[deliverable/linux.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);
	ASSERTCMP(op->object->state, >=, FSCACHE_OBJECT_AVAILABLE);
	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)
{
	_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);
	} else if (object->state == FSCACHE_OBJECT_CREATING) {
		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);
	} else {
		/* not allowed to submit ops in any other state */
		BUG();
	}

	spin_unlock(&object->lock);
	return 0;
}

/*
 * report an unexpected submission
 */
static void fscache_report_unexpected_submission(struct fscache_object *object,
						 struct fscache_operation *op,
						 unsigned long 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,
	       fscache_object_states[object->state]);
	kdebug("objstate=%s [%s]",
	       fscache_object_states[object->state],
	       fscache_object_states[ostate]);
	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)
{
	unsigned long 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 (object->state == FSCACHE_OBJECT_CREATING) {
		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 (object->state == FSCACHE_OBJECT_DYING ||
		   object->state == FSCACHE_OBJECT_LC_DYING ||
		   object->state == FSCACHE_OBJECT_WITHDRAWING) {
		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
 * - 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)
{
	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);
		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 of an in-progress operation.
 */
void fscache_op_complete(struct fscache_operation *op)
{
	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 = 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)) {
		if (atomic_dec_and_test(&object->n_reads)) {
			clear_bit(FSCACHE_COOKIE_WAITING_ON_READS,
				  &object->cookie->flags);
			wake_up_bit(&object->cookie->flags,
				    FSCACHE_COOKIE_WAITING_ON_READS);
		}
	}

	/* 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 DH	37	ASSERT(op->processor != NULL);
	38	ASSERTCMP(op->object->state, >=, FSCACHE_OBJECT_AVAILABLE);
	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	{
952efe7b DH	87	_enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
952efe7b DH	88
9f10523f DH	89	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
	90	ASSERTCMP(atomic_read(&op->usage), >, 0);
	91
952efe7b DH	92	spin_lock(&object->lock);
	93	ASSERTCMP(object->n_ops, >=, object->n_in_progress);
	94	ASSERTCMP(object->n_ops, >=, object->n_exclusive);
5753c441	95	ASSERT(list_empty(&op->pend_link));
952efe7b	96
9f10523f	97	op->state = FSCACHE_OP_ST_PENDING;
952efe7b DH	98	if (fscache_object_is_active(object)) {
	99	op->object = object;
	100	object->n_ops++;
	101	object->n_exclusive++; /* reads and writes must wait */
	102
9f10523f	103	if (object->n_in_progress > 0) {
952efe7b DH	104	atomic_inc(&op->usage);
	105	list_add_tail(&op->pend_link, &object->pending_ops);
	106	fscache_stat(&fscache_n_op_pend);
	107	} else if (!list_empty(&object->pending_ops)) {
	108	atomic_inc(&op->usage);
	109	list_add_tail(&op->pend_link, &object->pending_ops);
	110	fscache_stat(&fscache_n_op_pend);
	111	fscache_start_operations(object);
	112	} else {
	113	ASSERTCMP(object->n_in_progress, ==, 0);
	114	fscache_run_op(object, op);
	115	}
	116
	117	/* need to issue a new write op after this */
	118	clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
952efe7b DH	119	} else if (object->state == FSCACHE_OBJECT_CREATING) {
	120	op->object = object;
	121	object->n_ops++;
	122	object->n_exclusive++; /* reads and writes must wait */
	123	atomic_inc(&op->usage);
	124	list_add_tail(&op->pend_link, &object->pending_ops);
	125	fscache_stat(&fscache_n_op_pend);
952efe7b DH	126	} else {
	127	/* not allowed to submit ops in any other state */
	128	BUG();
	129	}
	130
	131	spin_unlock(&object->lock);
9f10523f	132	return 0;
952efe7b DH	133	}
	134
	135	/*
	136	* report an unexpected submission
	137	*/
	138	static void fscache_report_unexpected_submission(struct fscache_object *object,
