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                 printk(KERN_ERR "FS-Cache: Unexpected op type %lx",
  55                        op->flags);
  56                 BUG();
  57                 break;
  58         }
  59 }
  60 EXPORT_SYMBOL(fscache_enqueue_operation);
  61
  62 /*
  63  * start an op running
  64  */
  65 static 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  */
  84 int 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  */
 145 static 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  */
 187 int 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  */
 255 void 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
 264  */
 265 void fscache_start_operations(struct fscache_object *object)
 266 {
 267         struct fscache_operation *op;
 268         bool stop = false;
 269
 270         ASSERT(spin_is_locked(&object->lock));
 271
 272         while (!list_empty(&object->pending_ops) && !stop) {
 273                 op = list_entry(object->pending_ops.next,
 274                                 struct fscache_operation, pend_link);
 275
 276                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 277                         if (object->n_in_progress > 0)
 278                                 break;
 279                         stop = true;
 280                 }
 281                 list_del_init(&op->pend_link);
 282                 fscache_run_op(object, op);
 283
 284                 /* the pending queue was holding a ref on the object */
 285                 fscache_put_operation(op);
 286         }
 287
 288         ASSERTCMP(object->n_in_progress, <=, object->n_ops);
 289
 290         _debug("woke %d ops on OBJ%x",
 291                object->n_in_progress, object->debug_id);
 292 }
 293
 294 /*
 295  * cancel an operation that's pending on an object
 296  */
 297 int fscache_cancel_op(struct fscache_operation *op,
 298                       void (*do_cancel)(struct fscache_operation *))
 299 {
 300         struct fscache_object *object = op->object;
 301         int ret;
 302
 303         _enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
 304
 305         ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
 306         ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
 307         ASSERTCMP(atomic_read(&op->usage), >, 0);
 308
 309         spin_lock(&object->lock);
 310
 311         ret = -EBUSY;
 312         if (op->state == FSCACHE_OP_ST_PENDING) {
 313                 ASSERT(!list_empty(&op->pend_link));
 314                 fscache_stat(&fscache_n_op_cancelled);
 315                 list_del_init(&op->pend_link);
 316                 if (do_cancel)
 317                         do_cancel(op);
 318                 op->state = FSCACHE_OP_ST_CANCELLED;
 319                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 320                         object->n_exclusive--;
 321                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 322                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 323                 fscache_put_operation(op);
 324                 ret = 0;
 325         }
 326
 327         spin_unlock(&object->lock);
 328         _leave(" = %d", ret);
 329         return ret;
 330 }
 331
 332 /*
 333  * Cancel all pending operations on an object
 334  */
 335 void fscache_cancel_all_ops(struct fscache_object *object)
 336 {
 337         struct fscache_operation *op;
 338
 339         _enter("OBJ%x", object->debug_id);
 340
 341         spin_lock(&object->lock);
 342
 343         while (!list_empty(&object->pending_ops)) {
 344                 op = list_entry(object->pending_ops.next,
 345                                 struct fscache_operation, pend_link);
 346                 fscache_stat(&fscache_n_op_cancelled);
 347                 list_del_init(&op->pend_link);
 348
 349                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
 350                 op->state = FSCACHE_OP_ST_CANCELLED;
 351
 352                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 353                         object->n_exclusive--;
 354                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 355                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 356                 fscache_put_operation(op);
 357                 cond_resched_lock(&object->lock);
 358         }
 359
 360         spin_unlock(&object->lock);
 361         _leave("");
 362 }
 363
 364 /*
 365  * Record the completion or cancellation of an in-progress operation.
 366  */
 367 void fscache_op_complete(struct fscache_operation *op, bool cancelled)
 368 {
 369         struct fscache_object *object = op->object;
 370
 371         _enter("OBJ%x", object->debug_id);
 372
 373         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
 374         ASSERTCMP(object->n_in_progress, >, 0);
 375         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 376                     object->n_exclusive, >, 0);
 377         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 378                     object->n_in_progress, ==, 1);
 379
 380         spin_lock(&object->lock);
 381
 382         op->state = cancelled ?
