d67ea246d77eab69d2e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
// SPDX-License-Identifier: GPL-2.0
/*
 * Multipath support for RPC
 *
 * Copyright (c) 2015, 2016, Primary Data, Inc. All rights reserved.
 *
 * Trond Myklebust <trond.myklebust@primarydata.com>
 *
 */
#include <linux/types.h>
#include <linux/kref.h>
#include <linux/list.h>
#include <linux/rcupdate.h>
#include <linux/rculist.h>
#include <linux/slab.h>
#include <asm/cmpxchg.h>
#include <linux/spinlock.h>
#include <linux/sunrpc/xprt.h>
#include <linux/sunrpc/addr.h>
#include <linux/sunrpc/xprtmultipath.h>

#include "sysfs.h"

typedef struct rpc_xprt *(*xprt_switch_find_xprt_t)(struct rpc_xprt_switch *xps,
		const struct rpc_xprt *cur);

static const struct rpc_xprt_iter_ops rpc_xprt_iter_singular;
static const struct rpc_xprt_iter_ops rpc_xprt_iter_roundrobin;
static const struct rpc_xprt_iter_ops rpc_xprt_iter_listall;

static void xprt_switch_add_xprt_locked(struct rpc_xprt_switch *xps,
		struct rpc_xprt *xprt)
{
	if (unlikely(xprt_get(xprt) == NULL))
		return;
	list_add_tail_rcu(&xprt->xprt_switch, &xps->xps_xprt_list);
	smp_wmb();
	if (xps->xps_nxprts == 0)
		xps->xps_net = xprt->xprt_net;
	xps->xps_nxprts++;
	xps->xps_nactive++;
}

/**
 * rpc_xprt_switch_add_xprt - Add a new rpc_xprt to an rpc_xprt_switch
 * @xps: pointer to struct rpc_xprt_switch
 * @xprt: pointer to struct rpc_xprt
 *
 * Adds xprt to the end of the list of struct rpc_xprt in xps.
 */
void rpc_xprt_switch_add_xprt(struct rpc_xprt_switch *xps,
		struct rpc_xprt *xprt)
{
	if (xprt == NULL)
		return;
	spin_lock(&xps->xps_lock);
	if (xps->xps_net == xprt->xprt_net || xps->xps_net == NULL)
		xprt_switch_add_xprt_locked(xps, xprt);
	spin_unlock(&xps->xps_lock);
	rpc_sysfs_xprt_setup(xps, xprt, GFP_KERNEL);
}

static void xprt_switch_remove_xprt_locked(struct rpc_xprt_switch *xps,
		struct rpc_xprt *xprt)
{
	if (unlikely(xprt == NULL))
		return;
	if (!test_bit(XPRT_OFFLINE, &xprt->state))
		xps->xps_nactive--;
	xps->xps_nxprts--;
	if (xps->xps_nxprts == 0)
		xps->xps_net = NULL;
	smp_wmb();
	list_del_rcu(&xprt->xprt_switch);
}

/**
 * rpc_xprt_switch_remove_xprt - Removes an rpc_xprt from a rpc_xprt_switch
 * @xps: pointer to struct rpc_xprt_switch
 * @xprt: pointer to struct rpc_xprt
 *
 * Removes xprt from the list of struct rpc_xprt in xps.
 */
void rpc_xprt_switch_remove_xprt(struct rpc_xprt_switch *xps,
		struct rpc_xprt *xprt)
{
	spin_lock(&xps->xps_lock);
	xprt_switch_remove_xprt_locked(xps, xprt);
	spin_unlock(&xps->xps_lock);
	xprt_put(xprt);
}

static DEFINE_IDA(rpc_xprtswitch_ids);

void xprt_multipath_cleanup_ids(void)
{
	ida_destroy(&rpc_xprtswitch_ids);
}

static int xprt_switch_alloc_id(struct rpc_xprt_switch *xps, gfp_t gfp_flags)
{
	int id;

	id = ida_simple_get(&rpc_xprtswitch_ids, 0, 0, gfp_flags);
	if (id < 0)
		return id;

	xps->xps_id = id;
	return 0;
}

static void xprt_switch_free_id(struct rpc_xprt_switch *xps)
{
	ida_simple_remove(&rpc_xprtswitch_ids, xps->xps_id);
}

