fs/fscache/operation.c

   1 /* FS-Cache worker operation management routines
   2  *
   3  * Copyright (C) 2008 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 License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  *
  11  * See Documentation/filesystems/caching/operations.txt
  12  */
  13
  14 #define FSCACHE_DEBUG_LEVEL OPERATION
  15 #include <linux/module.h>
  16 #include <linux/seq_file.h>
  17 #include <linux/slab.h>
  18 #include "internal.h"
  19
  20 atomic_t fscache_op_debug_id;
  21 EXPORT_SYMBOL(fscache_op_debug_id);
  22
  23 /**
  24  * fscache_enqueue_operation - Enqueue an operation for processing
  25  * @op: The operation to enqueue
  26  *
  27  * Enqueue an operation for processing by the FS-Cache thread pool.
  28  *
  29  * This will get its own ref on the object.
  30  */
  31 void fscache_enqueue_operation(struct fscache_operation *op)
  32 {
  33         _enter("{OBJ%x OP%x,%u}",
  34                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
  35
  36         ASSERT(list_empty(&op->pend_link));
  37         ASSERT(op->processor != NULL);
  38         ASSERT(fscache_object_is_available(op->object));
  39         ASSERTCMP(atomic_read(&op->usage), >, 0);
  40         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
  41
  42         fscache_stat(&fscache_n_op_enqueue);
  43         switch (op->flags & FSCACHE_OP_TYPE) {
  44         case FSCACHE_OP_ASYNC:
  45                 _debug("queue async");
  46                 atomic_inc(&op->usage);
  47                 if (!queue_work(fscache_op_wq, &op->work))
  48                         fscache_put_operation(op);
  49                 break;
  50         case FSCACHE_OP_MYTHREAD:
  51                 _debug("queue for caller's attention");
  52                 break;
  53         default:
  54                 pr_err("Unexpected op type %lx", op->flags);
  55                 BUG();
  56                 break;
  57         }
  58 }
  59 EXPORT_SYMBOL(fscache_enqueue_operation);
  60
  61 /*
  62  * start an op running
  63  */
  64 static void fscache_run_op(struct fscache_object *object,
  65                            struct fscache_operation *op)
  66 {
  67         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
  68
  69         op->state = FSCACHE_OP_ST_IN_PROGRESS;
  70         object->n_in_progress++;
  71         if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
  72                 wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
  73         if (op->processor)
  74                 fscache_enqueue_operation(op);
  75         fscache_stat(&fscache_n_op_run);
  76 }
  77
  78 /*
  79  * submit an exclusive operation for an object
  80  * - other ops are excluded from running simultaneously with this one
  81  * - this gets any extra refs it needs on an op
  82  */
  83 int fscache_submit_exclusive_op(struct fscache_object *object,
  84                                 struct fscache_operation *op)
  85 {
  86         int ret;
  87
  88         _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
  89
  90         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
  91         ASSERTCMP(atomic_read(&op->usage), >, 0);
  92
  93         spin_lock(&object->lock);
  94         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
  95         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
  96         ASSERT(list_empty(&op->pend_link));
  97
  98         op->state = FSCACHE_OP_ST_PENDING;
  99         if (fscache_object_is_active(object)) {
 100                 op->object = object;
 101                 object->n_ops++;
 102                 object->n_exclusive++;  /* reads and writes must wait */
 103
 104                 if (object->n_in_progress > 0) {
 105                         atomic_inc(&op->usage);
 106                         list_add_tail(&op->pend_link, &object->pending_ops);
 107                         fscache_stat(&fscache_n_op_pend);
 108                 } else if (!list_empty(&object->pending_ops)) {
 109                         atomic_inc(&op->usage);
 110                         list_add_tail(&op->pend_link, &object->pending_ops);
 111                         fscache_stat(&fscache_n_op_pend);
 112                         fscache_start_operations(object);
 113                 } else {
 114                         ASSERTCMP(object->n_in_progress, ==, 0);
 115                         fscache_run_op(object, op);
 116                 }
 117
 118                 /* need to issue a new write op after this */
 119                 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 120                 ret = 0;
 121         } else if (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 122                 op->object = object;
 123                 object->n_ops++;
 124                 object->n_exclusive++;  /* reads and writes must wait */
 125                 atomic_inc(&op->usage);
 126                 list_add_tail(&op->pend_link, &object->pending_ops);
 127                 fscache_stat(&fscache_n_op_pend);
 128                 ret = 0;
 129         } else {
 130                 /* If we're in any other state, there must have been an I/O
 131                  * error of some nature.
