[mirror_ubuntu-focal-kernel.git] / arch / um / os-Linux / aio.c

/*
 * Copyright (C) 2004 Jeff Dike (jdike@addtoit.com)
 * Licensed under the GPL
 */

#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <sched.h>
#include <sys/syscall.h>
#include "os.h"
#include "aio.h"
#include "init.h"
#include "user.h"
#include "mode.h"

struct aio_thread_req {
	enum aio_type type;
	int io_fd;
	unsigned long long offset;
	char *buf;
	int len;
	struct aio_context *aio;
};

#if defined(HAVE_AIO_ABI)
#include <linux/aio_abi.h>

/* If we have the headers, we are going to build with AIO enabled.
 * If we don't have aio in libc, we define the necessary stubs here.
 */

#if !defined(HAVE_AIO_LIBC)

static long io_setup(int n, aio_context_t *ctxp)
{
	return syscall(__NR_io_setup, n, ctxp);
}

static long io_submit(aio_context_t ctx, long nr, struct iocb **iocbpp)
{
	return syscall(__NR_io_submit, ctx, nr, iocbpp);
}

static long io_getevents(aio_context_t ctx_id, long min_nr, long nr,
			 struct io_event *events, struct timespec *timeout)
{
	return syscall(__NR_io_getevents, ctx_id, min_nr, nr, events, timeout);
}

#endif

/* The AIO_MMAP cases force the mmapped page into memory here
 * rather than in whatever place first touches the data.  I used
 * to do this by touching the page, but that's delicate because
 * gcc is prone to optimizing that away.  So, what's done here
 * is we read from the descriptor from which the page was
 * mapped.  The caller is required to pass an offset which is
 * inside the page that was mapped.  Thus, when the read
 * returns, we know that the page is in the page cache, and
 * that it now backs the mmapped area.
 */

static int do_aio(aio_context_t ctx, enum aio_type type, int fd, char *buf,
		  int len, unsigned long long offset, struct aio_context *aio)
{
	struct iocb iocb, *iocbp = &iocb;
	char c;
	int err;

	iocb = ((struct iocb) { .aio_data 	= (unsigned long) aio,
				.aio_reqprio	= 0,
				.aio_fildes	= fd,
				.aio_buf	= (unsigned long) buf,
				.aio_nbytes	= len,
				.aio_offset	= offset,
				.aio_reserved1	= 0,
				.aio_reserved2	= 0,
				.aio_reserved3	= 0 });

	switch(type){
	case AIO_READ:
		iocb.aio_lio_opcode = IOCB_CMD_PREAD;
		err = io_submit(ctx, 1, &iocbp);
		break;
	case AIO_WRITE:
		iocb.aio_lio_opcode = IOCB_CMD_PWRITE;
		err = io_submit(ctx, 1, &iocbp);
		break;
	case AIO_MMAP:
		iocb.aio_lio_opcode = IOCB_CMD_PREAD;
		iocb.aio_buf = (unsigned long) &c;
		iocb.aio_nbytes = sizeof(c);
		err = io_submit(ctx, 1, &iocbp);
		break;
	default:
		printk("Bogus op in do_aio - %d\n", type);
		err = -EINVAL;
		break;
	}

	if(err > 0)
		err = 0;
	else
		err = -errno;

	return err;
}

/* Initialized in an initcall and unchanged thereafter */
static aio_context_t ctx = 0;

static int aio_thread(void *arg)
{
	struct aio_thread_reply reply;
	struct io_event event;
	int err, n, reply_fd;

	signal(SIGWINCH, SIG_IGN);

	while(1){
		n = io_getevents(ctx, 1, 1, &event, NULL);
		if(n < 0){
			if(errno == EINTR)
				continue;
			printk("aio_thread - io_getevents failed, "
			       "errno = %d\n", errno);
		}
		else {
			reply = ((struct aio_thread_reply)
				{ .data = (void *) (long) event.data,
						.err	= event.res });
			reply_fd = ((struct aio_context *) reply.data)->reply_fd;
			err = write(reply_fd, &reply, sizeof(reply));
			if(err != sizeof(reply))
				printk("aio_thread - write failed, fd = %d, "
				       "err = %d\n", reply_fd, errno);
		}
	}
	return 0;
}

