Merge tag 'acpi-5.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael...
[sfrench/cifs-2.6.git] / net / sunrpc / xprtmultipath.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Multipath support for RPC
4  *
5  * Copyright (c) 2015, 2016, Primary Data, Inc. All rights reserved.
6  *
7  * Trond Myklebust <trond.myklebust@primarydata.com>
8  *
9  */
10 #include <linux/types.h>
11 #include <linux/kref.h>
12 #include <linux/list.h>
13 #include <linux/rcupdate.h>
14 #include <linux/rculist.h>
15 #include <linux/slab.h>
16 #include <asm/cmpxchg.h>
17 #include <linux/spinlock.h>
18 #include <linux/sunrpc/xprt.h>
19 #include <linux/sunrpc/addr.h>
20 #include <linux/sunrpc/xprtmultipath.h>
21
22 typedef struct rpc_xprt *(*xprt_switch_find_xprt_t)(struct list_head *head,
23                 const struct rpc_xprt *cur);
24
25 static const struct rpc_xprt_iter_ops rpc_xprt_iter_singular;
26 static const struct rpc_xprt_iter_ops rpc_xprt_iter_roundrobin;
27 static const struct rpc_xprt_iter_ops rpc_xprt_iter_listall;
28
29 static void xprt_switch_add_xprt_locked(struct rpc_xprt_switch *xps,
30                 struct rpc_xprt *xprt)
31 {
32         if (unlikely(xprt_get(xprt) == NULL))
33                 return;
34         list_add_tail_rcu(&xprt->xprt_switch, &xps->xps_xprt_list);
35         smp_wmb();
36         if (xps->xps_nxprts == 0)
37                 xps->xps_net = xprt->xprt_net;
38         xps->xps_nxprts++;
39 }
40
41 /**
42  * rpc_xprt_switch_add_xprt - Add a new rpc_xprt to an rpc_xprt_switch
43  * @xps: pointer to struct rpc_xprt_switch
44  * @xprt: pointer to struct rpc_xprt
45  *
46  * Adds xprt to the end of the list of struct rpc_xprt in xps.
47  */
48 void rpc_xprt_switch_add_xprt(struct rpc_xprt_switch *xps,
49                 struct rpc_xprt *xprt)
50 {
51         if (xprt == NULL)
52                 return;
53         spin_lock(&xps->xps_lock);
54         if ((xps->xps_net == xprt->xprt_net || xps->xps_net == NULL) &&
55             !rpc_xprt_switch_has_addr(xps, (struct sockaddr *)&xprt->addr))
56                 xprt_switch_add_xprt_locked(xps, xprt);
57         spin_unlock(&xps->xps_lock);
58 }
59
60 static void xprt_switch_remove_xprt_locked(struct rpc_xprt_switch *xps,
61                 struct rpc_xprt *xprt)
62 {
63         if (unlikely(xprt == NULL))
64                 return;
65         xps->xps_nxprts--;
66         if (xps->xps_nxprts == 0)
67                 xps->xps_net = NULL;
68         smp_wmb();
69         list_del_rcu(&xprt->xprt_switch);
70 }
71
72 /**
73  * rpc_xprt_switch_remove_xprt - Removes an rpc_xprt from a rpc_xprt_switch
74  * @xps: pointer to struct rpc_xprt_switch
75  * @xprt: pointer to struct rpc_xprt
76  *
77  * Removes xprt from the list of struct rpc_xprt in xps.
78  */
79 void rpc_xprt_switch_remove_xprt(struct rpc_xprt_switch *xps,
80                 struct rpc_xprt *xprt)
81 {
82         spin_lock(&xps->xps_lock);
83         xprt_switch_remove_xprt_locked(xps, xprt);
84         spin_unlock(&xps->xps_lock);
85         xprt_put(xprt);
86 }
87
88 /**
89  * xprt_switch_alloc - Allocate a new struct rpc_xprt_switch
90  * @xprt: pointer to struct rpc_xprt
91  * @gfp_flags: allocation flags
92  *
93  * On success, returns an initialised struct rpc_xprt_switch, containing
94  * the entry xprt. Returns NULL on failure.
