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![Akshat Aranya](/assets/img/avatar_default.png)
fscache_submit_exclusive_op() adds an operation to the pending list if other operations are pending. Fix the check for pending ops as n_ops must be greater than 0 at the point it is checked as it is incremented immediately before under lock. Signed-off-by: Akshat Aranya <aranya@nec-labs.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
473 lines
12 KiB
C
473 lines
12 KiB
C
/* FS-Cache worker operation management routines
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*
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* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* See Documentation/filesystems/caching/operations.txt
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*/
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#define FSCACHE_DEBUG_LEVEL OPERATION
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#include <linux/module.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include "internal.h"
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atomic_t fscache_op_debug_id;
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EXPORT_SYMBOL(fscache_op_debug_id);
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/**
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* fscache_enqueue_operation - Enqueue an operation for processing
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* @op: The operation to enqueue
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*
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* Enqueue an operation for processing by the FS-Cache thread pool.
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*
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* This will get its own ref on the object.
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*/
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void fscache_enqueue_operation(struct fscache_operation *op)
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{
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_enter("{OBJ%x OP%x,%u}",
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op->object->debug_id, op->debug_id, atomic_read(&op->usage));
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fscache_set_op_state(op, "EnQ");
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ASSERT(list_empty(&op->pend_link));
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ASSERT(op->processor != NULL);
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ASSERTCMP(op->object->state, >=, FSCACHE_OBJECT_AVAILABLE);
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ASSERTCMP(atomic_read(&op->usage), >, 0);
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fscache_stat(&fscache_n_op_enqueue);
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switch (op->flags & FSCACHE_OP_TYPE) {
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case FSCACHE_OP_ASYNC:
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_debug("queue async");
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atomic_inc(&op->usage);
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if (!queue_work(fscache_op_wq, &op->work))
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fscache_put_operation(op);
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break;
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case FSCACHE_OP_MYTHREAD:
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_debug("queue for caller's attention");
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break;
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default:
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printk(KERN_ERR "FS-Cache: Unexpected op type %lx",
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op->flags);
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BUG();
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break;
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}
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}
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EXPORT_SYMBOL(fscache_enqueue_operation);
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/*
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* start an op running
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*/
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static void fscache_run_op(struct fscache_object *object,
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struct fscache_operation *op)
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{
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fscache_set_op_state(op, "Run");
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object->n_in_progress++;
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if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
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wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
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if (op->processor)
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fscache_enqueue_operation(op);
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fscache_stat(&fscache_n_op_run);
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}
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/*
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* submit an exclusive operation for an object
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* - other ops are excluded from running simultaneously with this one
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* - this gets any extra refs it needs on an op
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*/
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int fscache_submit_exclusive_op(struct fscache_object *object,
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struct fscache_operation *op)
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{
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int ret;
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_enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
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fscache_set_op_state(op, "SubmitX");
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spin_lock(&object->lock);
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ASSERTCMP(object->n_ops, >=, object->n_in_progress);
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ASSERTCMP(object->n_ops, >=, object->n_exclusive);
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ASSERT(list_empty(&op->pend_link));
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ret = -ENOBUFS;
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if (fscache_object_is_active(object)) {
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op->object = object;
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object->n_ops++;
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object->n_exclusive++; /* reads and writes must wait */
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if (object->n_ops > 1) {
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atomic_inc(&op->usage);
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list_add_tail(&op->pend_link, &object->pending_ops);
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fscache_stat(&fscache_n_op_pend);
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} else if (!list_empty(&object->pending_ops)) {
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atomic_inc(&op->usage);
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list_add_tail(&op->pend_link, &object->pending_ops);
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fscache_stat(&fscache_n_op_pend);
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fscache_start_operations(object);
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} else {
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ASSERTCMP(object->n_in_progress, ==, 0);
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fscache_run_op(object, op);
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}
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/* need to issue a new write op after this */
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clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
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ret = 0;
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} else if (object->state == FSCACHE_OBJECT_CREATING) {
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op->object = object;
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object->n_ops++;
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object->n_exclusive++; /* reads and writes must wait */
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atomic_inc(&op->usage);
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list_add_tail(&op->pend_link, &object->pending_ops);
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fscache_stat(&fscache_n_op_pend);
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ret = 0;
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} else {
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/* not allowed to submit ops in any other state */
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BUG();
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}
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spin_unlock(&object->lock);
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return ret;
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}
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/*
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* report an unexpected submission
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*/
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static void fscache_report_unexpected_submission(struct fscache_object *object,
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struct fscache_operation *op,
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unsigned long ostate)
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{
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static bool once_only;
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struct fscache_operation *p;
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unsigned n;
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if (once_only)
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return;
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once_only = true;
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kdebug("unexpected submission OP%x [OBJ%x %s]",
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op->debug_id, object->debug_id,