#endif

static int do_not_aio(struct aio_thread_req *req)
{
	char c;
	unsigned long long actual;
	int n;

	actual = lseek64(req->io_fd, req->offset, SEEK_SET);
	if(actual != req->offset)
		return -errno;

	switch(req->type){
	case AIO_READ:
		n = read(req->io_fd, req->buf, req->len);
		break;
	case AIO_WRITE:
		n = write(req->io_fd, req->buf, req->len);
		break;
	case AIO_MMAP:
		n = read(req->io_fd, &c, sizeof(c));
		break;
	default:
		printk("do_not_aio - bad request type : %d\n", req->type);
		return -EINVAL;
	}

	if(n < 0)
		return -errno;
	return 0;
}

/* These are initialized in initcalls and not changed */
static int aio_req_fd_r = -1;
static int aio_req_fd_w = -1;
static int aio_pid = -1;

static int not_aio_thread(void *arg)
{
	struct aio_thread_req req;
	struct aio_thread_reply reply;
	int err;

	signal(SIGWINCH, SIG_IGN);
	while(1){
		err = read(aio_req_fd_r, &req, sizeof(req));
		if(err != sizeof(req)){
			if(err < 0)
				printk("not_aio_thread - read failed, "
				       "fd = %d, err = %d\n", aio_req_fd_r,
				       errno);
			else {
				printk("not_aio_thread - short read, fd = %d, "
				       "length = %d\n", aio_req_fd_r, err);
			}
			continue;
		}
		err = do_not_aio(&req);
		reply = ((struct aio_thread_reply) { .data 	= req.aio,
						     .err	= err });
		err = write(req.aio->reply_fd, &reply, sizeof(reply));
		if(err != sizeof(reply))
			printk("not_aio_thread - write failed, fd = %d, "
			       "err = %d\n", req.aio->reply_fd, errno);
	}

	return 0;
}

static int init_aio_24(void)
{
	unsigned long stack;
	int fds[2], err;

	err = os_pipe(fds, 1, 1);
	if(err)
		goto out;

	aio_req_fd_w = fds[0];
	aio_req_fd_r = fds[1];
	err = run_helper_thread(not_aio_thread, NULL,
				CLONE_FILES | CLONE_VM | SIGCHLD, &stack, 0);
	if(err < 0)
		goto out_close_pipe;

	aio_pid = err;
	goto out;

out_close_pipe:
	os_close_file(fds[0]);
	os_close_file(fds[1]);
	aio_req_fd_w = -1;
	aio_req_fd_r = -1;
out:
#ifndef HAVE_AIO_ABI
	printk("/usr/include/linux/aio_abi.h not present during build\n");
#endif
	printk("2.6 host AIO support not used - falling back to I/O "
	       "thread\n");
	return 0;
}

#ifdef HAVE_AIO_ABI
#define DEFAULT_24_AIO 0
static int init_aio_26(void)
{
	unsigned long stack;
	int err;

	if(io_setup(256, &ctx)){
		err = -errno;
		printk("aio_thread failed to initialize context, err = %d\n",
		       errno);
		return err;
	}

	err = run_helper_thread(aio_thread, NULL,
				CLONE_FILES | CLONE_VM | SIGCHLD, &stack, 0);
	if(err < 0)
		return err;

	aio_pid = err;

	printk("Using 2.6 host AIO\n");
	return 0;
}

static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
			 unsigned long long offset, struct aio_context *aio)
{
	struct aio_thread_reply reply;
	int err;

