[mirror_ubuntu-hirsute-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 <string.h>
#include <errno.h>
#include <sched.h>
#include <sys/syscall.h>
#include "os.h"
#include "helper.h"
#include "aio.h"
#include "init.h"
#include "user.h"
#include "mode.h"

static int aio_req_fd_r = -1;
static int aio_req_fd_w = -1;

static int update_aio(struct aio_context *aio, int res)
{
        if(res < 0)
                aio->len = res;
        else if((res == 0) && (aio->type == AIO_READ)){
                /* This is the EOF case - we have hit the end of the file
                 * and it ends in a partial block, so we fill the end of
                 * the block with zeros and claim success.
                 */
                memset(aio->data, 0, aio->len);
                aio->len = 0;
        }
        else if(res > 0){
                aio->len -= res;
                aio->data += res;
                aio->offset += res;
                return aio->len;
        }

        return 0;
}

#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, 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	= aio->fd,
                                .aio_buf	= (unsigned long) aio->data,
                                .aio_nbytes	= aio->len,
                                .aio_offset	= aio->offset,
                                .aio_reserved1	= 0,
                                .aio_reserved2	= 0,
                                .aio_reserved3	= 0 });

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

        err = io_submit(ctx, 1, &iocbp);
        if(err > 0)
                err = 0;

 out:
        return err;
}

static aio_context_t ctx = 0;

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

        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 {
			aio = (struct aio_context *) event.data;
			if(update_aio(aio, event.res)){
				do_aio(ctx, aio);
				continue;
			}

                        reply = ((struct aio_thread_reply)
				{ .data = aio,
				  .err	= aio->len });
			err = os_write_file(aio->reply_fd, &reply,
					    sizeof(reply));
                        if(err != sizeof(reply))
				printk("aio_thread - write failed, "
				       "fd = %d, err = %d\n", aio->reply_fd,
				       -err);
                }
        }
        return 0;
}

#endif

static int do_not_aio(struct aio_context *aio)
{
        char c;
        int err;

        switch(aio->type){
        case AIO_READ:
                err = os_seek_file(aio->fd, aio->offset);
                if(err)
                        goto out;

                err = os_read_file(aio->fd, aio->data, aio->len);
                break;
        case AIO_WRITE:
                err = os_seek_file(aio->fd, aio->offset);
                if(err)
                        goto out;

                err = os_write_file(aio->fd, aio->data, aio->len);
                break;
        case AIO_MMAP:
                err = os_seek_file(aio->fd, aio->offset);
                if(err)
                        goto out;

                err = os_read_file(aio->fd, &c, sizeof(c));
                break;
        default:
                printk("do_not_aio - bad request type : %d\n", aio->type);
                err = -EINVAL;
                break;
        }

 out:
        return err;
}

static int not_aio_thread(void *arg)
{
        struct aio_context *aio;
        struct aio_thread_reply reply;
        int err;

        signal(SIGWINCH, SIG_IGN);
        while(1){
                err = os_read_file(aio_req_fd_r, &aio, sizeof(aio));
                if(err != sizeof(aio)){
                        if(err < 0)
                                printk("not_aio_thread - read failed, "
                                       "fd = %d, err = %d\n", aio_req_fd_r,
                                       -err);
                        else {
                                printk("not_aio_thread - short read, fd = %d, "
                                       "length = %d\n", aio_req_fd_r, err);
                        }
                        continue;
                }
 again:
                err = do_not_aio(aio);

                if(update_aio(aio, err))
                        goto again;

                reply = ((struct aio_thread_reply) { .data 	= aio,
                                                     .err	= aio->len });
                err = os_write_file(aio->reply_fd, &reply, sizeof(reply));
                if(err != sizeof(reply))
                        printk("not_aio_thread - write failed, fd = %d, "
                               "err = %d\n", aio_req_fd_r, -err);
        }
}

static int submit_aio_24(struct aio_context *aio)
{
        int err;

        err = os_write_file(aio_req_fd_w, &aio, sizeof(aio));
        if(err == sizeof(aio))
                err = 0;

        return err;
}

static int aio_pid = -1;
static int (*submit_proc)(struct aio_context *aio);

