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
  41         fscache_stat(&fscache_n_op_enqueue);
  42         switch (op->flags & FSCACHE_OP_TYPE) {
  43         case FSCACHE_OP_ASYNC:
  44                 _debug("queue async");
  45                 atomic_inc(&op->usage);
  46                 if (!queue_work(fscache_op_wq, &op->work))
  47                         fscache_put_operation(op);
  48                 break;
  49         case FSCACHE_OP_MYTHREAD:
  50                 _debug("queue for caller's attention");
  51                 break;
  52         default:
  53                 printk(KERN_ERR "FS-Cache: Unexpected op type %lx",
  54                        op->flags);
  55                 BUG();
  56                 break;
  57         }
  58 }
  59 EXPORT_SYMBOL(fscache_enqueue_operation);
  60
  61 /*
  62  * start an op running
  63  */
  64 static void fscache_run_op(struct fscache_object *object,
  65                            struct fscache_operation *op)
  66 {
  67         object->n_in_progress++;
  68         if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
  69                 wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
  70         if (op->processor)
  71                 fscache_enqueue_operation(op);
  72         fscache_stat(&fscache_n_op_run);
  73 }
  74
  75 /*
  76  * submit an exclusive operation for an object
  77  * - other ops are excluded from running simultaneously with this one
  78  * - this gets any extra refs it needs on an op
  79  */
  80 int fscache_submit_exclusive_op(struct fscache_object *object,
  81                                 struct fscache_operation *op)
  82 {
  83         int ret;
  84
  85         _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
  86
  87         spin_lock(&object->lock);
  88         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
  89         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
  90         ASSERT(list_empty(&op->pend_link));
  91
  92         ret = -ENOBUFS;
  93         if (fscache_object_is_active(object)) {
  94                 op->object = object;
  95                 object->n_ops++;
  96                 object->n_exclusive++;  /* reads and writes must wait */
  97
  98                 if (object->n_ops > 1) {
  99                         atomic_inc(&op->usage);
 100                         list_add_tail(&op->pend_link, &object->pending_ops);
 101                         fscache_stat(&fscache_n_op_pend);
 102                 } else if (!list_empty(&object->pending_ops)) {
 103                         atomic_inc(&op->usage);
 104                         list_add_tail(&op->pend_link, &object->pending_ops);
 105                         fscache_stat(&fscache_n_op_pend);
 106                         fscache_start_operations(object);
 107                 } else {
 108                         ASSERTCMP(object->n_in_progress, ==, 0);
 109                         fscache_run_op(object, op);
 110                 }
 111
 112                 /* need to issue a new write op after this */
 113                 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 114                 ret = 0;
 115         } else if (object->state == FSCACHE_OBJECT_CREATING) {
 116                 op->object = object;
 117                 object->n_ops++;
 118                 object->n_exclusive++;  /* reads and writes must wait */
 119                 atomic_inc(&op->usage);
 120                 list_add_tail(&op->pend_link, &object->pending_ops);
 121                 fscache_stat(&fscache_n_op_pend);
 122                 ret = 0;
 123         } else {
 124                 /* not allowed to submit ops in any other state */
 125                 BUG();
 126         }
 127
 128         spin_unlock(&object->lock);
 129         return ret;
 130 }
 131
 132 /*
 133  * report an unexpected submission
 134  */
 135 static void fscache_report_unexpected_submission(struct fscache_object *object,
 136                                                  struct fscache_operation *op,
 137                                                  unsigned long ostate)
 138 {
 139         static bool once_only;
 140         struct fscache_operation *p;
 141         unsigned n;
 142
 143         if (once_only)
 144                 return;
 145         once_only = true;
 146
 147         kdebug("unexpected submission OP%x [OBJ%x %s]",
 148                op->debug_id, object->debug_id,
 149                fscache_object_states[object->state]);
 150         kdebug("objstate=%s [%s]",
 151                fscache_object_states[object->state],
 152                fscache_object_states[ostate]);
 153         kdebug("objflags=%lx", object->flags);
 154         kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
 155         kdebug("ops=%u inp=%u exc=%u",
 156                object->n_ops, object->n_in_progress, object->n_exclusive);
 157
 158         if (!list_empty(&object->pending_ops)) {
 159                 n = 0;
 160                 list_for_each_entry(p, &object->pending_ops, pend_link) {
 161                         ASSERTCMP(p->object, ==, object);
 162                         kdebug("%p %p", op->processor, op->release);
 163                         n++;
 164                 }
 165
 166                 kdebug("n=%u", n);
 167         }
 168
 169         dump_stack();
 170 }
 171
 172 /*
 173  * submit an operation for an object