	err = do_aio(ctx, type, io_fd, buf, len, offset, aio);
	if(err){
		reply = ((struct aio_thread_reply) { .data = aio,
					 .err  = err });
		err = write(aio->reply_fd, &reply, sizeof(reply));
		if(err != sizeof(reply)){
			err = -errno;
			printk("submit_aio_26 - write failed, "
			       "fd = %d, err = %d\n", aio->reply_fd, -err);
		}
		else err = 0;
	}

	return err;
}

#else
#define DEFAULT_24_AIO 1
static int init_aio_26(void)
{
	return -ENOSYS;
}

static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
			 unsigned long long offset, struct aio_context *aio)
{
	return -ENOSYS;
}
#endif

/* Initialized in an initcall and unchanged thereafter */
static int aio_24 = DEFAULT_24_AIO;

static int __init set_aio_24(char *name, int *add)
{
	aio_24 = 1;
	return 0;
}

__uml_setup("aio=2.4", set_aio_24,
"aio=2.4\n"
"    This is used to force UML to use 2.4-style AIO even when 2.6 AIO is\n"
"    available.  2.4 AIO is a single thread that handles one request at a\n"
"    time, synchronously.  2.6 AIO is a thread which uses the 2.6 AIO \n"
"    interface to handle an arbitrary number of pending requests.  2.6 AIO \n"
"    is not available in tt mode, on 2.4 hosts, or when UML is built with\n"
"    /usr/include/linux/aio_abi.h not available.  Many distributions don't\n"
"    include aio_abi.h, so you will need to copy it from a kernel tree to\n"
"    your /usr/include/linux in order to build an AIO-capable UML\n\n"
);

static int init_aio(void)
{
	int err;

	CHOOSE_MODE(({ if(!aio_24){
			    printk("Disabling 2.6 AIO in tt mode\n");
			    aio_24 = 1;
		    } }), (void) 0);

	if(!aio_24){
		err = init_aio_26();
		if(err && (errno == ENOSYS)){
			printk("2.6 AIO not supported on the host - "
			       "reverting to 2.4 AIO\n");
			aio_24 = 1;
		}
		else return err;
	}

	if(aio_24)
		return init_aio_24();

	return 0;
}

/* The reason for the __initcall/__uml_exitcall asymmetry is that init_aio
 * needs to be called when the kernel is running because it calls run_helper,
 * which needs get_free_page.  exit_aio is a __uml_exitcall because the generic
 * kernel does not run __exitcalls on shutdown, and can't because many of them
 * break when called outside of module unloading.
 */
__initcall(init_aio);

static void exit_aio(void)
{
	if(aio_pid != -1)
		os_kill_process(aio_pid, 1);
}

__uml_exitcall(exit_aio);

static int submit_aio_24(enum aio_type type, int io_fd, char *buf, int len,
			 unsigned long long offset, struct aio_context *aio)
{
	struct aio_thread_req req = { .type 		= type,
				      .io_fd		= io_fd,
				      .offset		= offset,
				      .buf		= buf,
				      .len		= len,
				      .aio		= aio,
	};
	int err;

	err = write(aio_req_fd_w, &req, sizeof(req));
	if(err == sizeof(req))
		err = 0;
	else err = -errno;

