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_constants.h"
  15 #include "kern_util.h"
  16 #include "os.h"
  17 #include "user.h"
  18
  19 struct aio_thread_req {
  20         enum aio_type type;
  21         int io_fd;
  22         unsigned long long offset;
  23         char *buf;
  24         int len;
  25         struct aio_context *aio;
  26 };
  27
  28 #if defined(HAVE_AIO_ABI)
  29 #include <linux/aio_abi.h>
  30
  31 /*
  32  * If we have the headers, we are going to build with AIO enabled.
  33  * If we don't have aio in libc, we define the necessary stubs here.
  34  */
  35
  36 #if !defined(HAVE_AIO_LIBC)
  37
  38 static long io_setup(int n, aio_context_t *ctxp)
  39 {
  40         return syscall(__NR_io_setup, n, ctxp);
  41 }
  42
  43 static long io_submit(aio_context_t ctx, long nr, struct iocb **iocbpp)
  44 {
  45         return syscall(__NR_io_submit, ctx, nr, iocbpp);
  46 }
  47
  48 static long io_getevents(aio_context_t ctx_id, long min_nr, long nr,
  49                          struct io_event *events, struct timespec *timeout)
  50 {
  51         return syscall(__NR_io_getevents, ctx_id, min_nr, nr, events, timeout);
  52 }
  53
  54 #endif
  55
  56 /*
  57  * The AIO_MMAP cases force the mmapped page into memory here
  58  * rather than in whatever place first touches the data.  I used
  59  * to do this by touching the page, but that's delicate because
  60  * gcc is prone to optimizing that away.  So, what's done here
  61  * is we read from the descriptor from which the page was
  62  * mapped.  The caller is required to pass an offset which is
  63  * inside the page that was mapped.  Thus, when the read
  64  * returns, we know that the page is in the page cache, and
  65  * that it now backs the mmapped area.
  66  */
  67
  68 static int do_aio(aio_context_t ctx, enum aio_type type, int fd, char *buf,
  69                   int len, unsigned long long offset, struct aio_context *aio)
  70 {
  71         struct iocb *iocbp = & ((struct iocb) {
  72                                     .aio_data       = (unsigned long) aio,
  73                                     .aio_fildes     = fd,
  74                                     .aio_buf        = (unsigned long) buf,
  75                                     .aio_nbytes     = len,
  76                                     .aio_offset     = offset
  77                              });
  78         char c;
  79
  80         switch (type) {
  81         case AIO_READ:
  82                 iocbp->aio_lio_opcode = IOCB_CMD_PREAD;
  83                 break;
  84         case AIO_WRITE:
  85                 iocbp->aio_lio_opcode = IOCB_CMD_PWRITE;
  86                 break;
  87         case AIO_MMAP:
  88                 iocbp->aio_lio_opcode = IOCB_CMD_PREAD;
  89                 iocbp->aio_buf = (unsigned long) &c;
  90                 iocbp->aio_nbytes = sizeof(c);
  91                 break;
  92         default:
  93                 printk(UM_KERN_ERR "Bogus op in do_aio - %d\n", type);
  94                 return -EINVAL;
  95         }
  96
  97         return (io_submit(ctx, 1, &iocbp) > 0) ? 0 : -errno;
  98 }
  99
 100 /* Initialized in an initcall and unchanged thereafter */
 101 static aio_context_t ctx = 0;
 102
 103 static int aio_thread(void *arg)
 104 {
 105         struct aio_thread_reply reply;
 106         struct io_event event;
 107         int err, n, reply_fd;
 108
 109         signal(SIGWINCH, SIG_IGN);
 110
 111         while (1) {
 112                 n = io_getevents(ctx, 1, 1, &event, NULL);
 113                 if (n < 0) {
 114                         if (errno == EINTR)
 115                                 continue;
 116                         printk(UM_KERN_ERR "aio_thread - io_getevents failed, "
 117                                "errno = %d\n", errno);
 118                 }
 119                 else {
 120                         reply = ((struct aio_thread_reply)
 121                                 { .data = (void *) (long) event.data,
 122                                                 .err    = event.res });
 123                         reply_fd = ((struct aio_context *) reply.data)->reply_fd;
 124                         err = write(reply_fd, &reply, sizeof(reply));
 125                         if (err != sizeof(reply))
 126                                 printk(UM_KERN_ERR "aio_thread - write failed, "
 127                                        "fd = %d, err = %d\n", reply_fd, errno);
 128                 }
 129         }
 130         return 0;
 131 }
 132
 133 #endif
 134