 174  * - objects may be submitted only in the following states:
 175  *   - during object creation (write ops may be submitted)
 176  *   - whilst the object is active
 177  *   - after an I/O error incurred in one of the two above states (op rejected)
 178  * - this gets any extra refs it needs on an op
 179  */
 180 int fscache_submit_op(struct fscache_object *object,
 181                       struct fscache_operation *op)
 182 {
 183         unsigned long ostate;
 184         int ret;
 185
 186         _enter("{OBJ%x OP%x},{%u}",
 187                object->debug_id, op->debug_id, atomic_read(&op->usage));
 188
 189         ASSERTCMP(atomic_read(&op->usage), >, 0);
 190
 191         spin_lock(&object->lock);
 192         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
 193         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
 194         ASSERT(list_empty(&op->pend_link));
 195
 196         ostate = object->state;
 197         smp_rmb();
 198
 199         if (fscache_object_is_active(object)) {
 200                 op->object = object;
 201                 object->n_ops++;
 202
 203                 if (object->n_exclusive > 0) {
 204                         atomic_inc(&op->usage);
 205                         list_add_tail(&op->pend_link, &object->pending_ops);
 206                         fscache_stat(&fscache_n_op_pend);
 207                 } else if (!list_empty(&object->pending_ops)) {
 208                         atomic_inc(&op->usage);
 209                         list_add_tail(&op->pend_link, &object->pending_ops);
 210                         fscache_stat(&fscache_n_op_pend);
 211                         fscache_start_operations(object);
 212                 } else {
 213                         ASSERTCMP(object->n_exclusive, ==, 0);
 214                         fscache_run_op(object, op);
 215                 }
 216                 ret = 0;
 217         } else if (object->state == FSCACHE_OBJECT_CREATING) {
 218                 op->object = object;
 219                 object->n_ops++;
 220                 atomic_inc(&op->usage);
 221                 list_add_tail(&op->pend_link, &object->pending_ops);
 222                 fscache_stat(&fscache_n_op_pend);
 223                 ret = 0;
 224         } else if (object->state == FSCACHE_OBJECT_DYING ||
 225                    object->state == FSCACHE_OBJECT_LC_DYING ||
 226                    object->state == FSCACHE_OBJECT_WITHDRAWING) {
 227                 fscache_stat(&fscache_n_op_rejected);
 228                 ret = -ENOBUFS;
 229         } else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 230                 fscache_report_unexpected_submission(object, op, ostate);
 231                 ASSERT(!fscache_object_is_active(object));
 232                 ret = -ENOBUFS;
 233         } else {
 234                 ret = -ENOBUFS;
 235         }
 236
 237         spin_unlock(&object->lock);
 238         return ret;
 239 }
 240
 241 /*
 242  * queue an object for withdrawal on error, aborting all following asynchronous
 243  * operations
 244  */
 245 void fscache_abort_object(struct fscache_object *object)
 246 {
 247         _enter("{OBJ%x}", object->debug_id);
 248
 249         fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 250 }
 251
 252 /*
 253  * jump start the operation processing on an object
 254  * - caller must hold object->lock
 255  */
 256 void fscache_start_operations(struct fscache_object *object)
 257 {
 258         struct fscache_operation *op;
 259         bool stop = false;
 260
 261         while (!list_empty(&object->pending_ops) && !stop) {
 262                 op = list_entry(object->pending_ops.next,
 263                                 struct fscache_operation, pend_link);
 264
 265                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 266                         if (object->n_in_progress > 0)
 267                                 break;
 268                         stop = true;
 269                 }
 270                 list_del_init(&op->pend_link);
 271                 fscache_run_op(object, op);
 272
 273                 /* the pending queue was holding a ref on the object */
 274                 fscache_put_operation(op);
 275         }
 276
 277         ASSERTCMP(object->n_in_progress, <=, object->n_ops);
 278
 279         _debug("woke %d ops on OBJ%x",
 280                object->n_in_progress, object->debug_id);
 281 }
 282
 283 /*
 284  * cancel an operation that's pending on an object
 285  */
 286 int fscache_cancel_op(struct fscache_operation *op)
 287 {
 288         struct fscache_object *object = op->object;
 289         int ret;
 290
 291         _enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
 292
 293         spin_lock(&object->lock);
 294
 295         ret = -EBUSY;
 296         if (!list_empty(&op->pend_link)) {
 297                 fscache_stat(&fscache_n_op_cancelled);
 298                 list_del_init(&op->pend_link);
 299                 object->n_ops--;
 300                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 301                         object->n_exclusive--;
 302                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 303                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 304                 fscache_put_operation(op);
 305                 ret = 0;
 306         }
 307
 308         spin_unlock(&object->lock);
 309         _leave(" = %d", ret);
