arch/um/os-Linux/aio.c

   1 /*
   2  * Copyright (C) 2004 Jeff Dike (jdike@addtoit.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8 #include <signal.h>
   9 #include <errno.h>
  10 #include <sched.h>
  11 #include <sys/syscall.h>
  12 #include "os.h"
  13 #include "aio.h"
  14 #include "init.h"
  15 #include "user.h"
  16 #include "mode.h"
  17
  18 struct aio_thread_req {
  19         enum aio_type type;
  20         int io_fd;
  21         unsigned long long offset;
  22         char *buf;
  23         int len;
  24         struct aio_context *aio;
  25 };
  26
  27 #if defined(HAVE_AIO_ABI)
  28 #include <linux/aio_abi.h>
  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 /* The AIO_MMAP cases force the mmapped page into memory here
  55  * rather than in whatever place first touches the data.  I used
  56  * to do this by touching the page, but that's delicate because
  57  * gcc is prone to optimizing that away.  So, what's done here
  58  * is we read from the descriptor from which the page was
  59  * mapped.  The caller is required to pass an offset which is
  60  * inside the page that was mapped.  Thus, when the read
  61  * returns, we know that the page is in the page cache, and
  62  * that it now backs the mmapped area.
  63  */
  64
  65 static int do_aio(aio_context_t ctx, enum aio_type type, int fd, char *buf,
  66                   int len, unsigned long long offset, struct aio_context *aio)
  67 {
  68         struct iocb iocb, *iocbp = &iocb;
  69         char c;
  70         int err;
  71
  72         iocb = ((struct iocb) { .aio_data       = (unsigned long) aio,
  73                                 .aio_reqprio    = 0,
  74                                 .aio_fildes     = fd,
  75                                 .aio_buf        = (unsigned long) buf,
  76                                 .aio_nbytes     = len,
  77                                 .aio_offset     = offset,
  78                                 .aio_reserved1  = 0,
  79                                 .aio_reserved2  = 0,
  80                                 .aio_reserved3  = 0 });
  81
  82         switch(type){
  83         case AIO_READ:
  84                 iocb.aio_lio_opcode = IOCB_CMD_PREAD;
  85                 err = io_submit(ctx, 1, &iocbp);
  86                 break;
  87         case AIO_WRITE:
  88                 iocb.aio_lio_opcode = IOCB_CMD_PWRITE;
  89                 err = io_submit(ctx, 1, &iocbp);
  90                 break;
  91         case AIO_MMAP:
  92                 iocb.aio_lio_opcode = IOCB_CMD_PREAD;
  93                 iocb.aio_buf = (unsigned long) &c;
  94                 iocb.aio_nbytes = sizeof(c);
  95                 err = io_submit(ctx, 1, &iocbp);
  96                 break;
  97         default:
  98                 printk("Bogus op in do_aio - %d\n", type);
  99                 err = -EINVAL;
 100                 break;
 101         }
 102
 103         if(err > 0)
 104                 err = 0;
 105         else
 106                 err = -errno;
 107
 108         return err;
 109 }
 110
 111 /* Initialized in an initcall and unchanged thereafter */
 112 static aio_context_t ctx = 0;
 113
 114 static int aio_thread(void *arg)
 115 {
 116         struct aio_thread_reply reply;
 117         struct io_event event;
 118         int err, n, reply_fd;
 119
 120         signal(SIGWINCH, SIG_IGN);
 121
 122         while(1){
 123                 n = io_getevents(ctx, 1, 1, &event, NULL);
 124                 if(n < 0){
 125                         if(errno == EINTR)
 126                                 continue;
 127                         printk("aio_thread - io_getevents failed, "
 128                                "errno = %d\n", errno);
 129                 }
 130                 else {
 131                         reply = ((struct aio_thread_reply)
 132                                 { .data = (void *) (long) event.data,
 133                                                 .err    = event.res });
 134                         reply_fd = ((struct aio_context *) reply.data)->reply_fd;
 135                         err = write(reply_fd, &reply, sizeof(reply));
 136                         if(err != sizeof(reply))
 137                                 printk("aio_thread - write failed, fd = %d, "
 138                                        "err = %d\n", reply_fd, errno);
 139                 }
 140         }
 141         return 0;
 142 }
 143
 144 #endif
 145
 146 static int do_not_aio(struct aio_thread_req *req)