 135 static int do_not_aio(struct aio_thread_req *req)
 136 {
 137         char c;
 138         unsigned long long actual;
 139         int n;
 140
 141         actual = lseek64(req->io_fd, req->offset, SEEK_SET);
 142         if (actual != req->offset)
 143                 return -errno;
 144
 145         switch (req->type) {
 146         case AIO_READ:
 147                 n = read(req->io_fd, req->buf, req->len);
 148                 break;
 149         case AIO_WRITE:
 150                 n = write(req->io_fd, req->buf, req->len);
 151                 break;
 152         case AIO_MMAP:
 153                 n = read(req->io_fd, &c, sizeof(c));
 154                 break;
 155         default:
 156                 printk(UM_KERN_ERR "do_not_aio - bad request type : %d\n",
 157                        req->type);
 158                 return -EINVAL;
 159         }
 160
 161         if (n < 0)
 162                 return -errno;
 163         return 0;
 164 }
 165
 166 /* These are initialized in initcalls and not changed */
 167 static int aio_req_fd_r = -1;
 168 static int aio_req_fd_w = -1;
 169 static int aio_pid = -1;
 170 static unsigned long aio_stack;
 171
 172 static int not_aio_thread(void *arg)
 173 {
 174         struct aio_thread_req req;
 175         struct aio_thread_reply reply;
 176         int err;
 177
 178         signal(SIGWINCH, SIG_IGN);
 179         while (1) {
 180                 err = read(aio_req_fd_r, &req, sizeof(req));
 181                 if (err != sizeof(req)) {
 182                         if (err < 0)
 183                                 printk(UM_KERN_ERR "not_aio_thread - "
 184                                        "read failed, fd = %d, err = %d\n",
 185                                        aio_req_fd_r,
 186                                        errno);
 187                         else {
 188                                 printk(UM_KERN_ERR "not_aio_thread - short "
 189                                        "read, fd = %d, length = %d\n",
 190                                        aio_req_fd_r, err);
 191                         }
 192                         continue;
 193                 }
 194                 err = do_not_aio(&req);
 195                 reply = ((struct aio_thread_reply) { .data      = req.aio,
 196                                                      .err       = err });
 197                 err = write(req.aio->reply_fd, &reply, sizeof(reply));
 198                 if (err != sizeof(reply))
 199                         printk(UM_KERN_ERR "not_aio_thread - write failed, "
 200                                "fd = %d, err = %d\n", req.aio->reply_fd, errno);
 201         }
 202
 203         return 0;
 204 }
 205
 206 static int init_aio_24(void)
 207 {
 208         int fds[2], err;
 209
 210         err = os_pipe(fds, 1, 1);
 211         if (err)
 212                 goto out;
 213
 214         aio_req_fd_w = fds[0];
 215         aio_req_fd_r = fds[1];
 216
 217         err = os_set_fd_block(aio_req_fd_w, 0);
 218         if (err)
 219                 goto out_close_pipe;
 220
 221         err = run_helper_thread(not_aio_thread, NULL,
 222                                 CLONE_FILES | CLONE_VM, &aio_stack);
 223         if (err < 0)
 224                 goto out_close_pipe;
 225
 226         aio_pid = err;
 227         goto out;
 228
 229 out_close_pipe:
 230         close(fds[0]);
 231         close(fds[1]);
 232         aio_req_fd_w = -1;
 233         aio_req_fd_r = -1;
 234 out:
 235 #ifndef HAVE_AIO_ABI
 236         printk(UM_KERN_INFO "/usr/include/linux/aio_abi.h not present during "
 237                "build\n");
 238 #endif
 239         printk(UM_KERN_INFO "2.6 host AIO support not used - falling back to "
 240                "I/O thread\n");
 241         return 0;
 242 }
 243
 244 #ifdef HAVE_AIO_ABI
 245 #define DEFAULT_24_AIO 0
 246 static int init_aio_26(void)
 247 {
 248         int err;
 249
 250         if (io_setup(256, &ctx)) {
 251                 err = -errno;
 252                 printk(UM_KERN_ERR "aio_thread failed to initialize context, "
 253                        "err = %d\n", errno);
 254                 return err;
 255         }
 256
 257         err = run_helper_thread(aio_thread, NULL,
 258                                 CLONE_FILES | CLONE_VM, &aio_stack);
 259         if (err < 0)
 260                 return err;
 261
 262         aio_pid = err;
 263
 264         printk(UM_KERN_INFO "Using 2.6 host AIO\n");
 265         return 0;
 266 }
 267
 268 static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
