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[mirror_ubuntu-bionic-kernel.git] / net / sunrpc / xprtmultipath.c
1 /*
2 * Multipath support for RPC
3 *
4 * Copyright (c) 2015, 2016, Primary Data, Inc. All rights reserved.
5 *
6 * Trond Myklebust <trond.myklebust@primarydata.com>
7 *
8 */
9 #include <linux/types.h>
10 #include <linux/kref.h>
11 #include <linux/list.h>
12 #include <linux/rcupdate.h>
13 #include <linux/rculist.h>
14 #include <linux/slab.h>
15 #include <asm/cmpxchg.h>
16 #include <linux/spinlock.h>
17 #include <linux/sunrpc/xprt.h>
18 #include <linux/sunrpc/addr.h>
19 #include <linux/sunrpc/xprtmultipath.h>
20
21 typedef struct rpc_xprt *(*xprt_switch_find_xprt_t)(struct list_head *head,
22 const struct rpc_xprt *cur);
23
24 static const struct rpc_xprt_iter_ops rpc_xprt_iter_singular;
25 static const struct rpc_xprt_iter_ops rpc_xprt_iter_roundrobin;
26 static const struct rpc_xprt_iter_ops rpc_xprt_iter_listall;
27
28 static void xprt_switch_add_xprt_locked(struct rpc_xprt_switch *xps,
29 struct rpc_xprt *xprt)
30 {
31 if (unlikely(xprt_get(xprt) == NULL))
32 return;
33 list_add_tail_rcu(&xprt->xprt_switch, &xps->xps_xprt_list);
34 smp_wmb();
35 if (xps->xps_nxprts == 0)
36 xps->xps_net = xprt->xprt_net;
37 xps->xps_nxprts++;
38 }
39
40 /**
41 * rpc_xprt_switch_add_xprt - Add a new rpc_xprt to an rpc_xprt_switch
42 * @xps: pointer to struct rpc_xprt_switch
43 * @xprt: pointer to struct rpc_xprt
44 *
45 * Adds xprt to the end of the list of struct rpc_xprt in xps.
46 */
47 void rpc_xprt_switch_add_xprt(struct rpc_xprt_switch *xps,
48 struct rpc_xprt *xprt)
49 {
50 if (xprt == NULL)
51 return;
52 spin_lock(&xps->xps_lock);
53 if ((xps->xps_net == xprt->xprt_net || xps->xps_net == NULL) &&
54 !rpc_xprt_switch_has_addr(xps, (struct sockaddr *)&xprt->addr))
55 xprt_switch_add_xprt_locked(xps, xprt);
56 spin_unlock(&xps->xps_lock);
57 }
58
59 static void xprt_switch_remove_xprt_locked(struct rpc_xprt_switch *xps,
60 struct rpc_xprt *xprt)
61 {
62 if (unlikely(xprt == NULL))
63 return;
64 xps->xps_nxprts--;
65 if (xps->xps_nxprts == 0)
66 xps->xps_net = NULL;
67 smp_wmb();
68 list_del_rcu(&xprt->xprt_switch);
69 }
70
71 /**
72 * rpc_xprt_switch_remove_xprt - Removes an rpc_xprt from a rpc_xprt_switch
73 * @xps: pointer to struct rpc_xprt_switch
74 * @xprt: pointer to struct rpc_xprt
75 *
76 * Removes xprt from the list of struct rpc_xprt in xps.
77 */
78 void rpc_xprt_switch_remove_xprt(struct rpc_xprt_switch *xps,
79 struct rpc_xprt *xprt)
80 {
81 spin_lock(&xps->xps_lock);
82 xprt_switch_remove_xprt_locked(xps, xprt);
83 spin_unlock(&xps->xps_lock);
84 xprt_put(xprt);
85 }
86
87 /**
88 * xprt_switch_alloc - Allocate a new struct rpc_xprt_switch
89 * @xprt: pointer to struct rpc_xprt
90 * @gfp_flags: allocation flags
91 *
92 * On success, returns an initialised struct rpc_xprt_switch, containing
93 * the entry xprt. Returns NULL on failure.
