arch/um/os-Linux/aio.c

   1 /*
   2  * Copyright (C) 2004 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <unistd.h>
   7 #include <sched.h>
   8 #include <signal.h>
   9 #include <errno.h>
  10 #include <sys/time.h>
  11 #include <asm/unistd.h>
  12 #include <aio.h>
  13 #include <init.h>
  14 #include <kern_util.h>
  15 #include <os.h>
  16
  17 struct aio_thread_req {
  18         enum aio_type type;
  19         int io_fd;
  20         unsigned long long offset;
  21         char *buf;
  22         int len;
  23         struct aio_context *aio;
  24 };
  25
  26 #if defined(HAVE_AIO_ABI)
  27 #include <linux/aio_abi.h>
  28
  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 {
  38         return syscall(__NR_io_setup, n, ctxp);
  39 }
  40
  41 static long io_submit(aio_context_t ctx, long nr, struct iocb **iocbpp)
  42 {
  43         return syscall(__NR_io_submit, ctx, nr, iocbpp);
  44 }
  45
  46 static long io_getevents(aio_context_t ctx_id, long min_nr, long nr,
  47                          struct io_event *events, struct timespec *timeout)
  48 {
  49         return syscall(__NR_io_getevents, ctx_id, min_nr, nr, events, timeout);
  50 }
  51
  52 #endif
  53
  54 /*
  55  * The AIO_MMAP cases force the mmapped page into memory here
  56  * rather than in whatever place first touches the data.  I used
  57  * to do this by touching the page, but that's delicate because
  58  * gcc is prone to optimizing that away.  So, what's done here
  59  * is we read from the descriptor from which the page was
  60  * mapped.  The caller is required to pass an offset which is
  61  * inside the page that was mapped.  Thus, when the read
  62  * returns, we know that the page is in the page cache, and
  63  * that it now backs the mmapped area.
  64  */
  65
  66 static int do_aio(aio_context_t ctx, enum aio_type type, int fd, char *buf,
  67                   int len, unsigned long long offset, struct aio_context *aio)
  68 {
  69         struct iocb *iocbp = & ((struct iocb) {
  70                                     .aio_data       = (unsigned long) aio,
  71                                     .aio_fildes     = fd,
  72                                     .aio_buf        = (unsigned long) buf,
  73                                     .aio_nbytes     = len,
  74                                     .aio_offset     = offset
  75                              });
  76         char c;
  77
  78         switch (type) {
  79         case AIO_READ:
  80                 iocbp->aio_lio_opcode = IOCB_CMD_PREAD;
  81                 break;
  82         case AIO_WRITE:
  83                 iocbp->aio_lio_opcode = IOCB_CMD_PWRITE;
  84                 break;
  85         case AIO_MMAP:
  86                 iocbp->aio_lio_opcode = IOCB_CMD_PREAD;
  87                 iocbp->aio_buf = (unsigned long) &c;
  88                 iocbp->aio_nbytes = sizeof(c);
  89                 break;
  90         default:
  91                 printk(UM_KERN_ERR "Bogus op in do_aio - %d\n", type);
  92                 return -EINVAL;
  93         }
  94
  95         return (io_submit(ctx, 1, &iocbp) > 0) ? 0 : -errno;
  96 }
  97
  98 /* Initialized in an initcall and unchanged thereafter */
  99 static aio_context_t ctx = 0;
 100
 101 static int aio_thread(void *arg)
 102 {
 103         struct aio_thread_reply reply;
 104         struct io_event event;
 105         int err, n, reply_fd;
 106
 107         signal(SIGWINCH, SIG_IGN);
 108
 109         while (1) {
 110                 n = io_getevents(ctx, 1, 1, &event, NULL);
 111                 if (n < 0) {
 112                         if (errno == EINTR)
 113                                 continue;
 114                         printk(UM_KERN_ERR "aio_thread - io_getevents failed, "
 115                                "errno = %d\n", errno);
 116                 }
 117                 else {
 118                         reply = ((struct aio_thread_reply)
 119                                 { .data = (void *) (long) event.data,
 120                                                 .err    = event.res });
 121                         reply_fd = ((struct aio_context *) reply.data)->reply_fd;
 122                         err = write(reply_fd, &reply, sizeof(reply));
 123                         if (err != sizeof(reply))
 124                                 printk(UM_KERN_ERR "aio_thread - write failed, "
 125                                        "fd = %d, err = %d\n", reply_fd, errno);
 126                 }
 127         }
 128         return 0;
 129 }
 130
 131 #endif
 132
