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 <linux/sched.h>
  21 #include "internal.h"
  22
  23 unsigned afs_vnode_update_timeout = 10;
  24
  25 #define afs_breakring_space(server) \
  26         CIRC_SPACE((server)->cb_break_head, (server)->cb_break_tail,    \
  27                    ARRAY_SIZE((server)->cb_break))
  28
  29 //static void afs_callback_updater(struct work_struct *);
  30
  31 static struct workqueue_struct *afs_callback_update_worker;
  32
  33 /*
  34  * allow the fileserver to request callback state (re-)initialisation
  35  */
  36 void afs_init_callback_state(struct afs_server *server)
  37 {
  38         struct afs_vnode *vnode;
  39
  40         _enter("{%p}", server);
  41
  42         spin_lock(&server->cb_lock);
  43
  44         /* kill all the promises on record from this server */
  45         while (!RB_EMPTY_ROOT(&server->cb_promises)) {
  46                 vnode = rb_entry(server->cb_promises.rb_node,
  47                                  struct afs_vnode, cb_promise);
  48                 _debug("UNPROMISE { vid=%x:%u uq=%u}",
  49                        vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
  50                 rb_erase(&vnode->cb_promise, &server->cb_promises);
  51                 vnode->cb_promised = false;
  52         }
  53
  54         spin_unlock(&server->cb_lock);
  55         _leave("");
  56 }
  57
  58 /*
  59  * handle the data invalidation side of a callback being broken
  60  */
  61 void afs_broken_callback_work(struct work_struct *work)
  62 {
  63         struct afs_vnode *vnode =
  64                 container_of(work, struct afs_vnode, cb_broken_work);
  65
  66         _enter("");
  67
  68         if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
  69                 return;
  70
  71         /* we're only interested in dealing with a broken callback on *this*
  72          * vnode and only if no-one else has dealt with it yet */
  73         if (!mutex_trylock(&vnode->validate_lock))
  74                 return; /* someone else is dealing with it */
  75
  76         if (test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags)) {
  77                 if (S_ISDIR(vnode->vfs_inode.i_mode))
  78                         afs_clear_permits(vnode);
  79
  80                 if (afs_vnode_fetch_status(vnode, NULL, NULL) < 0)
  81                         goto out;
  82
  83                 if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
  84                         goto out;
  85
  86                 /* if the vnode's data version number changed then its contents
  87                  * are different */
  88                 if (test_and_clear_bit(AFS_VNODE_ZAP_DATA, &vnode->flags))
  89                         afs_zap_data(vnode);
  90         }
  91
  92 out:
  93         mutex_unlock(&vnode->validate_lock);
  94
  95         /* avoid the potential race whereby the mutex_trylock() in this
  96          * function happens again between the clear_bit() and the
  97          * mutex_unlock() */
  98         if (test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags)) {
  99                 _debug("requeue");
 100                 queue_work(afs_callback_update_worker, &vnode->cb_broken_work);
 101         }
 102         _leave("");
 103 }
 104
 105 /*
 106  * actually break a callback
 107  */
 108 static void afs_break_callback(struct afs_server *server,
 109                                struct afs_vnode *vnode)
 110 {
 111         _enter("");
 112
 113         set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);
 114
 115         if (vnode->cb_promised) {
 116                 spin_lock(&vnode->lock);
 117
 118                 _debug("break callback");
 119
 120                 spin_lock(&server->cb_lock);
 121                 if (vnode->cb_promised) {
 122                         rb_erase(&vnode->cb_promise, &server->cb_promises);
 123                         vnode->cb_promised = false;
 124                 }
 125                 spin_unlock(&server->cb_lock);
 126
 127                 queue_work(afs_callback_update_worker, &vnode->cb_broken_work);
 128                 if (list_empty(&vnode->granted_locks) &&