 132                  */
 133                 ASSERT(test_bit(FSCACHE_IOERROR, &object->cache->flags));
 134                 ret = -EIO;
 135         }
 136
 137         spin_unlock(&object->lock);
 138         return ret;
 139 }
 140
 141 /*
 142  * report an unexpected submission
 143  */
 144 static void fscache_report_unexpected_submission(struct fscache_object *object,
 145                                                  struct fscache_operation *op,
 146                                                  const struct fscache_state *ostate)
 147 {
 148         static bool once_only;
 149         struct fscache_operation *p;
 150         unsigned n;
 151
 152         if (once_only)
 153                 return;
 154         once_only = true;
 155
 156         kdebug("unexpected submission OP%x [OBJ%x %s]",
 157                op->debug_id, object->debug_id, object->state->name);
 158         kdebug("objstate=%s [%s]", object->state->name, ostate->name);
 159         kdebug("objflags=%lx", object->flags);
 160         kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
 161         kdebug("ops=%u inp=%u exc=%u",
 162                object->n_ops, object->n_in_progress, object->n_exclusive);
 163
 164         if (!list_empty(&object->pending_ops)) {
 165                 n = 0;
 166                 list_for_each_entry(p, &object->pending_ops, pend_link) {
 167                         ASSERTCMP(p->object, ==, object);
 168                         kdebug("%p %p", op->processor, op->release);
 169                         n++;
 170                 }
 171
 172                 kdebug("n=%u", n);
 173         }
 174
 175         dump_stack();
 176 }
 177
 178 /*
 179  * submit an operation for an object
 180  * - objects may be submitted only in the following states:
 181  *   - during object creation (write ops may be submitted)
 182  *   - whilst the object is active
 183  *   - after an I/O error incurred in one of the two above states (op rejected)
 184  * - this gets any extra refs it needs on an op
 185  */
 186 int fscache_submit_op(struct fscache_object *object,
 187                       struct fscache_operation *op)
 188 {
 189         const struct fscache_state *ostate;
 190         int ret;
 191
 192         _enter("{OBJ%x OP%x},{%u}",
 193                object->debug_id, op->debug_id, atomic_read(&op->usage));
 194
 195         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
 196         ASSERTCMP(atomic_read(&op->usage), >, 0);
 197
 198         spin_lock(&object->lock);
 199         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
 200         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
 201         ASSERT(list_empty(&op->pend_link));
 202
 203         ostate = object->state;
 204         smp_rmb();
 205
 206         op->state = FSCACHE_OP_ST_PENDING;
 207         if (fscache_object_is_active(object)) {
 208                 op->object = object;
 209                 object->n_ops++;
 210
 211                 if (object->n_exclusive > 0) {
 212                         atomic_inc(&op->usage);
 213                         list_add_tail(&op->pend_link, &object->pending_ops);
 214                         fscache_stat(&fscache_n_op_pend);
 215                 } else if (!list_empty(&object->pending_ops)) {
 216                         atomic_inc(&op->usage);
 217                         list_add_tail(&op->pend_link, &object->pending_ops);
 218                         fscache_stat(&fscache_n_op_pend);
 219                         fscache_start_operations(object);
 220                 } else {
 221                         ASSERTCMP(object->n_exclusive, ==, 0);
 222                         fscache_run_op(object, op);
 223                 }
 224                 ret = 0;
 225         } else if (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 226                 op->object = object;
 227                 object->n_ops++;
 228                 atomic_inc(&op->usage);
 229                 list_add_tail(&op->pend_link, &object->pending_ops);
 230                 fscache_stat(&fscache_n_op_pend);
 231                 ret = 0;
 232         } else if (fscache_object_is_dying(object)) {
 233                 fscache_stat(&fscache_n_op_rejected);
 234                 op->state = FSCACHE_OP_ST_CANCELLED;
 235                 ret = -ENOBUFS;
 236         } else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 237                 fscache_report_unexpected_submission(object, op, ostate);
 238                 ASSERT(!fscache_object_is_active(object));
 239                 op->state = FSCACHE_OP_ST_CANCELLED;
 240                 ret = -ENOBUFS;
 241         } else {
 242                 op->state = FSCACHE_OP_ST_CANCELLED;
 243                 ret = -ENOBUFS;
 244         }
 245
 246         spin_unlock(&object->lock);
 247         return ret;
 248 }
 249
 250 /*
 251  * queue an object for withdrawal on error, aborting all following asynchronous
 252  * operations
 253  */
 254 void fscache_abort_object(struct fscache_object *object)
 255 {
 256         _enter("{OBJ%x}", object->debug_id);
 257
 258         fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 259 }
 260
 261 /*
 262  * Jump start the operation processing on an object.  The caller must hold
 263  * object->lock.