/**
 * xprt_switch_alloc - Allocate a new struct rpc_xprt_switch
 * @xprt: pointer to struct rpc_xprt
 * @gfp_flags: allocation flags
 *
 * On success, returns an initialised struct rpc_xprt_switch, containing
 * the entry xprt. Returns NULL on failure.
 */
struct rpc_xprt_switch *xprt_switch_alloc(struct rpc_xprt *xprt,
		gfp_t gfp_flags)
{
	struct rpc_xprt_switch *xps;

	xps = kmalloc(sizeof(*xps), gfp_flags);
	if (xps != NULL) {
		spin_lock_init(&xps->xps_lock);
		kref_init(&xps->xps_kref);
		xprt_switch_alloc_id(xps, gfp_flags);
		xps->xps_nxprts = xps->xps_nactive = 0;
		atomic_long_set(&xps->xps_queuelen, 0);
		xps->xps_net = NULL;
		INIT_LIST_HEAD(&xps->xps_xprt_list);
		xps->xps_iter_ops = &rpc_xprt_iter_singular;
		rpc_sysfs_xprt_switch_setup(xps, xprt, gfp_flags);
		xprt_switch_add_xprt_locked(xps, xprt);
		rpc_sysfs_xprt_setup(xps, xprt, gfp_flags);
	}

	return xps;
}

static void xprt_switch_free_entries(struct rpc_xprt_switch *xps)
{
	spin_lock(&xps->xps_lock);
	while (!list_empty(&xps->xps_xprt_list)) {
		struct rpc_xprt *xprt;

		xprt = list_first_entry(&xps->xps_xprt_list,
				struct rpc_xprt, xprt_switch);
		xprt_switch_remove_xprt_locked(xps, xprt);
		spin_unlock(&xps->xps_lock);
		xprt_put(xprt);
		spin_lock(&xps->xps_lock);
	}
	spin_unlock(&xps->xps_lock);
}

static void xprt_switch_free(struct kref *kref)
{
	struct rpc_xprt_switch *xps = container_of(kref,
			struct rpc_xprt_switch, xps_kref);

	xprt_switch_free_entries(xps);
	rpc_sysfs_xprt_switch_destroy(xps);
	xprt_switch_free_id(xps);
	kfree_rcu(xps, xps_rcu);
}

/**
 * xprt_switch_get - Return a reference to a rpc_xprt_switch
 * @xps: pointer to struct rpc_xprt_switch
 *
 * Returns a reference to xps unless the refcount is already zero.
 */
struct rpc_xprt_switch *xprt_switch_get(struct rpc_xprt_switch *xps)
{
	if (xps != NULL && kref_get_unless_zero(&xps->xps_kref))
		return xps;
	return NULL;
}

/**
 * xprt_switch_put - Release a reference to a rpc_xprt_switch
 * @xps: pointer to struct rpc_xprt_switch
 *
 * Release the reference to xps, and free it once the refcount is zero.
 */
void xprt_switch_put(struct rpc_xprt_switch *xps)
{
	if (xps != NULL)
		kref_put(&xps->xps_kref, xprt_switch_free);
}

