From 9ca93ced8bc719fbfc444c472cf0d058409cbce1 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Mon, 11 Dec 2006 08:53:29 +0000
Subject: r20104: this is a alternative events backend, which uses a hybrid of
 aio and epoll. It is not linked in anywhere yet - I'm committing it in case
 anyone else wants to have a look at it.

The concept is quite strange really, but it seems to be the only way
that Linux 2.6.x can currently use a unified event model allowing for
AIO events and socket events to be waited for by a single unified
event wait function. You setup a epoll system, then setup a weird aio
event that points at the epoll system, then use io_getevents() to
actually do the waiting.

I'm hoping that kevents or a proper integration of epoll will allow us
to avoid ths rather hackish scheme, but meanwhile this is the only
path to proper AIO in Samba on Linux (without a horrible signals mess)

(NOTE: this code requires some kernel patches to work at the moment)
(This used to be commit 195051fdee341e8d8cb76e5c91dcc0f6c246a870)
---
 source4/lib/events/events_aio.c | 518 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 518 insertions(+)
 create mode 100644 source4/lib/events/events_aio.c

diff --git a/source4/lib/events/events_aio.c b/source4/lib/events/events_aio.c
new file mode 100644
index 0000000000..97305fdeb3
--- /dev/null
+++ b/source4/lib/events/events_aio.c
@@ -0,0 +1,518 @@
+/* 
+   Unix SMB/CIFS implementation.
+
+   main select loop and event handling - aio/epoll hybrid implementation
+
+   Copyright (C) Andrew Tridgell	2006
+
+   based on events_standard.c
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+/*
+  this is a very strange beast. The Linux AIO implementation doesn't
+  yet integrate properly with epoll, but there is a kernel patch that
+  allows the aio wait primitives to be used to wait for epoll events,
+  and this can be used to give us a unified event system incorporating
+  both aio events and epoll events
+
+  this is _very_ experimental code
+*/
+
+#include "includes.h"
+#include "system/filesys.h"
+#include "system/select.h" /* needed for WITH_EPOLL */
+#include "lib/util/dlinklist.h"
+#include "lib/events/events.h"
+#include "lib/events/events_internal.h"
+#include <libaio.h>
+
+#define MAX_AIO_QUEUE_DEPTH	10
+#define IOCB_CMD_EPOLL_WAIT	9
+
+struct aio_event_context {
+	/* a pointer back to the generic event_context */
+	struct event_context *ev;
+
+	/* number of registered fd event handlers */
+	int num_fd_events;
+
+	/* list of timed events */
+	struct timed_event *timed_events;
+
+	uint32_t destruction_count;
+
+	io_context_t ioctx;
+
+	struct io_event events[MAX_AIO_QUEUE_DEPTH];
+	struct epoll_event epevent;
+
+	struct iocb *epoll_iocb;
+
+	int epoll_fd;
+};
+
+static void aio_event_loop_timer(struct aio_event_context *aio_ev);
+
+/*
+  map from EVENT_FD_* to EPOLLIN/EPOLLOUT
+*/
+static uint32_t epoll_map_flags(uint16_t flags)
+{
+	uint32_t ret = 0;
+	if (flags & EVENT_FD_READ) ret |= (EPOLLIN | EPOLLERR | EPOLLHUP);
+	if (flags & EVENT_FD_WRITE) ret |= (EPOLLOUT | EPOLLERR | EPOLLHUP);
+	return ret;
+}
+
+/*
+ free the epoll fd
+*/
+static int aio_ctx_destructor(struct aio_event_context *aio_ev)
+{
+	close(aio_ev->epoll_fd);
+	aio_ev->epoll_fd = -1;
+	return 0;
+}
+
+#define EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT	(1<<0)
+#define EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR	(1<<1)
+#define EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR	(1<<2)
+
+/*
+ add the epoll event to the given fd_event
+*/
+static void epoll_add_event(struct aio_event_context *aio_ev, struct fd_event *fde)
+{
+	struct epoll_event event;
+	if (aio_ev->epoll_fd == -1) return;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	/* if we don't want events yet, don't add an aio_event */
+	if (fde->flags == 0) return;
+
+	ZERO_STRUCT(event);
+	event.events = epoll_map_flags(fde->flags);
+	event.data.ptr = fde;
+	epoll_ctl(aio_ev->epoll_fd, EPOLL_CTL_ADD, fde->fd, &event);
+	fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+
+	/* only if we want to read we want to tell the event handler about errors */
+	if (fde->flags & EVENT_FD_READ) {
