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linux/arch/um/os-Linux/aio.c

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/*
* 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);
}
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