	139	struct fscache_operation *op,
	140	unsigned long ostate)
	141	{
	142	static bool once_only;
	143	struct fscache_operation *p;
	144	unsigned n;
	145
	146	if (once_only)
	147	return;
	148	once_only = true;
	149
	150	kdebug("unexpected submission OP%x [OBJ%x %s]",
	151	op->debug_id, object->debug_id,
	152	fscache_object_states[object->state]);
	153	kdebug("objstate=%s [%s]",
	154	fscache_object_states[object->state],
	155	fscache_object_states[ostate]);
	156	kdebug("objflags=%lx", object->flags);
	157	kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
	158	kdebug("ops=%u inp=%u exc=%u",
	159	object->n_ops, object->n_in_progress, object->n_exclusive);
	160
	161	if (!list_empty(&object->pending_ops)) {
	162	n = 0;
	163	list_for_each_entry(p, &object->pending_ops, pend_link) {
	164	ASSERTCMP(p->object, ==, object);
	165	kdebug("%p %p", op->processor, op->release);
	166	n++;
	167	}
	168
	169	kdebug("n=%u", n);
	170	}
	171
	172	dump_stack();
	173	}
	174
	175	/*
	176	* submit an operation for an object
	177	* - objects may be submitted only in the following states:
	178	* - during object creation (write ops may be submitted)
	179	* - whilst the object is active
	180	* - after an I/O error incurred in one of the two above states (op rejected)
	181	* - this gets any extra refs it needs on an op
	182	*/
	183	int fscache_submit_op(struct fscache_object *object,
	184	struct fscache_operation *op)
	185	{
	186	unsigned long ostate;
	187	int ret;
	188
	189	_enter("{OBJ%x OP%x},{%u}",
	190	object->debug_id, op->debug_id, atomic_read(&op->usage));
	191
9f10523f	192	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
952efe7b DH	193	ASSERTCMP(atomic_read(&op->usage), >, 0);
	194
	195	spin_lock(&object->lock);
	196	ASSERTCMP(object->n_ops, >=, object->n_in_progress);
	197	ASSERTCMP(object->n_ops, >=, object->n_exclusive);
5753c441	198	ASSERT(list_empty(&op->pend_link));
952efe7b DH	199
	200	ostate = object->state;
	201	smp_rmb();
	202
9f10523f	203	op->state = FSCACHE_OP_ST_PENDING;
952efe7b DH	204	if (fscache_object_is_active(object)) {
	205	op->object = object;
	206	object->n_ops++;
	207
	208	if (object->n_exclusive > 0) {
	209	atomic_inc(&op->usage);
	210	list_add_tail(&op->pend_link, &object->pending_ops);
	211	fscache_stat(&fscache_n_op_pend);
	212	} else if (!list_empty(&object->pending_ops)) {
	213	atomic_inc(&op->usage);
	214	list_add_tail(&op->pend_link, &object->pending_ops);
	215	fscache_stat(&fscache_n_op_pend);
	216	fscache_start_operations(object);
	217	} else {
	218	ASSERTCMP(object->n_exclusive, ==, 0);
	219	fscache_run_op(object, op);
	220	}
	221	ret = 0;
	222	} else if (object->state == FSCACHE_OBJECT_CREATING) {
	223	op->object = object;
	224	object->n_ops++;
	225	atomic_inc(&op->usage);
	226	list_add_tail(&op->pend_link, &object->pending_ops);
	227	fscache_stat(&fscache_n_op_pend);
	228	ret = 0;
e3d4d28b DH	229	} else if (object->state == FSCACHE_OBJECT_DYING \|\|
	230	object->state == FSCACHE_OBJECT_LC_DYING \|\|
	231	object->state == FSCACHE_OBJECT_WITHDRAWING) {
	232	fscache_stat(&fscache_n_op_rejected);
9f10523f	233	op->state = FSCACHE_OP_ST_CANCELLED;
e3d4d28b	234	ret = -ENOBUFS;
952efe7b DH	235	} else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
	236	fscache_report_unexpected_submission(object, op, ostate);
	237	ASSERT(!fscache_object_is_active(object));
9f10523f	238	op->state = FSCACHE_OP_ST_CANCELLED;
952efe7b DH	239	ret = -ENOBUFS;
952efe7b DH	240	} else {
9f10523f	241	op->state = FSCACHE_OP_ST_CANCELLED;
952efe7b DH	242	ret = -ENOBUFS;
	243	}
	244
	245	spin_unlock(&object->lock);
	246	return ret;
	247	}
	248
	249	/*
	250	* queue an object for withdrawal on error, aborting all following asynchronous
	251	* operations
	252	*/
	253	void fscache_abort_object(struct fscache_object *object)
	254	{
	255	_enter("{OBJ%x}", object->debug_id);
	256
	257	fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
	258	}
	259
	260	/*
	261	* jump start the operation processing on an object
	262	* - caller must hold object->lock
