linux/fs/fscache/operation.c
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   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
  20atomic_t fscache_op_debug_id;
  21EXPORT_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 */
  31void 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                printk(KERN_ERR "FS-Cache: Unexpected op type %lx",
  55                       op->flags);
  56                BUG();
  57                break;
  58        }
  59}
  60EXPORT_SYMBOL(fscache_enqueue_operation);
  61
  62/*
  63 * start an op running
  64 */
  65static void fscache_run_op(struct fscache_object *object,
  66                           struct fscache_operation *op)
  67{
  68        ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
  69
  70        op->state = FSCACHE_OP_ST_IN_PROGRESS;
  71        object->n_in_progress++;
  72        if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
  73                wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
  74        if (op->processor)
  75                fscache_enqueue_operation(op);
  76        fscache_stat(&fscache_n_op_run);
  77}
  78
  79/*
  80 * submit an exclusive operation for an object
  81 * - other ops are excluded from running simultaneously with this one
  82 * - this gets any extra refs it needs on an op
  83 */
  84int fscache_submit_exclusive_op(struct fscache_object *object,
  85                                struct fscache_operation *op)
  86{
  87        int ret;
  88
  89        _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
  90
  91        ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
  92        ASSERTCMP(atomic_read(&op->usage), >, 0);
  93
  94        spin_lock(&object->lock);
  95        ASSERTCMP(object->n_ops, >=, object->n_in_progress);
  96        ASSERTCMP(object->n_ops, >=, object->n_exclusive);
  97        ASSERT(list_empty(&op->pend_link));
  98
  99        op->state = FSCACHE_OP_ST_PENDING;
 100        if (fscache_object_is_active(object)) {
 101                op->object = object;
 102                object->n_ops++;
 103                object->n_exclusive++;  /* reads and writes must wait */
 104
 105                if (object->n_in_progress > 0) {
 106                        atomic_inc(&op->usage);
 107                        list_add_tail(&op->pend_link, &object->pending_ops);
 108                        fscache_stat(&fscache_n_op_pend);
 109                } else if (!list_empty(&object->pending_ops)) {
 110                        atomic_inc(&op->usage);
 111                        list_add_tail(&op->pend_link, &object->pending_ops);
 112                        fscache_stat(&fscache_n_op_pend);
 113                        fscache_start_operations(object);
 114                } else {
 115                        ASSERTCMP(object->n_in_progress, ==, 0);
 116                        fscache_run_op(object, op);
 117                }
 118
 119                /* need to issue a new write op after this */
 120                clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 121                ret = 0;
 122        } else if (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 123                op->object = object;
 124                object->n_ops++;
 125                object->n_exclusive++;  /* reads and writes must wait */
 126                atomic_inc(&op->usage);
 127                list_add_tail(&op->pend_link, &object->pending_ops);
 128                fscache_stat(&fscache_n_op_pend);
 129                ret = 0;
 130        } else {
 131                /* If we're in any other state, there must have been an I/O
 132                 * error of some nature.