 264  */
 265 void fscache_start_operations(struct fscache_object *object)
 266 {
 267         struct fscache_operation *op;
 268         bool stop = false;
 269
 270         while (!list_empty(&object->pending_ops) && !stop) {
 271                 op = list_entry(object->pending_ops.next,
 272                                 struct fscache_operation, pend_link);
 273
 274                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 275                         if (object->n_in_progress > 0)
 276                                 break;
 277                         stop = true;
 278                 }
 279                 list_del_init(&op->pend_link);
 280                 fscache_run_op(object, op);
 281
 282                 /* the pending queue was holding a ref on the object */
 283                 fscache_put_operation(op);
 284         }
 285
 286         ASSERTCMP(object->n_in_progress, <=, object->n_ops);
 287
 288         _debug("woke %d ops on OBJ%x",
 289                object->n_in_progress, object->debug_id);
 290 }
 291
 292 /*
 293  * cancel an operation that's pending on an object
 294  */
 295 int fscache_cancel_op(struct fscache_operation *op,
 296                       void (*do_cancel)(struct fscache_operation *))
 297 {
 298         struct fscache_object *object = op->object;
 299         int ret;
 300
 301         _enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
 302
 303         ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
 304         ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
 305         ASSERTCMP(atomic_read(&op->usage), >, 0);
 306
 307         spin_lock(&object->lock);
 308
 309         ret = -EBUSY;
 310         if (op->state == FSCACHE_OP_ST_PENDING) {
 311                 ASSERT(!list_empty(&op->pend_link));
 312                 fscache_stat(&fscache_n_op_cancelled);
 313                 list_del_init(&op->pend_link);
 314                 if (do_cancel)
 315                         do_cancel(op);
 316                 op->state = FSCACHE_OP_ST_CANCELLED;
 317                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 318                         object->n_exclusive--;
 319                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 320                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 321                 fscache_put_operation(op);
 322                 ret = 0;
 323         }
 324
 325         spin_unlock(&object->lock);
 326         _leave(" = %d", ret);
 327         return ret;
 328 }
 329
 330 /*
 331  * Cancel all pending operations on an object
 332  */
 333 void fscache_cancel_all_ops(struct fscache_object *object)
 334 {
 335         struct fscache_operation *op;
 336
 337         _enter("OBJ%x", object->debug_id);
 338
 339         spin_lock(&object->lock);
 340
 341         while (!list_empty(&object->pending_ops)) {
 342                 op = list_entry(object->pending_ops.next,
 343                                 struct fscache_operation, pend_link);
 344                 fscache_stat(&fscache_n_op_cancelled);
 345                 list_del_init(&op->pend_link);
 346
 347                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
 348                 op->state = FSCACHE_OP_ST_CANCELLED;
 349
 350                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 351                         object->n_exclusive--;
 352                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 353                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 354                 fscache_put_operation(op);
 355                 cond_resched_lock(&object->lock);
 356         }
 357
 358         spin_unlock(&object->lock);
 359         _leave("");
 360 }
 361
 362 /*
 363  * Record the completion or cancellation of an in-progress operation.
 364  */
 365 void fscache_op_complete(struct fscache_operation *op, bool cancelled)
 366 {
 367         struct fscache_object *object = op->object;
 368
 369         _enter("OBJ%x", object->debug_id);
 370
 371         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
 372         ASSERTCMP(object->n_in_progress, >, 0);
 373         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 374                     object->n_exclusive, >, 0);
 375         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 376                     object->n_in_progress, ==, 1);
 377
 378         spin_lock(&object->lock);
 379
 380         op->state = cancelled ?