94 */
95 struct rpc_xprt_switch *xprt_switch_alloc(struct rpc_xprt *xprt,
96 gfp_t gfp_flags)
97 {
98 struct rpc_xprt_switch *xps;
99
100 xps = kmalloc(sizeof(*xps), gfp_flags);
101 if (xps != NULL) {
102 spin_lock_init(&xps->xps_lock);
103 kref_init(&xps->xps_kref);
104 xps->xps_nxprts = 0;
105 INIT_LIST_HEAD(&xps->xps_xprt_list);
106 xps->xps_iter_ops = &rpc_xprt_iter_singular;
107 xprt_switch_add_xprt_locked(xps, xprt);
108 }
109
110 return xps;
111 }
112
113 static void xprt_switch_free_entries(struct rpc_xprt_switch *xps)
114 {
115 spin_lock(&xps->xps_lock);
116 while (!list_empty(&xps->xps_xprt_list)) {
117 struct rpc_xprt *xprt;
118
119 xprt = list_first_entry(&xps->xps_xprt_list,
120 struct rpc_xprt, xprt_switch);
121 xprt_switch_remove_xprt_locked(xps, xprt);
122 spin_unlock(&xps->xps_lock);
123 xprt_put(xprt);
124 spin_lock(&xps->xps_lock);
125 }
126 spin_unlock(&xps->xps_lock);
127 }
128
129 static void xprt_switch_free(struct kref *kref)
130 {
131 struct rpc_xprt_switch *xps = container_of(kref,
132 struct rpc_xprt_switch, xps_kref);
133
134 xprt_switch_free_entries(xps);
135 kfree_rcu(xps, xps_rcu);
136 }
137
138 /**
139 * xprt_switch_get - Return a reference to a rpc_xprt_switch
140 * @xps: pointer to struct rpc_xprt_switch
141 *
142 * Returns a reference to xps unless the refcount is already zero.
143 */
144 struct rpc_xprt_switch *xprt_switch_get(struct rpc_xprt_switch *xps)
145 {
146 if (xps != NULL && kref_get_unless_zero(&xps->xps_kref))
147 return xps;
148 return NULL;
149 }
150
151 /**
152 * xprt_switch_put - Release a reference to a rpc_xprt_switch
153 * @xps: pointer to struct rpc_xprt_switch
154 *
155 * Release the reference to xps, and free it once the refcount is zero.
156 */
157 void xprt_switch_put(struct rpc_xprt_switch *xps)
158 {
159 if (xps != NULL)
160 kref_put(&xps->xps_kref, xprt_switch_free);
161 }
162
163 /**
164 * rpc_xprt_switch_set_roundrobin - Set a round-robin policy on rpc_xprt_switch
165 * @xps: pointer to struct rpc_xprt_switch
166 *
167 * Sets a round-robin default policy for iterators acting on xps.
168 */
169 void rpc_xprt_switch_set_roundrobin(struct rpc_xprt_switch *xps)
170 {
171 if (READ_ONCE(xps->xps_iter_ops) != &rpc_xprt_iter_roundrobin)
172 WRITE_ONCE(xps->xps_iter_ops, &rpc_xprt_iter_roundrobin);
173 }
174
175 static
176 const struct rpc_xprt_iter_ops *xprt_iter_ops(const struct rpc_xprt_iter *xpi)
177 {
178 if (xpi->xpi_ops != NULL)
179 return xpi->xpi_ops;
180 return rcu_dereference(xpi->xpi_xpswitch)->xps_iter_ops;
181 }
182
183 static
184 void xprt_iter_no_rewind(struct rpc_xprt_iter *xpi)
185 {
186 }
187
188 static
189 void xprt_iter_default_rewind(struct rpc_xprt_iter *xpi)
190 {
191 WRITE_ONCE(xpi->xpi_cursor, NULL);
192 }
193
194 static
195 struct rpc_xprt *xprt_switch_find_first_entry(struct list_head *head)
196 {
197 return list_first_or_null_rcu(head, struct rpc_xprt, xprt_switch);
198 }
199
200 static
201 struct rpc_xprt *xprt_iter_first_entry(struct rpc_xprt_iter *xpi)
202 {
203 struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);
204
205 if (xps == NULL)
206 return NULL;
207 return xprt_switch_find_first_entry(&xps->xps_xprt_list);
208 }
209
210 static
211 struct rpc_xprt *xprt_switch_find_current_entry(struct list_head *head,
212 const struct rpc_xprt *cur)
213 {
214 struct rpc_xprt *pos;
215
216 list_for_each_entry_rcu(pos, head, xprt_switch) {
217 if (cur == pos)
218 return pos;
219 }
220 return NULL;
221 }
222
223 static
224 struct rpc_xprt *xprt_iter_current_entry(struct rpc_xprt_iter *xpi)
225 {
226 struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);
227 struct list_head *head;
228
229 if (xps == NULL)
230 return NULL;
231 head = &xps->xps_xprt_list;
232 if (xpi->xpi_cursor == NULL || xps->xps_nxprts < 2)