 133                 */
 134                ASSERT(test_bit(FSCACHE_IOERROR, &object->cache->flags));
 135                ret = -EIO;
 136        }
 137
 138        spin_unlock(&object->lock);
 139        return ret;
 140}
 141
 142/*
 143 * report an unexpected submission
 144 */
 145static void fscache_report_unexpected_submission(struct fscache_object *object,
 146                                                 struct fscache_operation *op,
 147                                                 const struct fscache_state *ostate)
 148{
 149        static bool once_only;
 150        struct fscache_operation *p;
 151        unsigned n;
 152
 153        if (once_only)
 154                return;
 155        once_only = true;
 156
 157        kdebug("unexpected submission OP%x [OBJ%x %s]",
 158               op->debug_id, object->debug_id, object->state->name);
 159        kdebug("objstate=%s [%s]", object->state->name, ostate->name);
 160        kdebug("objflags=%lx", object->flags);
 161        kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
 162        kdebug("ops=%u inp=%u exc=%u",
 163               object->n_ops, object->n_in_progress, object->n_exclusive);
 164
 165        if (!list_empty(&object->pending_ops)) {
 166                n = 0;
 167                list_for_each_entry(p, &object->pending_ops, pend_link) {
 168                        ASSERTCMP(p->object, ==, object);
 169                        kdebug("%p %p", op->processor, op->release);
 170                        n++;
 171                }
 172
 173                kdebug("n=%u", n);
 174        }
 175
 176        dump_stack();
 177}
 178
 179/*
 180 * submit an operation for an object
 181 * - objects may be submitted only in the following states:
 182 *   - during object creation (write ops may be submitted)
 183 *   - whilst the object is active
 184 *   - after an I/O error incurred in one of the two above states (op rejected)
 185 * - this gets any extra refs it needs on an op
 186 */
 187int fscache_submit_op(struct fscache_object *object,
 188                      struct fscache_operation *op)
 189{
 190        const struct fscache_state *ostate;
 191        int ret;
 192
 193        _enter("{OBJ%x OP%x},{%u}",
 194               object->debug_id, op->debug_id, atomic_read(&op->usage));
 195
 196        ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
 197        ASSERTCMP(atomic_read(&op->usage), >, 0);
 198
 199        spin_lock(&object->lock);
 200        ASSERTCMP(object->n_ops, >=, object->n_in_progress);
 201        ASSERTCMP(object->n_ops, >=, object->n_exclusive);
 202        ASSERT(list_empty(&op->pend_link));
 203
 204        ostate = object->state;
 205        smp_rmb();
 206
 207        op->state = FSCACHE_OP_ST_PENDING;
 208        if (fscache_object_is_active(object)) {
 209                op->object = object;
 210                object->n_ops++;
 211
 212                if (object->n_exclusive > 0) {
 213                        atomic_inc(&op->usage);
 214                        list_add_tail(&op->pend_link, &object->pending_ops);
 215                        fscache_stat(&fscache_n_op_pend);
 216                } else if (!list_empty(&object->pending_ops)) {
 217                        atomic_inc(&op->usage);
 218                        list_add_tail(&op->pend_link, &object->pending_ops);
 219                        fscache_stat(&fscache_n_op_pend);
 220                        fscache_start_operations(object);
 221                } else {
 222                        ASSERTCMP(object->n_exclusive, ==, 0);
 223                        fscache_run_op(object, op);
 224                }
 225                ret = 0;
 226        } else if (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 227                op->object = object;
 228                object->n_ops++;
 229                atomic_inc(&op->usage);
 230                list_add_tail(&op->pend_link, &object->pending_ops);
 231                fscache_stat(&fscache_n_op_pend);
 232                ret = 0;
 233        } else if (fscache_object_is_dying(object)) {
 234                fscache_stat(&fscache_n_op_rejected);
 235                op->state = FSCACHE_OP_ST_CANCELLED;
 236                ret = -ENOBUFS;
 237        } else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 238                fscache_report_unexpected_submission(object, op, ostate);
 239                ASSERT(!fscache_object_is_active(object));
 240                op->state = FSCACHE_OP_ST_CANCELLED;
 241                ret = -ENOBUFS;
 242        } else {
 243                op->state = FSCACHE_OP_ST_CANCELLED;
 244                ret = -ENOBUFS;
 245        }
 246
 247        spin_unlock(&object->lock);
 248        return ret;
 249}
 250
 251/*
 252 * queue an object for withdrawal on error, aborting all following asynchronous
 253 * operations
 254 */
 255void fscache_abort_object(struct fscache_object *object)
 256{
 257        _enter("{OBJ%x}", object->debug_id);
 258
 259        fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 260}
 261
 262/*
 263 * Jump start the operation processing on an object.  The caller must hold
 264 * object->lock.
