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* Simulate the Posix AIO using mmap/fork
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* Copyright (C) Volker Lendecke 2008
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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static int mmap_area_destructor(struct mmap_area *area)
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munmap((void *)area->ptr, area->size);
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static struct mmap_area *mmap_area_init(TALLOC_CTX *mem_ctx, size_t size)
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struct mmap_area *result;
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result = talloc(mem_ctx, struct mmap_area);
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DEBUG(0, ("talloc failed\n"));
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fd = open("/dev/zero", O_RDWR);
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DEBUG(3, ("open(\"/dev/zero\") failed: %s\n",
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result->ptr = mmap(NULL, size, PROT_READ|PROT_WRITE,
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MAP_SHARED|MAP_FILE, fd, 0);
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if (result->ptr == MAP_FAILED) {
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DEBUG(1, ("mmap failed: %s\n", strerror(errno)));
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talloc_set_destructor(result, mmap_area_destructor);
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struct aio_child_list;
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struct aio_child *prev, *next;
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struct aio_child_list *list;
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SMB_STRUCT_AIOCB *aiocb;
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struct fd_event *sock_event;
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struct mmap_area *map; /* ==NULL means write request */
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bool dont_delete; /* Marked as in use since last cleanup */
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struct aio_child_list {
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struct aio_child *children;
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struct timed_event *cleanup_event;
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static void free_aio_children(void **p)
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static ssize_t read_fd(int fd, void *ptr, size_t nbytes, int *recvfd)
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#ifndef HAVE_MSGHDR_MSG_CONTROL
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#ifdef HAVE_MSGHDR_MSG_CONTROL
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char control[CMSG_SPACE(sizeof(int))];
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struct cmsghdr *cmptr;
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msg.msg_control = control_un.control;
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msg.msg_controllen = sizeof(control_un.control);
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#if HAVE_MSGHDR_MSG_ACCTRIGHTS
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msg.msg_accrights = (caddr_t) &newfd;
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msg.msg_accrightslen = sizeof(int);
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#error Can not pass file descriptors
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iov[0].iov_base = ptr;
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iov[0].iov_len = nbytes;
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if ( (n = recvmsg(fd, &msg, 0)) <= 0) {
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#ifdef HAVE_MSGHDR_MSG_CONTROL
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if ((cmptr = CMSG_FIRSTHDR(&msg)) != NULL
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&& cmptr->cmsg_len == CMSG_LEN(sizeof(int))) {
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if (cmptr->cmsg_level != SOL_SOCKET) {
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DEBUG(10, ("control level != SOL_SOCKET"));
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if (cmptr->cmsg_type != SCM_RIGHTS) {
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DEBUG(10, ("control type != SCM_RIGHTS"));
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*recvfd = *((int *) CMSG_DATA(cmptr));
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*recvfd = -1; /* descriptor was not passed */
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if (msg.msg_accrightslen == sizeof(int)) {
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*recvfd = -1; /* descriptor was not passed */
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static ssize_t write_fd(int fd, void *ptr, size_t nbytes, int sendfd)
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#ifdef HAVE_MSGHDR_MSG_CONTROL
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char control[CMSG_SPACE(sizeof(int))];
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struct cmsghdr *cmptr;
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ZERO_STRUCT(control_un);
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msg.msg_control = control_un.control;
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msg.msg_controllen = sizeof(control_un.control);
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cmptr = CMSG_FIRSTHDR(&msg);
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cmptr->cmsg_len = CMSG_LEN(sizeof(int));
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cmptr->cmsg_level = SOL_SOCKET;
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cmptr->cmsg_type = SCM_RIGHTS;
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*((int *) CMSG_DATA(cmptr)) = sendfd;
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msg.msg_accrights = (caddr_t) &sendfd;
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msg.msg_accrightslen = sizeof(int);
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iov[0].iov_base = ptr;
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iov[0].iov_len = nbytes;
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return (sendmsg(fd, &msg, 0));
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static void aio_child_cleanup(struct event_context *event_ctx,
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struct timed_event *te,
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struct aio_child_list *list = talloc_get_type_abort(
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private_data, struct aio_child_list);
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struct aio_child *child, *next;
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TALLOC_FREE(list->cleanup_event);
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for (child = list->children; child != NULL; child = next) {
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if (child->aiocb != NULL) {
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DEBUG(10, ("child %d currently active\n",
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if (child->dont_delete) {
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DEBUG(10, ("Child %d was active since last cleanup\n",
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child->dont_delete = false;
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DEBUG(10, ("Child %d idle for more than 30 seconds, "
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"deleting\n", (int)child->pid));
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if (list->children != NULL) {
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* Re-schedule the next cleanup round
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list->cleanup_event = event_add_timed(smbd_event_context(), list,
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timeval_add(&now, 30, 0),
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aio_child_cleanup, list);
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static struct aio_child_list *init_aio_children(struct vfs_handle_struct *handle)
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struct aio_child_list *data = NULL;
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if (SMB_VFS_HANDLE_TEST_DATA(handle)) {
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SMB_VFS_HANDLE_GET_DATA(handle, data, struct aio_child_list,
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data = TALLOC_ZERO_P(NULL, struct aio_child_list);
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* Regardless of whether the child_list had been around or not, make
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* sure that we have a cleanup timed event. This timed event will
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* delete itself when it finds that no children are around anymore.
