fs/afs/vl_rotate.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Handle vlserver selection and rotation.
   3  *
   4  * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/kernel.h>
   9 #include <linux/sched.h>
  10 #include <linux/sched/signal.h>
  11 #include "internal.h"
  12 #include "afs_vl.h"
  13
  14 /*
  15  * Begin an operation on a volume location server.
  16  */
  17 bool afs_begin_vlserver_operation(struct afs_vl_cursor *vc, struct afs_cell *cell,
  18                                   struct key *key)
  19 {
  20         memset(vc, 0, sizeof(*vc));
  21         vc->cell = cell;
  22         vc->key = key;
  23         vc->error = -EDESTADDRREQ;
  24         vc->ac.error = SHRT_MAX;
  25
  26         if (signal_pending(current)) {
  27                 vc->error = -EINTR;
  28                 vc->flags |= AFS_VL_CURSOR_STOP;
  29                 return false;
  30         }
  31
  32         return true;
  33 }
  34
  35 /*
  36  * Begin iteration through a server list, starting with the last used server if
  37  * possible, or the last recorded good server if not.
  38  */
  39 static bool afs_start_vl_iteration(struct afs_vl_cursor *vc)
  40 {
  41         struct afs_cell *cell = vc->cell;
  42         unsigned int dns_lookup_count;
  43
  44         if (cell->dns_source == DNS_RECORD_UNAVAILABLE ||
  45             cell->dns_expiry <= ktime_get_real_seconds()) {
  46                 dns_lookup_count = smp_load_acquire(&cell->dns_lookup_count);
  47                 set_bit(AFS_CELL_FL_DO_LOOKUP, &cell->flags);
  48                 queue_work(afs_wq, &cell->manager);
  49
  50                 if (cell->dns_source == DNS_RECORD_UNAVAILABLE) {
  51                         if (wait_var_event_interruptible(
  52                                     &cell->dns_lookup_count,
  53                                     smp_load_acquire(&cell->dns_lookup_count)
  54                                     != dns_lookup_count) < 0) {
  55                                 vc->error = -ERESTARTSYS;
  56                                 return false;
  57                         }
  58                 }
  59
  60                 /* Status load is ordered after lookup counter load */
  61                 if (cell->dns_source == DNS_RECORD_UNAVAILABLE) {
  62                         vc->error = -EDESTADDRREQ;
  63                         return false;
  64                 }
  65         }
  66
  67         read_lock(&cell->vl_servers_lock);
  68         vc->server_list = afs_get_vlserverlist(
  69                 rcu_dereference_protected(cell->vl_servers,
  70                                           lockdep_is_held(&cell->vl_servers_lock)));
  71         read_unlock(&cell->vl_servers_lock);
  72         if (!vc->server_list->nr_servers)
  73                 return false;
  74
  75         vc->untried = (1UL << vc->server_list->nr_servers) - 1;
  76         vc->index = -1;
  77         return true;
  78 }
  79
  80 /*
  81  * Select the vlserver to use.  May be called multiple times to rotate
  82  * through the vlservers.
  83  */
  84 bool afs_select_vlserver(struct afs_vl_cursor *vc)
  85 {
  86         struct afs_addr_list *alist;
  87         struct afs_vlserver *vlserver;
  88         struct afs_error e;
  89         u32 rtt;
  90         int error = vc->ac.error, i;
  91
  92         _enter("%lx[%d],%lx[%d],%d,%d",
  93                vc->untried, vc->index,
  94                vc->ac.tried, vc->ac.index,
  95                error, vc->ac.abort_code);
  96
  97         if (vc->flags & AFS_VL_CURSOR_STOP) {
  98                 _leave(" = f [stopped]");
  99                 return false;
 100         }
 101
 102         vc->nr_iterations++;
 103
 104         /* Evaluate the result of the previous operation, if there was one. */
 105         switch (error) {
 106         case SHRT_MAX:
 107                 goto start;
 108
 109         default:
 110         case 0:
 111                 /* Success or local failure.  Stop. */
 112                 vc->error = error;
 113                 vc->flags |= AFS_VL_CURSOR_STOP;
 114                 _leave(" = f [okay/local %d]", vc->ac.error);
 115                 return false;
 116
 117         case -ECONNABORTED:
 118                 /* The far side rejected the operation on some grounds.  This
 119                  * might involve the server being busy or the volume having been moved.
