[mirror_ubuntu-zesty-kernel.git] / fs / fscache / operation.c

/* FS-Cache worker operation management routines
 *
 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 * See Documentation/filesystems/caching/operations.txt
 */

#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);

/**
 * 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)
{
	_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);
	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);

	fscache_stat(&fscache_n_op_enqueue);
	switch (op->flags & FSCACHE_OP_TYPE) {
	case FSCACHE_OP_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:
		_debug("queue for caller's attention");
		break;
	default:
		printk(KERN_ERR "FS-Cache: 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);
	fscache_stat(&fscache_n_op_run);
}

/*
 * 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)
{
	int ret;

	_enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);

	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));

	op->state = FSCACHE_OP_ST_PENDING;
	if (fscache_object_is_active(object)) {
		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 (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
		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 we're in any other state, there must have been an I/O
		 * error of some nature.
		 */
		ASSERT(test_bit(FSCACHE_IOERROR, &object->cache->flags));
		ret = -EIO;
	}

	spin_unlock(&object->lock);
	return ret;
}

/*
 * 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 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;
	int ret;

	_enter("{OBJ%x OP%x},{%u}",
	       object->debug_id, op->debug_id, atomic_read(&op->usage));

	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;
	if (fscache_object_is_active(object)) {
		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 (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
		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 (fscache_object_is_dying(object)) {
		fscache_stat(&fscache_n_op_rejected);
		op->state = FSCACHE_OP_ST_CANCELLED;
		ret = -ENOBUFS;
	} else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
		fscache_report_unexpected_submission(object, op, ostate);
		ASSERT(!fscache_object_is_active(object));
		op->state = FSCACHE_OP_ST_CANCELLED;
		ret = -ENOBUFS;
	} else {
		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,
		      void (*do_cancel)(struct fscache_operation *))
{
	struct fscache_object *object = op->object;
	int ret;

	_enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);

	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));
		fscache_stat(&fscache_n_op_cancelled);
		list_del_init(&op->pend_link);
		if (do_cancel)
			do_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);
		ret = 0;
	}

	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);

		ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
		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);

	op->state = cancelled ?
		FSCACHE_OP_ST_CANCELLED : FSCACHE_OP_ST_COMPLETE;

	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->debug_id, op->debug_id, atomic_read(&op->usage));

	ASSERTCMP(atomic_read(&op->usage), >, 0);

	if (!atomic_dec_and_test(&op->usage))
		return;

	_debug("PUT OP");
	ASSERTIFCMP(op->state != FSCACHE_OP_ST_COMPLETE,
		    op->state, ==, FSCACHE_OP_ST_CANCELLED);
	op->state = FSCACHE_OP_ST_DEAD;

	fscache_stat(&fscache_n_op_release);

	if (op->release) {
		op->release(op);
		op->release = NULL;
	}

	object = op->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;
		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));

	ASSERT(op->processor != NULL);
	start = jiffies;
	op->processor(op);
	fscache_hist(fscache_ops_histogram, start);
	fscache_put_operation(op);