 265 */
 266void fscache_start_operations(struct fscache_object *object)
 267{
 268        struct fscache_operation *op;
 269        bool stop = false;
 270
 271        while (!list_empty(&object->pending_ops) && !stop) {
 272                op = list_entry(object->pending_ops.next,
 273                                struct fscache_operation, pend_link);
 274
 275                if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 276                        if (object->n_in_progress > 0)
 277                                break;
 278                        stop = true;
 279                }
 280                list_del_init(&op->pend_link);
 281                fscache_run_op(object, op);
 282
 283                /* the pending queue was holding a ref on the object */
 284                fscache_put_operation(op);
 285        }
 286
 287        ASSERTCMP(object->n_in_progress, <=, object->n_ops);
 288
 289        _debug("woke %d ops on OBJ%x",
 290               object->n_in_progress, object->debug_id);
 291}
 292
 293/*
 294 * cancel an operation that's pending on an object
 295 */
 296int fscache_cancel_op(struct fscache_operation *op,
 297                      void (*do_cancel)(struct fscache_operation *))
 298{
 299        struct fscache_object *object = op->object;
 300        int ret;
 301
 302        _enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
 303
 304        ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
 305        ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
 306        ASSERTCMP(atomic_read(&op->usage), >, 0);
 307
 308        spin_lock(&object->lock);
 309
 310        ret = -EBUSY;
 311        if (op->state == FSCACHE_OP_ST_PENDING) {
 312                ASSERT(!list_empty(&op->pend_link));
 313                fscache_stat(&fscache_n_op_cancelled);
 314                list_del_init(&op->pend_link);
 315                if (do_cancel)
 316                        do_cancel(op);
 317                op->state = FSCACHE_OP_ST_CANCELLED;
 318                if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 319                        object->n_exclusive--;
 320                if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 321                        wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 322                fscache_put_operation(op);
 323                ret = 0;
 324        }
 325
 326        spin_unlock(&object->lock);
 327        _leave(" = %d", ret);
 328        return ret;
 329}
 330
 331/*
 332 * Cancel all pending operations on an object
 333 */
 334void fscache_cancel_all_ops(struct fscache_object *object)
 335{
 336        struct fscache_operation *op;
 337
 338        _enter("OBJ%x", object->debug_id);
 339
 340        spin_lock(&object->lock);
 341
 342        while (!list_empty(&object->pending_ops)) {
 343                op = list_entry(object->pending_ops.next,
 344                                struct fscache_operation, pend_link);
 345                fscache_stat(&fscache_n_op_cancelled);
 346                list_del_init(&op->pend_link);
 347
 348                ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
 349                op->state = FSCACHE_OP_ST_CANCELLED;
 350
 351                if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 352                        object->n_exclusive--;
 353                if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 354                        wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 355                fscache_put_operation(op);
 356                cond_resched_lock(&object->lock);
 357        }
 358
 359        spin_unlock(&object->lock);
 360        _leave("");
 361}
 362
 363/*
 364 * Record the completion or cancellation of an in-progress operation.
 365 */
 366void fscache_op_complete(struct fscache_operation *op, bool cancelled)
 367{
 368        struct fscache_object *object = op->object;
 369
 370        _enter("OBJ%x", object->debug_id);
 371
 372        ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
 373        ASSERTCMP(object->n_in_progress, >, 0);
 374        ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 375                    object->n_exclusive, >, 0);
 376        ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 377                    object->n_in_progress, ==, 1);
 378
 379        spin_lock(&object->lock);
 380
 381        op->state = cancelled ?
