Orange Pi5 kernel

// SPDX-License-Identifier: GPL-2.0-or-later
/* FS-Cache worker operation management routines
 *
 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * See Documentation/filesystems/caching/operations.rst
 */
 
#define FSCACHE_DEBUG_LEVEL OPERATION
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include "internal.h"
 
atomic_t fscache_op_debug_id;
EXPORT_SYMBOL(fscache_op_debug_id);
 
static void fscache_operation_dummy_cancel(struct fscache_operation *op)
{
}
 
/**
 * fscache_operation_init - Do basic initialisation of an operation
 * @op: The operation to initialise
 * @release: The release function to assign
 *
 * Do basic initialisation of an operation.  The caller must still set flags,
 * object and processor if needed.
 */
void fscache_operation_init(struct fscache_cookie *cookie,
<------><------><------>    struct fscache_operation *op,
<------><------><------>    fscache_operation_processor_t processor,
<------><------><------>    fscache_operation_cancel_t cancel,
<------><------><------>    fscache_operation_release_t release)
{
<------>INIT_WORK(&op->work, fscache_op_work_func);
<------>atomic_set(&op->usage, 1);
<------>op->state = FSCACHE_OP_ST_INITIALISED;
<------>op->debug_id = atomic_inc_return(&fscache_op_debug_id);
<------>op->processor = processor;
<------>op->cancel = cancel ?: fscache_operation_dummy_cancel;
<------>op->release = release;
<------>INIT_LIST_HEAD(&op->pend_link);
<------>fscache_stat(&fscache_n_op_initialised);
<------>trace_fscache_op(cookie, op, fscache_op_init);
}
EXPORT_SYMBOL(fscache_operation_init);
 
/**
 * fscache_enqueue_operation - Enqueue an operation for processing
 * @op: The operation to enqueue
 *
 * Enqueue an operation for processing by the FS-Cache thread pool.
 *
 * This will get its own ref on the object.
 */
void fscache_enqueue_operation(struct fscache_operation *op)
{
<------>struct fscache_cookie *cookie = op->object->cookie;
<------>
<------>_enter("{OBJ%x OP%x,%u}",
<------>       op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 
<------>ASSERT(list_empty(&op->pend_link));
<------>ASSERT(op->processor != NULL);
<------>ASSERT(fscache_object_is_available(op->object));
<------>ASSERTCMP(atomic_read(&op->usage), >, 0);
<------>ASSERTIFCMP(op->state != FSCACHE_OP_ST_IN_PROGRESS,
<------><------>    op->state, ==,  FSCACHE_OP_ST_CANCELLED);
 
<------>fscache_stat(&fscache_n_op_enqueue);
<------>switch (op->flags & FSCACHE_OP_TYPE) {
<------>case FSCACHE_OP_ASYNC:
<------><------>trace_fscache_op(cookie, op, fscache_op_enqueue_async);
<------><------>_debug("queue async");
<------><------>atomic_inc(&op->usage);
<------><------>if (!queue_work(fscache_op_wq, &op->work))
<------><------><------>fscache_put_operation(op);
<------><------>break;
<------>case FSCACHE_OP_MYTHREAD:
<------><------>trace_fscache_op(cookie, op, fscache_op_enqueue_mythread);
<------><------>_debug("queue for caller's attention");
<------><------>break;
<------>default:
<------><------>pr_err("Unexpected op type %lx", op->flags);
<------><------>BUG();
<------><------>break;
<------>}
}
EXPORT_SYMBOL(fscache_enqueue_operation);
 
/*
 * start an op running
 */
static void fscache_run_op(struct fscache_object *object,
<------><------><------>   struct fscache_operation *op)
{
<------>ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
 
<------>op->state = FSCACHE_OP_ST_IN_PROGRESS;
<------>object->n_in_progress++;
<------>if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
<------><------>wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
<------>if (op->processor)
<------><------>fscache_enqueue_operation(op);
<------>else
<------><------>trace_fscache_op(object->cookie, op, fscache_op_run);
<------>fscache_stat(&fscache_n_op_run);
}
 
/*
 * report an unexpected submission
 */
static void fscache_report_unexpected_submission(struct fscache_object *object,
<------><------><------><------><------><------> struct fscache_operation *op,
<------><------><------><------><------><------> const struct fscache_state *ostate)
{
<------>static bool once_only;
<------>struct fscache_operation *p;
<------>unsigned n;
 