+		fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+}
+
+/*
+ delete the epoll event for given fd_event
+*/
+static void epoll_del_event(struct aio_event_context *aio_ev, struct fd_event *fde)
+{
+	struct epoll_event event;
+	if (aio_ev->epoll_fd == -1) return;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	/* if there's no aio_event, we don't need to delete it */
+	if (!(fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT)) return;
+
+	ZERO_STRUCT(event);
+	event.events = epoll_map_flags(fde->flags);
+	event.data.ptr = fde;
+	epoll_ctl(aio_ev->epoll_fd, EPOLL_CTL_DEL, fde->fd, &event);
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+}
+
+/*
+ change the epoll event to the given fd_event
+*/
+static void epoll_mod_event(struct aio_event_context *aio_ev, struct fd_event *fde)
+{
+	struct epoll_event event;
+	if (aio_ev->epoll_fd == -1) return;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	ZERO_STRUCT(event);
+	event.events = epoll_map_flags(fde->flags);
+	event.data.ptr = fde;
+	epoll_ctl(aio_ev->epoll_fd, EPOLL_CTL_MOD, fde->fd, &event);
+
+	/* only if we want to read we want to tell the event handler about errors */
+	if (fde->flags & EVENT_FD_READ) {
+		fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+}
+
+static void epoll_change_event(struct aio_event_context *aio_ev, struct fd_event *fde)
+{
+	BOOL got_error = (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR);
+	BOOL want_read = (fde->flags & EVENT_FD_READ);
+	BOOL want_write= (fde->flags & EVENT_FD_WRITE);
+
+	if (aio_ev->epoll_fd == -1) return;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	/* there's already an event */
+	if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT) {
+		if (want_read || (want_write && !got_error)) {
+			epoll_mod_event(aio_ev, fde);
+			return;
+		}
+		epoll_del_event(aio_ev, fde);
+		return;
+	}
+
+	/* there's no aio_event attached to the fde */
+	if (want_read || (want_write && !got_error)) {
+		epoll_add_event(aio_ev, fde);
+		return;
+	}
+}
+
+static int setup_epoll_wait(struct aio_event_context *aio_ev)
+{
+	struct io_event r;
+	
+	memset(aio_ev->epoll_iocb, 0, sizeof(*aio_ev->epoll_iocb));
+	aio_ev->epoll_iocb->aio_fildes = aio_ev->epoll_fd;
+	aio_ev->epoll_iocb->aio_lio_opcode = IOCB_CMD_EPOLL_WAIT;
+	aio_ev->epoll_iocb->aio_reqprio = 0;
+
+	aio_ev->epoll_iocb->u.c.nbytes = 1;
+	aio_ev->epoll_iocb->u.c.offset = -1;
+	aio_ev->epoll_iocb->u.c.buf = &aio_ev->epevent;
+
+	if (io_submit(aio_ev->ioctx, 1, &aio_ev->epoll_iocb) != 1) {
+		return -1;
+	}
+}
+
+
+/*
+  event loop handling using aio/epoll hybrid
+*/
+static int aio_event_loop(struct aio_event_context *aio_ev, struct timeval *tvalp)
+{
+	int ret, i;
+	uint32_t destruction_count = aio_ev->destruction_count;
+	struct timespec timeout;
+
+	if (aio_ev->epoll_fd == -1) return -1;
+
+	if (tvalp) {
+		timeout.tv_sec = tvalp->tv_sec;
+		timeout.tv_nsec = tvalp->tv_usec;
+		timeout.tv_nsec *= 1000;
+	}
+
+	setup_epoll_wait(aio_ev);
+
+	ret = io_getevents(aio_ev->ioctx, 1, MAX_AIO_QUEUE_DEPTH,
+			   aio_ev->events, tvalp?&timeout:NULL);
+	if (ret == -EINTR) {
+		return 0;
+	}
+
+	if (ret == 0 && tvalp) {
+		aio_event_loop_timer(aio_ev);
+		return 0;
+	}
+
+	for (i=0;i<ret;i++) {
+		struct iocb *finished = aio_ev->events[i].obj;
+		switch (finished->aio_lio_opcode) {
+		case IOCB_CMD_EPOLL_WAIT: {
+			struct epoll_event *ep = (struct epoll_event *)finished->u.c.buf;
+			struct fd_event *fde = talloc_get_type(ep->data.ptr, 
+							       struct fd_event);
+			uint16_t flags = 0;
+
+			if (fde == NULL) {
+				return -1;
+			}
+			if (ep->events & (EPOLLHUP|EPOLLERR)) {
+				fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR;
+				if (!(fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR)) {
+					epoll_del_event(aio_ev, fde);
+					continue;
+				}
+				flags |= EVENT_FD_READ;
+			}
+			if (ep->events & EPOLLIN) flags |= EVENT_FD_READ;
+			if (ep->events & EPOLLOUT) flags |= EVENT_FD_WRITE;
+			if (flags) {
+				fde->handler(aio_ev->ev, fde, flags, fde->private_data);
+				if (destruction_count != aio_ev->destruction_count) {
+					return 0;
+				}
+			}
+			break;
+		}
+		}
+	}
+
+	return 0;
+}
+
+/*
+  create a aio_event_context structure.
