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         os_fix_helper_signals();
 108         while (1) {
 109                 n = io_getevents(ctx, 1, 1, &event, NULL);
 110                 if (n < 0) {
 111                         if (errno == EINTR)
 112                                 continue;
 113                         printk(UM_KERN_ERR "aio_thread - io_getevents failed, "
 114                                "errno = %d\n", errno);
 115                 }
 116                 else {
 117                         reply = ((struct aio_thread_reply)
 118                                 { .data = (void *) (long) event.data,
 119                                                 .err    = event.res });
 120                         reply_fd = ((struct aio_context *) reply.data)->reply_fd;
 121                         err = write(reply_fd, &reply, sizeof(reply));
 122                         if (err != sizeof(reply))
 123                                 printk(UM_KERN_ERR "aio_thread - write failed, "
 124                                        "fd = %d, err = %d\n", reply_fd, errno);
 125                 }
 126         }
 127         return 0;
 128 }
 129
 130 #endif
 131
 132 static int do_not_aio(struct aio_thread_req *req)
 133 {
 134         char c;
 135         unsigned long long actual;
 136         int n;
 137
 138         actual = lseek64(req->io_fd, req->offset, SEEK_SET);
 139         if (actual != req->offset)
 140                 return -errno;
 141
 142         switch (req->type) {
 143         case AIO_READ:
 144                 n = read(req->io_fd, req->buf, req->len);
 145                 break;
 146         case AIO_WRITE:
 147                 n = write(req->io_fd, req->buf, req->len);
 148                 break;
 149         case AIO_MMAP:
 150                 n = read(req->io_fd, &c, sizeof(c));
 151                 break;
 152         default:
 153                 printk(UM_KERN_ERR "do_not_aio - bad request type : %d\n",
 154                        req->type);
 155                 return -EINVAL;
 156         }
 157
 158         if (n < 0)
 159                 return -errno;
 160         return 0;
 161 }
 162
 163 /* These are initialized in initcalls and not changed */
 164 static int aio_req_fd_r = -1;
 165 static int aio_req_fd_w = -1;
 166 static int aio_pid = -1;
 167 static unsigned long aio_stack;
 168
 169 static int not_aio_thread(void *arg)
 170 {
 171         struct aio_thread_req req;
 172         struct aio_thread_reply reply;
 173         int err;
 174
 175         os_fix_helper_signals();
 176         while (1) {
 177                 err = read(aio_req_fd_r, &req, sizeof(req));
 178                 if (err != sizeof(req)) {
 179                         if (err < 0)
 180                                 printk(UM_KERN_ERR "not_aio_thread - "
 181                                        "read failed, fd = %d, err = %d\n",
 182                                        aio_req_fd_r,
 183                                        errno);
 184                         else {
 185                                 printk(UM_KERN_ERR "not_aio_thread - short "
 186                                        "read, fd = %d, length = %d\n",
 187                                        aio_req_fd_r, err);
 188                         }
 189                         continue;
 190                 }
 191                 err = do_not_aio(&req);
 192                 reply = ((struct aio_thread_reply) { .data      = req.aio,
 193                                                      .err       = err });
 194                 err = write(req.aio->reply_fd, &reply, sizeof(reply));
 195                 if (err != sizeof(reply))
 196                         printk(UM_KERN_ERR "not_aio_thread - write failed, "
 197                                "fd = %d, err = %d\n", req.aio->reply_fd, errno);
 198         }
 199
 200         return 0;
 201 }
 202
 203 static int init_aio_24(void)
 204 {
 205         int fds[2], err;
 206
 207         err = os_pipe(fds, 1, 1);
 208         if (err)
 209                 goto out;
 210
 211         aio_req_fd_w = fds[0];
 212         aio_req_fd_r = fds[1];
 213
 214         err = os_set_fd_block(aio_req_fd_w, 0);
 215         if (err)
 216                 goto out_close_pipe;
 217
 218         err = run_helper_thread(not_aio_thread, NULL,
 219                                 CLONE_FILES | CLONE_VM, &aio_stack);
 220         if (err < 0)
 221                 goto out_close_pipe;
 222
 223         aio_pid = err;
 224         goto out;
 225
 226 out_close_pipe:
 227         close(fds[0]);
 228         close(fds[1]);
 229         aio_req_fd_w = -1;
 230         aio_req_fd_r = -1;
 231 out:
 232 #ifndef HAVE_AIO_ABI
 233         printk(UM_KERN_INFO "/usr/include/linux/aio_abi.h not present during "
 234                "build\n");
 235 #endif
 236         printk(UM_KERN_INFO "2.6 host AIO support not used - falling back to "
 237                "I/O thread\n");
 238         return 0;
 239 }
 240
 241 #ifdef HAVE_AIO_ABI
 242 #define DEFAULT_24_AIO 0
 243 static int init_aio_26(void)
 244 {
 245         int err;
 246
 247         if (io_setup(256, &ctx)) {
