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         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 }
  61 EXPORT_SYMBOL(fscache_enqueue_operation);
  62
  63 /*
  64  * start an op running
  65  */
  66 static 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  */
  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         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  */
 141 static 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  */
 186 int 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  */
 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         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  */
 325 void 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 }
 392 EXPORT_SYMBOL(fscache_put_operation);
 393
 394 /*
 395  * garbage collect operations that have had their release deferred
 396  */
 397 void 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  */
 457 void 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 }