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        fscache_set_op_state(op, "EnQ");
  37
  38        ASSERT(list_empty(&op->pend_link));
  39        ASSERT(op->processor != NULL);
  40        ASSERTCMP(op->object->state, >=, FSCACHE_OBJECT_AVAILABLE);
  41        ASSERTCMP(atomic_read(&op->usage), >, 0);
  42
  43        fscache_stat(&fscache_n_op_enqueue);
  44        switch (op->flags & FSCACHE_OP_TYPE) {
  45        case FSCACHE_OP_ASYNC:
  46                _debug("queue async");
  47                atomic_inc(&op->usage);
  48                if (!queue_work(fscache_op_wq, &op->work))
  49                        fscache_put_operation(op);
  50                break;
  51        case FSCACHE_OP_MYTHREAD:
  52                _debug("queue for caller's attention");
  53                break;
  54        default:
  55                printk(KERN_ERR "FS-Cache: Unexpected op type %lx",
  56                       op->flags);
  57                BUG();
  58                break;
  59        }
  60}
  61EXPORT_SYMBOL(fscache_enqueue_operation);
  62
  63/*
  64 * start an op running
  65 */
  66static void fscache_run_op(struct fscache_object *object,
  67                           struct fscache_operation *op)
  68{
  69        fscache_set_op_state(op, "Run");
  70
  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        fscache_set_op_state(op, "SubmitX");
  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        ret = -ENOBUFS;
  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_ops > 1) {
 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 (object->state == FSCACHE_OBJECT_CREATING) {
 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                /* not allowed to submit ops in any other state */
 131                BUG();
 132        }
 133
 134        spin_unlock(&object->lock);
 135        return ret;
 136}
 137
 138/*
 139 * report an unexpected submission
 140 */
 141static void fscache_report_unexpected_submission(struct fscache_object *object,
 142                                                 struct fscache_operation *op,
 143                                                 unsigned long ostate)
 144{
 145        static bool once_only;
 146        struct fscache_operation *p;
 147        unsigned n;
 148
 149        if (once_only)
 150                return;
 151        once_only = true;
 152
 153        kdebug("unexpected submission OP%x [OBJ%x %s]",
 154               op->debug_id, object->debug_id,
 155               fscache_object_states[object->state]);
 156        kdebug("objstate=%s [%s]",
 157               fscache_object_states[object->state],
 158               fscache_object_states[ostate]);
 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 */
 186int fscache_submit_op(struct fscache_object *object,
 187                      struct fscache_operation *op)
 188{
 189        unsigned long 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(atomic_read(&op->usage), >, 0);
 196
 197        fscache_set_op_state(op, "Submit");
 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        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 (object->state == FSCACHE_OBJECT_CREATING) {
 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 (object->state == FSCACHE_OBJECT_DYING ||
 233                   object->state == FSCACHE_OBJECT_LC_DYING ||
 234                   object->state == FSCACHE_OBJECT_WITHDRAWING) {
 235                fscache_stat(&fscache_n_op_rejected);
 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                ret = -ENOBUFS;
 241        } else {
 242                ret = -ENOBUFS;
 243        }
 244
 245        spin_unlock(&object->lock);
 246        return ret;
 247}
 248
 249/*
 250 * queue an object for withdrawal on error, aborting all following asynchronous
 251 * operations
 252 */
 253void fscache_abort_object(struct fscache_object *object)
 254{
 255        _enter("{OBJ%x}", object->debug_id);
 256
 257        fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 258}
 259
 260/*
 261 * jump start the operation processing on an object
 262 * - caller must hold object->lock
 263 */
 264void fscache_start_operations(struct fscache_object *object)
 265{
 266        struct fscache_operation *op;
 267        bool stop = false;
 268
 269        while (!list_empty(&object->pending_ops) && !stop) {
 270                op = list_entry(object->pending_ops.next,
 271                                struct fscache_operation, pend_link);
 272
 273                if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 274                        if (object->n_in_progress > 0)
 275                                break;
 276                        stop = true;
 277                }
 278                list_del_init(&op->pend_link);
 279                fscache_run_op(object, op);
 280
 281                /* the pending queue was holding a ref on the object */
 282                fscache_put_operation(op);
 283        }
 284
 285        ASSERTCMP(object->n_in_progress, <=, object->n_ops);
 286
 287        _debug("woke %d ops on OBJ%x",
 288               object->n_in_progress, object->debug_id);
 289}
 290
 291/*
 292 * cancel an operation that's pending on an object
 293 */
 294int fscache_cancel_op(struct fscache_operation *op)
 295{
 296        struct fscache_object *object = op->object;
 297        int ret;
 298
 299        _enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
 300
 301        spin_lock(&object->lock);
 302
 303        ret = -EBUSY;
 304        if (!list_empty(&op->pend_link)) {
 305                fscache_stat(&fscache_n_op_cancelled);
 306                list_del_init(&op->pend_link);
 307                object->n_ops--;