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");

	submit_proc = submit_aio_24;

        return 0;
}

#ifdef HAVE_AIO_ABI
#define DEFAULT_24_AIO 0
static int submit_aio_26(struct aio_context *aio)
{
	struct aio_thread_reply reply;
	int err;

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

	return err;
}

static int init_aio_26(void)
{
        unsigned long stack;
        int err;

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

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

        aio_pid = err;

	printk("Using 2.6 host AIO\n");

	submit_proc = submit_aio_26;

        return 0;
}

#else
#define DEFAULT_24_AIO 1
static int submit_aio_26(struct aio_context *aio)
{
        return -ENOSYS;
}

static int init_aio_26(void)
{
	submit_proc = submit_aio_26;
        return -ENOSYS;
}
#endif

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);

int submit_aio(struct aio_context *aio)
{
	return (*submit_proc)(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>
09ace81c	9	#include <string.h>
75e5584c JD	10	#include <errno.h>
	11	#include <sched.h>
	12	#include <sys/syscall.h>
	13	#include "os.h"
	14	#include "helper.h"
	15	#include "aio.h"
	16	#include "init.h"
	17	#include "user.h"
	18	#include "mode.h"
	19
75e5584c JD	20	static int aio_req_fd_r = -1;
	21	static int aio_req_fd_w = -1;
	22
09ace81c JD	23	static int update_aio(struct aio_context *aio, int res)
	24	{
	25	if(res < 0)
	26	aio->len = res;
	27	else if((res == 0) && (aio->type == AIO_READ)){
	28	/* This is the EOF case - we have hit the end of the file
	29	* and it ends in a partial block, so we fill the end of
	30	* the block with zeros and claim success.
	31	*/
	32	memset(aio->data, 0, aio->len);
	33	aio->len = 0;
	34	}
	35	else if(res > 0){
	36	aio->len -= res;
	37	aio->data += res;
	38	aio->offset += res;
	39	return aio->len;
	40	}
	41
	42	return 0;
	43	}
	44
75e5584c JD	45	#if defined(HAVE_AIO_ABI)
	46	#include <linux/aio_abi.h>
	47
	48	/* If we have the headers, we are going to build with AIO enabled.
	49	* If we don't have aio in libc, we define the necessary stubs here.
	50	*/
	51
	52	#if !defined(HAVE_AIO_LIBC)
	53
	54	static long io_setup(int n, aio_context_t *ctxp)
	55	{
	56	return syscall(__NR_io_setup, n, ctxp);
	57	}
	58
	59	static long io_submit(aio_context_t ctx, long nr, struct iocb **iocbpp)
	60	{
	61	return syscall(__NR_io_submit, ctx, nr, iocbpp);
	62	}
	63
	64	static long io_getevents(aio_context_t ctx_id, long min_nr, long nr,
	65	struct io_event events, struct timespec timeout)
	66	{
	67	return syscall(__NR_io_getevents, ctx_id, min_nr, nr, events, timeout);
	68	}
	69
	70	#endif
	71
	72	/* The AIO_MMAP cases force the mmapped page into memory here
	73	* rather than in whatever place first touches the data. I used
	74	* to do this by touching the page, but that's delicate because
	75	* gcc is prone to optimizing that away. So, what's done here
	76	* is we read from the descriptor from which the page was