+*/
+static int aio_event_context_init(struct event_context *ev, void *private_data)
+{
+	struct aio_event_context *aio_ev;
+	
+	aio_ev = talloc_zero(ev, struct aio_event_context);
+	if (!aio_ev) return -1;
+
+	aio_ev->ev = ev;
+	aio_ev->epoll_iocb = talloc(aio_ev, struct iocb);
+
+	if (io_queue_init(MAX_AIO_QUEUE_DEPTH, &aio_ev->ioctx) != 0) {
+		return -1;
+	}
+
+	aio_ev->epoll_fd = epoll_create(MAX_AIO_QUEUE_DEPTH);
+	if (aio_ev->epoll_fd == -1) return -1;
+
+	talloc_set_destructor(aio_ev, aio_ctx_destructor);
+
+	ev->additional_data = aio_ev;
+	return 0;
+}
+
+/*
+  destroy an fd_event
+*/
+static int aio_event_fd_destructor(struct fd_event *fde)
+{
+	struct event_context *ev = fde->event_ctx;
+	struct aio_event_context *aio_ev = talloc_get_type(ev->additional_data,
+							   struct aio_event_context);
+
+	aio_ev->num_fd_events--;
+	aio_ev->destruction_count++;
+
+	epoll_del_event(aio_ev, fde);
+
+	return 0;
+}
+
+/*
+  add a fd based event
+  return NULL on failure (memory allocation error)
+*/
+static struct fd_event *aio_event_add_fd(struct event_context *ev, TALLOC_CTX *mem_ctx,
+					 int fd, uint16_t flags,
+					 event_fd_handler_t handler,
+					 void *private_data)
+{
+	struct aio_event_context *aio_ev = talloc_get_type(ev->additional_data,
+							   struct aio_event_context);
+	struct fd_event *fde;
+
+	fde = talloc(mem_ctx?mem_ctx:ev, struct fd_event);
+	if (!fde) return NULL;
+
+	fde->event_ctx		= ev;
+	fde->fd			= fd;
+	fde->flags		= flags;
+	fde->handler		= handler;
+	fde->private_data	= private_data;
+	fde->additional_flags	= 0;
+	fde->additional_data	= NULL;
+
+	aio_ev->num_fd_events++;
+	talloc_set_destructor(fde, aio_event_fd_destructor);
+
+	epoll_add_event(aio_ev, fde);
+
+	return fde;
+}
+
+
+/*
+  return the fd event flags
+*/
+static uint16_t aio_event_get_fd_flags(struct fd_event *fde)
+{
+	return fde->flags;
+}
+
+/*
+  set the fd event flags
+*/
+static void aio_event_set_fd_flags(struct fd_event *fde, uint16_t flags)
+{
+	struct event_context *ev;
+	struct aio_event_context *aio_ev;
+
+	if (fde->flags == flags) return;
+
+	ev = fde->event_ctx;
+	aio_ev = talloc_get_type(ev->additional_data, struct aio_event_context);
+
+	fde->flags = flags;
+
+	epoll_change_event(aio_ev, fde);
+}
+
+/*
+  destroy a timed event
+*/
+static int aio_event_timed_destructor(struct timed_event *te)
+{
+	struct aio_event_context *aio_ev = talloc_get_type(te->event_ctx->additional_data,
+							   struct aio_event_context);
+	DLIST_REMOVE(aio_ev->timed_events, te);
+	return 0;
+}
+
+static int aio_event_timed_deny_destructor(struct timed_event *te)
+{
+	return -1;
+}
+
+/*
+  add a timed event
+  return NULL on failure (memory allocation error)
+*/
+static struct timed_event *aio_event_add_timed(struct event_context *ev, TALLOC_CTX *mem_ctx,
+					       struct timeval next_event, 
+					       event_timed_handler_t handler, 
+					       void *private_data) 
+{
+	struct aio_event_context *aio_ev = talloc_get_type(ev->additional_data,
+							   struct aio_event_context);
+	struct timed_event *te, *last_te, *cur_te;
+