 248                 err = -errno;
 249                 printk(UM_KERN_ERR "aio_thread failed to initialize context, "
 250                        "err = %d\n", errno);
 251                 return err;
 252         }
 253
 254         err = run_helper_thread(aio_thread, NULL,
 255                                 CLONE_FILES | CLONE_VM, &aio_stack);
 256         if (err < 0)
 257                 return err;
 258
 259         aio_pid = err;
 260
 261         printk(UM_KERN_INFO "Using 2.6 host AIO\n");
 262         return 0;
 263 }
 264
 265 static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
 266                          unsigned long long offset, struct aio_context *aio)
 267 {
 268         struct aio_thread_reply reply;
 269         int err;
 270
 271         err = do_aio(ctx, type, io_fd, buf, len, offset, aio);
 272         if (err) {
 273                 reply = ((struct aio_thread_reply) { .data = aio,
 274                                          .err  = err });
 275                 err = write(aio->reply_fd, &reply, sizeof(reply));
 276                 if (err != sizeof(reply)) {
 277                         err = -errno;
 278                         printk(UM_KERN_ERR "submit_aio_26 - write failed, "
 279                                "fd = %d, err = %d\n", aio->reply_fd, -err);
 280                 }
 281                 else err = 0;
 282         }
 283
 284         return err;
 285 }
 286
 287 #else
 288 #define DEFAULT_24_AIO 1
 289 static int init_aio_26(void)
 290 {
 291         return -ENOSYS;
 292 }
 293
 294 static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
 295                          unsigned long long offset, struct aio_context *aio)
 296 {
 297         return -ENOSYS;
 298 }
 299 #endif
 300
 301 /* Initialized in an initcall and unchanged thereafter */
 302 static int aio_24 = DEFAULT_24_AIO;
 303
 304 static int __init set_aio_24(char *name, int *add)
 305 {
 306         aio_24 = 1;
 307         return 0;
 308 }
 309
 310 __uml_setup("aio=2.4", set_aio_24,
 311 "aio=2.4\n"
 312 "    This is used to force UML to use 2.4-style AIO even when 2.6 AIO is\n"
 313 "    available.  2.4 AIO is a single thread that handles one request at a\n"
 314 "    time, synchronously.  2.6 AIO is a thread which uses the 2.6 AIO \n"
 315 "    interface to handle an arbitrary number of pending requests.  2.6 AIO \n"
 316 "    is not available in tt mode, on 2.4 hosts, or when UML is built with\n"
 317 "    /usr/include/linux/aio_abi.h not available.  Many distributions don't\n"
 318 "    include aio_abi.h, so you will need to copy it from a kernel tree to\n"
 319 "    your /usr/include/linux in order to build an AIO-capable UML\n\n"
 320 );
 321
 322 static int init_aio(void)
 323 {
 324         int err;
 325
 326         if (!aio_24) {
 327                 err = init_aio_26();
 328                 if (err && (errno == ENOSYS)) {
 329                         printk(UM_KERN_INFO "2.6 AIO not supported on the "
 330                                "host - reverting to 2.4 AIO\n");
 331                         aio_24 = 1;
 332                 }
 333                 else return err;
 334         }
 335
 336         if (aio_24)
 337                 return init_aio_24();
 338
 339         return 0;
 340 }
 341
 342 /*
 343  * The reason for the __initcall/__uml_exitcall asymmetry is that init_aio
 344  * needs to be called when the kernel is running because it calls run_helper,
 345  * which needs get_free_page.  exit_aio is a __uml_exitcall because the generic
 346  * kernel does not run __exitcalls on shutdown, and can't because many of them
 347  * break when called outside of module unloading.
 348  */
 349 __initcall(init_aio);
 350
 351 static void exit_aio(void)
 352 {
 353         if (aio_pid != -1) {
 354                 os_kill_process(aio_pid, 1);
 355                 free_stack(aio_stack, 0);
 356         }
 357 }
 358
 359 __uml_exitcall(exit_aio);
 360
 361 static int submit_aio_24(enum aio_type type, int io_fd, char *buf, int len,
 362                          unsigned long long offset, struct aio_context *aio)
 363 {
 364         struct aio_thread_req req = { .type             = type,
 365                                       .io_fd            = io_fd,
 366                                       .offset           = offset,
 367                                       .buf              = buf,
 368                                       .len              = len,
 369                                       .aio              = aio,
 370         };
 371         int err;
 372
 373         err = write(aio_req_fd_w, &req, sizeof(req));
 374         if (err == sizeof(req))
 375                 err = 0;
 376         else err = -errno;
 377
 378         return err;
 379 }
 380
 381 int submit_aio(enum aio_type type, int io_fd, char *buf, int len,
 382                unsigned long long offset, int reply_fd,
 383                struct aio_context *aio)
 384 {
 385         aio->reply_fd = reply_fd;
 386         if (aio_24)
 387                 return submit_aio_24(type, io_fd, buf, len, offset, aio);
 388         else
 389                 return submit_aio_26(type, io_fd, buf, len, offset, aio);
 390 }