 382                FSCACHE_OP_ST_CANCELLED : FSCACHE_OP_ST_COMPLETE;
 383
 384        if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 385                object->n_exclusive--;
 386        object->n_in_progress--;
 387        if (object->n_in_progress == 0)
 388                fscache_start_operations(object);
 389
 390        spin_unlock(&object->lock);
 391        _leave("");
 392}
 393EXPORT_SYMBOL(fscache_op_complete);
 394
 395/*
 396 * release an operation
 397 * - queues pending ops if this is the last in-progress op
 398 */
 399void fscache_put_operation(struct fscache_operation *op)
 400{
 401        struct fscache_object *object;
 402        struct fscache_cache *cache;
 403
 404        _enter("{OBJ%x OP%x,%d}",
 405               op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 406
 407        ASSERTCMP(atomic_read(&op->usage), >, 0);
 408
 409        if (!atomic_dec_and_test(&op->usage))
 410                return;
 411
 412        _debug("PUT OP");
 413        ASSERTIFCMP(op->state != FSCACHE_OP_ST_COMPLETE,
 414                    op->state, ==, FSCACHE_OP_ST_CANCELLED);
 415        op->state = FSCACHE_OP_ST_DEAD;
 416
 417        fscache_stat(&fscache_n_op_release);
 418
 419        if (op->release) {
 420                op->release(op);
 421                op->release = NULL;
 422        }
 423
 424        object = op->object;
 425
 426        if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
 427                atomic_dec(&object->n_reads);
 428        if (test_bit(FSCACHE_OP_UNUSE_COOKIE, &op->flags))
 429                fscache_unuse_cookie(object);
 430
 431        /* now... we may get called with the object spinlock held, so we
 432         * complete the cleanup here only if we can immediately acquire the
 433         * lock, and defer it otherwise */
 434        if (!spin_trylock(&object->lock)) {
 435                _debug("defer put");
 436                fscache_stat(&fscache_n_op_deferred_release);
 437
 438                cache = object->cache;
 439                spin_lock(&cache->op_gc_list_lock);
 440                list_add_tail(&op->pend_link, &cache->op_gc_list);
 441                spin_unlock(&cache->op_gc_list_lock);
 442                schedule_work(&cache->op_gc);
 443                _leave(" [defer]");
 444                return;
 445        }
 446
 447        ASSERTCMP(object->n_ops, >, 0);
 448        object->n_ops--;
 449        if (object->n_ops == 0)
 450                fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 451
 452        spin_unlock(&object->lock);
 453
 454        kfree(op);
 455        _leave(" [done]");
 456}
 457EXPORT_SYMBOL(fscache_put_operation);
 458
 459/*
 460 * garbage collect operations that have had their release deferred
 461 */
 462void fscache_operation_gc(struct work_struct *work)
 463{
 464        struct fscache_operation *op;
 465        struct fscache_object *object;
 466        struct fscache_cache *cache =
 467                container_of(work, struct fscache_cache, op_gc);
 468        int count = 0;
 469
 470        _enter("");
 471
 472        do {
 473                spin_lock(&cache->op_gc_list_lock);
 474                if (list_empty(&cache->op_gc_list)) {
 475                        spin_unlock(&cache->op_gc_list_lock);
 476                        break;
 477                }
 478
 479                op = list_entry(cache->op_gc_list.next,
 480                                struct fscache_operation, pend_link);
 481                list_del(&op->pend_link);
 482                spin_unlock(&cache->op_gc_list_lock);
 483
 484                object = op->object;
 485                spin_lock(&object->lock);
 486
 487                _debug("GC DEFERRED REL OBJ%x OP%x",
 488                       object->debug_id, op->debug_id);
 489                fscache_stat(&fscache_n_op_gc);
 490
 491                ASSERTCMP(atomic_read(&op->usage), ==, 0);
 492                ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
 493
 494                ASSERTCMP(object->n_ops, >, 0);
 495                object->n_ops--;
 496                if (object->n_ops == 0)
 497                        fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 498
 499                spin_unlock(&object->lock);
 500                kfree(op);
 501
 502        } while (count++ < 20);
 503
 504        if (!list_empty(&cache->op_gc_list))
 505                schedule_work(&cache->op_gc);
 506
 507        _leave("");
 508}
 509
 510/*
 511 * execute an operation using fs_op_wq to provide processing context -
 512 * the caller holds a ref to this object, so we don't need to hold one
 513 */
 514void fscache_op_work_func(struct work_struct *work)
 515{
 516        struct fscache_operation *op =
 517                container_of(work, struct fscache_operation, work);
 518        unsigned long start;
 519
 520        _enter("{OBJ%x OP%x,%d}",
 521               op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 522
 523        ASSERT(op->processor != NULL);
 524        start = jiffies;
 525        op->processor(op);
 526        fscache_hist(fscache_ops_histogram, start);
 527        fscache_put_operation(op);
 528
 529        _leave("");
 530}
 531