 147 {
 148         char c;
 149         unsigned long long actual;
 150         int n;
 151
 152         actual = lseek64(req->io_fd, req->offset, SEEK_SET);
 153         if(actual != req->offset)
 154                 return -errno;
 155
 156         switch(req->type){
 157         case AIO_READ:
 158                 n = read(req->io_fd, req->buf, req->len);
 159                 break;
 160         case AIO_WRITE:
 161                 n = write(req->io_fd, req->buf, req->len);
 162                 break;
 163         case AIO_MMAP:
 164                 n = read(req->io_fd, &c, sizeof(c));
 165                 break;
 166         default:
 167                 printk("do_not_aio - bad request type : %d\n", req->type);
 168                 return -EINVAL;
 169         }
 170
 171         if(n < 0)
 172                 return -errno;
 173         return 0;
 174 }
 175
 176 /* These are initialized in initcalls and not changed */
 177 static int aio_req_fd_r = -1;
 178 static int aio_req_fd_w = -1;
 179 static int aio_pid = -1;
 180
 181 static int not_aio_thread(void *arg)
 182 {
 183         struct aio_thread_req req;
 184         struct aio_thread_reply reply;
 185         int err;
 186
 187         signal(SIGWINCH, SIG_IGN);
 188         while(1){
 189                 err = read(aio_req_fd_r, &req, sizeof(req));
 190                 if(err != sizeof(req)){
 191                         if(err < 0)
 192                                 printk("not_aio_thread - read failed, "
 193                                        "fd = %d, err = %d\n", aio_req_fd_r,
 194                                        errno);
 195                         else {
 196                                 printk("not_aio_thread - short read, fd = %d, "
 197                                        "length = %d\n", aio_req_fd_r, err);
 198                         }
 199                         continue;
 200                 }
 201                 err = do_not_aio(&req);
 202                 reply = ((struct aio_thread_reply) { .data      = req.aio,
 203                                                      .err       = err });
 204                 err = write(req.aio->reply_fd, &reply, sizeof(reply));
 205                 if(err != sizeof(reply))
 206                         printk("not_aio_thread - write failed, fd = %d, "
 207                                "err = %d\n", req.aio->reply_fd, errno);
 208         }
 209
 210         return 0;
 211 }
 212
 213 static int init_aio_24(void)
 214 {
 215         unsigned long stack;
 216         int fds[2], err;
 217
 218         err = os_pipe(fds, 1, 1);
 219         if(err)
 220                 goto out;
 221
 222         aio_req_fd_w = fds[0];
 223         aio_req_fd_r = fds[1];
 224
 225         err = os_set_fd_block(aio_req_fd_w, 0);
 226         if(err)
 227                 goto out_close_pipe;
 228
 229         err = run_helper_thread(not_aio_thread, NULL,
 230                                 CLONE_FILES | CLONE_VM | SIGCHLD, &stack, 0);
 231         if(err < 0)
 232                 goto out_close_pipe;
 233
 234         aio_pid = err;
 235         goto out;
 236
 237 out_close_pipe:
 238         os_close_file(fds[0]);
 239         os_close_file(fds[1]);
 240         aio_req_fd_w = -1;
 241         aio_req_fd_r = -1;
 242 out:
 243 #ifndef HAVE_AIO_ABI
 244         printk("/usr/include/linux/aio_abi.h not present during build\n");
 245 #endif
 246         printk("2.6 host AIO support not used - falling back to I/O "
 247                "thread\n");
 248         return 0;
 249 }
 250
 251 #ifdef HAVE_AIO_ABI
 252 #define DEFAULT_24_AIO 0
 253 static int init_aio_26(void)
 254 {
 255         unsigned long stack;
 256         int err;
 257
 258         if(io_setup(256, &ctx)){
 259                 err = -errno;
 260                 printk("aio_thread failed to initialize context, err = %d\n",
 261                        errno);
 262                 return err;
 263         }
 264
 265         err = run_helper_thread(aio_thread, NULL,
 266                                 CLONE_FILES | CLONE_VM | SIGCHLD, &stack, 0);
 267         if(err < 0)
 268                 return err;
 269
 270         aio_pid = err;
 271
 272         printk("Using 2.6 host AIO\n");
 273         return 0;
 274 }
 275
 276 static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
 277                          unsigned long long offset, struct aio_context *aio)
 278 {
 279         struct aio_thread_reply reply;
 280         int err;
 281
