summaryrefslogtreecommitdiff
path: root/arch/um/os-Linux/aio.c
blob: b04897cd995d02d021ec82864f24ad82d6de6b25 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
/*
 * 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);
}