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@infradead.org>
  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 #if 0
  24 unsigned afs_vnode_update_timeout = 10;
  25 #endif  /*  0  */
  26
  27 #define afs_breakring_space(server) \
  28         CIRC_SPACE((server)->cb_break_head, (server)->cb_break_tail,    \
  29                    ARRAY_SIZE((server)->cb_break))
  30
  31 //static void afs_callback_updater(struct work_struct *);
  32
  33 static struct workqueue_struct *afs_callback_update_worker;
  34
  35 /*
  36  * allow the fileserver to request callback state (re-)initialisation
  37  */
  38 void afs_init_callback_state(struct afs_server *server)
  39 {
  40         struct afs_vnode *vnode;
  41
  42         _enter("{%p}", server);
  43
  44         spin_lock(&server->cb_lock);
  45
  46         /* kill all the promises on record from this server */
  47         while (!RB_EMPTY_ROOT(&server->cb_promises)) {
  48                 vnode = rb_entry(server->cb_promises.rb_node,
  49                                  struct afs_vnode, cb_promise);
  50                 _debug("UNPROMISE { vid=%x:%u uq=%u}",
  51                        vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
  52                 rb_erase(&vnode->cb_promise, &server->cb_promises);
  53                 vnode->cb_promised = false;
  54         }
  55
  56         spin_unlock(&server->cb_lock);
  57         _leave("");
  58 }
  59
  60 /*
  61  * handle the data invalidation side of a callback being broken
  62  */
  63 void afs_broken_callback_work(struct work_struct *work)
  64 {
  65         struct afs_vnode *vnode =
  66                 container_of(work, struct afs_vnode, cb_broken_work);
  67
  68         _enter("");
  69
  70         if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
  71                 return;
  72
  73         /* we're only interested in dealing with a broken callback on *this*
  74          * vnode and only if no-one else has dealt with it yet */
  75         if (!mutex_trylock(&vnode->validate_lock))
  76                 return; /* someone else is dealing with it */
  77
  78         if (test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags)) {
  79                 if (S_ISDIR(vnode->vfs_inode.i_mode))
  80                         afs_clear_permits(vnode);
  81
  82                 if (afs_vnode_fetch_status(vnode, NULL, NULL) < 0)
  83                         goto out;
  84
  85                 if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
  86                         goto out;
  87
  88                 /* if the vnode's data version number changed then its contents
  89                  * are different */
  90                 if (test_and_clear_bit(AFS_VNODE_ZAP_DATA, &vnode->flags))
  91                         afs_zap_data(vnode);
  92         }
  93
  94 out:
  95         mutex_unlock(&vnode->validate_lock);
  96
  97         /* avoid the potential race whereby the mutex_trylock() in this
  98          * function happens again between the clear_bit() and the
  99          * mutex_unlock() */
 100         if (test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags)) {
 101                 _debug("requeue");
 102                 queue_work(afs_callback_update_worker, &vnode->cb_broken_work);
 103         }
 104         _leave("");
 105 }
 106
 107 /*
 108  * actually break a callback
 109  */
 110 static void afs_break_callback(struct afs_server *server,
 111                                struct afs_vnode *vnode)
 112 {
 113         _enter("");
 114
 115         set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);
 116
 117         if (vnode->cb_promised) {
 118                 spin_lock(&vnode->lock);
 119
 120                 _debug("break callback");
 121
 122                 spin_lock(&server->cb_lock);
 123                 if (vnode->cb_promised) {
 124                         rb_erase(&vnode->cb_promise, &server->cb_promises);
 125                         vnode->cb_promised = false;
 126                 }
 127                 spin_unlock(&server->cb_lock);
