fs/afs/callback.c

   1 /*
   2  * Copyright (c) 2002, 2007 Red Hat, Inc. All rights reserved.
   3  *
   4  * This software may be freely redistributed under the terms of the
   5  * GNU General Public License.
   6  *
   7  * You should have received a copy of the GNU General Public License
   8  * along with this program; if not, write to the Free Software
   9  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  10  *
  11  * Authors: David Woodhouse <dwmw2@cambridge.redhat.com>
  12  *          David Howells <dhowells@redhat.com>
  13  *
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18 #include <linux/init.h>
  19 #include <linux/circ_buf.h>
  20 #include "internal.h"
  21
  22 unsigned afs_vnode_update_timeout = 10;
  23
  24 #define afs_breakring_space(server) \
  25         CIRC_SPACE((server)->cb_break_head, (server)->cb_break_tail,    \
  26                    ARRAY_SIZE((server)->cb_break))
  27
  28 //static void afs_callback_updater(struct work_struct *);
  29
  30 static struct workqueue_struct *afs_callback_update_worker;
  31
  32 /*
  33  * allow the fileserver to request callback state (re-)initialisation
  34  */
  35 void afs_init_callback_state(struct afs_server *server)
  36 {
  37         struct afs_vnode *vnode;
  38
  39         _enter("{%p}", server);
  40
  41         spin_lock(&server->cb_lock);
  42
  43         /* kill all the promises on record from this server */
  44         while (!RB_EMPTY_ROOT(&server->cb_promises)) {
  45                 vnode = rb_entry(server->cb_promises.rb_node,
  46                                  struct afs_vnode, cb_promise);
  47                 _debug("UNPROMISE { vid=%x:%u uq=%u}",
  48                        vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
  49                 rb_erase(&vnode->cb_promise, &server->cb_promises);
  50                 vnode->cb_promised = false;
  51         }
  52
  53         spin_unlock(&server->cb_lock);
  54         _leave("");
  55 }
  56
  57 /*
  58  * handle the data invalidation side of a callback being broken
  59  */
  60 void afs_broken_callback_work(struct work_struct *work)
  61 {
  62         struct afs_vnode *vnode =
  63                 container_of(work, struct afs_vnode, cb_broken_work);
  64
  65         _enter("");
  66
  67         if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
  68                 return;
  69
  70         /* we're only interested in dealing with a broken callback on *this*
  71          * vnode and only if no-one else has dealt with it yet */
  72         if (!mutex_trylock(&vnode->validate_lock))
  73                 return; /* someone else is dealing with it */
  74
  75         if (test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags)) {
  76                 if (S_ISDIR(vnode->vfs_inode.i_mode))
  77                         afs_clear_permits(vnode);
  78
  79                 if (afs_vnode_fetch_status(vnode, NULL, NULL) < 0)
  80                         goto out;
  81
  82                 if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
  83                         goto out;
  84
  85                 /* if the vnode's data version number changed then its contents
  86                  * are different */
  87                 if (test_and_clear_bit(AFS_VNODE_ZAP_DATA, &vnode->flags))
  88                         afs_zap_data(vnode);
  89         }
  90
  91 out:
  92         mutex_unlock(&vnode->validate_lock);
  93
  94         /* avoid the potential race whereby the mutex_trylock() in this
  95          * function happens again between the clear_bit() and the
  96          * mutex_unlock() */
  97         if (test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags)) {
  98                 _debug("requeue");
  99                 queue_work(afs_callback_update_worker, &vnode->cb_broken_work);
 100         }
 101         _leave("");
 102 }
 103
 104 /*
 105  * actually break a callback
 106  */
 107 static void afs_break_callback(struct afs_server *server,
 108                                struct afs_vnode *vnode)
 109 {
 110         _enter("");
 111
 112         set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);
 113
 114         if (vnode->cb_promised) {
 115                 spin_lock(&vnode->lock);