	77	* mapped. The caller is required to pass an offset which is
	78	* inside the page that was mapped. Thus, when the read
	79	* returns, we know that the page is in the page cache, and
	80	* that it now backs the mmapped area.
	81	*/
	82
09ace81c	83	static int do_aio(aio_context_t ctx, struct aio_context *aio)
75e5584c JD	84	{
	85	struct iocb iocb, *iocbp = &iocb;
	86	char c;
	87	int err;
	88
	89	iocb = ((struct iocb) { .aio_data = (unsigned long) aio,
	90	.aio_reqprio = 0,
09ace81c JD	91	.aio_fildes = aio->fd,
	92	.aio_buf = (unsigned long) aio->data,
	93	.aio_nbytes = aio->len,
	94	.aio_offset = aio->offset,
75e5584c JD	95	.aio_reserved1 = 0,
	96	.aio_reserved2 = 0,
	97	.aio_reserved3 = 0 });
	98
09ace81c	99	switch(aio->type){
75e5584c JD	100	case AIO_READ:
75e5584c JD	101	iocb.aio_lio_opcode = IOCB_CMD_PREAD;
75e5584c JD	102	break;
	103	case AIO_WRITE:
	104	iocb.aio_lio_opcode = IOCB_CMD_PWRITE;
75e5584c JD	105	break;
	106	case AIO_MMAP:
	107	iocb.aio_lio_opcode = IOCB_CMD_PREAD;
	108	iocb.aio_buf = (unsigned long) &c;
	109	iocb.aio_nbytes = sizeof(c);
75e5584c JD	110	break;
75e5584c JD	111	default:
09ace81c	112	printk("Bogus op in do_aio - %d\n", aio->type);
75e5584c	113	err = -EINVAL;
09ace81c	114	goto out;
75e5584c	115	}
09ace81c JD	116
09ace81c JD	117	err = io_submit(ctx, 1, &iocbp);
75e5584c JD	118	if(err > 0)
	119	err = 0;
	120
09ace81c	121	out:
75e5584c JD	122	return err;
	123	}
	124
	125	static aio_context_t ctx = 0;
	126
	127	static int aio_thread(void *arg)
	128	{
	129	struct aio_thread_reply reply;
09ace81c	130	struct aio_context *aio;
75e5584c	131	struct io_event event;
09ace81c	132	int err, n;
75e5584c JD	133
	134	signal(SIGWINCH, SIG_IGN);
	135
	136	while(1){
	137	n = io_getevents(ctx, 1, 1, &event, NULL);
	138	if(n < 0){
	139	if(errno == EINTR)
	140	continue;
	141	printk("aio_thread - io_getevents failed, "
	142	"errno = %d\n", errno);
	143	}
	144	else {
09ace81c JD	145	aio = (struct aio_context *) event.data;
	146	if(update_aio(aio, event.res)){
	147	do_aio(ctx, aio);
	148	continue;
	149	}
	150
75e5584c	151	reply = ((struct aio_thread_reply)
09ace81c JD	152	{ .data = aio,
	153	.err = aio->len });
	154	err = os_write_file(aio->reply_fd, &reply,
	155	sizeof(reply));
75e5584c	156	if(err != sizeof(reply))
09ace81c JD	157	printk("aio_thread - write failed, "
	158	"fd = %d, err = %d\n", aio->reply_fd,
	159	-err);
75e5584c JD	160	}
	161	}
	162	return 0;
	163	}
	164
	165	#endif
	166
09ace81c	167	static int do_not_aio(struct aio_context *aio)
75e5584c JD	168	{
	169	char c;
	170	int err;
	171
09ace81c	172	switch(aio->type){
75e5584c	173	case AIO_READ:
09ace81c	174	err = os_seek_file(aio->fd, aio->offset);
75e5584c JD	175	if(err)
	176	goto out;
	177
09ace81c	178	err = os_read_file(aio->fd, aio->data, aio->len);
75e5584c JD	179	break;
75e5584c JD	180	case AIO_WRITE:
09ace81c	181	err = os_seek_file(aio->fd, aio->offset);
75e5584c JD	182	if(err)
	183	goto out;
	184
09ace81c	185	err = os_write_file(aio->fd, aio->data, aio->len);
75e5584c JD	186	break;