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if (data->cleanup_event == NULL) {
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data->cleanup_event = event_add_timed(smbd_event_context(), data,
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timeval_current_ofs(30, 0),
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aio_child_cleanup, data);
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if (data->cleanup_event == NULL) {
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if (!SMB_VFS_HANDLE_TEST_DATA(handle)) {
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SMB_VFS_HANDLE_SET_DATA(handle, data, free_aio_children,
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struct aio_child_list, return False);
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static void aio_child_loop(int sockfd, struct mmap_area *map)
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struct rw_cmd cmd_struct;
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struct rw_ret ret_struct;
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ret = read_fd(sockfd, &cmd_struct, sizeof(cmd_struct), &fd);
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if (ret != sizeof(cmd_struct)) {
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DEBUG(10, ("read_fd returned %d: %s\n", (int)ret,
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DEBUG(10, ("aio_child_loop: %s %d bytes at %d from fd %d\n",
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cmd_struct.read_cmd ? "read" : "write",
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(int)cmd_struct.n, (int)cmd_struct.offset, fd));
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#ifdef ENABLE_BUILD_FARM_HACKS
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* In the build farm, we want erratic behaviour for
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* use generate_random_buffer, we just forked from a
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* common parent state
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generate_random_buffer(&randval, sizeof(randval));
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msecs = randval + 20;
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DEBUG(10, ("delaying for %u msecs\n", msecs));
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ZERO_STRUCT(ret_struct);
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if (cmd_struct.read_cmd) {
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ret_struct.size = sys_pread(
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fd, (void *)map->ptr, cmd_struct.n,
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ret_struct.size = sys_pwrite(
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fd, (void *)map->ptr, cmd_struct.n,
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DEBUG(10, ("aio_child_loop: syscall returned %d\n",
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(int)ret_struct.size));
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if (ret_struct.size == -1) {
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ret_struct.ret_errno = errno;
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* Close the fd before telling our parent we're done. The
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* parent might close and re-open the file very quickly, and
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* with system-level share modes (GPFS) we would get an
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* unjustified SHARING_VIOLATION.
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ret = write_data(sockfd, (char *)&ret_struct,
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if (ret != sizeof(ret_struct)) {
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DEBUG(10, ("could not write ret_struct: %s\n",
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static void handle_aio_completion(struct event_context *event_ctx,
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struct fd_event *event, uint16 flags,
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struct aio_child *child = (struct aio_child *)p;
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DEBUG(10, ("handle_aio_completion called with flags=%d\n", flags));
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if ((flags & EVENT_FD_READ) == 0) {
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if (!NT_STATUS_IS_OK(read_data(child->sockfd,
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(char *)&child->retval,
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sizeof(child->retval)))) {
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DEBUG(0, ("aio child %d died\n", (int)child->pid));
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child->retval.size = -1;
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child->retval.ret_errno = EIO;
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if (child->cancelled) {
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child->cancelled = false;
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if (child->read_cmd && (child->retval.size > 0)) {
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SMB_ASSERT(child->retval.size <= child->aiocb->aio_nbytes);
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memcpy((void *)child->aiocb->aio_buf, (void *)child->map->ptr,
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mid = child->aiocb->aio_sigevent.sigev_value.sival_int;
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DEBUG(10, ("mid %d finished\n", (int)mid));
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smbd_aio_complete_mid(mid);
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static int aio_child_destructor(struct aio_child *child)
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SMB_ASSERT((child->aiocb == NULL) || child->cancelled);
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close(child->sockfd);
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DLIST_REMOVE(child->list->children, child);
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* We have to close all fd's in open files, we might incorrectly hold a system
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* level share mode on a file.