 116
 117                 _debug("break callback");
 118
 119                 spin_lock(&server->cb_lock);
 120                 if (vnode->cb_promised) {
 121                         rb_erase(&vnode->cb_promise, &server->cb_promises);
 122                         vnode->cb_promised = false;
 123                 }
 124                 spin_unlock(&server->cb_lock);
 125
 126                 queue_work(afs_callback_update_worker, &vnode->cb_broken_work);
 127                 spin_unlock(&vnode->lock);
 128         }
 129 }
 130
 131 /*
 132  * allow the fileserver to explicitly break one callback
 133  * - happens when
 134  *   - the backing file is changed
 135  *   - a lock is released
 136  */
 137 static void afs_break_one_callback(struct afs_server *server,
 138                                    struct afs_fid *fid)
 139 {
 140         struct afs_vnode *vnode;
 141         struct rb_node *p;
 142
 143         _debug("find");
 144         spin_lock(&server->fs_lock);
 145         p = server->fs_vnodes.rb_node;
 146         while (p) {
 147                 vnode = rb_entry(p, struct afs_vnode, server_rb);
 148                 if (fid->vid < vnode->fid.vid)
 149                         p = p->rb_left;
 150                 else if (fid->vid > vnode->fid.vid)
 151                         p = p->rb_right;
 152                 else if (fid->vnode < vnode->fid.vnode)
 153                         p = p->rb_left;
 154                 else if (fid->vnode > vnode->fid.vnode)
 155                         p = p->rb_right;
 156                 else if (fid->unique < vnode->fid.unique)
 157                         p = p->rb_left;
 158                 else if (fid->unique > vnode->fid.unique)
 159                         p = p->rb_right;
 160                 else
 161                         goto found;
 162         }
 163
 164         /* not found so we just ignore it (it may have moved to another
 165          * server) */
 166 not_available:
 167         _debug("not avail");
 168         spin_unlock(&server->fs_lock);
 169         _leave("");
 170         return;
 171
 172 found:
 173         _debug("found");
 174         ASSERTCMP(server, ==, vnode->server);
 175
 176         if (!igrab(AFS_VNODE_TO_I(vnode)))
 177                 goto not_available;
 178         spin_unlock(&server->fs_lock);
 179
 180         afs_break_callback(server, vnode);
 181         iput(&vnode->vfs_inode);
 182         _leave("");
 183 }
 184
 185 /*
 186  * allow the fileserver to break callback promises
 187  */
 188 void afs_break_callbacks(struct afs_server *server, size_t count,
 189                          struct afs_callback callbacks[])
 190 {
 191         _enter("%p,%zu,", server, count);
 192
 193         ASSERT(server != NULL);
 194         ASSERTCMP(count, <=, AFSCBMAX);
 195
 196         for (; count > 0; callbacks++, count--) {
 197                 _debug("- Fid { vl=%08x n=%u u=%u }  CB { v=%u x=%u t=%u }",
 198                        callbacks->fid.vid,
 199                        callbacks->fid.vnode,
 200                        callbacks->fid.unique,
 201                        callbacks->version,
 202                        callbacks->expiry,
 203                        callbacks->type
 204                        );
 205                 afs_break_one_callback(server, &callbacks->fid);
 206         }
 207
 208         _leave("");
 209         return;
 210 }
 211
 212 /*
 213  * record the callback for breaking
 214  * - the caller must hold server->cb_lock
 215  */
 216 static void afs_do_give_up_callback(struct afs_server *server,
 217                                     struct afs_vnode *vnode)
 218 {
 219         struct afs_callback *cb;
 220
 221         _enter("%p,%p", server, vnode);
 222
 223         cb = &server->cb_break[server->cb_break_head];
 224         cb->fid         = vnode->fid;
 225         cb->version     = vnode->cb_version;
 226         cb->expiry      = vnode->cb_expiry;
 227         cb->type        = vnode->cb_type;
 228         smp_wmb();
 229         server->cb_break_head =
 230                 (server->cb_break_head + 1) &
 231                 (ARRAY_SIZE(server->cb_break) - 1);
 232
 233         /* defer the breaking of callbacks to try and collect as many as
