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/*

 * QEMU aio implementation

 *

 * Copyright IBM, Corp. 2008

 *

 * Authors:

 *  Anthony Liguori   <aliguori@us.ibm.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2.  See

 * the COPYING file in the top-level directory.

 *

 * Contributions after 2012-01-13 are licensed under the terms of the

 * GNU GPL, version 2 or (at your option) any later version.

 */

#include "qemu-common.h"

#include "block.h"

#include "qemu-queue.h"

#include "qemu_socket.h"

typedef struct AioHandler AioHandler;

/* The list of registered AIO handlers */

static QLIST_HEAD(, AioHandler) aio_handlers;

/* This is a simple lock used to protect the aio_handlers list.  Specifically,

 * it's used to ensure that no callbacks are removed while we're walking and

 * dispatching callbacks.

 */

static int walking_handlers;

struct AioHandler

{

    int fd;

    IOHandler *io_read;

    IOHandler *io_write;

    AioFlushHandler *io_flush;

    int deleted;

    void *opaque;

    QLIST_ENTRY(AioHandler) node;

};

static AioHandler *find_aio_handler(int fd)

{

    AioHandler *node;

    QLIST_FOREACH(node, &aio_handlers, node) {

        if (node->fd == fd)

            if (!node->deleted)

                return node;

    }

    return NULL;

}

int qemu_aio_set_fd_handler(int fd,

                            IOHandler *io_read,

                            IOHandler *io_write,

                            AioFlushHandler *io_flush,

                            void *opaque)

{

    AioHandler *node;

    node = find_aio_handler(fd);

    /* Are we deleting the fd handler? */

    if (!io_read && !io_write) {

        if (node) {

            /* If the lock is held, just mark the node as deleted */

            if (walking_handlers)

                node->deleted = 1;

            else {

                /* Otherwise, delete it for real.  We can't just mark it as

                 * deleted because deleted nodes are only cleaned up after

                 * releasing the walking_handlers lock.

                 */

                QLIST_REMOVE(node, node);

                g_free(node);

            }

        }

    } else {

        if (node == NULL) {

            /* Alloc and insert if it's not already there */

            node = g_malloc0(sizeof(AioHandler));

            node->fd = fd;

            QLIST_INSERT_HEAD(&aio_handlers, node, node);

        }

        /* Update handler with latest information */

        node->io_read = io_read;

        node->io_write = io_write;

        node->io_flush = io_flush;

        node->opaque = opaque;

    }

    qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque);

    return 0;

}

void qemu_aio_flush(void)

{

    while (qemu_aio_wait());

}

bool qemu_aio_wait(void)

{

    AioHandler *node;

    fd_set rdfds, wrfds;

    int max_fd = -1;

    int ret;

    bool busy;

    /*

     * If there are callbacks left that have been queued, we need to call then.

     * Do not call select in this case, because it is possible that the caller

     * does not need a complete flush (as is the case for qemu_aio_wait loops).

     */

    if (qemu_bh_poll()) {

        return true;

    }

    walking_handlers = 1;

    FD_ZERO(&rdfds);

    FD_ZERO(&wrfds);

    /* fill fd sets */

    busy = false;

    QLIST_FOREACH(node, &aio_handlers, node) {

        /* If there aren't pending AIO operations, don't invoke callbacks.

         * Otherwise, if there are no AIO requests, qemu_aio_wait() would

         * wait indefinitely.

         */

        if (node->io_flush) {

            if (node->io_flush(node->opaque) == 0) {

                continue;

            }

            busy = true;

        }

        if (!node->deleted && node->io_read) {

            FD_SET(node->fd, &rdfds);

            max_fd = MAX(max_fd, node->fd + 1);

        }

        if (!node->deleted && node->io_write) {

            FD_SET(node->fd, &wrfds);

            max_fd = MAX(max_fd, node->fd + 1);

        }

    }

    walking_handlers = 0;

    /* No AIO operations?  Get us out of here */

    if (!busy) {

        return false;

    }

    /* wait until next event */

    ret = select(max_fd, &rdfds, &wrfds, NULL, NULL);

    /* if we have any readable fds, dispatch event */

    if (ret > 0) {

        walking_handlers = 1;

        /* we have to walk very carefully in case

         * qemu_aio_set_fd_handler is called while we're walking */

        node = QLIST_FIRST(&aio_handlers);

        while (node) {

            AioHandler *tmp;

            if (!node->deleted &&

                FD_ISSET(node->fd, &rdfds) &&

                node->io_read) {

                node->io_read(node->opaque);

            }

            if (!node->deleted &&

                FD_ISSET(node->fd, &wrfds) &&

                node->io_write) {

                node->io_write(node->opaque);

            }

            tmp = node;

            node = QLIST_NEXT(node, node);

            if (tmp->deleted) {

                QLIST_REMOVE(tmp, node);

                g_free(tmp);

            }

        }

        walking_handlers = 0;

    }

    return true;

}