75e5584c JD	187	case AIO_MMAP:
09ace81c	188	err = os_seek_file(aio->fd, aio->offset);
75e5584c JD	189	if(err)
	190	goto out;
	191
09ace81c	192	err = os_read_file(aio->fd, &c, sizeof(c));
75e5584c JD	193	break;
75e5584c JD	194	default:
09ace81c	195	printk("do_not_aio - bad request type : %d\n", aio->type);
75e5584c JD	196	err = -EINVAL;
	197	break;
	198	}
	199
	200	out:
	201	return err;
	202	}
	203
	204	static int not_aio_thread(void *arg)
	205	{
09ace81c	206	struct aio_context *aio;
75e5584c JD	207	struct aio_thread_reply reply;
	208	int err;
	209
	210	signal(SIGWINCH, SIG_IGN);
	211	while(1){
09ace81c JD	212	err = os_read_file(aio_req_fd_r, &aio, sizeof(aio));
09ace81c JD	213	if(err != sizeof(aio)){
75e5584c JD	214	if(err < 0)
	215	printk("not_aio_thread - read failed, "
	216	"fd = %d, err = %d\n", aio_req_fd_r,
	217	-err);
	218	else {
	219	printk("not_aio_thread - short read, fd = %d, "
	220	"length = %d\n", aio_req_fd_r, err);
	221	}
	222	continue;
	223	}
09ace81c JD	224	again:
	225	err = do_not_aio(aio);
	226
	227	if(update_aio(aio, err))
	228	goto again;
	229
	230	reply = ((struct aio_thread_reply) { .data = aio,
	231	.err = aio->len });
	232	err = os_write_file(aio->reply_fd, &reply, sizeof(reply));
75e5584c JD	233	if(err != sizeof(reply))
	234	printk("not_aio_thread - write failed, fd = %d, "
	235	"err = %d\n", aio_req_fd_r, -err);
	236	}
	237	}
	238
09ace81c JD	239	static int submit_aio_24(struct aio_context *aio)
	240	{
	241	int err;
	242
	243	err = os_write_file(aio_req_fd_w, &aio, sizeof(aio));
	244	if(err == sizeof(aio))
	245	err = 0;
	246
	247	return err;
	248	}
	249
75e5584c	250	static int aio_pid = -1;
09ace81c	251	static int (submit_proc)(struct aio_context aio);
75e5584c JD	252
	253	static int init_aio_24(void)
	254	{
	255	unsigned long stack;
	256	int fds[2], err;
	257
	258	err = os_pipe(fds, 1, 1);
	259	if(err)
	260	goto out;
	261
	262	aio_req_fd_w = fds[0];
	263	aio_req_fd_r = fds[1];
	264	err = run_helper_thread(not_aio_thread, NULL,
	265	CLONE_FILES \| CLONE_VM \| SIGCHLD, &stack, 0);
	266	if(err < 0)
	267	goto out_close_pipe;
	268
	269	aio_pid = err;
	270	goto out;
	271
	272	out_close_pipe:
	273	os_close_file(fds[0]);
	274	os_close_file(fds[1]);
	275	aio_req_fd_w = -1;
	276	aio_req_fd_r = -1;
	277	out:
	278	#ifndef HAVE_AIO_ABI
	279	printk("/usr/include/linux/aio_abi.h not present during build\n");
	280	#endif
	281	printk("2.6 host AIO support not used - falling back to I/O "
	282	"thread\n");
09ace81c JD	283
	284	submit_proc = submit_aio_24;
	285
75e5584c JD	286	return 0;
	287	}
	288
	289	#ifdef HAVE_AIO_ABI
	290	#define DEFAULT_24_AIO 0
09ace81c JD	291	static int submit_aio_26(struct aio_context *aio)
	292	{
	293	struct aio_thread_reply reply;
	294	int err;
	295
	296	err = do_aio(ctx, aio);
	297	if(err){
	298	reply = ((struct aio_thread_reply) { .data = aio,
	299	.err = err });
	300	err = os_write_file(aio->reply_fd, &reply, sizeof(reply));
	301	if(err != sizeof(reply))
	302	printk("submit_aio_26 - write failed, "