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static struct files_struct *close_fsp_fd(struct files_struct *fsp,
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if ((fsp->fh != NULL) && (fsp->fh->fd != -1)) {
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static NTSTATUS create_aio_child(struct aio_child_list *children,
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struct aio_child **presult)
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struct aio_child *result;
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fdpair[0] = fdpair[1] = -1;
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result = TALLOC_ZERO_P(children, struct aio_child);
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NT_STATUS_HAVE_NO_MEMORY(result);
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if (socketpair(AF_UNIX, SOCK_STREAM, 0, fdpair) == -1) {
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status = map_nt_error_from_unix(errno);
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DEBUG(10, ("socketpair() failed: %s\n", strerror(errno)));
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DEBUG(10, ("fdpair = %d/%d\n", fdpair[0], fdpair[1]));
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result->map = mmap_area_init(result, map_size);
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if (result->map == NULL) {
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status = map_nt_error_from_unix(errno);
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DEBUG(0, ("Could not create mmap area\n"));
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result->pid = sys_fork();
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if (result->pid == -1) {
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status = map_nt_error_from_unix(errno);
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DEBUG(0, ("fork failed: %s\n", strerror(errno)));
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if (result->pid == 0) {
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result->sockfd = fdpair[1];
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file_walk_table(close_fsp_fd, NULL);
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aio_child_loop(result->sockfd, result->map);
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DEBUG(10, ("Child %d created\n", result->pid));
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result->sockfd = fdpair[0];
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result->sock_event = event_add_fd(smbd_event_context(), result,
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result->sockfd, EVENT_FD_READ,
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handle_aio_completion,
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if (result->sock_event == NULL) {
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status = NT_STATUS_NO_MEMORY;
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DEBUG(0, ("event_add_fd failed\n"));
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result->list = children;
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DLIST_ADD(children->children, result);
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talloc_set_destructor(result, aio_child_destructor);
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if (fdpair[0] != -1) close(fdpair[0]);
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if (fdpair[1] != -1) close(fdpair[1]);
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static NTSTATUS get_idle_child(struct vfs_handle_struct *handle,
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struct aio_child **pchild)
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struct aio_child_list *children;
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struct aio_child *child;
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children = init_aio_children(handle);
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if (children == NULL) {
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return NT_STATUS_NO_MEMORY;
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for (child = children->children; child != NULL; child = child->next) {
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if (child->aiocb == NULL) {
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DEBUG(10, ("no idle child found, creating new one\n"));
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status = create_aio_child(children, 128*1024, &child);
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if (!NT_STATUS_IS_OK(status)) {
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DEBUG(10, ("create_aio_child failed: %s\n",
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child->dont_delete = true;
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static int aio_fork_read(struct vfs_handle_struct *handle,
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struct files_struct *fsp, SMB_STRUCT_AIOCB *aiocb)
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struct aio_child *child;
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if (aiocb->aio_nbytes > 128*1024) {
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/* TODO: support variable buffers */
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status = get_idle_child(handle, &child);
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if (!NT_STATUS_IS_OK(status)) {
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DEBUG(10, ("Could not get an idle child\n"));
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child->read_cmd = true;
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child->aiocb = aiocb;
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child->retval.ret_errno = EINPROGRESS;
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cmd.n = aiocb->aio_nbytes;
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cmd.offset = aiocb->aio_offset;
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cmd.read_cmd = child->read_cmd;
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DEBUG(10, ("sending fd %d to child %d\n", fsp->fh->fd,
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ret = write_fd(child->sockfd, &cmd, sizeof(cmd), fsp->fh->fd);
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DEBUG(10, ("write_fd failed: %s\n", strerror(errno)));