 308                if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 309                        object->n_exclusive--;
 310                if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 311                        wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 312                fscache_put_operation(op);
 313                ret = 0;
 314        }
 315
 316        spin_unlock(&object->lock);
 317        _leave(" = %d", ret);
 318        return ret;
 319}
 320
 321/*
 322 * release an operation
 323 * - queues pending ops if this is the last in-progress op
 324 */
 325void fscache_put_operation(struct fscache_operation *op)
 326{
 327        struct fscache_object *object;
 328        struct fscache_cache *cache;
 329
 330        _enter("{OBJ%x OP%x,%d}",
 331               op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 332
 333        ASSERTCMP(atomic_read(&op->usage), >, 0);
 334
 335        if (!atomic_dec_and_test(&op->usage))
 336                return;
 337
 338        fscache_set_op_state(op, "Put");
 339
 340        _debug("PUT OP");
 341        if (test_and_set_bit(FSCACHE_OP_DEAD, &op->flags))
 342                BUG();
 343
 344        fscache_stat(&fscache_n_op_release);
 345
 346        if (op->release) {
 347                op->release(op);
 348                op->release = NULL;
 349        }
 350
 351        object = op->object;
 352
 353        if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
 354                atomic_dec(&object->n_reads);
 355
 356        /* now... we may get called with the object spinlock held, so we
 357         * complete the cleanup here only if we can immediately acquire the
 358         * lock, and defer it otherwise */
 359        if (!spin_trylock(&object->lock)) {
 360                _debug("defer put");
 361                fscache_stat(&fscache_n_op_deferred_release);
 362
 363                cache = object->cache;
 364                spin_lock(&cache->op_gc_list_lock);
 365                list_add_tail(&op->pend_link, &cache->op_gc_list);
 366                spin_unlock(&cache->op_gc_list_lock);
 367                schedule_work(&cache->op_gc);
 368                _leave(" [defer]");
 369                return;
 370        }
 371
 372        if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 373                ASSERTCMP(object->n_exclusive, >, 0);
 374                object->n_exclusive--;
 375        }
 376
 377        ASSERTCMP(object->n_in_progress, >, 0);
 378        object->n_in_progress--;
 379        if (object->n_in_progress == 0)
 380                fscache_start_operations(object);
 381
 382        ASSERTCMP(object->n_ops, >, 0);
 383        object->n_ops--;
 384        if (object->n_ops == 0)
 385                fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 386
 387        spin_unlock(&object->lock);
 388
 389        kfree(op);
 390        _leave(" [done]");
 391}
 392EXPORT_SYMBOL(fscache_put_operation);
 393
 394/*
 395 * garbage collect operations that have had their release deferred
 396 */
 397void fscache_operation_gc(struct work_struct *work)
 398{
 399        struct fscache_operation *op;
 400        struct fscache_object *object;
 401        struct fscache_cache *cache =
 402                container_of(work, struct fscache_cache, op_gc);
 403        int count = 0;
 404
 405        _enter("");
 406
 407        do {
 408                spin_lock(&cache->op_gc_list_lock);
 409                if (list_empty(&cache->op_gc_list)) {
 410                        spin_unlock(&cache->op_gc_list_lock);
 411                        break;
 412                }
 413
 414                op = list_entry(cache->op_gc_list.next,
 415                                struct fscache_operation, pend_link);
 416                list_del(&op->pend_link);
 417                spin_unlock(&cache->op_gc_list_lock);
 418
 419                object = op->object;
 420
 421                _debug("GC DEFERRED REL OBJ%x OP%x",
 422                       object->debug_id, op->debug_id);
 423                fscache_stat(&fscache_n_op_gc);
 424
 425                ASSERTCMP(atomic_read(&op->usage), ==, 0);
 426
 427                spin_lock(&object->lock);
 428                if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 429                        ASSERTCMP(object->n_exclusive, >, 0);
 430                        object->n_exclusive--;
 431                }
 432
 433                ASSERTCMP(object->n_in_progress, >, 0);
 434                object->n_in_progress--;
 435                if (object->n_in_progress == 0)
 436                        fscache_start_operations(object);
 437
 438                ASSERTCMP(object->n_ops, >, 0);
 439                object->n_ops--;
 440                if (object->n_ops == 0)
 441                        fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 442
 443                spin_unlock(&object->lock);
 444
 445        } while (count++ < 20);
 446
 447        if (!list_empty(&cache->op_gc_list))
 448                schedule_work(&cache->op_gc);
 449
 450        _leave("");
 451}
 452
 453/*
 454 * execute an operation using fs_op_wq to provide processing context -
 455 * the caller holds a ref to this object, so we don't need to hold one
 456 */
 457void fscache_op_work_func(struct work_struct *work)
 458{
 459        struct fscache_operation *op =
 460                container_of(work, struct fscache_operation, work);
 461        unsigned long start;
 462
 463        _enter("{OBJ%x OP%x,%d}",
 464               op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 465
 466        ASSERT(op->processor != NULL);
 467        start = jiffies;
 468        op->processor(op);
 469        fscache_hist(fscache_ops_histogram, start);
 470        fscache_put_operation(op);
 471
 472        _leave("");
 473}
 474