tools/blktap2/drivers/tapdisk-queue.c


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/* 
 * Copyright (c) 2008, XenSource Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of XenSource Inc. nor the names of its contributors
 *       may be used to endorse or promote products derived from this software
 *       without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <libaio.h>
#ifdef __linux__
#include <linux/version.h>
#endif

#include "tapdisk.h"
#include "tapdisk-log.h"
#include "tapdisk-queue.h"
#include "tapdisk-filter.h"
#include "tapdisk-server.h"
#include "tapdisk-utils.h"

#include "libaio-compat.h"
#include "atomicio.h"

#define WARN(_f, _a...) tlog_write(TLOG_WARN, _f, ##_a)
#define DBG(_f, _a...) tlog_write(TLOG_DBG, _f, ##_a)
#define ERR(_err, _f, _a...) tlog_error(_err, _f, ##_a)

/*
 * We used a kernel patch to return an fd associated with the AIO context
 * so that we can concurrently poll on synchronous and async descriptors.
 * This is signalled by passing 1 as the io context to io_setup.
 */
#define REQUEST_ASYNC_FD ((io_context_t)1)

static inline void
queue_tiocb(struct tqueue *queue, struct tiocb *tiocb)
{
	struct iocb *iocb = &tiocb->iocb;

	if (queue->queued) {
		struct tiocb *prev = (struct tiocb *)
			queue->iocbs[queue->queued - 1]->data;
		prev->next = tiocb;
	}

	queue->iocbs[queue->queued++] = iocb;
}

static inline int
deferred_tiocbs(struct tqueue *queue)
{
	return (queue->deferred.head != NULL);
}

static inline void
defer_tiocb(struct tqueue *queue, struct tiocb *tiocb)
{
	struct tlist *list = &queue->deferred;

	if (!list->head)
		list->head = list->tail = tiocb;
	else
		list->tail = list->tail->next = tiocb;

	queue->tiocbs_deferred++;
	queue->deferrals++;
}

static inline void
queue_deferred_tiocb(struct tqueue *queue)
{
	struct tlist *list = &queue->deferred;

	if (list->head) {
		struct tiocb *tiocb = list->head;

		list->head = tiocb->next;
		if (!list->head)
			list->tail = NULL;

		queue_tiocb(queue, tiocb);
		queue->tiocbs_deferred--;
	}
}

static inline void
queue_deferred_tiocbs(struct tqueue *queue)
{
	while (!tapdisk_queue_full(queue) && deferred_tiocbs(queue))