 120                  */
 121                 switch (vc->ac.abort_code) {
 122                 case AFSVL_IO:
 123                 case AFSVL_BADVOLOPER:
 124                 case AFSVL_NOMEM:
 125                         /* The server went weird. */
 126                         vc->error = -EREMOTEIO;
 127                         //write_lock(&vc->cell->vl_servers_lock);
 128                         //vc->server_list->weird_mask |= 1 << vc->index;
 129                         //write_unlock(&vc->cell->vl_servers_lock);
 130                         goto next_server;
 131
 132                 default:
 133                         vc->error = afs_abort_to_error(vc->ac.abort_code);
 134                         goto failed;
 135                 }
 136
 137         case -ERFKILL:
 138         case -EADDRNOTAVAIL:
 139         case -ENETUNREACH:
 140         case -EHOSTUNREACH:
 141         case -EHOSTDOWN:
 142         case -ECONNREFUSED:
 143         case -ETIMEDOUT:
 144         case -ETIME:
 145                 _debug("no conn %d", error);
 146                 vc->error = error;
 147                 goto iterate_address;
 148
 149         case -ECONNRESET:
 150                 _debug("call reset");
 151                 vc->error = error;
 152                 vc->flags |= AFS_VL_CURSOR_RETRY;
 153                 goto next_server;
 154         }
 155
 156 restart_from_beginning:
 157         _debug("restart");
 158         afs_end_cursor(&vc->ac);
 159         afs_put_vlserverlist(vc->cell->net, vc->server_list);
 160         vc->server_list = NULL;
 161         if (vc->flags & AFS_VL_CURSOR_RETRIED)
 162                 goto failed;
 163         vc->flags |= AFS_VL_CURSOR_RETRIED;
 164 start:
 165         _debug("start");
 166
 167         if (!afs_start_vl_iteration(vc))
 168                 goto failed;
 169
 170         error = afs_send_vl_probes(vc->cell->net, vc->key, vc->server_list);
 171         if (error < 0)
 172                 goto failed_set_error;
 173
 174 pick_server:
 175         _debug("pick [%lx]", vc->untried);
 176
 177         error = afs_wait_for_vl_probes(vc->server_list, vc->untried);
 178         if (error < 0)
 179                 goto failed_set_error;
 180
 181         /* Pick the untried server with the lowest RTT. */
 182         vc->index = vc->server_list->preferred;
 183         if (test_bit(vc->index, &vc->untried))
 184                 goto selected_server;
 185
 186         vc->index = -1;
 187         rtt = U32_MAX;
 188         for (i = 0; i < vc->server_list->nr_servers; i++) {
 189                 struct afs_vlserver *s = vc->server_list->servers[i].server;
 190
 191                 if (!test_bit(i, &vc->untried) || !s->probe.responded)
 192                         continue;
 193                 if (s->probe.rtt < rtt) {
 194                         vc->index = i;
 195                         rtt = s->probe.rtt;
 196                 }
 197         }
 198
 199         if (vc->index == -1)
 200                 goto no_more_servers;
 201
 202 selected_server:
 203         _debug("use %d", vc->index);
 204         __clear_bit(vc->index, &vc->untried);
 205
 206         /* We're starting on a different vlserver from the list.  We need to
 207          * check it, find its address list and probe its capabilities before we
 208          * use it.
 209          */
 210         ASSERTCMP(vc->ac.alist, ==, NULL);
 211         vlserver = vc->server_list->servers[vc->index].server;
 212         vc->server = vlserver;
 213
 214         _debug("USING VLSERVER: %s", vlserver->name);
 215
 216         read_lock(&vlserver->lock);
 217         alist = rcu_dereference_protected(vlserver->addresses,
 218                                           lockdep_is_held(&vlserver->lock));
 219         afs_get_addrlist(alist);
 220         read_unlock(&vlserver->lock);
 221
 222         memset(&vc->ac, 0, sizeof(vc->ac));
 223
 224         if (!vc->ac.alist)
 225                 vc->ac.alist = alist;
 226         else
 227                 afs_put_addrlist(alist);
 228
 229         vc->ac.index = -1;
 230
 231 iterate_address:
 232         ASSERT(vc->ac.alist);
 233         /* Iterate over the current server's address list to try and find an
 234          * address on which it will respond to us.