 310         return ret;
 311 }
 312
 313 /*
 314  * release an operation
 315  * - queues pending ops if this is the last in-progress op
 316  */
 317 void fscache_put_operation(struct fscache_operation *op)
 318 {
 319         struct fscache_object *object;
 320         struct fscache_cache *cache;
 321
 322         _enter("{OBJ%x OP%x,%d}",
 323                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 324
 325         ASSERTCMP(atomic_read(&op->usage), >, 0);
 326
 327         if (!atomic_dec_and_test(&op->usage))
 328                 return;
 329
 330         _debug("PUT OP");
 331         if (test_and_set_bit(FSCACHE_OP_DEAD, &op->flags))
 332                 BUG();
 333
 334         fscache_stat(&fscache_n_op_release);
 335
 336         if (op->release) {
 337                 op->release(op);
 338                 op->release = NULL;
 339         }
 340
 341         object = op->object;
 342
 343         if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
 344                 atomic_dec(&object->n_reads);
 345
 346         /* now... we may get called with the object spinlock held, so we
 347          * complete the cleanup here only if we can immediately acquire the
 348          * lock, and defer it otherwise */
 349         if (!spin_trylock(&object->lock)) {
 350                 _debug("defer put");
 351                 fscache_stat(&fscache_n_op_deferred_release);
 352
 353                 cache = object->cache;
 354                 spin_lock(&cache->op_gc_list_lock);
 355                 list_add_tail(&op->pend_link, &cache->op_gc_list);
 356                 spin_unlock(&cache->op_gc_list_lock);
 357                 schedule_work(&cache->op_gc);
 358                 _leave(" [defer]");
 359                 return;
 360         }
 361
 362         if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 363                 ASSERTCMP(object->n_exclusive, >, 0);
 364                 object->n_exclusive--;
 365         }
 366
 367         ASSERTCMP(object->n_in_progress, >, 0);
 368         object->n_in_progress--;
 369         if (object->n_in_progress == 0)
 370                 fscache_start_operations(object);
 371
 372         ASSERTCMP(object->n_ops, >, 0);
 373         object->n_ops--;
 374         if (object->n_ops == 0)
 375                 fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 376
 377         spin_unlock(&object->lock);
 378
 379         kfree(op);
 380         _leave(" [done]");
 381 }
 382 EXPORT_SYMBOL(fscache_put_operation);
 383
 384 /*
 385  * garbage collect operations that have had their release deferred
 386  */
 387 void fscache_operation_gc(struct work_struct *work)
 388 {
 389         struct fscache_operation *op;
 390         struct fscache_object *object;
 391         struct fscache_cache *cache =
 392                 container_of(work, struct fscache_cache, op_gc);
 393         int count = 0;
 394
 395         _enter("");
 396
 397         do {
 398                 spin_lock(&cache->op_gc_list_lock);
 399                 if (list_empty(&cache->op_gc_list)) {
 400                         spin_unlock(&cache->op_gc_list_lock);
 401                         break;
 402                 }
 403
 404                 op = list_entry(cache->op_gc_list.next,
 405                                 struct fscache_operation, pend_link);
 406                 list_del(&op->pend_link);
 407                 spin_unlock(&cache->op_gc_list_lock);
 408
 409                 object = op->object;
 410
 411                 _debug("GC DEFERRED REL OBJ%x OP%x",
 412                        object->debug_id, op->debug_id);
 413                 fscache_stat(&fscache_n_op_gc);
 414
 415                 ASSERTCMP(atomic_read(&op->usage), ==, 0);
 416
 417                 spin_lock(&object->lock);
 418                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 419                         ASSERTCMP(object->n_exclusive, >, 0);
 420                         object->n_exclusive--;
 421                 }
 422
 423                 ASSERTCMP(object->n_in_progress, >, 0);
 424                 object->n_in_progress--;
 425                 if (object->n_in_progress == 0)
 426                         fscache_start_operations(object);
 427
 428                 ASSERTCMP(object->n_ops, >, 0);
 429                 object->n_ops--;
 430                 if (object->n_ops == 0)
 431                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 432
 433                 spin_unlock(&object->lock);
 434
 435         } while (count++ < 20);
 436
 437         if (!list_empty(&cache->op_gc_list))
 438                 schedule_work(&cache->op_gc);
 439
 440         _leave("");
 441 }
 442
 443 /*
 444  * execute an operation using fs_op_wq to provide processing context -
 445  * the caller holds a ref to this object, so we don't need to hold one
 446  */
 447 void fscache_op_work_func(struct work_struct *work)
 448 {
 449         struct fscache_operation *op =
 450                 container_of(work, struct fscache_operation, work);
 451         unsigned long start;
 452
 453         _enter("{OBJ%x OP%x,%d}",
 454                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 455
 456         ASSERT(op->processor != NULL);
 457         start = jiffies;
 458         op->processor(op);
 459         fscache_hist(fscache_ops_histogram, start);
 460         fscache_put_operation(op);
 461
 462         _leave("");
 463 }