	return err;
}

int submit_aio(enum aio_type type, int io_fd, char *buf, int len,
	       unsigned long long offset, int reply_fd,
	       struct aio_context *aio)
{
	aio->reply_fd = reply_fd;
	if(aio_24)
		return submit_aio_24(type, io_fd, buf, len, offset, aio);
	else {
		return submit_aio_26(type, io_fd, buf, len, offset, aio);
	}
}
Commit	Line	Data
75e5584c JD	1	/*
	2	* Copyright (C) 2004 Jeff Dike (jdike@addtoit.com)
	3	* Licensed under the GPL
	4	*/
	5
	6	#include <stdlib.h>
	7	#include <unistd.h>
	8	#include <signal.h>
	9	#include <errno.h>
	10	#include <sched.h>
	11	#include <sys/syscall.h>
	12	#include "os.h"
75e5584c JD	13	#include "aio.h"
	14	#include "init.h"
	15	#include "user.h"
	16	#include "mode.h"
	17
91acb21f	18	struct aio_thread_req {
d50084a2 JD	19	enum aio_type type;
	20	int io_fd;
	21	unsigned long long offset;
	22	char *buf;
	23	int len;
	24	struct aio_context *aio;
91acb21f JD	25	};
91acb21f JD	26
75e5584c JD	27	#if defined(HAVE_AIO_ABI)
	28	#include <linux/aio_abi.h>
	29
	30	/* If we have the headers, we are going to build with AIO enabled.
	31	* If we don't have aio in libc, we define the necessary stubs here.
	32	*/
	33
	34	#if !defined(HAVE_AIO_LIBC)
	35
	36	static long io_setup(int n, aio_context_t *ctxp)
	37	{
d50084a2	38	return syscall(__NR_io_setup, n, ctxp);
75e5584c JD	39	}
	40
	41	static long io_submit(aio_context_t ctx, long nr, struct iocb **iocbpp)
	42	{
d50084a2	43	return syscall(__NR_io_submit, ctx, nr, iocbpp);
75e5584c JD	44	}
	45
	46	static long io_getevents(aio_context_t ctx_id, long min_nr, long nr,
d50084a2	47	struct io_event events, struct timespec timeout)
75e5584c	48	{
d50084a2	49	return syscall(__NR_io_getevents, ctx_id, min_nr, nr, events, timeout);
75e5584c JD	50	}
	51
	52	#endif
	53
	54	/* The AIO_MMAP cases force the mmapped page into memory here
	55	* rather than in whatever place first touches the data. I used
	56	* to do this by touching the page, but that's delicate because
	57	* gcc is prone to optimizing that away. So, what's done here
	58	* is we read from the descriptor from which the page was
	59	* mapped. The caller is required to pass an offset which is
	60	* inside the page that was mapped. Thus, when the read
	61	* returns, we know that the page is in the page cache, and
	62	* that it now backs the mmapped area.
	63	*/
	64
91acb21f	65	static int do_aio(aio_context_t ctx, enum aio_type type, int fd, char *buf,
d50084a2	66	int len, unsigned long long offset, struct aio_context *aio)
75e5584c	67	{
d50084a2 JD	68	struct iocb iocb, *iocbp = &iocb;
	69	char c;
	70	int err;
	71
	72	iocb = ((struct iocb) { .aio_data = (unsigned long) aio,
	73	.aio_reqprio = 0,
	74	.aio_fildes = fd,
	75	.aio_buf = (unsigned long) buf,
	76	.aio_nbytes = len,
	77	.aio_offset = offset,
	78	.aio_reserved1 = 0,
	79	.aio_reserved2 = 0,
	80	.aio_reserved3 = 0 });
	81
	82	switch(type){
	83	case AIO_READ:
	84	iocb.aio_lio_opcode = IOCB_CMD_PREAD;
	85	err = io_submit(ctx, 1, &iocbp);
	86	break;
	87	case AIO_WRITE:
	88	iocb.aio_lio_opcode = IOCB_CMD_PWRITE;