 234          * possible to ship in one operation */
 235         switch (atomic_inc_return(&server->cb_break_n)) {
 236         case 1 ... AFSCBMAX - 1:
 237                 queue_delayed_work(afs_callback_update_worker,
 238                                    &server->cb_break_work, HZ * 2);
 239                 break;
 240         case AFSCBMAX:
 241                 afs_flush_callback_breaks(server);
 242                 break;
 243         default:
 244                 break;
 245         }
 246
 247         ASSERT(server->cb_promises.rb_node != NULL);
 248         rb_erase(&vnode->cb_promise, &server->cb_promises);
 249         vnode->cb_promised = false;
 250         _leave("");
 251 }
 252
 253 /*
 254  * discard the callback on a deleted item
 255  */
 256 void afs_discard_callback_on_delete(struct afs_vnode *vnode)
 257 {
 258         struct afs_server *server = vnode->server;
 259
 260         _enter("%d", vnode->cb_promised);
 261
 262         if (!vnode->cb_promised) {
 263                 _leave(" [not promised]");
 264                 return;
 265         }
 266
 267         ASSERT(server != NULL);
 268
 269         spin_lock(&server->cb_lock);
 270         if (vnode->cb_promised) {
 271                 ASSERT(server->cb_promises.rb_node != NULL);
 272                 rb_erase(&vnode->cb_promise, &server->cb_promises);
 273                 vnode->cb_promised = false;
 274         }
 275         spin_unlock(&server->cb_lock);
 276         _leave("");
 277 }
 278
 279 /*
 280  * give up the callback registered for a vnode on the file server when the
 281  * inode is being cleared
 282  */
 283 void afs_give_up_callback(struct afs_vnode *vnode)
 284 {
 285         struct afs_server *server = vnode->server;
 286
 287         DECLARE_WAITQUEUE(myself, current);
 288
 289         _enter("%d", vnode->cb_promised);
 290
 291         _debug("GIVE UP INODE %p", &vnode->vfs_inode);
 292
 293         if (!vnode->cb_promised) {
 294                 _leave(" [not promised]");
 295                 return;
 296         }
 297
 298         ASSERT(server != NULL);
 299
 300         spin_lock(&server->cb_lock);
 301         if (vnode->cb_promised && afs_breakring_space(server) == 0) {
 302                 add_wait_queue(&server->cb_break_waitq, &myself);
 303                 for (;;) {
 304                         set_current_state(TASK_UNINTERRUPTIBLE);
 305                         if (!vnode->cb_promised ||
 306                             afs_breakring_space(server) != 0)
 307                                 break;
 308                         spin_unlock(&server->cb_lock);
 309                         schedule();
 310                         spin_lock(&server->cb_lock);
 311                 }
 312                 remove_wait_queue(&server->cb_break_waitq, &myself);
 313                 __set_current_state(TASK_RUNNING);
 314         }
 315
 316         /* of course, it's always possible for the server to break this vnode's
 317          * callback first... */
 318         if (vnode->cb_promised)
 319                 afs_do_give_up_callback(server, vnode);
 320
 321         spin_unlock(&server->cb_lock);
 322         _leave("");
 323 }
 324
 325 /*
 326  * dispatch a deferred give up callbacks operation
 327  */
 328 void afs_dispatch_give_up_callbacks(struct work_struct *work)
 329 {
 330         struct afs_server *server =
 331                 container_of(work, struct afs_server, cb_break_work.work);
 332
 333         _enter("");
 334
 335         /* tell the fileserver to discard the callback promises it has
 336          * - in the event of ENOMEM or some other error, we just forget that we
 337          *   had callbacks entirely, and the server will call us later to break
 338          *   them
 339          */
 340         afs_fs_give_up_callbacks(server, &afs_async_call);
 341 }
 342
 343 /*
 344  * flush the outstanding callback breaks on a server
 345  */
 346 void afs_flush_callback_breaks(struct afs_server *server)
 347 {
 348         cancel_delayed_work(&server->cb_break_work);
 349         queue_delayed_work(afs_callback_update_worker,
 350                            &server->cb_break_work, 0);
 351 }
 352
 353 #if 0
 354 /*
 355  * update a bunch of callbacks
 356  */