/**
 * rpc_xprt_switch_set_roundrobin - Set a round-robin policy on rpc_xprt_switch
 * @xps: pointer to struct rpc_xprt_switch
 *
 * Sets a round-robin default policy for iterators acting on xps.
 */
void rpc_xprt_switch_set_roundrobin(struct rpc_xprt_switch *xps)
{
	if (READ_ONCE(xps->xps_iter_ops) != &rpc_xprt_iter_roundrobin)
		WRITE_ONCE(xps->xps_iter_ops, &rpc_xprt_iter_roundrobin);
}

static
const struct rpc_xprt_iter_ops *xprt_iter_ops(const struct rpc_xprt_iter *xpi)
{
	if (xpi->xpi_ops != NULL)
		return xpi->xpi_ops;
	return rcu_dereference(xpi->xpi_xpswitch)->xps_iter_ops;
}

static
void xprt_iter_no_rewind(struct rpc_xprt_iter *xpi)
{
}

static
void xprt_iter_default_rewind(struct rpc_xprt_iter *xpi)
{
	WRITE_ONCE(xpi->xpi_cursor, NULL);
}

static
bool xprt_is_active(const struct rpc_xprt *xprt)
{
	return (kref_read(&xprt->kref) != 0 &&
		!test_bit(XPRT_OFFLINE, &xprt->state));
}

static
struct rpc_xprt *xprt_switch_find_first_entry(struct list_head *head)
{
	struct rpc_xprt *pos;

	list_for_each_entry_rcu(pos, head, xprt_switch) {
		if (xprt_is_active(pos))
			return pos;
	}
	return NULL;
}

static
struct rpc_xprt *xprt_iter_first_entry(struct rpc_xprt_iter *xpi)
{
	struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);

	if (xps == NULL)
		return NULL;
	return xprt_switch_find_first_entry(&xps->xps_xprt_list);
}

static
struct rpc_xprt *xprt_switch_find_current_entry(struct list_head *head,
		const struct rpc_xprt *cur)
{
	struct rpc_xprt *pos;
	bool found = false;

	list_for_each_entry_rcu(pos, head, xprt_switch) {
		if (cur == pos)
			found = true;
		if (found && xprt_is_active(pos))
			return pos;
	}
	return NULL;
}

static
struct rpc_xprt *xprt_iter_current_entry(struct rpc_xprt_iter *xpi)
{
	struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);
	struct list_head *head;

	if (xps == NULL)
		return NULL;
	head = &xps->xps_xprt_list;
	if (xpi->xpi_cursor == NULL || xps->xps_nxprts < 2)
		return xprt_switch_find_first_entry(head);
	return xprt_switch_find_current_entry(head, xpi->xpi_cursor);
}

bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
			      const struct sockaddr *sap)
{
	struct list_head *head;
	struct rpc_xprt *pos;

	if (xps == NULL || sap == NULL)
		return false;

	head = &xps->xps_xprt_list;
	list_for_each_entry_rcu(pos, head, xprt_switch) {
		if (rpc_cmp_addr_port(sap, (struct sockaddr *)&pos->addr)) {
			pr_info("RPC:   addr %s already in xprt switch\n",
				pos->address_strings[RPC_DISPLAY_ADDR]);
			return true;
		}
	}
	return false;
}

static
struct rpc_xprt *xprt_switch_find_next_entry(struct list_head *head,
		const struct rpc_xprt *cur)
{
	struct rpc_xprt *pos, *prev = NULL;
	bool found = false;

	list_for_each_entry_rcu(pos, head, xprt_switch) {
		if (cur == prev)
			found = true;
		if (found && xprt_is_active(pos))
			return pos;
		prev = pos;
	}
	return NULL;
}

static
struct rpc_xprt *xprt_switch_set_next_cursor(struct rpc_xprt_switch *xps,
		struct rpc_xprt **cursor,
		xprt_switch_find_xprt_t find_next)
{
	struct rpc_xprt *pos, *old;

	old = smp_load_acquire(cursor);
	pos = find_next(xps, old);
	smp_store_release(cursor, pos);
	return pos;
}

static
struct rpc_xprt *xprt_iter_next_entry_multiple(struct rpc_xprt_iter *xpi,
		xprt_switch_find_xprt_t find_next)
{
	struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);

	if (xps == NULL)
		return NULL;
	return xprt_switch_set_next_cursor(xps, &xpi->xpi_cursor, find_next);
}

static
struct rpc_xprt *__xprt_switch_find_next_entry_roundrobin(struct list_head *head,
		const struct rpc_xprt *cur)
{
	struct rpc_xprt *ret;