95  */
96 struct rpc_xprt_switch *xprt_switch_alloc(struct rpc_xprt *xprt,
97                 gfp_t gfp_flags)
98 {
99         struct rpc_xprt_switch *xps;
100
101         xps = kmalloc(sizeof(*xps), gfp_flags);
102         if (xps != NULL) {
103                 spin_lock_init(&xps->xps_lock);
104                 kref_init(&xps->xps_kref);
105                 xps->xps_nxprts = 0;
106                 INIT_LIST_HEAD(&xps->xps_xprt_list);
107                 xps->xps_iter_ops = &rpc_xprt_iter_singular;
108                 xprt_switch_add_xprt_locked(xps, xprt);
109         }
110
111         return xps;
112 }
113
114 static void xprt_switch_free_entries(struct rpc_xprt_switch *xps)
115 {
116         spin_lock(&xps->xps_lock);
117         while (!list_empty(&xps->xps_xprt_list)) {
118                 struct rpc_xprt *xprt;
119
120                 xprt = list_first_entry(&xps->xps_xprt_list,
121                                 struct rpc_xprt, xprt_switch);
122                 xprt_switch_remove_xprt_locked(xps, xprt);
123                 spin_unlock(&xps->xps_lock);
124                 xprt_put(xprt);
125                 spin_lock(&xps->xps_lock);
126         }
127         spin_unlock(&xps->xps_lock);
128 }
129
130 static void xprt_switch_free(struct kref *kref)
131 {
132         struct rpc_xprt_switch *xps = container_of(kref,
133                         struct rpc_xprt_switch, xps_kref);
134
135         xprt_switch_free_entries(xps);
136         kfree_rcu(xps, xps_rcu);
137 }
138
139 /**
140  * xprt_switch_get - Return a reference to a rpc_xprt_switch
141  * @xps: pointer to struct rpc_xprt_switch
142  *
143  * Returns a reference to xps unless the refcount is already zero.
144  */
145 struct rpc_xprt_switch *xprt_switch_get(struct rpc_xprt_switch *xps)
146 {
147         if (xps != NULL && kref_get_unless_zero(&xps->xps_kref))
148                 return xps;
149         return NULL;
150 }
151
152 /**
153  * xprt_switch_put - Release a reference to a rpc_xprt_switch
154  * @xps: pointer to struct rpc_xprt_switch
155  *
156  * Release the reference to xps, and free it once the refcount is zero.
157  */
158 void xprt_switch_put(struct rpc_xprt_switch *xps)
159 {
160         if (xps != NULL)
161                 kref_put(&xps->xps_kref, xprt_switch_free);
162 }
163
164 /**
165  * rpc_xprt_switch_set_roundrobin - Set a round-robin policy on rpc_xprt_switch
166  * @xps: pointer to struct rpc_xprt_switch
167  *
168  * Sets a round-robin default policy for iterators acting on xps.
169  */
170 void rpc_xprt_switch_set_roundrobin(struct rpc_xprt_switch *xps)
171 {
172         if (READ_ONCE(xps->xps_iter_ops) != &rpc_xprt_iter_roundrobin)
173                 WRITE_ONCE(xps->xps_iter_ops, &rpc_xprt_iter_roundrobin);
174 }
175
176 static
177 const struct rpc_xprt_iter_ops *xprt_iter_ops(const struct rpc_xprt_iter *xpi)
178 {
179         if (xpi->xpi_ops != NULL)
180                 return xpi->xpi_ops;
181         return rcu_dereference(xpi->xpi_xpswitch)->xps_iter_ops;
182 }
183
184 static
185 void xprt_iter_no_rewind(struct rpc_xprt_iter *xpi)
186 {
187 }
188
189 static
190 void xprt_iter_default_rewind(struct rpc_xprt_iter *xpi)
191 {
192         WRITE_ONCE(xpi->xpi_cursor, NULL);
193 }
194
195 static
196 struct rpc_xprt *xprt_switch_find_first_entry(struct list_head *head)
197 {
198         return list_first_or_null_rcu(head, struct rpc_xprt, xprt_switch);
199 }
200
201 static
202 struct rpc_xprt *xprt_iter_first_entry(struct rpc_xprt_iter *xpi)
203 {
204         struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);
205
206         if (xps == NULL)
207                 return NULL;
208         return xprt_switch_find_first_entry(&xps->xps_xprt_list);
209 }
210
211 static
212 struct rpc_xprt *xprt_switch_find_current_entry(struct list_head *head,
213                 const struct rpc_xprt *cur)
214 {
215         struct rpc_xprt *pos;
216
217         list_for_each_entry_rcu(pos, head, xprt_switch) {
218                 if (cur == pos)
219                         return pos;
220         }
221         return NULL;
222 }
223
224 static
225 struct rpc_xprt *xprt_iter_current_entry(struct rpc_xprt_iter *xpi)
226 {
227         struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);
228         struct list_head *head;
229
230         if (xps == NULL)
231                 return NULL;
232         head = &xps->xps_xprt_list;
233         if (xpi->xpi_cursor == NULL || xps->xps_nxprts < 2)
234                 return xprt_switch_find_first_entry(head);