	263	*/
	264	void fscache_start_operations(struct fscache_object *object)
	265	{
	266	struct fscache_operation *op;
	267	bool stop = false;
	268
	269	while (!list_empty(&object->pending_ops) && !stop) {
	270	op = list_entry(object->pending_ops.next,
	271	struct fscache_operation, pend_link);
	272
	273	if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
	274	if (object->n_in_progress > 0)
	275	break;
	276	stop = true;
	277	}
	278	list_del_init(&op->pend_link);
5753c441	279	fscache_run_op(object, op);
952efe7b DH	280
	281	/* the pending queue was holding a ref on the object */
	282	fscache_put_operation(op);
	283	}
	284
	285	ASSERTCMP(object->n_in_progress, <=, object->n_ops);
	286
	287	_debug("woke %d ops on OBJ%x",
	288	object->n_in_progress, object->debug_id);
	289	}
	290
5753c441 DH	291	/*
	292	* cancel an operation that's pending on an object
	293	*/
	294	int fscache_cancel_op(struct fscache_operation *op)
	295	{
	296	struct fscache_object *object = op->object;
	297	int ret;
	298
	299	_enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
	300
9f10523f DH	301	ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
	302	ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
	303	ASSERTCMP(atomic_read(&op->usage), >, 0);
	304
5753c441 DH	305	spin_lock(&object->lock);
	306
	307	ret = -EBUSY;
9f10523f DH	308	if (op->state == FSCACHE_OP_ST_PENDING) {
9f10523f DH	309	ASSERT(!list_empty(&op->pend_link));
5753c441 DH	310	fscache_stat(&fscache_n_op_cancelled);
5753c441 DH	311	list_del_init(&op->pend_link);
9f10523f	312	op->state = FSCACHE_OP_ST_CANCELLED;
5753c441 DH	313	if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
	314	object->n_exclusive--;
	315	if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
	316	wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
	317	fscache_put_operation(op);
	318	ret = 0;
	319	}
	320
	321	spin_unlock(&object->lock);
	322	_leave(" = %d", ret);
	323	return ret;
	324	}
	325
ef778e7a DH	326	/*
	327	* Cancel all pending operations on an object
	328	*/
	329	void fscache_cancel_all_ops(struct fscache_object *object)
	330	{
	331	struct fscache_operation *op;
	332
	333	_enter("OBJ%x", object->debug_id);
	334
	335	spin_lock(&object->lock);
	336
	337	while (!list_empty(&object->pending_ops)) {
	338	op = list_entry(object->pending_ops.next,
	339	struct fscache_operation, pend_link);
	340	fscache_stat(&fscache_n_op_cancelled);
	341	list_del_init(&op->pend_link);
	342
	343	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
	344	op->state = FSCACHE_OP_ST_CANCELLED;
	345
	346	if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
	347	object->n_exclusive--;
	348	if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
	349	wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
	350	fscache_put_operation(op);
	351	cond_resched_lock(&object->lock);
	352	}
	353
	354	spin_unlock(&object->lock);
	355	_leave("");
	356	}
	357
9f10523f DH	358	/*
	359	* Record the completion of an in-progress operation.
	360	*/
	361	void fscache_op_complete(struct fscache_operation *op)
	362	{
	363	struct fscache_object *object = op->object;
	364
	365	_enter("OBJ%x", object->debug_id);
	366
	367	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
	368	ASSERTCMP(object->n_in_progress, >, 0);
	369	ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
	370	object->n_exclusive, >, 0);
	371	ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
	372	object->n_in_progress, ==, 1);
	373
	374	spin_lock(&object->lock);
	375
	376	op->state = FSCACHE_OP_ST_COMPLETE;
	377
	378	if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
	379	object->n_exclusive--;
	380	object->n_in_progress--;
	381	if (object->n_in_progress == 0)
	382	fscache_start_operations(object);
	383
	384	spin_unlock(&object->lock);
	385	_leave("");
	386	}
	387	EXPORT_SYMBOL(fscache_op_complete);
	388
952efe7b DH	389	/*
	390	* release an operation
	391	* - queues pending ops if this is the last in-progress op
	392	*/
