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         ASSERTCMP(op->object->state, >=, FSCACHE_OBJECT_AVAILABLE);
  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         _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
  88
  89         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
  90         ASSERTCMP(atomic_read(&op->usage), >, 0);
  91
  92         spin_lock(&object->lock);
  93         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
  94         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
  95         ASSERT(list_empty(&op->pend_link));
  96
  97         op->state = FSCACHE_OP_ST_PENDING;
  98         if (fscache_object_is_active(object)) {
  99                 op->object = object;
 100                 object->n_ops++;
 101                 object->n_exclusive++;  /* reads and writes must wait */
 102
 103                 if (object->n_in_progress > 0) {
 104                         atomic_inc(&op->usage);
 105                         list_add_tail(&op->pend_link, &object->pending_ops);
 106                         fscache_stat(&fscache_n_op_pend);
 107                 } else if (!list_empty(&object->pending_ops)) {
 108                         atomic_inc(&op->usage);
 109                         list_add_tail(&op->pend_link, &object->pending_ops);
 110                         fscache_stat(&fscache_n_op_pend);
 111                         fscache_start_operations(object);
 112                 } else {
 113                         ASSERTCMP(object->n_in_progress, ==, 0);
 114                         fscache_run_op(object, op);
 115                 }
 116
 117                 /* need to issue a new write op after this */
 118                 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 119         } else if (object->state == FSCACHE_OBJECT_CREATING) {
 120                 op->object = object;
 121                 object->n_ops++;
 122                 object->n_exclusive++;  /* reads and writes must wait */
 123                 atomic_inc(&op->usage);
 124                 list_add_tail(&op->pend_link, &object->pending_ops);
 125                 fscache_stat(&fscache_n_op_pend);
 126         } else {
 127                 /* not allowed to submit ops in any other state */
 128                 BUG();
 129         }
 130
 131         spin_unlock(&object->lock);
 132         return 0;
 133 }
 134
 135 /*
 136  * report an unexpected submission
 137  */
 138 static void fscache_report_unexpected_submission(struct fscache_object *object,
 139                                                  struct fscache_operation *op,
 140                                                  unsigned long ostate)
 141 {
 142         static bool once_only;
 143         struct fscache_operation *p;
 144         unsigned n;
 145
 146         if (once_only)
 147                 return;
 148         once_only = true;
 149
 150         kdebug("unexpected submission OP%x [OBJ%x %s]",
 151                op->debug_id, object->debug_id,
 152                fscache_object_states[object->state]);
 153         kdebug("objstate=%s [%s]",
 154                fscache_object_states[object->state],
 155                fscache_object_states[ostate]);
 156         kdebug("objflags=%lx", object->flags);
 157         kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
 158         kdebug("ops=%u inp=%u exc=%u",
 159                object->n_ops, object->n_in_progress, object->n_exclusive);
 160
 161         if (!list_empty(&object->pending_ops)) {
 162                 n = 0;
 163                 list_for_each_entry(p, &object->pending_ops, pend_link) {
 164                         ASSERTCMP(p->object, ==, object);
 165                         kdebug("%p %p", op->processor, op->release);
 166                         n++;
 167                 }
 168
 169                 kdebug("n=%u", n);
 170         }
 171
 172         dump_stack();
 173 }
 174
 175 /*
 176  * submit an operation for an object
 177  * - objects may be submitted only in the following states:
 178  *   - during object creation (write ops may be submitted)
 179  *   - whilst the object is active
 180  *   - after an I/O error incurred in one of the two above states (op rejected)
 181  * - this gets any extra refs it needs on an op
 182  */
 183 int fscache_submit_op(struct fscache_object *object,
 184                       struct fscache_operation *op)
 185 {
 186         unsigned long ostate;
 187         int ret;
 188
 189         _enter("{OBJ%x OP%x},{%u}",
 190                object->debug_id, op->debug_id, atomic_read(&op->usage));
 191
 192         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
 193         ASSERTCMP(atomic_read(&op->usage), >, 0);
 194
 195         spin_lock(&object->lock);
 196         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