235         return xprt_switch_find_current_entry(head, xpi->xpi_cursor);
236 }
237
238 bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
239                               const struct sockaddr *sap)
240 {
241         struct list_head *head;
242         struct rpc_xprt *pos;
243
244         if (xps == NULL || sap == NULL)
245                 return false;
246
247         head = &xps->xps_xprt_list;
248         list_for_each_entry_rcu(pos, head, xprt_switch) {
249                 if (rpc_cmp_addr_port(sap, (struct sockaddr *)&pos->addr)) {
250                         pr_info("RPC:   addr %s already in xprt switch\n",
251                                 pos->address_strings[RPC_DISPLAY_ADDR]);
252                         return true;
253                 }
254         }
255         return false;
256 }
257
258 static
259 struct rpc_xprt *xprt_switch_find_next_entry(struct list_head *head,
260                 const struct rpc_xprt *cur)
261 {
262         struct rpc_xprt *pos, *prev = NULL;
263
264         list_for_each_entry_rcu(pos, head, xprt_switch) {
265                 if (cur == prev)
266                         return pos;
267                 prev = pos;
268         }
269         return NULL;
270 }
271
272 static
273 struct rpc_xprt *xprt_switch_set_next_cursor(struct list_head *head,
274                 struct rpc_xprt **cursor,
275                 xprt_switch_find_xprt_t find_next)
276 {
277         struct rpc_xprt *cur, *pos, *old;
278
279         cur = READ_ONCE(*cursor);
280         for (;;) {
281                 old = cur;
282                 pos = find_next(head, old);
283                 if (pos == NULL)
284                         break;
285                 cur = cmpxchg_relaxed(cursor, old, pos);
286                 if (cur == old)
287                         break;
288         }
289         return pos;
290 }
291
292 static
293 struct rpc_xprt *xprt_iter_next_entry_multiple(struct rpc_xprt_iter *xpi,
294                 xprt_switch_find_xprt_t find_next)
295 {
296         struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);
297
298         if (xps == NULL)
299                 return NULL;
300         return xprt_switch_set_next_cursor(&xps->xps_xprt_list,
301                         &xpi->xpi_cursor,
302                         find_next);
303 }
304
305 static
306 struct rpc_xprt *xprt_switch_find_next_entry_roundrobin(struct list_head *head,
307                 const struct rpc_xprt *cur)
308 {
309         struct rpc_xprt *ret;
310
311         ret = xprt_switch_find_next_entry(head, cur);
312         if (ret != NULL)
313                 return ret;
314         return xprt_switch_find_first_entry(head);
315 }
316
317 static
318 struct rpc_xprt *xprt_iter_next_entry_roundrobin(struct rpc_xprt_iter *xpi)
319 {
320         return xprt_iter_next_entry_multiple(xpi,
321                         xprt_switch_find_next_entry_roundrobin);
322 }
323
324 static
325 struct rpc_xprt *xprt_iter_next_entry_all(struct rpc_xprt_iter *xpi)
326 {
327         return xprt_iter_next_entry_multiple(xpi, xprt_switch_find_next_entry);
328 }
329
330 /*
331  * xprt_iter_rewind - Resets the xprt iterator
332  * @xpi: pointer to rpc_xprt_iter
333  *
334  * Resets xpi to ensure that it points to the first entry in the list
335  * of transports.
336  */
337 static
338 void xprt_iter_rewind(struct rpc_xprt_iter *xpi)
339 {
340         rcu_read_lock();
341         xprt_iter_ops(xpi)->xpi_rewind(xpi);
342         rcu_read_unlock();
343 }
344
345 static void __xprt_iter_init(struct rpc_xprt_iter *xpi,
346                 struct rpc_xprt_switch *xps,
347                 const struct rpc_xprt_iter_ops *ops)
348 {
349         rcu_assign_pointer(xpi->xpi_xpswitch, xprt_switch_get(xps));
350         xpi->xpi_cursor = NULL;
351         xpi->xpi_ops = ops;
352 }
353
354 /**
355  * xprt_iter_init - Initialise an xprt iterator
356  * @xpi: pointer to rpc_xprt_iter
357  * @xps: pointer to rpc_xprt_switch
358  *
359  * Initialises the iterator to use the default iterator ops
360  * as set in xps. This function is mainly intended for internal
361  * use in the rpc_client.
362  */
363 void xprt_iter_init(struct rpc_xprt_iter *xpi,
364                 struct rpc_xprt_switch *xps)
365 {
366         __xprt_iter_init(xpi, xps, NULL);
367 }
368
369 /**
370  * xprt_iter_init_listall - Initialise an xprt iterator
371  * @xpi: pointer to rpc_xprt_iter
372  * @xps: pointer to rpc_xprt_switch
373  *
374  * Initialises the iterator to iterate once through the entire list
375  * of entries in xps.