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fscache_object_states[object->state]);
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kdebug("objstate=%s [%s]",
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fscache_object_states[object->state],
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fscache_object_states[ostate]);
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kdebug("objflags=%lx", object->flags);
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kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
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kdebug("ops=%u inp=%u exc=%u",
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object->n_ops, object->n_in_progress, object->n_exclusive);
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if (!list_empty(&object->pending_ops)) {
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n = 0;
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list_for_each_entry(p, &object->pending_ops, pend_link) {
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ASSERTCMP(p->object, ==, object);
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kdebug("%p %p", op->processor, op->release);
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n++;
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}
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kdebug("n=%u", n);
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}
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dump_stack();
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}
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/*
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* submit an operation for an object
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* - objects may be submitted only in the following states:
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* - during object creation (write ops may be submitted)
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* - whilst the object is active
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* - after an I/O error incurred in one of the two above states (op rejected)
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* - this gets any extra refs it needs on an op
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*/
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int fscache_submit_op(struct fscache_object *object,
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struct fscache_operation *op)
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{
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unsigned long ostate;
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int ret;
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_enter("{OBJ%x OP%x},{%u}",
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object->debug_id, op->debug_id, atomic_read(&op->usage));
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ASSERTCMP(atomic_read(&op->usage), >, 0);
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fscache_set_op_state(op, "Submit");
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spin_lock(&object->lock);
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ASSERTCMP(object->n_ops, >=, object->n_in_progress);
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ASSERTCMP(object->n_ops, >=, object->n_exclusive);
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ASSERT(list_empty(&op->pend_link));
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ostate = object->state;
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smp_rmb();
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if (fscache_object_is_active(object)) {
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op->object = object;
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object->n_ops++;
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if (object->n_exclusive > 0) {
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atomic_inc(&op->usage);
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list_add_tail(&op->pend_link, &object->pending_ops);
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fscache_stat(&fscache_n_op_pend);
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} else if (!list_empty(&object->pending_ops)) {
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atomic_inc(&op->usage);
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list_add_tail(&op->pend_link, &object->pending_ops);
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fscache_stat(&fscache_n_op_pend);
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fscache_start_operations(object);
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} else {
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ASSERTCMP(object->n_exclusive, ==, 0);
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fscache_run_op(object, op);
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}
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ret = 0;
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} else if (object->state == FSCACHE_OBJECT_CREATING) {
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op->object = object;
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object->n_ops++;
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atomic_inc(&op->usage);
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list_add_tail(&op->pend_link, &object->pending_ops);
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fscache_stat(&fscache_n_op_pend);
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ret = 0;
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} else if (object->state == FSCACHE_OBJECT_DYING ||
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object->state == FSCACHE_OBJECT_LC_DYING ||
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object->state == FSCACHE_OBJECT_WITHDRAWING) {
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fscache_stat(&fscache_n_op_rejected);
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ret = -ENOBUFS;
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} else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
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fscache_report_unexpected_submission(object, op, ostate);
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ASSERT(!fscache_object_is_active(object));
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ret = -ENOBUFS;
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} else {
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ret = -ENOBUFS;
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}
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spin_unlock(&object->lock);
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return ret;
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}
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/*
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* queue an object for withdrawal on error, aborting all following asynchronous
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* operations
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*/
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void fscache_abort_object(struct fscache_object *object)
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{
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_enter("{OBJ%x}", object->debug_id);
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fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
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}
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/*
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* jump start the operation processing on an object
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* - caller must hold object->lock
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*/
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void fscache_start_operations(struct fscache_object *object)
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{
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struct fscache_operation *op;
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bool stop = false;
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while (!list_empty(&object->pending_ops) && !stop) {
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op = list_entry(object->pending_ops.next,
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struct fscache_operation, pend_link);
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if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
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if (object->n_in_progress > 0)
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break;
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stop = true;
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}
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list_del_init(&op->pend_link);
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fscache_run_op(object, op);
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/* the pending queue was holding a ref on the object */
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fscache_put_operation(op);
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}
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ASSERTCMP(object->n_in_progress, <=, object->n_ops);
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_debug("woke %d ops on OBJ%x",
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object->n_in_progress, object->debug_id);
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}
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/*
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* cancel an operation that's pending on an object
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*/
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int fscache_cancel_op(struct fscache_operation *op)
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{
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struct fscache_object *object = op->object;
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int ret;
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_enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
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spin_lock(&object->lock);
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ret = -EBUSY;
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if (!list_empty(&op->pend_link)) {
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fscache_stat(&fscache_n_op_cancelled);
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list_del_init(&op->pend_link);
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object->n_ops--;