 197         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
 198         ASSERT(list_empty(&op->pend_link));
 199
 200         ostate = object->state;
 201         smp_rmb();
 202
 203         op->state = FSCACHE_OP_ST_PENDING;
 204         if (fscache_object_is_active(object)) {
 205                 op->object = object;
 206                 object->n_ops++;
 207
 208                 if (object->n_exclusive > 0) {
 209                         atomic_inc(&op->usage);
 210                         list_add_tail(&op->pend_link, &object->pending_ops);
 211                         fscache_stat(&fscache_n_op_pend);
 212                 } else if (!list_empty(&object->pending_ops)) {
 213                         atomic_inc(&op->usage);
 214                         list_add_tail(&op->pend_link, &object->pending_ops);
 215                         fscache_stat(&fscache_n_op_pend);
 216                         fscache_start_operations(object);
 217                 } else {
 218                         ASSERTCMP(object->n_exclusive, ==, 0);
 219                         fscache_run_op(object, op);
 220                 }
 221                 ret = 0;
 222         } else if (object->state == FSCACHE_OBJECT_CREATING) {
 223                 op->object = object;
 224                 object->n_ops++;
 225                 atomic_inc(&op->usage);
 226                 list_add_tail(&op->pend_link, &object->pending_ops);
 227                 fscache_stat(&fscache_n_op_pend);
 228                 ret = 0;
 229         } else if (object->state == FSCACHE_OBJECT_DYING ||
 230                    object->state == FSCACHE_OBJECT_LC_DYING ||
 231                    object->state == FSCACHE_OBJECT_WITHDRAWING) {
 232                 fscache_stat(&fscache_n_op_rejected);
 233                 op->state = FSCACHE_OP_ST_CANCELLED;
 234                 ret = -ENOBUFS;
 235         } else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 236                 fscache_report_unexpected_submission(object, op, ostate);
 237                 ASSERT(!fscache_object_is_active(object));
 238                 op->state = FSCACHE_OP_ST_CANCELLED;
 239                 ret = -ENOBUFS;
 240         } else {
 241                 op->state = FSCACHE_OP_ST_CANCELLED;
 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  */
 253 void 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  */
 264 void 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  */
 294 int 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         ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
 302         ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
 303         ASSERTCMP(atomic_read(&op->usage), >, 0);
 304
 305         spin_lock(&object->lock);
 306
 307         ret = -EBUSY;
 308         if (op->state == FSCACHE_OP_ST_PENDING) {
 309                 ASSERT(!list_empty(&op->pend_link));
 310                 fscache_stat(&fscache_n_op_cancelled);
 311                 list_del_init(&op->pend_link);
 312                 op->state = FSCACHE_OP_ST_CANCELLED;
 313                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 314                         object->n_exclusive--;
 315                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 316                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 317                 fscache_put_operation(op);
 318                 ret = 0;
 319         }
 320
 321         spin_unlock(&object->lock);
 322         _leave(" = %d", ret);
 323         return ret;
 324 }
 325
 326 /*
 327  * Cancel all pending operations on an object
 328  */
 329 void fscache_cancel_all_ops(struct fscache_object *object)
 330 {
 331         struct fscache_operation *op;
 332
 333         _enter("OBJ%x", object->debug_id);
 334
 335         spin_lock(&object->lock);
 336
 337         while (!list_empty(&object->pending_ops)) {
 338                 op = list_entry(object->pending_ops.next,
 339                                 struct fscache_operation, pend_link);
 340                 fscache_stat(&fscache_n_op_cancelled);
 341                 list_del_init(&op->pend_link);
 342
 343                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
 344                 op->state = FSCACHE_OP_ST_CANCELLED;
 345
 346                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 347                         object->n_exclusive--;
 348                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 349                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 350                 fscache_put_operation(op);
 351                 cond_resched_lock(&object->lock);
 352         }
 353
 354         spin_unlock(&object->lock);
 355         _leave("");
 356 }
 357
 358 /*
 359  * Record the completion of an in-progress operation.
