/* * 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++; 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--; /* 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) { /* 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; walking_handlers++; 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); walking_handlers--; if (!walking_handlers && tmp->deleted) { QLIST_REMOVE(tmp, node); g_free(tmp); } } } return true; }