<------>if (once_only)
<------><------>return;
<------>once_only = true;
 
<------>kdebug("unexpected submission OP%x [OBJ%x %s]",
<------>       op->debug_id, object->debug_id, object->state->name);
<------>kdebug("objstate=%s [%s]", object->state->name, ostate->name);
<------>kdebug("objflags=%lx", object->flags);
<------>kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
<------>kdebug("ops=%u inp=%u exc=%u",
<------>       object->n_ops, object->n_in_progress, object->n_exclusive);
 
<------>if (!list_empty(&object->pending_ops)) {
<------><------>n = 0;
<------><------>list_for_each_entry(p, &object->pending_ops, pend_link) {
<------><------><------>ASSERTCMP(p->object, ==, object);
<------><------><------>kdebug("%p %p", op->processor, op->release);
<------><------><------>n++;
<------><------>}
 
<------><------>kdebug("n=%u", n);
<------>}
 
<------>dump_stack();
}
 
/*
 * submit an exclusive operation for an object
 * - other ops are excluded from running simultaneously with this one
 * - this gets any extra refs it needs on an op
 */
int fscache_submit_exclusive_op(struct fscache_object *object,
<------><------><------><------>struct fscache_operation *op)
{
<------>const struct fscache_state *ostate;
<------>unsigned long flags;
<------>int ret;
 
<------>_enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
 
<------>trace_fscache_op(object->cookie, op, fscache_op_submit_ex);
 
<------>ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
<------>ASSERTCMP(atomic_read(&op->usage), >, 0);
 
<------>spin_lock(&object->lock);
<------>ASSERTCMP(object->n_ops, >=, object->n_in_progress);
<------>ASSERTCMP(object->n_ops, >=, object->n_exclusive);
<------>ASSERT(list_empty(&op->pend_link));
 
<------>ostate = object->state;
<------>smp_rmb();
 
<------>op->state = FSCACHE_OP_ST_PENDING;
<------>flags = READ_ONCE(object->flags);
<------>if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
<------><------>fscache_stat(&fscache_n_op_rejected);
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------><------>ret = -ENOBUFS;
<------>} else if (unlikely(fscache_cache_is_broken(object))) {
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------><------>ret = -EIO;
<------>} else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
<------><------>op->object = object;
<------><------>object->n_ops++;
<------><------>object->n_exclusive++;	/* reads and writes must wait */
 
<------><------>if (object->n_in_progress > 0) {
<------><------><------>atomic_inc(&op->usage);
<------><------><------>list_add_tail(&op->pend_link, &object->pending_ops);
<------><------><------>fscache_stat(&fscache_n_op_pend);
<------><------>} else if (!list_empty(&object->pending_ops)) {
<------><------><------>atomic_inc(&op->usage);
<------><------><------>list_add_tail(&op->pend_link, &object->pending_ops);
<------><------><------>fscache_stat(&fscache_n_op_pend);
<------><------><------>fscache_start_operations(object);
<------><------>} else {
<------><------><------>ASSERTCMP(object->n_in_progress, ==, 0);
<------><------><------>fscache_run_op(object, op);
<------><------>}
 
<------><------>/* need to issue a new write op after this */
<------><------>clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
<------><------>ret = 0;
<------>} else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
<------><------>op->object = object;
<------><------>object->n_ops++;
<------><------>object->n_exclusive++;	/* reads and writes must wait */
<------><------>atomic_inc(&op->usage);
<------><------>list_add_tail(&op->pend_link, &object->pending_ops);
<------><------>fscache_stat(&fscache_n_op_pend);
<------><------>ret = 0;
<------>} else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------><------>ret = -ENOBUFS;
<------>} else {
<------><------>fscache_report_unexpected_submission(object, op, ostate);
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------><------>ret = -ENOBUFS;
<------>}
 
<------>spin_unlock(&object->lock);
<------>return ret;
}
 
/*
 * submit an operation for an object
 * - objects may be submitted only in the following states:
 *   - during object creation (write ops may be submitted)
 *   - whilst the object is active
 *   - after an I/O error incurred in one of the two above states (op rejected)
 * - this gets any extra refs it needs on an op
 */
int fscache_submit_op(struct fscache_object *object,
<------><------>      struct fscache_operation *op)
{
<------>const struct fscache_state *ostate;
<------>unsigned long flags;
<------>int ret;
 