 381                 FSCACHE_OP_ST_CANCELLED : FSCACHE_OP_ST_COMPLETE;
 382
 383         if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 384                 object->n_exclusive--;
 385         object->n_in_progress--;
 386         if (object->n_in_progress == 0)
 387                 fscache_start_operations(object);
 388
 389         spin_unlock(&object->lock);
 390         _leave("");
 391 }
 392 EXPORT_SYMBOL(fscache_op_complete);
 393
 394 /*
 395  * release an operation
 396  * - queues pending ops if this is the last in-progress op
 397  */
 398 void fscache_put_operation(struct fscache_operation *op)
 399 {
 400         struct fscache_object *object;
 401         struct fscache_cache *cache;
 402
 403         _enter("{OBJ%x OP%x,%d}",
 404                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 405
 406         ASSERTCMP(atomic_read(&op->usage), >, 0);
 407
 408         if (!atomic_dec_and_test(&op->usage))
 409                 return;
 410
 411         _debug("PUT OP");
 412         ASSERTIFCMP(op->state != FSCACHE_OP_ST_COMPLETE,
 413                     op->state, ==, FSCACHE_OP_ST_CANCELLED);
 414         op->state = FSCACHE_OP_ST_DEAD;
 415
 416         fscache_stat(&fscache_n_op_release);
 417
 418         if (op->release) {
 419                 op->release(op);
 420                 op->release = NULL;
 421         }
 422
 423         object = op->object;
 424
 425         if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
 426                 atomic_dec(&object->n_reads);
 427         if (test_bit(FSCACHE_OP_UNUSE_COOKIE, &op->flags))
 428                 fscache_unuse_cookie(object);
 429
 430         /* now... we may get called with the object spinlock held, so we
 431          * complete the cleanup here only if we can immediately acquire the
 432          * lock, and defer it otherwise */
 433         if (!spin_trylock(&object->lock)) {
 434                 _debug("defer put");
 435                 fscache_stat(&fscache_n_op_deferred_release);
 436
 437                 cache = object->cache;
 438                 spin_lock(&cache->op_gc_list_lock);
 439                 list_add_tail(&op->pend_link, &cache->op_gc_list);
 440                 spin_unlock(&cache->op_gc_list_lock);
 441                 schedule_work(&cache->op_gc);
 442                 _leave(" [defer]");
 443                 return;
 444         }
 445
 446         ASSERTCMP(object->n_ops, >, 0);
 447         object->n_ops--;
 448         if (object->n_ops == 0)
 449                 fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 450
 451         spin_unlock(&object->lock);
 452
 453         kfree(op);
 454         _leave(" [done]");
 455 }
 456 EXPORT_SYMBOL(fscache_put_operation);
 457
 458 /*
 459  * garbage collect operations that have had their release deferred
 460  */
 461 void fscache_operation_gc(struct work_struct *work)
 462 {
 463         struct fscache_operation *op;
 464         struct fscache_object *object;
 465         struct fscache_cache *cache =
 466                 container_of(work, struct fscache_cache, op_gc);
 467         int count = 0;
 468
 469         _enter("");
 470
 471         do {
 472                 spin_lock(&cache->op_gc_list_lock);
 473                 if (list_empty(&cache->op_gc_list)) {
 474                         spin_unlock(&cache->op_gc_list_lock);
 475                         break;
 476                 }
 477
 478                 op = list_entry(cache->op_gc_list.next,
 479                                 struct fscache_operation, pend_link);
 480                 list_del(&op->pend_link);
 481                 spin_unlock(&cache->op_gc_list_lock);
 482
 483                 object = op->object;
 484                 spin_lock(&object->lock);
 485
 486                 _debug("GC DEFERRED REL OBJ%x OP%x",
 487                        object->debug_id, op->debug_id);
 488                 fscache_stat(&fscache_n_op_gc);
 489
 490                 ASSERTCMP(atomic_read(&op->usage), ==, 0);
 491                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
 492
 493                 ASSERTCMP(object->n_ops, >, 0);
 494                 object->n_ops--;
 495                 if (object->n_ops == 0)
 496                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 497
 498                 spin_unlock(&object->lock);
 499                 kfree(op);
 500
 501         } while (count++ < 20);
 502
 503         if (!list_empty(&cache->op_gc_list))
 504                 schedule_work(&cache->op_gc);
 505
 506         _leave("");
 507 }
 508
 509 /*
 510  * execute an operation using fs_op_wq to provide processing context -
 511  * the caller holds a ref to this object, so we don't need to hold one
 512  */
 513 void fscache_op_work_func(struct work_struct *work)
 514 {
 515         struct fscache_operation *op =
 516                 container_of(work, struct fscache_operation, work);
 517         unsigned long start;
 518
 519         _enter("{OBJ%x OP%x,%d}",
 520                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 521
 522         ASSERT(op->processor != NULL);
 523         start = jiffies;
 524         op->processor(op);
 525         fscache_hist(fscache_ops_histogram, start);
 526         fscache_put_operation(op);
 527
 528         _leave("");
 529 }