fs/pipe.c

   1 /*
   2  *  linux/fs/pipe.c
   3  *
   4  *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
   5  */
   6
   7 #include <linux/mm.h>
   8 #include <linux/file.h>
   9 #include <linux/poll.h>
  10 #include <linux/slab.h>
  11 #include <linux/module.h>
  12 #include <linux/init.h>
  13 #include <linux/fs.h>
  14 #include <linux/mount.h>
  15 #include <linux/pipe_fs_i.h>
  16 #include <linux/uio.h>
  17 #include <linux/highmem.h>
  18
  19 #include <asm/uaccess.h>
  20 #include <asm/ioctls.h>
  21
  22 /*
  23  * We use a start+len construction, which provides full use of the
  24  * allocated memory.
  25  * -- Florian Coosmann (FGC)
  26  *
  27  * Reads with count = 0 should always return 0.
  28  * -- Julian Bradfield 1999-06-07.
  29  *
  30  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  31  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  32  *
  33  * pipe_read & write cleanup
  34  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  35  */
  36
  37 /* Drop the inode semaphore and wait for a pipe event, atomically */
  38 void pipe_wait(struct inode * inode)
  39 {
  40         DEFINE_WAIT(wait);
  41
  42         /*
  43          * Pipes are system-local resources, so sleeping on them
  44          * is considered a noninteractive wait:
  45          */
  46         prepare_to_wait(PIPE_WAIT(*inode), &wait, TASK_INTERRUPTIBLE|TASK_NONINTERACTIVE);
  47         mutex_unlock(PIPE_MUTEX(*inode));
  48         schedule();
  49         finish_wait(PIPE_WAIT(*inode), &wait);
  50         mutex_lock(PIPE_MUTEX(*inode));
  51 }
  52
  53 static int
  54 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len)
  55 {
  56         unsigned long copy;
  57
  58         while (len > 0) {
  59                 while (!iov->iov_len)
  60                         iov++;
  61                 copy = min_t(unsigned long, len, iov->iov_len);
  62
  63                 if (copy_from_user(to, iov->iov_base, copy))
  64                         return -EFAULT;
  65                 to += copy;
  66                 len -= copy;
  67                 iov->iov_base += copy;
  68                 iov->iov_len -= copy;
  69         }
  70         return 0;
  71 }
  72
  73 static int
  74 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len)
  75 {
  76         unsigned long copy;
  77
  78         while (len > 0) {
  79                 while (!iov->iov_len)
  80                         iov++;
  81                 copy = min_t(unsigned long, len, iov->iov_len);
  82
  83                 if (copy_to_user(iov->iov_base, from, copy))
  84                         return -EFAULT;
  85                 from += copy;
  86                 len -= copy;
  87                 iov->iov_base += copy;
  88                 iov->iov_len -= copy;
  89         }
  90         return 0;
  91 }
  92
  93 static void anon_pipe_buf_release(struct pipe_inode_info *info, struct pipe_buffer *buf)
  94 {
  95         struct page *page = buf->page;
  96
  97         if (info->tmp_page) {
  98                 __free_page(page);
  99                 return;
 100         }
 101         info->tmp_page = page;
 102 }
 103
 104 static void *anon_pipe_buf_map(struct file *file, struct pipe_inode_info *info, struct pipe_buffer *buf)
 105 {
 106         return kmap(buf->page);
 107 }
 108
 109 static void anon_pipe_buf_unmap(struct pipe_inode_info *info, struct pipe_buffer *buf)
 110 {
 111         kunmap(buf->page);
 112 }
 113
 114 static struct pipe_buf_operations anon_pipe_buf_ops = {
 115         .can_merge = 1,
 116         .map = anon_pipe_buf_map,
 117         .unmap = anon_pipe_buf_unmap,
 118         .release = anon_pipe_buf_release,
 119 };
 120
 121 static ssize_t
 122 pipe_readv(struct file *filp, const struct iovec *_iov,
 123            unsigned long nr_segs, loff_t *ppos)
 124 {
 125         struct inode *inode = filp->f_dentry->d_inode;
 126         struct pipe_inode_info *info;
 127         int do_wakeup;
 128         ssize_t ret;
 129         struct iovec *iov = (struct iovec *)_iov;
 130         size_t total_len;
 131
 132         total_len = iov_length(iov, nr_segs);
 133         /* Null read succeeds. */
 134         if (unlikely(total_len == 0))
 135                 return 0;
 136
 137         do_wakeup = 0;
 138         ret = 0;
 139         mutex_lock(PIPE_MUTEX(*inode));
 140         info = inode->i_pipe;
 141         for (;;) {
 142                 int bufs = info->nrbufs;
 143                 if (bufs) {
 144                         int curbuf = info->curbuf;
 145                         struct pipe_buffer *buf = info->bufs + curbuf;
 146                         struct pipe_buf_operations *ops = buf->ops;
 147                         void *addr;
 148                         size_t chars = buf->len;
 149                         int error;
 150
 151                         if (chars > total_len)
 152                                 chars = total_len;
 153
 154                         addr = ops->map(filp, info, buf);
 155                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars);
 156                         ops->unmap(info, buf);
 157                         if (unlikely(error)) {
 158                                 if (!ret) ret = -EFAULT;
 159                                 break;
 160                         }
 161                         ret += chars;
 162                         buf->offset += chars;
 163                         buf->len -= chars;
 164                         if (!buf->len) {
 165                                 buf->ops = NULL;
 166                                 ops->release(info, buf);
 167                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
 168                                 info->curbuf = curbuf;
 169                                 info->nrbufs = --bufs;
 170                                 do_wakeup = 1;
 171                         }
 172                         total_len -= chars;
 173                         if (!total_len)
 174                                 break;  /* common path: read succeeded */
 175                 }
 176                 if (bufs)       /* More to do? */
 177                         continue;
 178                 if (!PIPE_WRITERS(*inode))
 179                         break;
 180                 if (!PIPE_WAITING_WRITERS(*inode)) {
 181                         /* syscall merging: Usually we must not sleep
 182                          * if O_NONBLOCK is set, or if we got some data.
