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.  The caller must hold
 264  * object->lock.
 265  */
 266 void 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  */
 296 int 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  */
 334 void 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  */
 366 void 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 }
 393 EXPORT_SYMBOL(fscache_op_complete);
 394
 395 /*
 396  * release an operation
 397  * - queues pending ops if this is the last in-progress op
 398  */
 399 void 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 }
 457 EXPORT_SYMBOL(fscache_put_operation);
 458
 459 /*
 460  * garbage collect operations that have had their release deferred
 461  */
 462 void 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  */
 514 void 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 }