 128
 129                 queue_work(afs_callback_update_worker, &vnode->cb_broken_work);
 130                 if (list_empty(&vnode->granted_locks) &&
 131                     !list_empty(&vnode->pending_locks))
 132                         afs_lock_may_be_available(vnode);
 133                 spin_unlock(&vnode->lock);
 134         }
 135 }
 136
 137 /*
 138  * allow the fileserver to explicitly break one callback
 139  * - happens when
 140  *   - the backing file is changed
 141  *   - a lock is released
 142  */
 143 static void afs_break_one_callback(struct afs_server *server,
 144                                    struct afs_fid *fid)
 145 {
 146         struct afs_vnode *vnode;
 147         struct rb_node *p;
 148
 149         _debug("find");
 150         spin_lock(&server->fs_lock);
 151         p = server->fs_vnodes.rb_node;
 152         while (p) {
 153                 vnode = rb_entry(p, struct afs_vnode, server_rb);
 154                 if (fid->vid < vnode->fid.vid)
 155                         p = p->rb_left;
 156                 else if (fid->vid > vnode->fid.vid)
 157                         p = p->rb_right;
 158                 else if (fid->vnode < vnode->fid.vnode)
 159                         p = p->rb_left;
 160                 else if (fid->vnode > vnode->fid.vnode)
 161                         p = p->rb_right;
 162                 else if (fid->unique < vnode->fid.unique)
 163                         p = p->rb_left;
 164                 else if (fid->unique > vnode->fid.unique)
 165                         p = p->rb_right;
 166                 else
 167                         goto found;
 168         }
 169
 170         /* not found so we just ignore it (it may have moved to another
 171          * server) */
 172 not_available:
 173         _debug("not avail");
 174         spin_unlock(&server->fs_lock);
 175         _leave("");
 176         return;
 177
 178 found:
 179         _debug("found");
 180         ASSERTCMP(server, ==, vnode->server);
 181
 182         if (!igrab(AFS_VNODE_TO_I(vnode)))
 183                 goto not_available;
 184         spin_unlock(&server->fs_lock);
 185
 186         afs_break_callback(server, vnode);
 187         iput(&vnode->vfs_inode);
 188         _leave("");
 189 }
 190
 191 /*
 192  * allow the fileserver to break callback promises
 193  */
 194 void afs_break_callbacks(struct afs_server *server, size_t count,
 195                          struct afs_callback callbacks[])
 196 {
 197         _enter("%p,%zu,", server, count);
 198
 199         ASSERT(server != NULL);
 200         ASSERTCMP(count, <=, AFSCBMAX);
 201
 202         for (; count > 0; callbacks++, count--) {
 203                 _debug("- Fid { vl=%08x n=%u u=%u }  CB { v=%u x=%u t=%u }",
 204                        callbacks->fid.vid,
 205                        callbacks->fid.vnode,
 206                        callbacks->fid.unique,
 207                        callbacks->version,
 208                        callbacks->expiry,
 209                        callbacks->type
 210                        );
 211                 afs_break_one_callback(server, &callbacks->fid);
 212         }
 213
 214         _leave("");
 215         return;
 216 }
 217
 218 /*
 219  * record the callback for breaking
 220  * - the caller must hold server->cb_lock
 221  */
 222 static void afs_do_give_up_callback(struct afs_server *server,
 223                                     struct afs_vnode *vnode)
 224 {
 225         struct afs_callback *cb;
 226
 227         _enter("%p,%p", server, vnode);
 228
 229         cb = &server->cb_break[server->cb_break_head];
 230         cb->fid         = vnode->fid;
 231         cb->version     = vnode->cb_version;
 232         cb->expiry      = vnode->cb_expiry;
 233         cb->type        = vnode->cb_type;
 234         smp_wmb();
 235         server->cb_break_head =
 236                 (server->cb_break_head + 1) &
 237                 (ARRAY_SIZE(server->cb_break) - 1);
 238
 239         /* defer the breaking of callbacks to try and collect as many as