376  */
377 void xprt_iter_init_listall(struct rpc_xprt_iter *xpi,
378                 struct rpc_xprt_switch *xps)
379 {
380         __xprt_iter_init(xpi, xps, &rpc_xprt_iter_listall);
381 }
382
383 /**
384  * xprt_iter_xchg_switch - Atomically swap out the rpc_xprt_switch
385  * @xpi: pointer to rpc_xprt_iter
386  * @newswitch: pointer to a new rpc_xprt_switch or NULL
387  *
388  * Swaps out the existing xpi->xpi_xpswitch with a new value.
389  */
390 struct rpc_xprt_switch *xprt_iter_xchg_switch(struct rpc_xprt_iter *xpi,
391                 struct rpc_xprt_switch *newswitch)
392 {
393         struct rpc_xprt_switch __rcu *oldswitch;
394
395         /* Atomically swap out the old xpswitch */
396         oldswitch = xchg(&xpi->xpi_xpswitch, RCU_INITIALIZER(newswitch));
397         if (newswitch != NULL)
398                 xprt_iter_rewind(xpi);
399         return rcu_dereference_protected(oldswitch, true);
400 }
401
402 /**
403  * xprt_iter_destroy - Destroys the xprt iterator
404  * @xpi: pointer to rpc_xprt_iter
405  */
406 void xprt_iter_destroy(struct rpc_xprt_iter *xpi)
407 {
408         xprt_switch_put(xprt_iter_xchg_switch(xpi, NULL));
409 }
410
411 /**
412  * xprt_iter_xprt - Returns the rpc_xprt pointed to by the cursor
413  * @xpi: pointer to rpc_xprt_iter
414  *
415  * Returns a pointer to the struct rpc_xprt that is currently
416  * pointed to by the cursor.
417  * Caller must be holding rcu_read_lock().
418  */
419 struct rpc_xprt *xprt_iter_xprt(struct rpc_xprt_iter *xpi)
420 {
421         WARN_ON_ONCE(!rcu_read_lock_held());
422         return xprt_iter_ops(xpi)->xpi_xprt(xpi);
423 }
424
425 static
426 struct rpc_xprt *xprt_iter_get_helper(struct rpc_xprt_iter *xpi,
427                 struct rpc_xprt *(*fn)(struct rpc_xprt_iter *))
428 {
429         struct rpc_xprt *ret;
430
431         do {
432                 ret = fn(xpi);
433                 if (ret == NULL)
434                         break;
435                 ret = xprt_get(ret);
436         } while (ret == NULL);
437         return ret;
438 }
439
440 /**
441  * xprt_iter_get_xprt - Returns the rpc_xprt pointed to by the cursor
442  * @xpi: pointer to rpc_xprt_iter
443  *
444  * Returns a reference to the struct rpc_xprt that is currently
445  * pointed to by the cursor.
446  */
447 struct rpc_xprt *xprt_iter_get_xprt(struct rpc_xprt_iter *xpi)
448 {
449         struct rpc_xprt *xprt;
450
451         rcu_read_lock();
452         xprt = xprt_iter_get_helper(xpi, xprt_iter_ops(xpi)->xpi_xprt);
453         rcu_read_unlock();
454         return xprt;
455 }
456
457 /**
458  * xprt_iter_get_next - Returns the next rpc_xprt following the cursor
459  * @xpi: pointer to rpc_xprt_iter
460  *
461  * Returns a reference to the struct rpc_xprt that immediately follows the
462  * entry pointed to by the cursor.
463  */
464 struct rpc_xprt *xprt_iter_get_next(struct rpc_xprt_iter *xpi)
465 {
466         struct rpc_xprt *xprt;
467
468         rcu_read_lock();
469         xprt = xprt_iter_get_helper(xpi, xprt_iter_ops(xpi)->xpi_next);
470         rcu_read_unlock();
471         return xprt;
472 }
473
474 /* Policy for always returning the first entry in the rpc_xprt_switch */
475 static
476 const struct rpc_xprt_iter_ops rpc_xprt_iter_singular = {
477         .xpi_rewind = xprt_iter_no_rewind,
478         .xpi_xprt = xprt_iter_first_entry,
479         .xpi_next = xprt_iter_first_entry,
480 };
481
482 /* Policy for round-robin iteration of entries in the rpc_xprt_switch */
483 static
484 const struct rpc_xprt_iter_ops rpc_xprt_iter_roundrobin = {
485         .xpi_rewind = xprt_iter_default_rewind,
486         .xpi_xprt = xprt_iter_current_entry,
487         .xpi_next = xprt_iter_next_entry_roundrobin,
488 };
489
490 /* Policy for once-through iteration of entries in the rpc_xprt_switch */
491 static
492 const struct rpc_xprt_iter_ops rpc_xprt_iter_listall = {
493         .xpi_rewind = xprt_iter_default_rewind,
494         .xpi_xprt = xprt_iter_current_entry,
495         .xpi_next = xprt_iter_next_entry_all,
496 };