<------>_enter("{OBJ%x OP%x},{%u}",
<------>       object->debug_id, op->debug_id, atomic_read(&op->usage));
 
<------>trace_fscache_op(object->cookie, op, fscache_op_submit);
 
<------>ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
<------>ASSERTCMP(atomic_read(&op->usage), >, 0);
 
<------>spin_lock(&object->lock);
<------>ASSERTCMP(object->n_ops, >=, object->n_in_progress);
<------>ASSERTCMP(object->n_ops, >=, object->n_exclusive);
<------>ASSERT(list_empty(&op->pend_link));
 
<------>ostate = object->state;
<------>smp_rmb();
 
<------>op->state = FSCACHE_OP_ST_PENDING;
<------>flags = READ_ONCE(object->flags);
<------>if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
<------><------>fscache_stat(&fscache_n_op_rejected);
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------><------>ret = -ENOBUFS;
<------>} else if (unlikely(fscache_cache_is_broken(object))) {
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------><------>ret = -EIO;
<------>} else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
<------><------>op->object = object;
<------><------>object->n_ops++;
 
<------><------>if (object->n_exclusive > 0) {
<------><------><------>atomic_inc(&op->usage);
<------><------><------>list_add_tail(&op->pend_link, &object->pending_ops);
<------><------><------>fscache_stat(&fscache_n_op_pend);
<------><------>} else if (!list_empty(&object->pending_ops)) {
<------><------><------>atomic_inc(&op->usage);
<------><------><------>list_add_tail(&op->pend_link, &object->pending_ops);
<------><------><------>fscache_stat(&fscache_n_op_pend);
<------><------><------>fscache_start_operations(object);
<------><------>} else {
<------><------><------>ASSERTCMP(object->n_exclusive, ==, 0);
<------><------><------>fscache_run_op(object, op);
<------><------>}
<------><------>ret = 0;
<------>} else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
<------><------>op->object = object;
<------><------>object->n_ops++;
<------><------>atomic_inc(&op->usage);
<------><------>list_add_tail(&op->pend_link, &object->pending_ops);
<------><------>fscache_stat(&fscache_n_op_pend);
<------><------>ret = 0;
<------>} else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------><------>ret = -ENOBUFS;
<------>} else {
<------><------>fscache_report_unexpected_submission(object, op, ostate);
<------><------>ASSERT(!fscache_object_is_active(object));
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------><------>ret = -ENOBUFS;
<------>}
 
<------>spin_unlock(&object->lock);
<------>return ret;
}
 
/*
 * queue an object for withdrawal on error, aborting all following asynchronous
 * operations
 */
void fscache_abort_object(struct fscache_object *object)
{
<------>_enter("{OBJ%x}", object->debug_id);
 
<------>fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
}
 
/*
 * Jump start the operation processing on an object.  The caller must hold
 * object->lock.
 */
void fscache_start_operations(struct fscache_object *object)
{
<------>struct fscache_operation *op;
<------>bool stop = false;
 
<------>while (!list_empty(&object->pending_ops) && !stop) {
<------><------>op = list_entry(object->pending_ops.next,
<------><------><------><------>struct fscache_operation, pend_link);
 
<------><------>if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
<------><------><------>if (object->n_in_progress > 0)
<------><------><------><------>break;
<------><------><------>stop = true;
<------><------>}
<------><------>list_del_init(&op->pend_link);
<------><------>fscache_run_op(object, op);
 
<------><------>/* the pending queue was holding a ref on the object */
<------><------>fscache_put_operation(op);
<------>}
 
<------>ASSERTCMP(object->n_in_progress, <=, object->n_ops);
 
<------>_debug("woke %d ops on OBJ%x",
<------>       object->n_in_progress, object->debug_id);
}
 
/*
 * cancel an operation that's pending on an object
 */
int fscache_cancel_op(struct fscache_operation *op,
<------><------>      bool cancel_in_progress_op)
{
<------>struct fscache_object *object = op->object;
<------>bool put = false;
<------>int ret;
 
<------>_enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
 
<------>trace_fscache_op(object->cookie, op, fscache_op_cancel);
 
<------>ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
<------>ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
<------>ASSERTCMP(atomic_read(&op->usage), >, 0);
 
<------>spin_lock(&object->lock);
 