 129                     !list_empty(&vnode->pending_locks))
 130                         afs_lock_may_be_available(vnode);
 131                 spin_unlock(&vnode->lock);
 132         }
 133 }
 134
 135 /*
 136  * allow the fileserver to explicitly break one callback
 137  * - happens when
 138  *   - the backing file is changed
 139  *   - a lock is released
 140  */
 141 static void afs_break_one_callback(struct afs_server *server,
 142                                    struct afs_fid *fid)
 143 {
 144         struct afs_vnode *vnode;
 145         struct rb_node *p;
 146
 147         _debug("find");
 148         spin_lock(&server->fs_lock);
 149         p = server->fs_vnodes.rb_node;
 150         while (p) {
 151                 vnode = rb_entry(p, struct afs_vnode, server_rb);
 152                 if (fid->vid < vnode->fid.vid)
 153                         p = p->rb_left;
 154                 else if (fid->vid > vnode->fid.vid)
 155                         p = p->rb_right;
 156                 else if (fid->vnode < vnode->fid.vnode)
 157                         p = p->rb_left;
 158                 else if (fid->vnode > vnode->fid.vnode)
 159                         p = p->rb_right;
 160                 else if (fid->unique < vnode->fid.unique)
 161                         p = p->rb_left;
 162                 else if (fid->unique > vnode->fid.unique)
 163                         p = p->rb_right;
 164                 else
 165                         goto found;
 166         }
 167
 168         /* not found so we just ignore it (it may have moved to another
 169          * server) */
 170 not_available:
 171         _debug("not avail");
 172         spin_unlock(&server->fs_lock);
 173         _leave("");
 174         return;
 175
 176 found:
 177         _debug("found");
 178         ASSERTCMP(server, ==, vnode->server);
 179
 180         if (!igrab(AFS_VNODE_TO_I(vnode)))
 181                 goto not_available;
 182         spin_unlock(&server->fs_lock);
 183
 184         afs_break_callback(server, vnode);
 185         iput(&vnode->vfs_inode);
 186         _leave("");
 187 }
 188
 189 /*
 190  * allow the fileserver to break callback promises
 191  */
 192 void afs_break_callbacks(struct afs_server *server, size_t count,
 193                          struct afs_callback callbacks[])
 194 {
 195         _enter("%p,%zu,", server, count);
 196
 197         ASSERT(server != NULL);
 198         ASSERTCMP(count, <=, AFSCBMAX);
 199
 200         for (; count > 0; callbacks++, count--) {
 201                 _debug("- Fid { vl=%08x n=%u u=%u }  CB { v=%u x=%u t=%u }",
 202                        callbacks->fid.vid,
 203                        callbacks->fid.vnode,
 204                        callbacks->fid.unique,
 205                        callbacks->version,
 206                        callbacks->expiry,
 207                        callbacks->type
 208                        );
 209                 afs_break_one_callback(server, &callbacks->fid);
 210         }
 211
 212         _leave("");
 213         return;
 214 }
 215
 216 /*
 217  * record the callback for breaking
 218  * - the caller must hold server->cb_lock
 219  */
 220 static void afs_do_give_up_callback(struct afs_server *server,
 221                                     struct afs_vnode *vnode)
 222 {
 223         struct afs_callback *cb;
 224
 225         _enter("%p,%p", server, vnode);
 226
 227         cb = &server->cb_break[server->cb_break_head];
 228         cb->fid         = vnode->fid;
 229         cb->version     = vnode->cb_version;
 230         cb->expiry      = vnode->cb_expiry;
 231         cb->type        = vnode->cb_type;
 232         smp_wmb();
 233         server->cb_break_head =
 234                 (server->cb_break_head + 1) &
 235                 (ARRAY_SIZE(server->cb_break) - 1);
 236
 237         /* defer the breaking of callbacks to try and collect as many as
 238          * possible to ship in one operation */
 239         switch (atomic_inc_return(&server->cb_break_n)) {
 240         case 1 ... AFSCBMAX - 1:
 241                 queue_delayed_work(afs_callback_update_worker,
