MFP4 (with some minor changes):

Implement the linux_io_* syscalls (AIO). They are only enabled if the native
AIO code is available (either compiled in to the kernel or as a module) at
the time the functions are used. If the AIO stuff is not available there
will be a ENOSYS.

From the submitter:
---snip---
DESIGN NOTES:

1. Linux permits a process to own multiple AIO queues (distinguished by
   "context"), but FreeBSD creates only one single AIO queue per process.
   My code maintains a request queue (STAILQ of queue(3)) per "context",
   and throws all AIO requests of all contexts owned by a process into
   the single FreeBSD per-process AIO queue.

   When the process calls io_destroy(2), io_getevents(2), io_submit(2) and
   io_cancel(2), my code can pick out requests owned by the specified context
   from the single FreeBSD per-process AIO queue according to the per-context
   request queues maintained by my code.

2. The request queue maintained by my code stores contrast information between
   Linux IO control blocks (struct linux_iocb) and FreeBSD IO control blocks
   (struct aiocb). FreeBSD IO control block actually exists in userland memory
   space, required by FreeBSD native aio_XXXXXX(2).

3. It is quite troubling that the function io_getevents() of libaio-0.3.105
   needs to use Linux-specific "struct aio_ring", which is a partial mirror
   of context in user space. I would rather take the address of context in
   kernel as the context ID, but the io_getevents() of libaio forces me to
   take the address of the "ring" in user space as the context ID.

   To my surprise, one comment line in the file "io_getevents.c" of
   libaio-0.3.105 reads:

             Ben will hate me for this

REFERENCE:

1. Linux kernel source code:   http://www.kernel.org/pub/linux/kernel/v2.6/
   (include/linux/aio_abi.h, fs/aio.c)

2. Linux manual pages:         http://www.kernel.org/pub/linux/docs/manpages/
   (io_setup(2), io_destroy(2), io_getevents(2), io_submit(2), io_cancel(2))

3. Linux Scalability Effort:   http://lse.sourceforge.net/io/aio.html
   The design notes:           http://lse.sourceforge.net/io/aionotes.txt

4. The package libaio, both source and binary:
       http://rpmfind.net/linux/rpm2html/search.php?query=libaio
   Simple transparent interface to Linux AIO system calls.

5. Libaio-oracle:              http://oss.oracle.com/projects/libaio-oracle/
   POSIX AIO implementation based on Linux AIO system calls (depending on
   libaio).
---snip---

Submitted by:	Li, Xiao <intron@intron.ac>

1 files changed, 7 insertions, 5 deletions

diff --git a/sys/modules/linux/Makefile b/sys/modules/linux/Makefile
index db8ea9c..ca6b467 100644
--- a/sys/modules/linux/Makefile
+++ b/sys/modules/linux/Makefile
@@ -8,11 +8,13 @@ CFLAGS+=-DCOMPAT_IA32 -DCOMPAT_LINUX32
 .PATH: ${.CURDIR}/../../compat/linux ${.CURDIR}/../../${MACHINE_ARCH}/linux${SFX}
 
 KMOD=	linux
-SRCS=	linux${SFX}_dummy.c linux_emul.c linux_file.c linux_futex.c linux_getcwd.c linux_ioctl.c \
-	linux_ipc.c linux${SFX}_machdep.c linux_mib.c linux_misc.c linux_signal.c \
-	linux_socket.c linux_stats.c linux_sysctl.c linux${SFX}_sysent.c linux${SFX}_sysvec.c \
-	linux_uid16.c linux_util.c linux_time.c opt_inet6.h opt_mac.h opt_compat.h opt_posix.h \
-	vnode_if.h device_if.h bus_if.h
+SRCS=	linux_aio.c linux${SFX}_dummy.c linux_emul.c linux_file.c \
+	linux_futex.c linux_getcwd.c linux_ioctl.c linux_ipc.c \
+	linux${SFX}_machdep.c linux_mib.c linux_misc.c linux_signal.c \
+	linux_socket.c linux_stats.c linux_sysctl.c linux${SFX}_sysent.c \
+	linux${SFX}_sysvec.c linux_uid16.c linux_util.c linux_time.c \
+	opt_inet6.h opt_mac.h opt_compat.h opt_posix.h vnode_if.h \
+	device_if.h bus_if.h
 OBJS=	linux${SFX}_locore.o
 
 .if ${MACHINE_ARCH} == "i386"