	_leave("");
}
Commit	Line	Data
952efe7b DH	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>
440f0aff	16	#include <linux/seq_file.h>
5a0e3ad6	17	#include <linux/slab.h>
952efe7b DH	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
5753c441	36	ASSERT(list_empty(&op->pend_link));
952efe7b	37	ASSERT(op->processor != NULL);
493f7bc1	38	ASSERT(fscache_object_is_available(op->object));
952efe7b	39	ASSERTCMP(atomic_read(&op->usage), >, 0);
9f10523f	40	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
952efe7b	41
5753c441 DH	42	fscache_stat(&fscache_n_op_enqueue);
5753c441 DH	43	switch (op->flags & FSCACHE_OP_TYPE) {
8af7c124 TH	44	case FSCACHE_OP_ASYNC:
8af7c124 TH	45	_debug("queue async");
5753c441	46	atomic_inc(&op->usage);
8af7c124	47	if (!queue_work(fscache_op_wq, &op->work))
5753c441 DH	48	fscache_put_operation(op);
5753c441 DH	49	break;
5753c441 DH	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;
952efe7b DH	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	{
9f10523f DH	68	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
	69
	70	op->state = FSCACHE_OP_ST_IN_PROGRESS;
952efe7b DH	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	{
8d76349d DH	87	int ret;
8d76349d DH	88
952efe7b DH	89	_enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
952efe7b DH	90
9f10523f DH	91	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
	92	ASSERTCMP(atomic_read(&op->usage), >, 0);
	93
952efe7b DH	94	spin_lock(&object->lock);
	95	ASSERTCMP(object->n_ops, >=, object->n_in_progress);
	96	ASSERTCMP(object->n_ops, >=, object->n_exclusive);
5753c441	97	ASSERT(list_empty(&op->pend_link));
952efe7b	98
9f10523f	99	op->state = FSCACHE_OP_ST_PENDING;
952efe7b DH	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
9f10523f	105	if (object->n_in_progress > 0) {
952efe7b DH	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);
8d76349d	121	ret = 0;
caaef690	122	} else if (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
952efe7b DH	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);
8d76349d	129	ret = 0;
952efe7b	130	} else {
8d76349d DH	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;
952efe7b DH	136	}
	137
	138	spin_unlock(&object->lock);
8d76349d	139	return ret;
952efe7b DH	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,
caaef690	147	const struct fscache_state *ostate)
952efe7b DH	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]",
caaef690 DH	158	op->debug_id, object->debug_id, object->state->name);
caaef690 DH	159	kdebug("objstate=%s [%s]", object->state->name, ostate->name);
952efe7b DH	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	{
caaef690	190	const struct fscache_state *ostate;
952efe7b DH	191	int ret;
	192
	193	_enter("{OBJ%x OP%x},{%u}",
	194	object->debug_id, op->debug_id, atomic_read(&op->usage));
	195
9f10523f	196	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
952efe7b DH	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);
5753c441	202	ASSERT(list_empty(&op->pend_link));
952efe7b DH	203
	204	ostate = object->state;
	205	smp_rmb();
	206
9f10523f	207	op->state = FSCACHE_OP_ST_PENDING;
952efe7b DH	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;
caaef690	226	} else if (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
952efe7b DH	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;
caaef690	233	} else if (fscache_object_is_dying(object)) {
e3d4d28b	234	fscache_stat(&fscache_n_op_rejected);
9f10523f	235	op->state = FSCACHE_OP_ST_CANCELLED;
e3d4d28b	236	ret = -ENOBUFS;
952efe7b DH	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));
9f10523f	240	op->state = FSCACHE_OP_ST_CANCELLED;
952efe7b DH	241	ret = -ENOBUFS;
952efe7b DH	242	} else {
9f10523f	243	op->state = FSCACHE_OP_ST_CANCELLED;
952efe7b DH	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	/*
dcfae32f DH	263	* Jump start the operation processing on an object. The caller must hold
dcfae32f DH	264	* object->lock.
952efe7b DH	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);
5753c441	281	fscache_run_op(object, op);
952efe7b DH	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
5753c441 DH	293	/*
	294	* cancel an operation that's pending on an object
	295	*/
91c7fbbf DH	296	int fscache_cancel_op(struct fscache_operation *op,
91c7fbbf DH	297	void (do_cancel)(struct fscache_operation ))
5753c441 DH	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
9f10523f DH	304	ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
	305	ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
	306	ASSERTCMP(atomic_read(&op->usage), >, 0);
	307
5753c441 DH	308	spin_lock(&object->lock);
	309
	310	ret = -EBUSY;
9f10523f DH	311	if (op->state == FSCACHE_OP_ST_PENDING) {
9f10523f DH	312	ASSERT(!list_empty(&op->pend_link));
5753c441 DH	313	fscache_stat(&fscache_n_op_cancelled);
5753c441 DH	314	list_del_init(&op->pend_link);
91c7fbbf DH	315	if (do_cancel)
91c7fbbf DH	316	do_cancel(op);
9f10523f	317	op->state = FSCACHE_OP_ST_CANCELLED;
5753c441 DH	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
ef778e7a DH	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
9f10523f	363	/*
1f372dff	364	* Record the completion or cancellation of an in-progress operation.
9f10523f	365	*/
1f372dff	366	void fscache_op_complete(struct fscache_operation *op, bool cancelled)
9f10523f DH	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
1f372dff DH	381	op->state = cancelled ?
1f372dff DH	382	FSCACHE_OP_ST_CANCELLED : FSCACHE_OP_ST_COMPLETE;
9f10523f DH	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
952efe7b DH	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");
9f10523f DH	413	ASSERTIFCMP(op->state != FSCACHE_OP_ST_COMPLETE,
	414	op->state, ==, FSCACHE_OP_ST_CANCELLED);
	415	op->state = FSCACHE_OP_ST_DEAD;
952efe7b DH	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
1362729b DH	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);
4fbf4291	430
952efe7b DH	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
952efe7b DH	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;
9f10523f	485	spin_lock(&object->lock);
952efe7b DH	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);
9f10523f	492	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
952efe7b DH	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);
9f10523f	500	kfree(op);
952efe7b DH	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	/*
8af7c124 TH	511	* execute an operation using fs_op_wq to provide processing context -
8af7c124 TH	512	* the caller holds a ref to this object, so we don't need to hold one
952efe7b	513	*/
8af7c124	514	void fscache_op_work_func(struct work_struct *work)
952efe7b DH	515	{
952efe7b DH	516	struct fscache_operation *op =
8af7c124	517	container_of(work, struct fscache_operation, work);
952efe7b DH	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);
8af7c124	527	fscache_put_operation(op);
952efe7b DH	528
	529	_leave("");
	530	}