 242                                    &server->cb_break_work, HZ * 2);
 243                 break;
 244         case AFSCBMAX:
 245                 afs_flush_callback_breaks(server);
 246                 break;
 247         default:
 248                 break;
 249         }
 250
 251         ASSERT(server->cb_promises.rb_node != NULL);
 252         rb_erase(&vnode->cb_promise, &server->cb_promises);
 253         vnode->cb_promised = false;
 254         _leave("");
 255 }
 256
 257 /*
 258  * discard the callback on a deleted item
 259  */
 260 void afs_discard_callback_on_delete(struct afs_vnode *vnode)
 261 {
 262         struct afs_server *server = vnode->server;
 263
 264         _enter("%d", vnode->cb_promised);
 265
 266         if (!vnode->cb_promised) {
 267                 _leave(" [not promised]");
 268                 return;
 269         }
 270
 271         ASSERT(server != NULL);
 272
 273         spin_lock(&server->cb_lock);
 274         if (vnode->cb_promised) {
 275                 ASSERT(server->cb_promises.rb_node != NULL);
 276                 rb_erase(&vnode->cb_promise, &server->cb_promises);
 277                 vnode->cb_promised = false;
 278         }
 279         spin_unlock(&server->cb_lock);
 280         _leave("");
 281 }
 282
 283 /*
 284  * give up the callback registered for a vnode on the file server when the
 285  * inode is being cleared
 286  */
 287 void afs_give_up_callback(struct afs_vnode *vnode)
 288 {
 289         struct afs_server *server = vnode->server;
 290
 291         DECLARE_WAITQUEUE(myself, current);
 292
 293         _enter("%d", vnode->cb_promised);
 294
 295         _debug("GIVE UP INODE %p", &vnode->vfs_inode);
 296
 297         if (!vnode->cb_promised) {
 298                 _leave(" [not promised]");
 299                 return;
 300         }
 301
 302         ASSERT(server != NULL);
 303
 304         spin_lock(&server->cb_lock);
 305         if (vnode->cb_promised && afs_breakring_space(server) == 0) {
 306                 add_wait_queue(&server->cb_break_waitq, &myself);
 307                 for (;;) {
 308                         set_current_state(TASK_UNINTERRUPTIBLE);
 309                         if (!vnode->cb_promised ||
 310                             afs_breakring_space(server) != 0)
 311                                 break;
 312                         spin_unlock(&server->cb_lock);
 313                         schedule();
 314                         spin_lock(&server->cb_lock);
 315                 }
 316                 remove_wait_queue(&server->cb_break_waitq, &myself);
 317                 __set_current_state(TASK_RUNNING);
 318         }
 319
 320         /* of course, it's always possible for the server to break this vnode's
 321          * callback first... */
 322         if (vnode->cb_promised)
 323                 afs_do_give_up_callback(server, vnode);
 324
 325         spin_unlock(&server->cb_lock);
 326         _leave("");
 327 }
 328
 329 /*
 330  * dispatch a deferred give up callbacks operation
 331  */
 332 void afs_dispatch_give_up_callbacks(struct work_struct *work)
 333 {
 334         struct afs_server *server =
 335                 container_of(work, struct afs_server, cb_break_work.work);
 336
 337         _enter("");
 338
 339         /* tell the fileserver to discard the callback promises it has
 340          * - in the event of ENOMEM or some other error, we just forget that we
 341          *   had callbacks entirely, and the server will call us later to break
 342          *   them
 343          */
 344         afs_fs_give_up_callbacks(server, &afs_async_call);
 345 }
 346
 347 /*
 348  * flush the outstanding callback breaks on a server
 349  */
 350 void afs_flush_callback_breaks(struct afs_server *server)
 351 {
 352         cancel_delayed_work(&server->cb_break_work);
 353         queue_delayed_work(afs_callback_update_worker,
 354                            &server->cb_break_work, 0);
 355 }
 356
 357 #if 0
 358 /*
 359  * update a bunch of callbacks
 360  */
 361 static void afs_callback_updater(struct work_struct *work)
 362 {
 363         struct afs_server *server;
