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/*
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* QEMU aio implementation
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*
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* Copyright IBM, Corp. 2008
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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* Contributions after 2012-01-13 are licensed under the terms of the
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* GNU GPL, version 2 or (at your option) any later version.
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*/
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#include "qemu-common.h" |
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#include "block.h" |
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#include "qemu-queue.h" |
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#include "qemu_socket.h" |
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typedef struct AioHandler AioHandler; |
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/* The list of registered AIO handlers */
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static QLIST_HEAD(, AioHandler) aio_handlers;
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/* This is a simple lock used to protect the aio_handlers list. Specifically,
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* it's used to ensure that no callbacks are removed while we're walking and
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* dispatching callbacks.
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*/
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static int walking_handlers; |
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struct AioHandler
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{ |
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int fd;
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IOHandler *io_read; |
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IOHandler *io_write; |
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AioFlushHandler *io_flush; |
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int deleted;
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void *opaque;
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QLIST_ENTRY(AioHandler) node; |
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}; |
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static AioHandler *find_aio_handler(int fd) |
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{ |
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AioHandler *node; |
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QLIST_FOREACH(node, &aio_handlers, node) { |
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if (node->fd == fd)
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if (!node->deleted)
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return node;
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} |
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return NULL; |
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} |
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int qemu_aio_set_fd_handler(int fd, |
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IOHandler *io_read, |
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IOHandler *io_write, |
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AioFlushHandler *io_flush, |
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void *opaque)
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{ |
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AioHandler *node; |
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node = find_aio_handler(fd); |
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/* Are we deleting the fd handler? */
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if (!io_read && !io_write) {
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if (node) {
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/* If the lock is held, just mark the node as deleted */
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if (walking_handlers)
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node->deleted = 1;
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else {
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/* Otherwise, delete it for real. We can't just mark it as
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* deleted because deleted nodes are only cleaned up after
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* releasing the walking_handlers lock.
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*/
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QLIST_REMOVE(node, node); |
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g_free(node); |
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} |
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} |
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} else {
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if (node == NULL) { |
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/* Alloc and insert if it's not already there */
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node = g_malloc0(sizeof(AioHandler));
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node->fd = fd; |
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QLIST_INSERT_HEAD(&aio_handlers, node, node); |
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} |
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/* Update handler with latest information */
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node->io_read = io_read; |
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node->io_write = io_write; |
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node->io_flush = io_flush; |
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node->opaque = opaque; |
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} |
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qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque);
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return 0; |
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} |
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void qemu_aio_flush(void) |
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{ |
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while (qemu_aio_wait());
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} |
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bool qemu_aio_wait(void) |
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{ |
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AioHandler *node; |
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fd_set rdfds, wrfds; |
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int max_fd = -1; |
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int ret;
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bool busy;
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/*
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* If there are callbacks left that have been queued, we need to call then.
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* Do not call select in this case, because it is possible that the caller
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* does not need a complete flush (as is the case for qemu_aio_wait loops).
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*/
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if (qemu_bh_poll()) {
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return true; |
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} |
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walking_handlers = 1;
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FD_ZERO(&rdfds); |
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FD_ZERO(&wrfds); |
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/* fill fd sets */
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busy = false;
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QLIST_FOREACH(node, &aio_handlers, node) { |
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/* If there aren't pending AIO operations, don't invoke callbacks.
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* Otherwise, if there are no AIO requests, qemu_aio_wait() would
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* wait indefinitely.
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*/
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if (node->io_flush) {
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if (node->io_flush(node->opaque) == 0) { |
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continue;
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} |
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busy = true;
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} |
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if (!node->deleted && node->io_read) {
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FD_SET(node->fd, &rdfds); |
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max_fd = MAX(max_fd, node->fd + 1);
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} |
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if (!node->deleted && node->io_write) {
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FD_SET(node->fd, &wrfds); |
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max_fd = MAX(max_fd, node->fd + 1);
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} |
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} |
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walking_handlers = 0;
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/* No AIO operations? Get us out of here */
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if (!busy) {
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return false; |
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} |
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/* wait until next event */
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ret = select(max_fd, &rdfds, &wrfds, NULL, NULL); |
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/* if we have any readable fds, dispatch event */
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if (ret > 0) { |
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walking_handlers = 1;
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/* we have to walk very carefully in case
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* qemu_aio_set_fd_handler is called while we're walking */
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node = QLIST_FIRST(&aio_handlers); |
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while (node) {
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AioHandler *tmp; |
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if (!node->deleted &&
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FD_ISSET(node->fd, &rdfds) && |
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node->io_read) { |
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node->io_read(node->opaque); |
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} |
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if (!node->deleted &&
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FD_ISSET(node->fd, &wrfds) && |
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node->io_write) { |
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node->io_write(node->opaque); |
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} |
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tmp = node; |
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node = QLIST_NEXT(node, node); |
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if (tmp->deleted) {
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QLIST_REMOVE(tmp, node); |
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g_free(tmp); |
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} |
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} |
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walking_handlers = 0;
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} |
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return true; |
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} |