	ret = xprt_switch_find_next_entry(head, cur);
	if (ret != NULL)
		return ret;
	return xprt_switch_find_first_entry(head);
}

static
struct rpc_xprt *xprt_switch_find_next_entry_roundrobin(struct rpc_xprt_switch *xps,
		const struct rpc_xprt *cur)
{
	struct list_head *head = &xps->xps_xprt_list;
	struct rpc_xprt *xprt;
	unsigned int nactive;

	for (;;) {
		unsigned long xprt_queuelen, xps_queuelen;

		xprt = __xprt_switch_find_next_entry_roundrobin(head, cur);
		if (!xprt)
			break;
		xprt_queuelen = atomic_long_read(&xprt->queuelen);
		xps_queuelen = atomic_long_read(&xps->xps_queuelen);
		nactive = READ_ONCE(xps->xps_nactive);
		/* Exit loop if xprt_queuelen <= average queue length */
		if (xprt_queuelen * nactive <= xps_queuelen)
			break;
		cur = xprt;
	}
	return xprt;
}

static
struct rpc_xprt *xprt_iter_next_entry_roundrobin(struct rpc_xprt_iter *xpi)
{
	return xprt_iter_next_entry_multiple(xpi,
			xprt_switch_find_next_entry_roundrobin);
}

static
struct rpc_xprt *xprt_switch_find_next_entry_all(struct rpc_xprt_switch *xps,
		const struct rpc_xprt *cur)
{
	return xprt_switch_find_next_entry(&xps->xps_xprt_list, cur);
}

static
struct rpc_xprt *xprt_iter_next_entry_all(struct rpc_xprt_iter *xpi)
{
	return xprt_iter_next_entry_multiple(xpi,
			xprt_switch_find_next_entry_all);
}

/*
 * xprt_iter_rewind - Resets the xprt iterator
 * @xpi: pointer to rpc_xprt_iter
 *
 * Resets xpi to ensure that it points to the first entry in the list
 * of transports.
 */
static
void xprt_iter_rewind(struct rpc_xprt_iter *xpi)
{
	rcu_read_lock();
	xprt_iter_ops(xpi)->xpi_rewind(xpi);
	rcu_read_unlock();
}

static void __xprt_iter_init(struct rpc_xprt_iter *xpi,
		struct rpc_xprt_switch *xps,
		const struct rpc_xprt_iter_ops *ops)
{
	rcu_assign_pointer(xpi->xpi_xpswitch, xprt_switch_get(xps));
	xpi->xpi_cursor = NULL;
	xpi->xpi_ops = ops;
}

/**
 * xprt_iter_init - Initialise an xprt iterator
 * @xpi: pointer to rpc_xprt_iter
 * @xps: pointer to rpc_xprt_switch
 *
 * Initialises the iterator to use the default iterator ops
 * as set in xps. This function is mainly intended for internal
 * use in the rpc_client.
 */
void xprt_iter_init(struct rpc_xprt_iter *xpi,
		struct rpc_xprt_switch *xps)
{
	__xprt_iter_init(xpi, xps, NULL);
}

/**
 * xprt_iter_init_listall - Initialise an xprt iterator
 * @xpi: pointer to rpc_xprt_iter
 * @xps: pointer to rpc_xprt_switch
 *
 * Initialises the iterator to iterate once through the entire list
 * of entries in xps.
 */
void xprt_iter_init_listall(struct rpc_xprt_iter *xpi,
		struct rpc_xprt_switch *xps)
{
	__xprt_iter_init(xpi, xps, &rpc_xprt_iter_listall);
}

/**
 * xprt_iter_xchg_switch - Atomically swap out the rpc_xprt_switch
 * @xpi: pointer to rpc_xprt_iter
 * @newswitch: pointer to a new rpc_xprt_switch or NULL
 *
 * Swaps out the existing xpi->xpi_xpswitch with a new value.
 */
struct rpc_xprt_switch *xprt_iter_xchg_switch(struct rpc_xprt_iter *xpi,
		struct rpc_xprt_switch *newswitch)
{
	struct rpc_xprt_switch __rcu *oldswitch;