 235          */
 236         if (!afs_iterate_addresses(&vc->ac))
 237                 goto next_server;
 238
 239         _debug("VL address %d/%d", vc->ac.index, vc->ac.alist->nr_addrs);
 240
 241         _leave(" = t %pISpc", &vc->ac.alist->addrs[vc->ac.index].transport);
 242         return true;
 243
 244 next_server:
 245         _debug("next");
 246         afs_end_cursor(&vc->ac);
 247         goto pick_server;
 248
 249 no_more_servers:
 250         /* That's all the servers poked to no good effect.  Try again if some
 251          * of them were busy.
 252          */
 253         if (vc->flags & AFS_VL_CURSOR_RETRY)
 254                 goto restart_from_beginning;
 255
 256         e.error = -EDESTADDRREQ;
 257         e.responded = false;
 258         for (i = 0; i < vc->server_list->nr_servers; i++) {
 259                 struct afs_vlserver *s = vc->server_list->servers[i].server;
 260
 261                 afs_prioritise_error(&e, READ_ONCE(s->probe.error),
 262                                      s->probe.abort_code);
 263         }
 264
 265 failed_set_error:
 266         vc->error = error;
 267 failed:
 268         vc->flags |= AFS_VL_CURSOR_STOP;
 269         afs_end_cursor(&vc->ac);
 270         _leave(" = f [failed %d]", vc->error);
 271         return false;
 272 }
 273
 274 /*
 275  * Dump cursor state in the case of the error being EDESTADDRREQ.
 276  */
 277 static void afs_vl_dump_edestaddrreq(const struct afs_vl_cursor *vc)
 278 {
 279         static int count;
 280         int i;
 281
 282         if (!IS_ENABLED(CONFIG_AFS_DEBUG_CURSOR) || count > 3)
 283                 return;
 284         count++;
 285
 286         rcu_read_lock();
 287         pr_notice("EDESTADDR occurred\n");
 288         pr_notice("VC: ut=%lx ix=%u ni=%hu fl=%hx err=%hd\n",
 289                   vc->untried, vc->index, vc->nr_iterations, vc->flags, vc->error);
 290
 291         if (vc->server_list) {
 292                 const struct afs_vlserver_list *sl = vc->server_list;
 293                 pr_notice("VC: SL nr=%u ix=%u\n",
 294                           sl->nr_servers, sl->index);
 295                 for (i = 0; i < sl->nr_servers; i++) {
 296                         const struct afs_vlserver *s = sl->servers[i].server;
 297                         pr_notice("VC: server %s+%hu fl=%lx E=%hd\n",
 298                                   s->name, s->port, s->flags, s->probe.error);
 299                         if (s->addresses) {
 300                                 const struct afs_addr_list *a =
 301                                         rcu_dereference(s->addresses);
 302                                 pr_notice("VC:  - nr=%u/%u/%u pf=%u\n",
 303                                           a->nr_ipv4, a->nr_addrs, a->max_addrs,
 304                                           a->preferred);
 305                                 pr_notice("VC:  - pr=%lx R=%lx F=%lx\n",
 306                                           a->probed, a->responded, a->failed);
 307                                 if (a == vc->ac.alist)
 308                                         pr_notice("VC:  - current\n");
 309                         }
 310                 }
 311         }
 312
 313         pr_notice("AC: t=%lx ax=%u ac=%d er=%d r=%u ni=%u\n",
 314                   vc->ac.tried, vc->ac.index, vc->ac.abort_code, vc->ac.error,
 315                   vc->ac.responded, vc->ac.nr_iterations);
 316         rcu_read_unlock();
 317 }
 318
 319 /*
 320  * Tidy up a volume location server cursor and unlock the vnode.
 321  */
 322 int afs_end_vlserver_operation(struct afs_vl_cursor *vc)
 323 {
 324         struct afs_net *net = vc->cell->net;
 325
 326         if (vc->error == -EDESTADDRREQ ||
 327             vc->error == -EADDRNOTAVAIL ||
 328             vc->error == -ENETUNREACH ||
 329             vc->error == -EHOSTUNREACH)
 330                 afs_vl_dump_edestaddrreq(vc);
 331
 332         afs_end_cursor(&vc->ac);
 333         afs_put_vlserverlist(net, vc->server_list);
 334
 335         if (vc->error == -ECONNABORTED)
 336                 vc->error = afs_abort_to_error(vc->ac.abort_code);
 337
 338         return vc->error;
 339 }