fs/afs/vl_rotate.c

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