	/* Atomically swap out the old xpswitch */
	oldswitch = xchg(&xpi->xpi_xpswitch, RCU_INITIALIZER(newswitch));
	if (newswitch != NULL)
		xprt_iter_rewind(xpi);
	return rcu_dereference_protected(oldswitch, true);
}

/**
 * xprt_iter_destroy - Destroys the xprt iterator
 * @xpi: pointer to rpc_xprt_iter
 */
void xprt_iter_destroy(struct rpc_xprt_iter *xpi)
{
	xprt_switch_put(xprt_iter_xchg_switch(xpi, NULL));
}

/**
 * xprt_iter_xprt - Returns the rpc_xprt pointed to by the cursor
 * @xpi: pointer to rpc_xprt_iter
 *
 * Returns a pointer to the struct rpc_xprt that is currently
 * pointed to by the cursor.
 * Caller must be holding rcu_read_lock().
 */
struct rpc_xprt *xprt_iter_xprt(struct rpc_xprt_iter *xpi)
{
	WARN_ON_ONCE(!rcu_read_lock_held());
	return xprt_iter_ops(xpi)->xpi_xprt(xpi);
}

static
struct rpc_xprt *xprt_iter_get_helper(struct rpc_xprt_iter *xpi,
		struct rpc_xprt *(*fn)(struct rpc_xprt_iter *))
{
	struct rpc_xprt *ret;

	do {
		ret = fn(xpi);
		if (ret == NULL)
			break;
		ret = xprt_get(ret);
	} while (ret == NULL);
	return ret;
}

/**
 * xprt_iter_get_xprt - Returns the rpc_xprt pointed to by the cursor
 * @xpi: pointer to rpc_xprt_iter
 *
 * Returns a reference to the struct rpc_xprt that is currently
 * pointed to by the cursor.
 */
struct rpc_xprt *xprt_iter_get_xprt(struct rpc_xprt_iter *xpi)
{
	struct rpc_xprt *xprt;

	rcu_read_lock();
	xprt = xprt_iter_get_helper(xpi, xprt_iter_ops(xpi)->xpi_xprt);
	rcu_read_unlock();
	return xprt;
}

/**
 * xprt_iter_get_next - Returns the next rpc_xprt following the cursor
 * @xpi: pointer to rpc_xprt_iter
 *
 * Returns a reference to the struct rpc_xprt that immediately follows the
 * entry pointed to by the cursor.
 */
struct rpc_xprt *xprt_iter_get_next(struct rpc_xprt_iter *xpi)
{
	struct rpc_xprt *xprt;

	rcu_read_lock();
	xprt = xprt_iter_get_helper(xpi, xprt_iter_ops(xpi)->xpi_next);
	rcu_read_unlock();
	return xprt;
}

/* Policy for always returning the first entry in the rpc_xprt_switch */
static
const struct rpc_xprt_iter_ops rpc_xprt_iter_singular = {
	.xpi_rewind = xprt_iter_no_rewind,
	.xpi_xprt = xprt_iter_first_entry,
	.xpi_next = xprt_iter_first_entry,
};

/* Policy for round-robin iteration of entries in the rpc_xprt_switch */
static
const struct rpc_xprt_iter_ops rpc_xprt_iter_roundrobin = {
	.xpi_rewind = xprt_iter_default_rewind,
	.xpi_xprt = xprt_iter_current_entry,
	.xpi_next = xprt_iter_next_entry_roundrobin,
};

/* Policy for once-through iteration of entries in the rpc_xprt_switch */
static
const struct rpc_xprt_iter_ops rpc_xprt_iter_listall = {
	.xpi_rewind = xprt_iter_default_rewind,
	.xpi_xprt = xprt_iter_current_entry,
	.xpi_next = xprt_iter_next_entry_all,
};