+	te = talloc(mem_ctx?mem_ctx:ev, struct timed_event);
+	if (te == NULL) return NULL;
+
+	te->event_ctx		= ev;
+	te->next_event		= next_event;
+	te->handler		= handler;
+	te->private_data	= private_data;
+	te->additional_data	= NULL;
+
+	/* keep the list ordered */
+	last_te = NULL;
+	for (cur_te = aio_ev->timed_events; cur_te; cur_te = cur_te->next) {
+		/* if the new event comes before the current one break */
+		if (!timeval_is_zero(&cur_te->next_event) &&
+		    timeval_compare(&te->next_event,
+				    &cur_te->next_event) < 0) {
+			break;
+		}
+
+		last_te = cur_te;
+	}
+
+	DLIST_ADD_AFTER(aio_ev->timed_events, te, last_te);
+
+	talloc_set_destructor(te, aio_event_timed_destructor);
+
+	return te;
+}
+
+/*
+  a timer has gone off - call it
+*/
+static void aio_event_loop_timer(struct aio_event_context *aio_ev)
+{
+	struct timeval t = timeval_current();
+	struct timed_event *te = aio_ev->timed_events;
+
+	if (te == NULL) {
+		return;
+	}
+
+	/* deny the handler to free the event */
+	talloc_set_destructor(te, aio_event_timed_deny_destructor);
+
+	/* We need to remove the timer from the list before calling the
+	 * handler because in a semi-async inner event loop called from the
+	 * handler we don't want to come across this event again -- vl */
+	DLIST_REMOVE(aio_ev->timed_events, te);
+
+	te->handler(aio_ev->ev, te, t, te->private_data);
+
+	/* The destructor isn't necessary anymore, we've already removed the
+	 * event from the list. */
+	talloc_set_destructor(te, NULL);
+
+	talloc_free(te);
+}
+
+/*
+  do a single event loop using the events defined in ev 
+*/
+static int aio_event_loop_once(struct event_context *ev)
+{
+	struct aio_event_context *aio_ev = talloc_get_type(ev->additional_data,
+		 					   struct aio_event_context);
+	struct timeval tval;
+
+	/* work out the right timeout for all timed events */
+	if (aio_ev->timed_events) {
+		struct timeval t = timeval_current();
+		tval = timeval_until(&t, &aio_ev->timed_events->next_event);
+		if (timeval_is_zero(&tval)) {
+			aio_event_loop_timer(aio_ev);
+			return 0;
+		}
+	} else {
+		/* have a default tick time of 30 seconds. This guarantees
+		   that code that uses its own timeout checking will be
+		   able to proceeed eventually */
+		tval = timeval_set(30, 0);
+	}
+
+	return aio_event_loop(aio_ev, &tval);
+}
+
+/*
+  return on failure or (with 0) if all fd events are removed
+*/
+static int aio_event_loop_wait(struct event_context *ev)
+{
+	struct aio_event_context *aio_ev = talloc_get_type(ev->additional_data,
+							   struct aio_event_context);
+	while (aio_ev->num_fd_events) {
+		if (aio_event_loop_once(ev) != 0) {
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static const struct event_ops aio_event_ops = {
+	.context_init	= aio_event_context_init,
+	.add_fd		= aio_event_add_fd,
+	.get_fd_flags	= aio_event_get_fd_flags,
+	.set_fd_flags	= aio_event_set_fd_flags,
+	.add_timed	= aio_event_add_timed,
+	.loop_once	= aio_event_loop_once,
+	.loop_wait	= aio_event_loop_wait,
+};
+
+const struct event_ops *event_aio_get_ops(void)
+{
+	return &aio_event_ops;
+}
-- 
cgit