	89	err = io_submit(ctx, 1, &iocbp);
	90	break;
	91	case AIO_MMAP:
	92	iocb.aio_lio_opcode = IOCB_CMD_PREAD;
	93	iocb.aio_buf = (unsigned long) &c;
	94	iocb.aio_nbytes = sizeof(c);
	95	err = io_submit(ctx, 1, &iocbp);
	96	break;
	97	default:
	98	printk("Bogus op in do_aio - %d\n", type);
	99	err = -EINVAL;
	100	break;
	101	}
	102
	103	if(err > 0)
	104	err = 0;
2867ace6 JD	105	else
2867ace6 JD	106	err = -errno;
75e5584c	107
d50084a2	108	return err;
75e5584c JD	109	}
75e5584c JD	110
9683da91	111	/* Initialized in an initcall and unchanged thereafter */
75e5584c JD	112	static aio_context_t ctx = 0;
	113
	114	static int aio_thread(void *arg)
	115	{
d50084a2 JD	116	struct aio_thread_reply reply;
	117	struct io_event event;
	118	int err, n, reply_fd;
	119
	120	signal(SIGWINCH, SIG_IGN);
	121
	122	while(1){
	123	n = io_getevents(ctx, 1, 1, &event, NULL);
	124	if(n < 0){
	125	if(errno == EINTR)
	126	continue;
	127	printk("aio_thread - io_getevents failed, "
	128	"errno = %d\n", errno);
	129	}
	130	else {
	131	reply = ((struct aio_thread_reply)
	132	{ .data = (void *) (long) event.data,
	133	.err = event.res });
91acb21f	134	reply_fd = ((struct aio_context *) reply.data)->reply_fd;
a61f334f	135	err = write(reply_fd, &reply, sizeof(reply));
d50084a2	136	if(err != sizeof(reply))
91acb21f	137	printk("aio_thread - write failed, fd = %d, "
a61f334f	138	"err = %d\n", reply_fd, errno);
d50084a2 JD	139	}
	140	}
	141	return 0;
75e5584c JD	142	}
	143
	144	#endif
	145
91acb21f	146	static int do_not_aio(struct aio_thread_req *req)
75e5584c	147	{
d50084a2	148	char c;
ef0470c0	149	unsigned long long actual;
a61f334f	150	int n;
d50084a2	151
ef0470c0 JD	152	actual = lseek64(req->io_fd, req->offset, SEEK_SET);
	153	if(actual != req->offset)
	154	return -errno;
	155
d50084a2 JD	156	switch(req->type){
d50084a2 JD	157	case AIO_READ:
a61f334f	158	n = read(req->io_fd, req->buf, req->len);
d50084a2 JD	159	break;
d50084a2 JD	160	case AIO_WRITE:
a61f334f	161	n = write(req->io_fd, req->buf, req->len);
d50084a2 JD	162	break;
d50084a2 JD	163	case AIO_MMAP:
a61f334f	164	n = read(req->io_fd, &c, sizeof(c));
d50084a2 JD	165	break;
	166	default:
	167	printk("do_not_aio - bad request type : %d\n", req->type);
a61f334f	168	return -EINVAL;
d50084a2 JD	169	}
d50084a2 JD	170
a61f334f JD	171	if(n < 0)
	172	return -errno;
	173	return 0;
75e5584c JD	174	}
75e5584c JD	175
9683da91 JD	176	/* These are initialized in initcalls and not changed */
	177	static int aio_req_fd_r = -1;
	178	static int aio_req_fd_w = -1;
	179	static int aio_pid = -1;
	180
75e5584c JD	181	static int not_aio_thread(void *arg)
75e5584c JD	182	{
d50084a2 JD	183	struct aio_thread_req req;
	184	struct aio_thread_reply reply;
	185	int err;
	186
	187	signal(SIGWINCH, SIG_IGN);
	188	while(1){
a61f334f	189	err = read(aio_req_fd_r, &req, sizeof(req));
d50084a2 JD	190	if(err != sizeof(req)){
	191	if(err < 0)
	192	printk("not_aio_thread - read failed, "
	193	"fd = %d, err = %d\n", aio_req_fd_r,
a61f334f	194	errno);
d50084a2 JD	195	else {
	196	printk("not_aio_thread - short read, fd = %d, "