233 return xprt_switch_find_first_entry(head);
234 return xprt_switch_find_current_entry(head, xpi->xpi_cursor);
235 }
236
237 bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
238 const struct sockaddr *sap)
239 {
240 struct list_head *head;
241 struct rpc_xprt *pos;
242
243 if (xps == NULL || sap == NULL)
244 return false;
245
246 head = &xps->xps_xprt_list;
247 list_for_each_entry_rcu(pos, head, xprt_switch) {
248 if (rpc_cmp_addr_port(sap, (struct sockaddr *)&pos->addr)) {
249 pr_info("RPC: addr %s already in xprt switch\n",
250 pos->address_strings[RPC_DISPLAY_ADDR]);
251 return true;
252 }
253 }
254 return false;
255 }
256
257 static
258 struct rpc_xprt *xprt_switch_find_next_entry(struct list_head *head,
259 const struct rpc_xprt *cur)
260 {
261 struct rpc_xprt *pos, *prev = NULL;
262
263 list_for_each_entry_rcu(pos, head, xprt_switch) {
264 if (cur == prev)
265 return pos;
266 prev = pos;
267 }
268 return NULL;
269 }
270
271 static
272 struct rpc_xprt *xprt_switch_set_next_cursor(struct list_head *head,
273 struct rpc_xprt **cursor,
274 xprt_switch_find_xprt_t find_next)
275 {
276 struct rpc_xprt *cur, *pos, *old;
277
278 cur = READ_ONCE(*cursor);
279 for (;;) {
280 old = cur;
281 pos = find_next(head, old);
282 if (pos == NULL)
283 break;
284 cur = cmpxchg_relaxed(cursor, old, pos);
285 if (cur == old)
286 break;
287 }
288 return pos;
289 }
290
291 static
292 struct rpc_xprt *xprt_iter_next_entry_multiple(struct rpc_xprt_iter *xpi,
293 xprt_switch_find_xprt_t find_next)
294 {
295 struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);
296
297 if (xps == NULL)
298 return NULL;
299 return xprt_switch_set_next_cursor(&xps->xps_xprt_list,
300 &xpi->xpi_cursor,
301 find_next);
302 }
303
304 static
305 struct rpc_xprt *xprt_switch_find_next_entry_roundrobin(struct list_head *head,
306 const struct rpc_xprt *cur)
307 {
308 struct rpc_xprt *ret;
309
310 ret = xprt_switch_find_next_entry(head, cur);
311 if (ret != NULL)
312 return ret;
313 return xprt_switch_find_first_entry(head);
314 }
315
316 static
317 struct rpc_xprt *xprt_iter_next_entry_roundrobin(struct rpc_xprt_iter *xpi)
318 {
319 return xprt_iter_next_entry_multiple(xpi,
320 xprt_switch_find_next_entry_roundrobin);
321 }
322
323 static
324 struct rpc_xprt *xprt_iter_next_entry_all(struct rpc_xprt_iter *xpi)
325 {
326 return xprt_iter_next_entry_multiple(xpi, xprt_switch_find_next_entry);
327 }
328
329 /*
330 * xprt_iter_rewind - Resets the xprt iterator
331 * @xpi: pointer to rpc_xprt_iter
332 *
333 * Resets xpi to ensure that it points to the first entry in the list
334 * of transports.
335 */
336 static
337 void xprt_iter_rewind(struct rpc_xprt_iter *xpi)
338 {
339 rcu_read_lock();
340 xprt_iter_ops(xpi)->xpi_rewind(xpi);
341 rcu_read_unlock();
342 }
343
344 static void __xprt_iter_init(struct rpc_xprt_iter *xpi,
345 struct rpc_xprt_switch *xps,
346 const struct rpc_xprt_iter_ops *ops)
347 {
348 rcu_assign_pointer(xpi->xpi_xpswitch, xprt_switch_get(xps));
349 xpi->xpi_cursor = NULL;
350 xpi->xpi_ops = ops;
351 }
352
353 /**
354 * xprt_iter_init - Initialise an xprt iterator
355 * @xpi: pointer to rpc_xprt_iter
356 * @xps: pointer to rpc_xprt_switch
357 *
358 * Initialises the iterator to use the default iterator ops
359 * as set in xps. This function is mainly intended for internal
360 * use in the rpc_client.
361 */
362 void xprt_iter_init(struct rpc_xprt_iter *xpi,
363 struct rpc_xprt_switch *xps)
364 {
365 __xprt_iter_init(xpi, xps, NULL);
366 }
367
368 /**
369 * xprt_iter_init_listall - Initialise an xprt iterator
370 * @xpi: pointer to rpc_xprt_iter
371 * @xps: pointer to rpc_xprt_switch
372 *
373 * Initialises the iterator to iterate once through the entire list
374 * of entries in xps.