<------>ret = -EBUSY;
<------>if (op->state == FSCACHE_OP_ST_PENDING) {
<------><------>ASSERT(!list_empty(&op->pend_link));
<------><------>list_del_init(&op->pend_link);
<------><------>put = true;
 
<------><------>fscache_stat(&fscache_n_op_cancelled);
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------><------>if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
<------><------><------>object->n_exclusive--;
<------><------>if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
<------><------><------>wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
<------><------>ret = 0;
<------>} else if (op->state == FSCACHE_OP_ST_IN_PROGRESS && cancel_in_progress_op) {
<------><------>ASSERTCMP(object->n_in_progress, >, 0);
<------><------>if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
<------><------><------>object->n_exclusive--;
<------><------>object->n_in_progress--;
<------><------>if (object->n_in_progress == 0)
<------><------><------>fscache_start_operations(object);
 
<------><------>fscache_stat(&fscache_n_op_cancelled);
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------><------>if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
<------><------><------>object->n_exclusive--;
<------><------>if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
<------><------><------>wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
<------><------>ret = 0;
<------>}
 
<------>if (put)
<------><------>fscache_put_operation(op);
<------>spin_unlock(&object->lock);
<------>_leave(" = %d", ret);
<------>return ret;
}
 
/*
 * Cancel all pending operations on an object
 */
void fscache_cancel_all_ops(struct fscache_object *object)
{
<------>struct fscache_operation *op;
 
<------>_enter("OBJ%x", object->debug_id);
 
<------>spin_lock(&object->lock);
 
<------>while (!list_empty(&object->pending_ops)) {
<------><------>op = list_entry(object->pending_ops.next,
<------><------><------><------>struct fscache_operation, pend_link);
<------><------>fscache_stat(&fscache_n_op_cancelled);
<------><------>list_del_init(&op->pend_link);
 
<------><------>trace_fscache_op(object->cookie, op, fscache_op_cancel_all);
 
<------><------>ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
<------><------>op->cancel(op);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
 
<------><------>if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
<------><------><------>object->n_exclusive--;
<------><------>if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
<------><------><------>wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
<------><------>fscache_put_operation(op);
<------><------>cond_resched_lock(&object->lock);
<------>}
 
<------>spin_unlock(&object->lock);
<------>_leave("");
}
 
/*
 * Record the completion or cancellation of an in-progress operation.
 */
void fscache_op_complete(struct fscache_operation *op, bool cancelled)
{
<------>struct fscache_object *object = op->object;
 
<------>_enter("OBJ%x", object->debug_id);
 
<------>ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
<------>ASSERTCMP(object->n_in_progress, >, 0);
<------>ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
<------><------>    object->n_exclusive, >, 0);
<------>ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
<------><------>    object->n_in_progress, ==, 1);
 
<------>spin_lock(&object->lock);
 
<------>if (!cancelled) {
<------><------>trace_fscache_op(object->cookie, op, fscache_op_completed);
<------><------>op->state = FSCACHE_OP_ST_COMPLETE;
<------>} else {
<------><------>op->cancel(op);
<------><------>trace_fscache_op(object->cookie, op, fscache_op_cancelled);
<------><------>op->state = FSCACHE_OP_ST_CANCELLED;
<------>}
 
<------>if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
<------><------>object->n_exclusive--;
<------>object->n_in_progress--;
<------>if (object->n_in_progress == 0)
<------><------>fscache_start_operations(object);
 
<------>spin_unlock(&object->lock);
<------>_leave("");
}
EXPORT_SYMBOL(fscache_op_complete);
 
/*
 * release an operation
 * - queues pending ops if this is the last in-progress op
 */
void fscache_put_operation(struct fscache_operation *op)
{
<------>struct fscache_object *object;
<------>struct fscache_cache *cache;
 
<------>_enter("{OBJ%x OP%x,%d}",
<------>       op->object ? op->object->debug_id : 0,
<------>       op->debug_id, atomic_read(&op->usage));
 
<------>ASSERTCMP(atomic_read(&op->usage), >, 0);
 
<------>if (!atomic_dec_and_test(&op->usage))
<------><------>return;
 
<------>trace_fscache_op(op->object ? op->object->cookie : NULL, op, fscache_op_put);
 