 269                          unsigned long long offset, struct aio_context *aio)
 270 {
 271         struct aio_thread_reply reply;
 272         int err;
 273
 274         err = do_aio(ctx, type, io_fd, buf, len, offset, aio);
 275         if (err) {
 276                 reply = ((struct aio_thread_reply) { .data = aio,
 277                                          .err  = err });
 278                 err = write(aio->reply_fd, &reply, sizeof(reply));
 279                 if (err != sizeof(reply)) {
 280                         err = -errno;
 281                         printk(UM_KERN_ERR "submit_aio_26 - write failed, "
 282                                "fd = %d, err = %d\n", aio->reply_fd, -err);
 283                 }
 284                 else err = 0;
 285         }
 286
 287         return err;
 288 }
 289
 290 #else
 291 #define DEFAULT_24_AIO 1
 292 static int init_aio_26(void)
 293 {
 294         return -ENOSYS;
 295 }
 296
 297 static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
 298                          unsigned long long offset, struct aio_context *aio)
 299 {
 300         return -ENOSYS;
 301 }
 302 #endif
 303
 304 /* Initialized in an initcall and unchanged thereafter */
 305 static int aio_24 = DEFAULT_24_AIO;
 306
 307 static int __init set_aio_24(char *name, int *add)
 308 {
 309         aio_24 = 1;
 310         return 0;
 311 }
 312
 313 __uml_setup("aio=2.4", set_aio_24,
 314 "aio=2.4\n"
 315 "    This is used to force UML to use 2.4-style AIO even when 2.6 AIO is\n"
 316 "    available.  2.4 AIO is a single thread that handles one request at a\n"
 317 "    time, synchronously.  2.6 AIO is a thread which uses the 2.6 AIO \n"
 318 "    interface to handle an arbitrary number of pending requests.  2.6 AIO \n"
 319 "    is not available in tt mode, on 2.4 hosts, or when UML is built with\n"
 320 "    /usr/include/linux/aio_abi.h not available.  Many distributions don't\n"
 321 "    include aio_abi.h, so you will need to copy it from a kernel tree to\n"
 322 "    your /usr/include/linux in order to build an AIO-capable UML\n\n"
 323 );
 324
 325 static int init_aio(void)
 326 {
 327         int err;
 328
 329         if (!aio_24) {
 330                 err = init_aio_26();
 331                 if (err && (errno == ENOSYS)) {
 332                         printk(UM_KERN_INFO "2.6 AIO not supported on the "
 333                                "host - reverting to 2.4 AIO\n");
 334                         aio_24 = 1;
 335                 }
 336                 else return err;
 337         }
 338
 339         if (aio_24)
 340                 return init_aio_24();
 341
 342         return 0;
 343 }
 344
 345 /*
 346  * The reason for the __initcall/__uml_exitcall asymmetry is that init_aio
 347  * needs to be called when the kernel is running because it calls run_helper,
 348  * which needs get_free_page.  exit_aio is a __uml_exitcall because the generic
 349  * kernel does not run __exitcalls on shutdown, and can't because many of them
 350  * break when called outside of module unloading.
 351  */
 352 __initcall(init_aio);
 353
 354 static void exit_aio(void)
 355 {
 356         if (aio_pid != -1) {
 357                 os_kill_process(aio_pid, 1);
 358                 free_stack(aio_stack, 0);
 359         }
 360 }
 361
 362 __uml_exitcall(exit_aio);
 363
 364 static int submit_aio_24(enum aio_type type, int io_fd, char *buf, int len,
 365                          unsigned long long offset, struct aio_context *aio)
 366 {
 367         struct aio_thread_req req = { .type             = type,
 368                                       .io_fd            = io_fd,
 369                                       .offset           = offset,
 370                                       .buf              = buf,
 371                                       .len              = len,
 372                                       .aio              = aio,
 373         };
 374         int err;
 375
 376         err = write(aio_req_fd_w, &req, sizeof(req));
 377         if (err == sizeof(req))
 378                 err = 0;
 379         else err = -errno;
 380
 381         return err;
 382 }
 383
 384 int submit_aio(enum aio_type type, int io_fd, char *buf, int len,
 385                unsigned long long offset, int reply_fd,
 386                struct aio_context *aio)
 387 {
 388         aio->reply_fd = reply_fd;
 389         if (aio_24)
 390                 return submit_aio_24(type, io_fd, buf, len, offset, aio);
 391         else
 392                 return submit_aio_26(type, io_fd, buf, len, offset, aio);
 393 }