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static int aio_fork_write(struct vfs_handle_struct *handle,
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struct files_struct *fsp, SMB_STRUCT_AIOCB *aiocb)
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struct aio_child *child;
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if (aiocb->aio_nbytes > 128*1024) {
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/* TODO: support variable buffers */
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status = get_idle_child(handle, &child);
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if (!NT_STATUS_IS_OK(status)) {
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DEBUG(10, ("Could not get an idle child\n"));
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child->read_cmd = false;
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child->aiocb = aiocb;
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child->retval.ret_errno = EINPROGRESS;
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memcpy((void *)child->map->ptr, (void *)aiocb->aio_buf,
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cmd.n = aiocb->aio_nbytes;
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cmd.offset = aiocb->aio_offset;
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cmd.read_cmd = child->read_cmd;
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DEBUG(10, ("sending fd %d to child %d\n", fsp->fh->fd,
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ret = write_fd(child->sockfd, &cmd, sizeof(cmd), fsp->fh->fd);
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DEBUG(10, ("write_fd failed: %s\n", strerror(errno)));
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static struct aio_child *aio_fork_find_child(struct vfs_handle_struct *handle,
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SMB_STRUCT_AIOCB *aiocb)
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struct aio_child_list *children;
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struct aio_child *child;
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children = init_aio_children(handle);
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if (children == NULL) {
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for (child = children->children; child != NULL; child = child->next) {
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if (child->aiocb == aiocb) {
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static ssize_t aio_fork_return_fn(struct vfs_handle_struct *handle,
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struct files_struct *fsp,
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SMB_STRUCT_AIOCB *aiocb)
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struct aio_child *child = aio_fork_find_child(handle, aiocb);
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DEBUG(0, ("returning EINVAL\n"));
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if (child->retval.size == -1) {
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errno = child->retval.ret_errno;
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return child->retval.size;
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static int aio_fork_cancel(struct vfs_handle_struct *handle,
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struct files_struct *fsp,
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SMB_STRUCT_AIOCB *aiocb)
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struct aio_child_list *children;
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struct aio_child *child;
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children = init_aio_children(handle);
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if (children == NULL) {
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for (child = children->children; child != NULL; child = child->next) {
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if (child->aiocb == NULL) {
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if (child->aiocb->aio_fildes != fsp->fh->fd) {
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if ((aiocb != NULL) && (child->aiocb != aiocb)) {
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* We let the child do its job, but we discard the result when
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child->cancelled = true;
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static int aio_fork_error_fn(struct vfs_handle_struct *handle,
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struct files_struct *fsp,
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SMB_STRUCT_AIOCB *aiocb)
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struct aio_child *child = aio_fork_find_child(handle, aiocb);
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return child->retval.ret_errno;
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/* VFS operations structure */
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static vfs_op_tuple aio_fork_ops[] = {
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{SMB_VFS_OP(aio_fork_read), SMB_VFS_OP_AIO_READ,
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SMB_VFS_LAYER_TRANSPARENT},
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{SMB_VFS_OP(aio_fork_write), SMB_VFS_OP_AIO_WRITE,
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SMB_VFS_LAYER_TRANSPARENT},
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{SMB_VFS_OP(aio_fork_return_fn), SMB_VFS_OP_AIO_RETURN,
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SMB_VFS_LAYER_TRANSPARENT},
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{SMB_VFS_OP(aio_fork_cancel), SMB_VFS_OP_AIO_CANCEL,
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SMB_VFS_LAYER_TRANSPARENT},
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{SMB_VFS_OP(aio_fork_error_fn), SMB_VFS_OP_AIO_ERROR,
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SMB_VFS_LAYER_TRANSPARENT},
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{SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP,
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NTSTATUS vfs_aio_fork_init(void);
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NTSTATUS vfs_aio_fork_init(void)
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return smb_register_vfs(SMB_VFS_INTERFACE_VERSION,
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"aio_fork", aio_fork_ops);