 240          * possible to ship in one operation */
 241         switch (atomic_inc_return(&server->cb_break_n)) {
 242         case 1 ... AFSCBMAX - 1:
 243                 queue_delayed_work(afs_callback_update_worker,
 244                                    &server->cb_break_work, HZ * 2);
 245                 break;
 246         case AFSCBMAX:
 247                 afs_flush_callback_breaks(server);
 248                 break;
 249         default:
 250                 break;
 251         }
 252
 253         ASSERT(server->cb_promises.rb_node != NULL);
 254         rb_erase(&vnode->cb_promise, &server->cb_promises);
 255         vnode->cb_promised = false;
 256         _leave("");
 257 }
 258
 259 /*
 260  * discard the callback on a deleted item
 261  */
 262 void afs_discard_callback_on_delete(struct afs_vnode *vnode)
 263 {
 264         struct afs_server *server = vnode->server;
 265
 266         _enter("%d", vnode->cb_promised);
 267
 268         if (!vnode->cb_promised) {
 269                 _leave(" [not promised]");
 270                 return;
 271         }
 272
 273         ASSERT(server != NULL);
 274
 275         spin_lock(&server->cb_lock);
 276         if (vnode->cb_promised) {
 277                 ASSERT(server->cb_promises.rb_node != NULL);
 278                 rb_erase(&vnode->cb_promise, &server->cb_promises);
 279                 vnode->cb_promised = false;
 280         }
 281         spin_unlock(&server->cb_lock);
 282         _leave("");
 283 }
 284
 285 /*
 286  * give up the callback registered for a vnode on the file server when the
 287  * inode is being cleared
 288  */
 289 void afs_give_up_callback(struct afs_vnode *vnode)
 290 {
 291         struct afs_server *server = vnode->server;
 292
 293         DECLARE_WAITQUEUE(myself, current);
 294
 295         _enter("%d", vnode->cb_promised);
 296
 297         _debug("GIVE UP INODE %p", &vnode->vfs_inode);
 298
 299         if (!vnode->cb_promised) {
 300                 _leave(" [not promised]");
 301                 return;
 302         }
 303
 304         ASSERT(server != NULL);
 305
 306         spin_lock(&server->cb_lock);
 307         if (vnode->cb_promised && afs_breakring_space(server) == 0) {
 308                 add_wait_queue(&server->cb_break_waitq, &myself);
 309                 for (;;) {
 310                         set_current_state(TASK_UNINTERRUPTIBLE);
 311                         if (!vnode->cb_promised ||
 312                             afs_breakring_space(server) != 0)
 313                                 break;
 314                         spin_unlock(&server->cb_lock);
 315                         schedule();
 316                         spin_lock(&server->cb_lock);
 317                 }
 318                 remove_wait_queue(&server->cb_break_waitq, &myself);
 319                 __set_current_state(TASK_RUNNING);
 320         }
 321
 322         /* of course, it's always possible for the server to break this vnode's
 323          * callback first... */
 324         if (vnode->cb_promised)
 325                 afs_do_give_up_callback(server, vnode);
 326
 327         spin_unlock(&server->cb_lock);
 328         _leave("");
 329 }
 330
 331 /*
 332  * dispatch a deferred give up callbacks operation
 333  */
 334 void afs_dispatch_give_up_callbacks(struct work_struct *work)
 335 {
 336         struct afs_server *server =
 337                 container_of(work, struct afs_server, cb_break_work.work);
 338
 339         _enter("");
 340
 341         /* tell the fileserver to discard the callback promises it has
 342          * - in the event of ENOMEM or some other error, we just forget that we
 343          *   had callbacks entirely, and the server will call us later to break
 344          *   them
 345          */
 346         afs_fs_give_up_callbacks(server, &afs_async_call);
 347 }
 348
 349 /*
 350  * flush the outstanding callback breaks on a server
 351  */
 352 void afs_flush_callback_breaks(struct afs_server *server)
 353 {
 354         mod_delayed_work(afs_callback_update_worker, &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 }