 357 static void afs_callback_updater(struct work_struct *work)
 358 {
 359         struct afs_server *server;
 360         struct afs_vnode *vnode, *xvnode;
 361         time_t now;
 362         long timeout;
 363         int ret;
 364
 365         server = container_of(work, struct afs_server, updater);
 366
 367         _enter("");
 368
 369         now = get_seconds();
 370
 371         /* find the first vnode to update */
 372         spin_lock(&server->cb_lock);
 373         for (;;) {
 374                 if (RB_EMPTY_ROOT(&server->cb_promises)) {
 375                         spin_unlock(&server->cb_lock);
 376                         _leave(" [nothing]");
 377                         return;
 378                 }
 379
 380                 vnode = rb_entry(rb_first(&server->cb_promises),
 381                                  struct afs_vnode, cb_promise);
 382                 if (atomic_read(&vnode->usage) > 0)
 383                         break;
 384                 rb_erase(&vnode->cb_promise, &server->cb_promises);
 385                 vnode->cb_promised = false;
 386         }
 387
 388         timeout = vnode->update_at - now;
 389         if (timeout > 0) {
 390                 queue_delayed_work(afs_vnode_update_worker,
 391                                    &afs_vnode_update, timeout * HZ);
 392                 spin_unlock(&server->cb_lock);
 393                 _leave(" [nothing]");
 394                 return;
 395         }
 396
 397         list_del_init(&vnode->update);
 398         atomic_inc(&vnode->usage);
 399         spin_unlock(&server->cb_lock);
 400
 401         /* we can now perform the update */
 402         _debug("update %s", vnode->vldb.name);
 403         vnode->state = AFS_VL_UPDATING;
 404         vnode->upd_rej_cnt = 0;
 405         vnode->upd_busy_cnt = 0;
 406
 407         ret = afs_vnode_update_record(vl, &vldb);
 408         switch (ret) {
 409         case 0:
 410                 afs_vnode_apply_update(vl, &vldb);
 411                 vnode->state = AFS_VL_UPDATING;
 412                 break;
 413         case -ENOMEDIUM:
 414                 vnode->state = AFS_VL_VOLUME_DELETED;
 415                 break;
 416         default:
 417                 vnode->state = AFS_VL_UNCERTAIN;
 418                 break;
 419         }
 420
 421         /* and then reschedule */
 422         _debug("reschedule");
 423         vnode->update_at = get_seconds() + afs_vnode_update_timeout;
 424
 425         spin_lock(&server->cb_lock);
 426
 427         if (!list_empty(&server->cb_promises)) {
 428                 /* next update in 10 minutes, but wait at least 1 second more
 429                  * than the newest record already queued so that we don't spam
 430                  * the VL server suddenly with lots of requests
 431                  */
 432                 xvnode = list_entry(server->cb_promises.prev,
 433                                     struct afs_vnode, update);
 434                 if (vnode->update_at <= xvnode->update_at)
 435                         vnode->update_at = xvnode->update_at + 1;
 436                 xvnode = list_entry(server->cb_promises.next,
 437                                     struct afs_vnode, update);
 438                 timeout = xvnode->update_at - now;
 439                 if (timeout < 0)
 440                         timeout = 0;
 441         } else {
 442                 timeout = afs_vnode_update_timeout;
 443         }
 444
 445         list_add_tail(&vnode->update, &server->cb_promises);
 446
 447         _debug("timeout %ld", timeout);
 448         queue_delayed_work(afs_vnode_update_worker,
 449                            &afs_vnode_update, timeout * HZ);
 450         spin_unlock(&server->cb_lock);
 451         afs_put_vnode(vl);
 452 }
 453 #endif
 454
 455 /*
 456  * initialise the callback update process
 457  */
 458 int __init afs_callback_update_init(void)
 459 {
 460         afs_callback_update_worker =
 461                 create_singlethread_workqueue("kafs_callbackd");
 462         return afs_callback_update_worker ? 0 : -ENOMEM;
 463 }
 464
 465 /*
 466  * shut down the callback update process
 467  */
 468 void afs_callback_update_kill(void)
 469 {
 470         destroy_workqueue(afs_callback_update_worker);
 471 }