 133 static int do_not_aio(struct aio_thread_req *req)
 134 {
 135         char c;
 136         unsigned long long actual;
 137         int n;
 138
 139         actual = lseek64(req->io_fd, req->offset, SEEK_SET);
 140         if (actual != req->offset)
 141                 return -errno;
 142
 143         switch (req->type) {
 144         case AIO_READ:
 145                 n = read(req->io_fd, req->buf, req->len);
 146                 break;
 147         case AIO_WRITE:
 148                 n = write(req->io_fd, req->buf, req->len);
 149                 break;
 150         case AIO_MMAP:
 151                 n = read(req->io_fd, &c, sizeof(c));
 152                 break;
 153         default:
 154                 printk(UM_KERN_ERR "do_not_aio - bad request type : %d\n",
 155                        req->type);
 156                 return -EINVAL;
 157         }
 158
 159         if (n < 0)
 160                 return -errno;
 161         return 0;
 162 }
 163
 164 /* These are initialized in initcalls and not changed */
 165 static int aio_req_fd_r = -1;
 166 static int aio_req_fd_w = -1;
 167 static int aio_pid = -1;
 168 static unsigned long aio_stack;
 169
 170 static int not_aio_thread(void *arg)
 171 {
 172         struct aio_thread_req req;
 173         struct aio_thread_reply reply;
 174         int err;
 175
 176         signal(SIGWINCH, SIG_IGN);
 177         while (1) {
 178                 err = read(aio_req_fd_r, &req, sizeof(req));
 179                 if (err != sizeof(req)) {
 180                         if (err < 0)
 181                                 printk(UM_KERN_ERR "not_aio_thread - "
 182                                        "read failed, fd = %d, err = %d\n",
 183                                        aio_req_fd_r,
 184                                        errno);
 185                         else {
 186                                 printk(UM_KERN_ERR "not_aio_thread - short "
 187                                        "read, fd = %d, length = %d\n",
 188                                        aio_req_fd_r, err);
 189                         }
 190                         continue;
 191                 }
 192                 err = do_not_aio(&req);
 193                 reply = ((struct aio_thread_reply) { .data      = req.aio,
 194                                                      .err       = err });
 195                 err = write(req.aio->reply_fd, &reply, sizeof(reply));
 196                 if (err != sizeof(reply))
 197                         printk(UM_KERN_ERR "not_aio_thread - write failed, "
 198                                "fd = %d, err = %d\n", req.aio->reply_fd, errno);
 199         }
 200
 201         return 0;
 202 }
 203
 204 static int init_aio_24(void)
 205 {
 206         int fds[2], err;
 207
 208         err = os_pipe(fds, 1, 1);
 209         if (err)
 210                 goto out;
 211
 212         aio_req_fd_w = fds[0];
 213         aio_req_fd_r = fds[1];
 214
 215         err = os_set_fd_block(aio_req_fd_w, 0);
 216         if (err)
 217                 goto out_close_pipe;
 218
 219         err = run_helper_thread(not_aio_thread, NULL,
 220                                 CLONE_FILES | CLONE_VM, &aio_stack);
 221         if (err < 0)
 222                 goto out_close_pipe;
 223
 224         aio_pid = err;
 225         goto out;
 226
 227 out_close_pipe:
 228         close(fds[0]);
 229         close(fds[1]);
 230         aio_req_fd_w = -1;
 231         aio_req_fd_r = -1;
 232 out:
 233 #ifndef HAVE_AIO_ABI
 234         printk(UM_KERN_INFO "/usr/include/linux/aio_abi.h not present during "
 235                "build\n");
 236 #endif
 237         printk(UM_KERN_INFO "2.6 host AIO support not used - falling back to "
 238                "I/O thread\n");
 239         return 0;
 240 }
 241
 242 #ifdef HAVE_AIO_ABI
 243 #define DEFAULT_24_AIO 0
 244 static int init_aio_26(void)
 245 {
 246         int err;
 247
 248         if (io_setup(256, &ctx)) {
 249                 err = -errno;
 250                 printk(UM_KERN_ERR "aio_thread failed to initialize context, "
 251                        "err = %d\n", errno);
 252                 return err;
 253         }
 254
 255         err = run_helper_thread(aio_thread, NULL,
 256                                 CLONE_FILES | CLONE_VM, &aio_stack);
 257         if (err < 0)
 258                 return err;
 259
 260         aio_pid = err;
 261
 262         printk(UM_KERN_INFO "Using 2.6 host AIO\n");
 263         return 0;
 264 }
 265
 266 static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