<------>_debug("PUT OP");
<------>ASSERTIFCMP(op->state != FSCACHE_OP_ST_INITIALISED &&
<------><------>    op->state != FSCACHE_OP_ST_COMPLETE,
<------><------>    op->state, ==, FSCACHE_OP_ST_CANCELLED);
 
<------>fscache_stat(&fscache_n_op_release);
 
<------>if (op->release) {
<------><------>op->release(op);
<------><------>op->release = NULL;
<------>}
<------>op->state = FSCACHE_OP_ST_DEAD;
 
<------>object = op->object;
<------>if (likely(object)) {
<------><------>if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
<------><------><------>atomic_dec(&object->n_reads);
<------><------>if (test_bit(FSCACHE_OP_UNUSE_COOKIE, &op->flags))
<------><------><------>fscache_unuse_cookie(object);
 
<------><------>/* now... we may get called with the object spinlock held, so we
<------><------> * complete the cleanup here only if we can immediately acquire the
<------><------> * lock, and defer it otherwise */
<------><------>if (!spin_trylock(&object->lock)) {
<------><------><------>_debug("defer put");
<------><------><------>fscache_stat(&fscache_n_op_deferred_release);
 
<------><------><------>cache = object->cache;
<------><------><------>spin_lock(&cache->op_gc_list_lock);
<------><------><------>list_add_tail(&op->pend_link, &cache->op_gc_list);
<------><------><------>spin_unlock(&cache->op_gc_list_lock);
<------><------><------>schedule_work(&cache->op_gc);
<------><------><------>_leave(" [defer]");
<------><------><------>return;
<------><------>}
 
<------><------>ASSERTCMP(object->n_ops, >, 0);
<------><------>object->n_ops--;
<------><------>if (object->n_ops == 0)
<------><------><------>fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 
<------><------>spin_unlock(&object->lock);
<------>}
 
<------>kfree(op);
<------>_leave(" [done]");
}
EXPORT_SYMBOL(fscache_put_operation);
 
/*
 * garbage collect operations that have had their release deferred
 */
void fscache_operation_gc(struct work_struct *work)
{
<------>struct fscache_operation *op;
<------>struct fscache_object *object;
<------>struct fscache_cache *cache =
<------><------>container_of(work, struct fscache_cache, op_gc);
<------>int count = 0;
 
<------>_enter("");
 
<------>do {
<------><------>spin_lock(&cache->op_gc_list_lock);
<------><------>if (list_empty(&cache->op_gc_list)) {
<------><------><------>spin_unlock(&cache->op_gc_list_lock);
<------><------><------>break;
<------><------>}
 
<------><------>op = list_entry(cache->op_gc_list.next,
<------><------><------><------>struct fscache_operation, pend_link);
<------><------>list_del(&op->pend_link);
<------><------>spin_unlock(&cache->op_gc_list_lock);
 
<------><------>object = op->object;
<------><------>trace_fscache_op(object->cookie, op, fscache_op_gc);
 
<------><------>spin_lock(&object->lock);
 
<------><------>_debug("GC DEFERRED REL OBJ%x OP%x",
<------><------>       object->debug_id, op->debug_id);
<------><------>fscache_stat(&fscache_n_op_gc);
 
<------><------>ASSERTCMP(atomic_read(&op->usage), ==, 0);
<------><------>ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
 
<------><------>ASSERTCMP(object->n_ops, >, 0);
<------><------>object->n_ops--;
<------><------>if (object->n_ops == 0)
<------><------><------>fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 
<------><------>spin_unlock(&object->lock);
<------><------>kfree(op);
 
<------>} while (count++ < 20);
 
<------>if (!list_empty(&cache->op_gc_list))
<------><------>schedule_work(&cache->op_gc);
 
<------>_leave("");
}
 
/*
 * execute an operation using fs_op_wq to provide processing context -
 * the caller holds a ref to this object, so we don't need to hold one
 */
void fscache_op_work_func(struct work_struct *work)
{
<------>struct fscache_operation *op =
<------><------>container_of(work, struct fscache_operation, work);
<------>unsigned long start;
 
<------>_enter("{OBJ%x OP%x,%d}",
<------>       op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 
<------>trace_fscache_op(op->object->cookie, op, fscache_op_work);
 
<------>ASSERT(op->processor != NULL);
<------>start = jiffies;
<------>op->processor(op);
<------>fscache_hist(fscache_ops_histogram, start);
<------>fscache_put_operation(op);
 
<------>_leave("");
}