 360  */
 361 void fscache_op_complete(struct fscache_operation *op)
 362 {
 363         struct fscache_object *object = op->object;
 364
 365         _enter("OBJ%x", object->debug_id);
 366
 367         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
 368         ASSERTCMP(object->n_in_progress, >, 0);
 369         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 370                     object->n_exclusive, >, 0);
 371         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 372                     object->n_in_progress, ==, 1);
 373
 374         spin_lock(&object->lock);
 375
 376         op->state = FSCACHE_OP_ST_COMPLETE;
 377
 378         if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 379                 object->n_exclusive--;
 380         object->n_in_progress--;
 381         if (object->n_in_progress == 0)
 382                 fscache_start_operations(object);
 383
 384         spin_unlock(&object->lock);
 385         _leave("");
 386 }
 387 EXPORT_SYMBOL(fscache_op_complete);
 388
 389 /*
 390  * release an operation
 391  * - queues pending ops if this is the last in-progress op
 392  */
 393 void fscache_put_operation(struct fscache_operation *op)
 394 {
 395         struct fscache_object *object;
 396         struct fscache_cache *cache;
 397
 398         _enter("{OBJ%x OP%x,%d}",
 399                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 400
 401         ASSERTCMP(atomic_read(&op->usage), >, 0);
 402
 403         if (!atomic_dec_and_test(&op->usage))
 404                 return;
 405
 406         _debug("PUT OP");
 407         ASSERTIFCMP(op->state != FSCACHE_OP_ST_COMPLETE,
 408                     op->state, ==, FSCACHE_OP_ST_CANCELLED);
 409         op->state = FSCACHE_OP_ST_DEAD;
 410
 411         fscache_stat(&fscache_n_op_release);
 412
 413         if (op->release) {
 414                 op->release(op);
 415                 op->release = NULL;
 416         }
 417
 418         object = op->object;
 419
 420         if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags)) {
 421                 if (atomic_dec_and_test(&object->n_reads)) {
 422                         clear_bit(FSCACHE_COOKIE_WAITING_ON_READS,
 423                                   &object->cookie->flags);
 424                         wake_up_bit(&object->cookie->flags,
 425                                     FSCACHE_COOKIE_WAITING_ON_READS);
 426                 }
 427         }
 428
 429         /* now... we may get called with the object spinlock held, so we
 430          * complete the cleanup here only if we can immediately acquire the
 431          * lock, and defer it otherwise */
 432         if (!spin_trylock(&object->lock)) {
 433                 _debug("defer put");
 434                 fscache_stat(&fscache_n_op_deferred_release);
 435
 436                 cache = object->cache;
 437                 spin_lock(&cache->op_gc_list_lock);
 438                 list_add_tail(&op->pend_link, &cache->op_gc_list);
 439                 spin_unlock(&cache->op_gc_list_lock);
 440                 schedule_work(&cache->op_gc);
 441                 _leave(" [defer]");
 442                 return;
 443         }
 444
 445         ASSERTCMP(object->n_ops, >, 0);
 446         object->n_ops--;
 447         if (object->n_ops == 0)
 448                 fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 449
 450         spin_unlock(&object->lock);
 451
 452         kfree(op);
 453         _leave(" [done]");
 454 }
 455 EXPORT_SYMBOL(fscache_put_operation);
 456
 457 /*
 458  * garbage collect operations that have had their release deferred
 459  */
 460 void fscache_operation_gc(struct work_struct *work)
 461 {
 462         struct fscache_operation *op;
 463         struct fscache_object *object;
 464         struct fscache_cache *cache =
 465                 container_of(work, struct fscache_cache, op_gc);
 466         int count = 0;
 467
 468         _enter("");
 469
 470         do {
 471                 spin_lock(&cache->op_gc_list_lock);
 472                 if (list_empty(&cache->op_gc_list)) {
 473                         spin_unlock(&cache->op_gc_list_lock);
 474                         break;
 475                 }
 476
 477                 op = list_entry(cache->op_gc_list.next,
 478                                 struct fscache_operation, pend_link);
 479                 list_del(&op->pend_link);
 480                 spin_unlock(&cache->op_gc_list_lock);
 481
 482                 object = op->object;
 483                 spin_lock(&object->lock);
 484
 485                 _debug("GC DEFERRED REL OBJ%x OP%x",
 486                        object->debug_id, op->debug_id);
 487                 fscache_stat(&fscache_n_op_gc);
 488
 489                 ASSERTCMP(atomic_read(&op->usage), ==, 0);
 490                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
 491
 492                 ASSERTCMP(object->n_ops, >, 0);
 493                 object->n_ops--;
 494                 if (object->n_ops == 0)
 495                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 496
 497                 spin_unlock(&object->lock);
 498                 kfree(op);
 499
 500         } while (count++ < 20);
 501
 502         if (!list_empty(&cache->op_gc_list))
 503                 schedule_work(&cache->op_gc);
 504
 505         _leave("");
 506 }
 507
 508 /*
 509  * execute an operation using fs_op_wq to provide processing context -
 510  * the caller holds a ref to this object, so we don't need to hold one
 511  */
 512 void fscache_op_work_func(struct work_struct *work)
 513 {
 514         struct fscache_operation *op =
 515                 container_of(work, struct fscache_operation, work);
 516         unsigned long start;
 517
 518         _enter("{OBJ%x OP%x,%d}",
 519                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 520
 521         ASSERT(op->processor != NULL);
 522         start = jiffies;
 523         op->processor(op);
 524         fscache_hist(fscache_ops_histogram, start);
 525         fscache_put_operation(op);
 526
 527         _leave("");
 528 }