 383                 FSCACHE_OP_ST_CANCELLED : FSCACHE_OP_ST_COMPLETE;
 384
 385         if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 386                 object->n_exclusive--;
 387         object->n_in_progress--;
 388         if (object->n_in_progress == 0)
 389                 fscache_start_operations(object);
 390
 391         spin_unlock(&object->lock);
 392         _leave("");
 393 }
 394 EXPORT_SYMBOL(fscache_op_complete);
 395
 396 /*
 397  * release an operation
 398  * - queues pending ops if this is the last in-progress op
 399  */
 400 void fscache_put_operation(struct fscache_operation *op)
 401 {
 402         struct fscache_object *object;
 403         struct fscache_cache *cache;
 404
 405         _enter("{OBJ%x OP%x,%d}",
 406                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 407
 408         ASSERTCMP(atomic_read(&op->usage), >, 0);
 409
 410         if (!atomic_dec_and_test(&op->usage))
 411                 return;
 412
 413         _debug("PUT OP");
 414         ASSERTIFCMP(op->state != FSCACHE_OP_ST_COMPLETE,
 415                     op->state, ==, FSCACHE_OP_ST_CANCELLED);
 416         op->state = FSCACHE_OP_ST_DEAD;
 417
 418         fscache_stat(&fscache_n_op_release);
 419
 420         if (op->release) {
 421                 op->release(op);
 422                 op->release = NULL;
 423         }
 424
 425         object = op->object;
 426
 427         if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
 428                 atomic_dec(&object->n_reads);
 429         if (test_bit(FSCACHE_OP_UNUSE_COOKIE, &op->flags))
 430                 fscache_unuse_cookie(object);
 431
 432         /* now... we may get called with the object spinlock held, so we
 433          * complete the cleanup here only if we can immediately acquire the
 434          * lock, and defer it otherwise */
 435         if (!spin_trylock(&object->lock)) {
 436                 _debug("defer put");
 437                 fscache_stat(&fscache_n_op_deferred_release);
 438
 439                 cache = object->cache;
 440                 spin_lock(&cache->op_gc_list_lock);
 441                 list_add_tail(&op->pend_link, &cache->op_gc_list);
 442                 spin_unlock(&cache->op_gc_list_lock);
 443                 schedule_work(&cache->op_gc);
 444                 _leave(" [defer]");
 445                 return;
 446         }
 447
 448         ASSERTCMP(object->n_ops, >, 0);
 449         object->n_ops--;
 450         if (object->n_ops == 0)
 451                 fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 452
 453         spin_unlock(&object->lock);
 454
 455         kfree(op);
 456         _leave(" [done]");
 457 }
 458 EXPORT_SYMBOL(fscache_put_operation);
 459
 460 /*
 461  * garbage collect operations that have had their release deferred
 462  */
 463 void fscache_operation_gc(struct work_struct *work)
 464 {
 465         struct fscache_operation *op;
 466         struct fscache_object *object;
 467         struct fscache_cache *cache =
 468                 container_of(work, struct fscache_cache, op_gc);
 469         int count = 0;
 470
 471         _enter("");
 472
 473         do {
 474                 spin_lock(&cache->op_gc_list_lock);
 475                 if (list_empty(&cache->op_gc_list)) {
 476                         spin_unlock(&cache->op_gc_list_lock);
 477                         break;
 478                 }
 479
 480                 op = list_entry(cache->op_gc_list.next,
 481                                 struct fscache_operation, pend_link);
 482                 list_del(&op->pend_link);
 483                 spin_unlock(&cache->op_gc_list_lock);
 484
 485                 object = op->object;
 486                 spin_lock(&object->lock);
 487
 488                 _debug("GC DEFERRED REL OBJ%x OP%x",
 489                        object->debug_id, op->debug_id);
 490                 fscache_stat(&fscache_n_op_gc);
 491
 492                 ASSERTCMP(atomic_read(&op->usage), ==, 0);
 493                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
 494
 495                 ASSERTCMP(object->n_ops, >, 0);
 496                 object->n_ops--;
 497                 if (object->n_ops == 0)
 498                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 499
 500                 spin_unlock(&object->lock);
 501                 kfree(op);
 502
 503         } while (count++ < 20);
 504
 505         if (!list_empty(&cache->op_gc_list))
 506                 schedule_work(&cache->op_gc);
 507
 508         _leave("");
 509 }
 510
 511 /*
 512  * execute an operation using fs_op_wq to provide processing context -
 513  * the caller holds a ref to this object, so we don't need to hold one
 514  */
 515 void fscache_op_work_func(struct work_struct *work)
 516 {
 517         struct fscache_operation *op =
 518                 container_of(work, struct fscache_operation, work);
 519         unsigned long start;
 520
 521         _enter("{OBJ%x OP%x,%d}",
 522                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 523
 524         ASSERT(op->processor != NULL);
 525         start = jiffies;
 526         op->processor(op);
 527         fscache_hist(fscache_ops_histogram, start);
 528         fscache_put_operation(op);
 529
 530         _leave("");
 531 }