 282         err = do_aio(ctx, type, io_fd, buf, len, offset, aio);
 283         if(err){
 284                 reply = ((struct aio_thread_reply) { .data = aio,
 285                                          .err  = err });
 286                 err = write(aio->reply_fd, &reply, sizeof(reply));
 287                 if(err != sizeof(reply)){
 288                         err = -errno;
 289                         printk("submit_aio_26 - write failed, "
 290                                "fd = %d, err = %d\n", aio->reply_fd, -err);
 291                 }
 292                 else err = 0;
 293         }
 294
 295         return err;
 296 }
 297
 298 #else
 299 #define DEFAULT_24_AIO 1
 300 static int init_aio_26(void)
 301 {
 302         return -ENOSYS;
 303 }
 304
 305 static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
 306                          unsigned long long offset, struct aio_context *aio)
 307 {
 308         return -ENOSYS;
 309 }
 310 #endif
 311
 312 /* Initialized in an initcall and unchanged thereafter */
 313 static int aio_24 = DEFAULT_24_AIO;
 314
 315 static int __init set_aio_24(char *name, int *add)
 316 {
 317         aio_24 = 1;
 318         return 0;
 319 }
 320
 321 __uml_setup("aio=2.4", set_aio_24,
 322 "aio=2.4\n"
 323 "    This is used to force UML to use 2.4-style AIO even when 2.6 AIO is\n"
 324 "    available.  2.4 AIO is a single thread that handles one request at a\n"
 325 "    time, synchronously.  2.6 AIO is a thread which uses the 2.6 AIO \n"
 326 "    interface to handle an arbitrary number of pending requests.  2.6 AIO \n"
 327 "    is not available in tt mode, on 2.4 hosts, or when UML is built with\n"
 328 "    /usr/include/linux/aio_abi.h not available.  Many distributions don't\n"
 329 "    include aio_abi.h, so you will need to copy it from a kernel tree to\n"
 330 "    your /usr/include/linux in order to build an AIO-capable UML\n\n"
 331 );
 332
 333 static int init_aio(void)
 334 {
 335         int err;
 336
 337         CHOOSE_MODE(({ if(!aio_24){
 338                             printk("Disabling 2.6 AIO in tt mode\n");
 339                             aio_24 = 1;
 340                     } }), (void) 0);
 341
 342         if(!aio_24){
 343                 err = init_aio_26();
 344                 if(err && (errno == ENOSYS)){
 345                         printk("2.6 AIO not supported on the host - "
 346                                "reverting to 2.4 AIO\n");
 347                         aio_24 = 1;
 348                 }
 349                 else return err;
 350         }
 351
 352         if(aio_24)
 353                 return init_aio_24();
 354
 355         return 0;
 356 }
 357
 358 /* The reason for the __initcall/__uml_exitcall asymmetry is that init_aio
 359  * needs to be called when the kernel is running because it calls run_helper,
 360  * which needs get_free_page.  exit_aio is a __uml_exitcall because the generic
 361  * kernel does not run __exitcalls on shutdown, and can't because many of them
 362  * break when called outside of module unloading.
 363  */
 364 __initcall(init_aio);
 365
 366 static void exit_aio(void)
 367 {
 368         if(aio_pid != -1)
 369                 os_kill_process(aio_pid, 1);
 370 }
 371
 372 __uml_exitcall(exit_aio);
 373
 374 static int submit_aio_24(enum aio_type type, int io_fd, char *buf, int len,
 375                          unsigned long long offset, struct aio_context *aio)
 376 {
 377         struct aio_thread_req req = { .type             = type,
 378                                       .io_fd            = io_fd,
 379                                       .offset           = offset,
 380                                       .buf              = buf,
 381                                       .len              = len,
 382                                       .aio              = aio,
 383         };
 384         int err;
 385
 386         err = write(aio_req_fd_w, &req, sizeof(req));
 387         if(err == sizeof(req))
 388                 err = 0;
 389         else err = -errno;
 390
 391         return err;
 392 }
 393
 394 int submit_aio(enum aio_type type, int io_fd, char *buf, int len,
 395                unsigned long long offset, int reply_fd,
 396                struct aio_context *aio)
 397 {
 398         aio->reply_fd = reply_fd;
 399         if(aio_24)
 400                 return submit_aio_24(type, io_fd, buf, len, offset, aio);
 401         else {
 402                 return submit_aio_26(type, io_fd, buf, len, offset, aio);
 403         }
 404 }