	197	"length = %d\n", aio_req_fd_r, err);
	198	}
	199	continue;
	200	}
	201	err = do_not_aio(&req);
	202	reply = ((struct aio_thread_reply) { .data = req.aio,
ef0470c0	203	.err = err });
a61f334f	204	err = write(req.aio->reply_fd, &reply, sizeof(reply));
d50084a2 JD	205	if(err != sizeof(reply))
d50084a2 JD	206	printk("not_aio_thread - write failed, fd = %d, "
a61f334f	207	"err = %d\n", req.aio->reply_fd, errno);
d50084a2	208	}
1b57e9c2 JD	209
1b57e9c2 JD	210	return 0;
75e5584c JD	211	}
75e5584c JD	212
75e5584c JD	213	static int init_aio_24(void)
75e5584c JD	214	{
d50084a2 JD	215	unsigned long stack;
	216	int fds[2], err;
	217
	218	err = os_pipe(fds, 1, 1);
	219	if(err)
	220	goto out;
	221
	222	aio_req_fd_w = fds[0];
	223	aio_req_fd_r = fds[1];
	224	err = run_helper_thread(not_aio_thread, NULL,
	225	CLONE_FILES \| CLONE_VM \| SIGCHLD, &stack, 0);
	226	if(err < 0)
	227	goto out_close_pipe;
	228
	229	aio_pid = err;
	230	goto out;
	231
	232	out_close_pipe:
	233	os_close_file(fds[0]);
	234	os_close_file(fds[1]);
	235	aio_req_fd_w = -1;
	236	aio_req_fd_r = -1;
	237	out:
75e5584c JD	238	#ifndef HAVE_AIO_ABI
	239	printk("/usr/include/linux/aio_abi.h not present during build\n");
	240	#endif
	241	printk("2.6 host AIO support not used - falling back to I/O "
	242	"thread\n");
d50084a2	243	return 0;
75e5584c JD	244	}
	245
	246	#ifdef HAVE_AIO_ABI
	247	#define DEFAULT_24_AIO 0
	248	static int init_aio_26(void)
	249	{
d50084a2 JD	250	unsigned long stack;
d50084a2 JD	251	int err;
75e5584c	252
d50084a2	253	if(io_setup(256, &ctx)){
b4fd310e	254	err = -errno;
d50084a2 JD	255	printk("aio_thread failed to initialize context, err = %d\n",
	256	errno);
	257	return err;
	258	}
75e5584c	259
d50084a2 JD	260	err = run_helper_thread(aio_thread, NULL,
	261	CLONE_FILES \| CLONE_VM \| SIGCHLD, &stack, 0);
	262	if(err < 0)
	263	return err;
75e5584c	264
d50084a2	265	aio_pid = err;
75e5584c JD	266
75e5584c JD	267	printk("Using 2.6 host AIO\n");
d50084a2	268	return 0;
91acb21f JD	269	}
	270
	271	static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
	272	unsigned long long offset, struct aio_context *aio)
	273	{
d50084a2 JD	274	struct aio_thread_reply reply;
	275	int err;
	276
	277	err = do_aio(ctx, type, io_fd, buf, len, offset, aio);
	278	if(err){
	279	reply = ((struct aio_thread_reply) { .data = aio,
	280	.err = err });
a61f334f JD	281	err = write(aio->reply_fd, &reply, sizeof(reply));
	282	if(err != sizeof(reply)){
	283	err = -errno;
d50084a2 JD	284	printk("submit_aio_26 - write failed, "
d50084a2 JD	285	"fd = %d, err = %d\n", aio->reply_fd, -err);
a61f334f	286	}
d50084a2 JD	287	else err = 0;
	288	}
	289
	290	return err;
75e5584c JD	291	}
	292
	293	#else
	294	#define DEFAULT_24_AIO 1
91acb21f	295	static int init_aio_26(void)
75e5584c	296	{
d50084a2	297	return -ENOSYS;
75e5584c JD	298	}
75e5584c JD	299
91acb21f JD	300	static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
91acb21f JD	301	unsigned long long offset, struct aio_context *aio)
75e5584c	302	{
d50084a2	303	return -ENOSYS;
75e5584c JD	304	}