 267                          unsigned long long offset, struct aio_context *aio)
 268 {
 269         struct aio_thread_reply reply;
 270         int err;
 271
 272         err = do_aio(ctx, type, io_fd, buf, len, offset, aio);
 273         if (err) {
 274                 reply = ((struct aio_thread_reply) { .data = aio,
 275                                          .err  = err });
 276                 err = write(aio->reply_fd, &reply, sizeof(reply));
 277                 if (err != sizeof(reply)) {
 278                         err = -errno;
 279                         printk(UM_KERN_ERR "submit_aio_26 - write failed, "
 280                                "fd = %d, err = %d\n", aio->reply_fd, -err);
 281                 }
 282                 else err = 0;
 283         }
 284
 285         return err;
 286 }
 287
 288 #else
 289 #define DEFAULT_24_AIO 1
 290 static int init_aio_26(void)
 291 {
 292         return -ENOSYS;
 293 }
 294
 295 static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
 296                          unsigned long long offset, struct aio_context *aio)
 297 {
 298         return -ENOSYS;
 299 }
 300 #endif
 301
 302 /* Initialized in an initcall and unchanged thereafter */
 303 static int aio_24 = DEFAULT_24_AIO;
 304
 305 static int __init set_aio_24(char *name, int *add)
 306 {
 307         aio_24 = 1;
 308         return 0;
 309 }
 310
 311 __uml_setup("aio=2.4", set_aio_24,
 312 "aio=2.4\n"
 313 "    This is used to force UML to use 2.4-style AIO even when 2.6 AIO is\n"
 314 "    available.  2.4 AIO is a single thread that handles one request at a\n"
 315 "    time, synchronously.  2.6 AIO is a thread which uses the 2.6 AIO \n"
 316 "    interface to handle an arbitrary number of pending requests.  2.6 AIO \n"
 317 "    is not available in tt mode, on 2.4 hosts, or when UML is built with\n"
 318 "    /usr/include/linux/aio_abi.h not available.  Many distributions don't\n"
 319 "    include aio_abi.h, so you will need to copy it from a kernel tree to\n"
 320 "    your /usr/include/linux in order to build an AIO-capable UML\n\n"
 321 );
 322
 323 static int init_aio(void)
 324 {
 325         int err;
 326
 327         if (!aio_24) {
 328                 err = init_aio_26();
 329                 if (err && (errno == ENOSYS)) {
 330                         printk(UM_KERN_INFO "2.6 AIO not supported on the "
 331                                "host - reverting to 2.4 AIO\n");
 332                         aio_24 = 1;
 333                 }
 334                 else return err;
 335         }
 336
 337         if (aio_24)
 338                 return init_aio_24();
 339
 340         return 0;
 341 }
 342
 343 /*
 344  * The reason for the __initcall/__uml_exitcall asymmetry is that init_aio
 345  * needs to be called when the kernel is running because it calls run_helper,
 346  * which needs get_free_page.  exit_aio is a __uml_exitcall because the generic
 347  * kernel does not run __exitcalls on shutdown, and can't because many of them
 348  * break when called outside of module unloading.
 349  */
 350 __initcall(init_aio);
 351
 352 static void exit_aio(void)
 353 {
 354         if (aio_pid != -1) {
 355                 os_kill_process(aio_pid, 1);
 356                 free_stack(aio_stack, 0);
 357         }
 358 }
 359
 360 __uml_exitcall(exit_aio);
 361
 362 static int submit_aio_24(enum aio_type type, int io_fd, char *buf, int len,
 363                          unsigned long long offset, struct aio_context *aio)
 364 {
 365         struct aio_thread_req req = { .type             = type,
 366                                       .io_fd            = io_fd,
 367                                       .offset           = offset,
 368                                       .buf              = buf,
 369                                       .len              = len,
 370                                       .aio              = aio,
 371         };
 372         int err;
 373
 374         err = write(aio_req_fd_w, &req, sizeof(req));
 375         if (err == sizeof(req))
 376                 err = 0;
 377         else err = -errno;
 378
 379         return err;
 380 }
 381
 382 int submit_aio(enum aio_type type, int io_fd, char *buf, int len,
 383                unsigned long long offset, int reply_fd,
 384                struct aio_context *aio)
 385 {
 386         aio->reply_fd = reply_fd;
 387         if (aio_24)
 388                 return submit_aio_24(type, io_fd, buf, len, offset, aio);
 389         else
 390                 return submit_aio_26(type, io_fd, buf, len, offset, aio);
 391 }