kernel-ark/include/linux/aio_abi.h
Davide Libenzi 9c3060bedd signal/timer/event: KAIO eventfd support example
This is an example about how to add eventfd support to the current KAIO code,
in order to enable KAIO to post readiness events to a pollable fd (hence
compatible with POSIX select/poll).  The KAIO code simply signals the eventfd
fd when events are ready, and this triggers a POLLIN in the fd.  This patch
uses a reserved for future use member of the struct iocb to pass an eventfd
file descriptor, that KAIO will use to post events every time a request
completes.  At that point, an aio_getevents() will return the completed result
to a struct io_event.  I made a quick test program to verify the patch, and it
runs fine here:

http://www.xmailserver.org/eventfd-aio-test.c

The test program uses poll(2), but it'd, of course, work with select and epoll
too.

This can allow to schedule both block I/O and other poll-able devices
requests, and wait for results using select/poll/epoll.  In a typical
scenario, an application would submit KAIO request using aio_submit(), and
will also use epoll_ctl() on the whole other class of devices (that with the
addition of signals, timers and user events, now it's pretty much complete),
and then would:

	epoll_wait(...);
	for_each_event {
		if (curr_event_is_kaiofd) {
			aio_getevents();
			dispatch_aio_events();
		} else {
			dispatch_epoll_event();
		}
	}

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-11 08:29:37 -07:00

111 lines
3.0 KiB
C

/* include/linux/aio_abi.h
*
* Copyright 2000,2001,2002 Red Hat.
*
* Written by Benjamin LaHaise <bcrl@kvack.org>
*
* Distribute under the terms of the GPLv2 (see ../../COPYING) or under
* the following terms.
*
* Permission to use, copy, modify, and distribute this software and its
* documentation is hereby granted, provided that the above copyright
* notice appears in all copies. This software is provided without any
* warranty, express or implied. Red Hat makes no representations about
* the suitability of this software for any purpose.
*
* IN NO EVENT SHALL RED HAT BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT,
* SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF
* THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF RED HAT HAS BEEN ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* RED HAT DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND
* RED HAT HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
* ENHANCEMENTS, OR MODIFICATIONS.
*/
#ifndef __LINUX__AIO_ABI_H
#define __LINUX__AIO_ABI_H
#include <asm/byteorder.h>
typedef unsigned long aio_context_t;
enum {
IOCB_CMD_PREAD = 0,
IOCB_CMD_PWRITE = 1,
IOCB_CMD_FSYNC = 2,
IOCB_CMD_FDSYNC = 3,
/* These two are experimental.
* IOCB_CMD_PREADX = 4,
* IOCB_CMD_POLL = 5,
*/
IOCB_CMD_NOOP = 6,
IOCB_CMD_PREADV = 7,
IOCB_CMD_PWRITEV = 8,
};
/*
* Valid flags for the "aio_flags" member of the "struct iocb".
*
* IOCB_FLAG_RESFD - Set if the "aio_resfd" member of the "struct iocb"
* is valid.
*/
#define IOCB_FLAG_RESFD (1 << 0)
/* read() from /dev/aio returns these structures. */
struct io_event {
__u64 data; /* the data field from the iocb */
__u64 obj; /* what iocb this event came from */
__s64 res; /* result code for this event */
__s64 res2; /* secondary result */
};
#if defined(__LITTLE_ENDIAN)
#define PADDED(x,y) x, y
#elif defined(__BIG_ENDIAN)
#define PADDED(x,y) y, x
#else
#error edit for your odd byteorder.
#endif
/*
* we always use a 64bit off_t when communicating
* with userland. its up to libraries to do the
* proper padding and aio_error abstraction
*/
struct iocb {
/* these are internal to the kernel/libc. */
__u64 aio_data; /* data to be returned in event's data */
__u32 PADDED(aio_key, aio_reserved1);
/* the kernel sets aio_key to the req # */
/* common fields */
__u16 aio_lio_opcode; /* see IOCB_CMD_ above */
__s16 aio_reqprio;
__u32 aio_fildes;
__u64 aio_buf;
__u64 aio_nbytes;
__s64 aio_offset;
/* extra parameters */
__u64 aio_reserved2; /* TODO: use this for a (struct sigevent *) */
/* flags for the "struct iocb" */
__u32 aio_flags;
/*
* if the IOCB_FLAG_RESFD flag of "aio_flags" is set, this is an
* eventfd to signal AIO readiness to
*/
__u32 aio_resfd;
}; /* 64 bytes */
#undef IFBIG
#undef IFLITTLE
#endif /* __LINUX__AIO_ABI_H */