 364         struct afs_vnode *vnode, *xvnode;
 365         time_t now;
 366         long timeout;
 367         int ret;
 368
 369         server = container_of(work, struct afs_server, updater);
 370
 371         _enter("");
 372
 373         now = get_seconds();
 374
 375         /* find the first vnode to update */
 376         spin_lock(&server->cb_lock);
 377         for (;;) {
 378                 if (RB_EMPTY_ROOT(&server->cb_promises)) {
 379                         spin_unlock(&server->cb_lock);
 380                         _leave(" [nothing]");
 381                         return;
 382                 }
 383
 384                 vnode = rb_entry(rb_first(&server->cb_promises),
 385                                  struct afs_vnode, cb_promise);
 386                 if (atomic_read(&vnode->usage) > 0)
 387                         break;
 388                 rb_erase(&vnode->cb_promise, &server->cb_promises);
 389                 vnode->cb_promised = false;
 390         }
 391
 392         timeout = vnode->update_at - now;
 393         if (timeout > 0) {
 394                 queue_delayed_work(afs_vnode_update_worker,
 395                                    &afs_vnode_update, timeout * HZ);
 396                 spin_unlock(&server->cb_lock);
 397                 _leave(" [nothing]");
 398                 return;
 399         }
 400
 401         list_del_init(&vnode->update);
 402         atomic_inc(&vnode->usage);
 403         spin_unlock(&server->cb_lock);
 404
 405         /* we can now perform the update */
 406         _debug("update %s", vnode->vldb.name);
 407         vnode->state = AFS_VL_UPDATING;
 408         vnode->upd_rej_cnt = 0;
 409         vnode->upd_busy_cnt = 0;
 410
 411         ret = afs_vnode_update_record(vl, &vldb);
 412         switch (ret) {
 413         case 0:
 414                 afs_vnode_apply_update(vl, &vldb);
 415                 vnode->state = AFS_VL_UPDATING;
 416                 break;
 417         case -ENOMEDIUM:
 418                 vnode->state = AFS_VL_VOLUME_DELETED;
 419                 break;
 420         default:
 421                 vnode->state = AFS_VL_UNCERTAIN;
 422                 break;
 423         }
 424
 425         /* and then reschedule */
 426         _debug("reschedule");
 427         vnode->update_at = get_seconds() + afs_vnode_update_timeout;
 428
 429         spin_lock(&server->cb_lock);
 430
 431         if (!list_empty(&server->cb_promises)) {
 432                 /* next update in 10 minutes, but wait at least 1 second more
 433                  * than the newest record already queued so that we don't spam
 434                  * the VL server suddenly with lots of requests
 435                  */
 436                 xvnode = list_entry(server->cb_promises.prev,
 437                                     struct afs_vnode, update);
 438                 if (vnode->update_at <= xvnode->update_at)
 439                         vnode->update_at = xvnode->update_at + 1;
 440                 xvnode = list_entry(server->cb_promises.next,
 441                                     struct afs_vnode, update);
 442                 timeout = xvnode->update_at - now;
 443                 if (timeout < 0)
 444                         timeout = 0;
 445         } else {
 446                 timeout = afs_vnode_update_timeout;
 447         }
 448
 449         list_add_tail(&vnode->update, &server->cb_promises);
 450
 451         _debug("timeout %ld", timeout);
 452         queue_delayed_work(afs_vnode_update_worker,
 453                            &afs_vnode_update, timeout * HZ);
 454         spin_unlock(&server->cb_lock);
 455         afs_put_vnode(vl);
 456 }
 457 #endif
 458
 459 /*
 460  * initialise the callback update process
 461  */
 462 int __init afs_callback_update_init(void)
 463 {
 464         afs_callback_update_worker =
 465                 create_singlethread_workqueue("kafs_callbackd");
 466         return afs_callback_update_worker ? 0 : -ENOMEM;
 467 }
 468
 469 /*
 470  * shut down the callback update process
 471  */
 472 void afs_callback_update_kill(void)
 473 {
 474         destroy_workqueue(afs_callback_update_worker);
 475 }