	303	"fd = %d, err = %d\n", aio->reply_fd, -err);
	304	else err = 0;
	305	}
	306
	307	return err;
	308	}
	309
75e5584c JD	310	static int init_aio_26(void)
	311	{
	312	unsigned long stack;
	313	int err;
	314
	315	if(io_setup(256, &ctx)){
	316	printk("aio_thread failed to initialize context, err = %d\n",
	317	errno);
	318	return -errno;
	319	}
	320
	321	err = run_helper_thread(aio_thread, NULL,
	322	CLONE_FILES \| CLONE_VM \| SIGCHLD, &stack, 0);
	323	if(err < 0)
	324	return -errno;
	325
	326	aio_pid = err;
	327
	328	printk("Using 2.6 host AIO\n");
75e5584c	329
09ace81c	330	submit_proc = submit_aio_26;
75e5584c	331
09ace81c	332	return 0;
75e5584c JD	333	}
	334
	335	#else
	336	#define DEFAULT_24_AIO 1
09ace81c	337	static int submit_aio_26(struct aio_context *aio)
75e5584c JD	338	{
	339	return -ENOSYS;
	340	}
	341
09ace81c	342	static int init_aio_26(void)
75e5584c	343	{
09ace81c	344	submit_proc = submit_aio_26;
75e5584c JD	345	return -ENOSYS;
	346	}
	347	#endif
	348
	349	static int aio_24 = DEFAULT_24_AIO;
	350
	351	static int __init set_aio_24(char name, int add)
	352	{
	353	aio_24 = 1;
	354	return 0;
	355	}
	356
	357	__uml_setup("aio=2.4", set_aio_24,
	358	"aio=2.4\n"
	359	" This is used to force UML to use 2.4-style AIO even when 2.6 AIO is\n"
	360	" available. 2.4 AIO is a single thread that handles one request at a\n"
	361	" time, synchronously. 2.6 AIO is a thread which uses the 2.6 AIO \n"
	362	" interface to handle an arbitrary number of pending requests. 2.6 AIO \n"
	363	" is not available in tt mode, on 2.4 hosts, or when UML is built with\n"
	364	" /usr/include/linux/aio_abi.h not available. Many distributions don't\n"
	365	" include aio_abi.h, so you will need to copy it from a kernel tree to\n"
	366	" your /usr/include/linux in order to build an AIO-capable UML\n\n"
	367	);
	368
	369	static int init_aio(void)
	370	{
	371	int err;
	372
	373	CHOOSE_MODE(({
	374	if(!aio_24){
	375	printk("Disabling 2.6 AIO in tt mode\n");
	376	aio_24 = 1;
	377	} }), (void) 0);
	378
	379	if(!aio_24){
	380	err = init_aio_26();
	381	if(err && (errno == ENOSYS)){
	382	printk("2.6 AIO not supported on the host - "
	383	"reverting to 2.4 AIO\n");
	384	aio_24 = 1;
	385	}
	386	else return err;
	387	}
	388
	389	if(aio_24)
	390	return init_aio_24();
	391
	392	return 0;
	393	}
	394
	395	/* The reason for the __initcall/__uml_exitcall asymmetry is that init_aio
	396	* needs to be called when the kernel is running because it calls run_helper,
	397	* which needs get_free_page. exit_aio is a __uml_exitcall because the generic
	398	* kernel does not run __exitcalls on shutdown, and can't because many of them
	399	* break when called outside of module unloading.
	400	*/
	401	__initcall(init_aio);
	402
	403	static void exit_aio(void)
	404	{
	405	if(aio_pid != -1)
	406	os_kill_process(aio_pid, 1);
	407	}
	408
409	__uml_exitcall(exit_aio);
410
09ace81c	411	int submit_aio(struct aio_context *aio)
75e5584c	412	{
09ace81c	413	return (*submit_proc)(aio);
75e5584c	414	}