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if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
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object->n_exclusive--;
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if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
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wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
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fscache_put_operation(op);
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ret = 0;
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}
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spin_unlock(&object->lock);
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_leave(" = %d", ret);
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return ret;
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}
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/*
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* release an operation
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* - queues pending ops if this is the last in-progress op
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*/
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void fscache_put_operation(struct fscache_operation *op)
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{
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struct fscache_object *object;
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struct fscache_cache *cache;
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_enter("{OBJ%x OP%x,%d}",
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op->object->debug_id, op->debug_id, atomic_read(&op->usage));
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ASSERTCMP(atomic_read(&op->usage), >, 0);
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if (!atomic_dec_and_test(&op->usage))
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return;
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fscache_set_op_state(op, "Put");
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_debug("PUT OP");
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if (test_and_set_bit(FSCACHE_OP_DEAD, &op->flags))
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BUG();
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fscache_stat(&fscache_n_op_release);
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if (op->release) {
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op->release(op);
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op->release = NULL;
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}
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object = op->object;
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if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
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atomic_dec(&object->n_reads);
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/* now... we may get called with the object spinlock held, so we
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* complete the cleanup here only if we can immediately acquire the
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* lock, and defer it otherwise */
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if (!spin_trylock(&object->lock)) {
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_debug("defer put");
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fscache_stat(&fscache_n_op_deferred_release);
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cache = object->cache;
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spin_lock(&cache->op_gc_list_lock);
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list_add_tail(&op->pend_link, &cache->op_gc_list);
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spin_unlock(&cache->op_gc_list_lock);
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schedule_work(&cache->op_gc);
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_leave(" [defer]");
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return;
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}
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if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
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ASSERTCMP(object->n_exclusive, >, 0);
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object->n_exclusive--;
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}
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ASSERTCMP(object->n_in_progress, >, 0);
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object->n_in_progress--;
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if (object->n_in_progress == 0)
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fscache_start_operations(object);
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ASSERTCMP(object->n_ops, >, 0);
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object->n_ops--;
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if (object->n_ops == 0)
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fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
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spin_unlock(&object->lock);
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kfree(op);
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_leave(" [done]");
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}
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EXPORT_SYMBOL(fscache_put_operation);
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/*
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* garbage collect operations that have had their release deferred
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*/
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void fscache_operation_gc(struct work_struct *work)
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{
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struct fscache_operation *op;
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struct fscache_object *object;
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struct fscache_cache *cache =
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container_of(work, struct fscache_cache, op_gc);
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int count = 0;
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_enter("");
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do {
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spin_lock(&cache->op_gc_list_lock);
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if (list_empty(&cache->op_gc_list)) {
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spin_unlock(&cache->op_gc_list_lock);
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break;
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}
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op = list_entry(cache->op_gc_list.next,
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struct fscache_operation, pend_link);
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list_del(&op->pend_link);
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spin_unlock(&cache->op_gc_list_lock);
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object = op->object;
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_debug("GC DEFERRED REL OBJ%x OP%x",
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object->debug_id, op->debug_id);
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fscache_stat(&fscache_n_op_gc);
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ASSERTCMP(atomic_read(&op->usage), ==, 0);
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spin_lock(&object->lock);
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if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
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ASSERTCMP(object->n_exclusive, >, 0);
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object->n_exclusive--;
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}
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ASSERTCMP(object->n_in_progress, >, 0);
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object->n_in_progress--;
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if (object->n_in_progress == 0)
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fscache_start_operations(object);
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ASSERTCMP(object->n_ops, >, 0);
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object->n_ops--;
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if (object->n_ops == 0)
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fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
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spin_unlock(&object->lock);
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} while (count++ < 20);
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if (!list_empty(&cache->op_gc_list))
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schedule_work(&cache->op_gc);
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_leave("");
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}
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/*
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* execute an operation using fs_op_wq to provide processing context -
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* the caller holds a ref to this object, so we don't need to hold one
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*/
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void fscache_op_work_func(struct work_struct *work)
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{
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struct fscache_operation *op =
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container_of(work, struct fscache_operation, work);
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unsigned long start;
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_enter("{OBJ%x OP%x,%d}",
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op->object->debug_id, op->debug_id, atomic_read(&op->usage));
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ASSERT(op->processor != NULL);
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start = jiffies;
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op->processor(op);
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fscache_hist(fscache_ops_histogram, start);
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fscache_put_operation(op);
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_leave("");
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}
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