375 */
376 void xprt_iter_init_listall(struct rpc_xprt_iter *xpi,
377 struct rpc_xprt_switch *xps)
378 {
379 __xprt_iter_init(xpi, xps, &rpc_xprt_iter_listall);
380 }
381
382 /**
383 * xprt_iter_xchg_switch - Atomically swap out the rpc_xprt_switch
384 * @xpi: pointer to rpc_xprt_iter
385 * @xps: pointer to a new rpc_xprt_switch or NULL
386 *
387 * Swaps out the existing xpi->xpi_xpswitch with a new value.
388 */
389 struct rpc_xprt_switch *xprt_iter_xchg_switch(struct rpc_xprt_iter *xpi,
390 struct rpc_xprt_switch *newswitch)
391 {
392 struct rpc_xprt_switch __rcu *oldswitch;
393
394 /* Atomically swap out the old xpswitch */
395 oldswitch = xchg(&xpi->xpi_xpswitch, RCU_INITIALIZER(newswitch));
396 if (newswitch != NULL)
397 xprt_iter_rewind(xpi);
398 return rcu_dereference_protected(oldswitch, true);
399 }
400
401 /**
402 * xprt_iter_destroy - Destroys the xprt iterator
403 * @xpi pointer to rpc_xprt_iter
404 */
405 void xprt_iter_destroy(struct rpc_xprt_iter *xpi)
406 {
407 xprt_switch_put(xprt_iter_xchg_switch(xpi, NULL));
408 }
409
410 /**
411 * xprt_iter_xprt - Returns the rpc_xprt pointed to by the cursor
412 * @xpi: pointer to rpc_xprt_iter
413 *
414 * Returns a pointer to the struct rpc_xprt that is currently
415 * pointed to by the cursor.
416 * Caller must be holding rcu_read_lock().
417 */
418 struct rpc_xprt *xprt_iter_xprt(struct rpc_xprt_iter *xpi)
419 {
420 WARN_ON_ONCE(!rcu_read_lock_held());
421 return xprt_iter_ops(xpi)->xpi_xprt(xpi);
422 }
423
424 static
425 struct rpc_xprt *xprt_iter_get_helper(struct rpc_xprt_iter *xpi,
426 struct rpc_xprt *(*fn)(struct rpc_xprt_iter *))
427 {
428 struct rpc_xprt *ret;
429
430 do {
431 ret = fn(xpi);
432 if (ret == NULL)
433 break;
434 ret = xprt_get(ret);
435 } while (ret == NULL);
436 return ret;
437 }
438
439 /**
440 * xprt_iter_get_xprt - Returns the rpc_xprt pointed to by the cursor
441 * @xpi: pointer to rpc_xprt_iter
442 *
443 * Returns a reference to the struct rpc_xprt that is currently
444 * pointed to by the cursor.
445 */
446 struct rpc_xprt *xprt_iter_get_xprt(struct rpc_xprt_iter *xpi)
447 {
448 struct rpc_xprt *xprt;
449
450 rcu_read_lock();
451 xprt = xprt_iter_get_helper(xpi, xprt_iter_ops(xpi)->xpi_xprt);
452 rcu_read_unlock();
453 return xprt;
454 }
455
456 /**
457 * xprt_iter_get_next - Returns the next rpc_xprt following the cursor
458 * @xpi: pointer to rpc_xprt_iter
459 *
460 * Returns a reference to the struct rpc_xprt that immediately follows the
461 * entry pointed to by the cursor.
462 */
463 struct rpc_xprt *xprt_iter_get_next(struct rpc_xprt_iter *xpi)
464 {
465 struct rpc_xprt *xprt;
466
467 rcu_read_lock();
468 xprt = xprt_iter_get_helper(xpi, xprt_iter_ops(xpi)->xpi_next);
469 rcu_read_unlock();
470 return xprt;
471 }
472
473 /* Policy for always returning the first entry in the rpc_xprt_switch */
474 static
475 const struct rpc_xprt_iter_ops rpc_xprt_iter_singular = {
476 .xpi_rewind = xprt_iter_no_rewind,
477 .xpi_xprt = xprt_iter_first_entry,
478 .xpi_next = xprt_iter_first_entry,
479 };
480
481 /* Policy for round-robin iteration of entries in the rpc_xprt_switch */
482 static
483 const struct rpc_xprt_iter_ops rpc_xprt_iter_roundrobin = {
484 .xpi_rewind = xprt_iter_default_rewind,
485 .xpi_xprt = xprt_iter_current_entry,
486 .xpi_next = xprt_iter_next_entry_roundrobin,
487 };
488
489 /* Policy for once-through iteration of entries in the rpc_xprt_switch */
490 static
491 const struct rpc_xprt_iter_ops rpc_xprt_iter_listall = {
492 .xpi_rewind = xprt_iter_default_rewind,
493 .xpi_xprt = xprt_iter_current_entry,
494 .xpi_next = xprt_iter_next_entry_all,
495 };