	305	#endif
	306
9683da91	307	/* Initialized in an initcall and unchanged thereafter */
75e5584c JD	308	static int aio_24 = DEFAULT_24_AIO;
	309
	310	static int __init set_aio_24(char name, int add)
	311	{
d50084a2 JD	312	aio_24 = 1;
d50084a2 JD	313	return 0;
75e5584c JD	314	}
	315
	316	__uml_setup("aio=2.4", set_aio_24,
	317	"aio=2.4\n"
	318	" This is used to force UML to use 2.4-style AIO even when 2.6 AIO is\n"
	319	" available. 2.4 AIO is a single thread that handles one request at a\n"
	320	" time, synchronously. 2.6 AIO is a thread which uses the 2.6 AIO \n"
	321	" interface to handle an arbitrary number of pending requests. 2.6 AIO \n"
	322	" is not available in tt mode, on 2.4 hosts, or when UML is built with\n"
	323	" /usr/include/linux/aio_abi.h not available. Many distributions don't\n"
	324	" include aio_abi.h, so you will need to copy it from a kernel tree to\n"
	325	" your /usr/include/linux in order to build an AIO-capable UML\n\n"
	326	);
	327
	328	static int init_aio(void)
	329	{
d50084a2 JD	330	int err;
	331
	332	CHOOSE_MODE(({ if(!aio_24){
	333	printk("Disabling 2.6 AIO in tt mode\n");
	334	aio_24 = 1;
	335	} }), (void) 0);
	336
	337	if(!aio_24){
	338	err = init_aio_26();
	339	if(err && (errno == ENOSYS)){
	340	printk("2.6 AIO not supported on the host - "
	341	"reverting to 2.4 AIO\n");
	342	aio_24 = 1;
	343	}
	344	else return err;
	345	}
	346
	347	if(aio_24)
	348	return init_aio_24();
	349
	350	return 0;
75e5584c JD	351	}
	352
	353	/* The reason for the __initcall/__uml_exitcall asymmetry is that init_aio
	354	* needs to be called when the kernel is running because it calls run_helper,
	355	* which needs get_free_page. exit_aio is a __uml_exitcall because the generic
	356	* kernel does not run __exitcalls on shutdown, and can't because many of them
	357	* break when called outside of module unloading.
	358	*/
	359	__initcall(init_aio);
	360
	361	static void exit_aio(void)
	362	{
d50084a2 JD	363	if(aio_pid != -1)
d50084a2 JD	364	os_kill_process(aio_pid, 1);
75e5584c JD	365	}
	366
	367	__uml_exitcall(exit_aio);
	368
91acb21f JD	369	static int submit_aio_24(enum aio_type type, int io_fd, char *buf, int len,
91acb21f JD	370	unsigned long long offset, struct aio_context *aio)
75e5584c	371	{
d50084a2 JD	372	struct aio_thread_req req = { .type = type,
	373	.io_fd = io_fd,
	374	.offset = offset,
	375	.buf = buf,
	376	.len = len,
	377	.aio = aio,
	378	};
	379	int err;
	380
a61f334f	381	err = write(aio_req_fd_w, &req, sizeof(req));
d50084a2 JD	382	if(err == sizeof(req))
d50084a2 JD	383	err = 0;
a61f334f	384	else err = -errno;
d50084a2 JD	385
d50084a2 JD	386	return err;
91acb21f JD	387	}
	388
	389	int submit_aio(enum aio_type type, int io_fd, char *buf, int len,
d50084a2 JD	390	unsigned long long offset, int reply_fd,
d50084a2 JD	391	struct aio_context *aio)
91acb21f	392	{
d50084a2 JD	393	aio->reply_fd = reply_fd;
	394	if(aio_24)
	395	return submit_aio_24(type, io_fd, buf, len, offset, aio);
	396	else {
	397	return submit_aio_26(type, io_fd, buf, len, offset, aio);
	398	}
75e5584c	399	}