diff options
Diffstat (limited to 'aio.c')
| -rw-r--r-- | aio.c | 192 |
1 files changed, 192 insertions, 0 deletions
@@ -0,0 +1,192 @@ +/* + * 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. + * + */ + +#include "qemu-common.h" +#include "block.h" +#include "sys-queue.h" +#include "qemu_socket.h" + +typedef struct AioHandler AioHandler; + +/* The list of registered AIO handlers */ +static LIST_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; + LIST_ENTRY(AioHandler) node; +}; + +static AioHandler *find_aio_handler(int fd) +{ + AioHandler *node; + + LIST_FOREACH(node, &aio_handlers, node) { + if (node->fd == fd) + 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. + */ + LIST_REMOVE(node, node); + qemu_free(node); + } + } + } else { + if (node == NULL) { + /* Alloc and insert if it's not already there */ + node = qemu_mallocz(sizeof(AioHandler)); + if (node == NULL) + return -ENOMEM; + node->fd = fd; + LIST_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) +{ + AioHandler *node; + int ret; + + do { + ret = 0; + + LIST_FOREACH(node, &aio_handlers, node) { + ret |= node->io_flush(node->opaque); + } + + qemu_aio_wait(); + } while (ret > 0); +} + +void qemu_aio_wait(void) +{ + int ret; + + if (qemu_bh_poll()) + return; + + do { + AioHandler *node; + fd_set rdfds, wrfds; + int max_fd = -1; + + walking_handlers = 1; + + /* fill fd sets */ + LIST_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 && node->io_flush(node->opaque) == 0) + continue; + + 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 (max_fd == -1) + break; + + /* wait until next event */ + ret = select(max_fd, &rdfds, &wrfds, NULL, NULL); + if (ret == -1 && errno == EINTR) + continue; + + /* 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 = LIST_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 = LIST_NEXT(node, node); + + if (tmp->deleted) { + LIST_REMOVE(tmp, node); + qemu_free(tmp); + } + } + + walking_handlers = 0; + } + } while (ret == 0); +} |