	393	void fscache_put_operation(struct fscache_operation *op)
	394	{
	395	struct fscache_object *object;
	396	struct fscache_cache *cache;
	397
	398	_enter("{OBJ%x OP%x,%d}",
	399	op->object->debug_id, op->debug_id, atomic_read(&op->usage));
	400
	401	ASSERTCMP(atomic_read(&op->usage), >, 0);
	402
	403	if (!atomic_dec_and_test(&op->usage))
	404	return;
	405
	406	_debug("PUT OP");
9f10523f DH	407	ASSERTIFCMP(op->state != FSCACHE_OP_ST_COMPLETE,
	408	op->state, ==, FSCACHE_OP_ST_CANCELLED);
	409	op->state = FSCACHE_OP_ST_DEAD;
952efe7b DH	410
	411	fscache_stat(&fscache_n_op_release);
	412
	413	if (op->release) {
	414	op->release(op);
	415	op->release = NULL;
	416	}
	417
	418	object = op->object;
	419
ef46ed88 DH	420	if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags)) {
	421	if (atomic_dec_and_test(&object->n_reads)) {
	422	clear_bit(FSCACHE_COOKIE_WAITING_ON_READS,
	423	&object->cookie->flags);
	424	wake_up_bit(&object->cookie->flags,
	425	FSCACHE_COOKIE_WAITING_ON_READS);
	426	}
	427	}
4fbf4291	428
952efe7b DH	429	/* now... we may get called with the object spinlock held, so we
	430	* complete the cleanup here only if we can immediately acquire the
	431	* lock, and defer it otherwise */
	432	if (!spin_trylock(&object->lock)) {
	433	_debug("defer put");
	434	fscache_stat(&fscache_n_op_deferred_release);
	435
	436	cache = object->cache;
	437	spin_lock(&cache->op_gc_list_lock);
	438	list_add_tail(&op->pend_link, &cache->op_gc_list);
	439	spin_unlock(&cache->op_gc_list_lock);
	440	schedule_work(&cache->op_gc);
	441	_leave(" [defer]");
	442	return;
	443	}
	444
952efe7b DH	445	ASSERTCMP(object->n_ops, >, 0);
	446	object->n_ops--;
	447	if (object->n_ops == 0)
	448	fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
	449
	450	spin_unlock(&object->lock);
	451
	452	kfree(op);
	453	_leave(" [done]");
	454	}
	455	EXPORT_SYMBOL(fscache_put_operation);
	456
	457	/*
	458	* garbage collect operations that have had their release deferred
	459	*/
	460	void fscache_operation_gc(struct work_struct *work)
	461	{
	462	struct fscache_operation *op;
	463	struct fscache_object *object;
	464	struct fscache_cache *cache =
	465	container_of(work, struct fscache_cache, op_gc);
	466	int count = 0;
	467
	468	_enter("");
	469
	470	do {
	471	spin_lock(&cache->op_gc_list_lock);
	472	if (list_empty(&cache->op_gc_list)) {
	473	spin_unlock(&cache->op_gc_list_lock);
	474	break;
	475	}
	476
	477	op = list_entry(cache->op_gc_list.next,
	478	struct fscache_operation, pend_link);
	479	list_del(&op->pend_link);
	480	spin_unlock(&cache->op_gc_list_lock);
	481
	482	object = op->object;
9f10523f	483	spin_lock(&object->lock);
952efe7b DH	484
	485	_debug("GC DEFERRED REL OBJ%x OP%x",
	486	object->debug_id, op->debug_id);
	487	fscache_stat(&fscache_n_op_gc);
	488
	489	ASSERTCMP(atomic_read(&op->usage), ==, 0);
9f10523f	490	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
952efe7b DH	491
	492	ASSERTCMP(object->n_ops, >, 0);
	493	object->n_ops--;
	494	if (object->n_ops == 0)
	495	fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
	496
	497	spin_unlock(&object->lock);
9f10523f	498	kfree(op);
952efe7b DH	499
	500	} while (count++ < 20);
	501
	502	if (!list_empty(&cache->op_gc_list))
	503	schedule_work(&cache->op_gc);
	504
	505	_leave("");
	506	}
	507
	508	/*
8af7c124 TH	509	* execute an operation using fs_op_wq to provide processing context -
8af7c124 TH	510	* the caller holds a ref to this object, so we don't need to hold one
952efe7b	511	*/
8af7c124	512	void fscache_op_work_func(struct work_struct *work)
952efe7b DH	513	{
952efe7b DH	514	struct fscache_operation *op =
8af7c124	515	container_of(work, struct fscache_operation, work);
952efe7b DH	516	unsigned long start;
	517
	518	_enter("{OBJ%x OP%x,%d}",
	519	op->object->debug_id, op->debug_id, atomic_read(&op->usage));
	520
	521	ASSERT(op->processor != NULL);
	522	start = jiffies;
	523	op->processor(op);
	524	fscache_hist(fscache_ops_histogram, start);
8af7c124	525	fscache_put_operation(op);
952efe7b DH	526
	527	_leave("");
	528	}