 183                          * But if a writer sleeps in kernel space, then
 184                          * we can wait for that data without violating POSIX.
 185                          */
 186                         if (ret)
 187                                 break;
 188                         if (filp->f_flags & O_NONBLOCK) {
 189                                 ret = -EAGAIN;
 190                                 break;
 191                         }
 192                 }
 193                 if (signal_pending(current)) {
 194                         if (!ret) ret = -ERESTARTSYS;
 195                         break;
 196                 }
 197                 if (do_wakeup) {
 198                         wake_up_interruptible_sync(PIPE_WAIT(*inode));
 199                         kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
 200                 }
 201                 pipe_wait(inode);
 202         }
 203         mutex_unlock(PIPE_MUTEX(*inode));
 204         /* Signal writers asynchronously that there is more room.  */
 205         if (do_wakeup) {
 206                 wake_up_interruptible(PIPE_WAIT(*inode));
 207                 kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
 208         }
 209         if (ret > 0)
 210                 file_accessed(filp);
 211         return ret;
 212 }
 213
 214 static ssize_t
 215 pipe_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 216 {
 217         struct iovec iov = { .iov_base = buf, .iov_len = count };
 218         return pipe_readv(filp, &iov, 1, ppos);
 219 }
 220
 221 static ssize_t
 222 pipe_writev(struct file *filp, const struct iovec *_iov,
 223             unsigned long nr_segs, loff_t *ppos)
 224 {
 225         struct inode *inode = filp->f_dentry->d_inode;
 226         struct pipe_inode_info *info;
 227         ssize_t ret;
 228         int do_wakeup;
 229         struct iovec *iov = (struct iovec *)_iov;
 230         size_t total_len;
 231         ssize_t chars;
 232
 233         total_len = iov_length(iov, nr_segs);
 234         /* Null write succeeds. */
 235         if (unlikely(total_len == 0))
 236                 return 0;
 237
 238         do_wakeup = 0;
 239         ret = 0;
 240         mutex_lock(PIPE_MUTEX(*inode));
 241         info = inode->i_pipe;
 242
 243         if (!PIPE_READERS(*inode)) {
 244                 send_sig(SIGPIPE, current, 0);
 245                 ret = -EPIPE;
 246                 goto out;
 247         }
 248
 249         /* We try to merge small writes */
 250         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 251         if (info->nrbufs && chars != 0) {
 252                 int lastbuf = (info->curbuf + info->nrbufs - 1) & (PIPE_BUFFERS-1);
 253                 struct pipe_buffer *buf = info->bufs + lastbuf;
 254                 struct pipe_buf_operations *ops = buf->ops;
 255                 int offset = buf->offset + buf->len;
 256                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 257                         void *addr = ops->map(filp, info, buf);
 258                         int error = pipe_iov_copy_from_user(offset + addr, iov, chars);
 259                         ops->unmap(info, buf);
 260                         ret = error;
 261                         do_wakeup = 1;
 262                         if (error)
 263                                 goto out;
 264                         buf->len += chars;
 265                         total_len -= chars;
 266                         ret = chars;
 267                         if (!total_len)
 268                                 goto out;
 269                 }
 270         }
 271
 272         for (;;) {
 273                 int bufs;
 274                 if (!PIPE_READERS(*inode)) {
 275                         send_sig(SIGPIPE, current, 0);
 276                         if (!ret) ret = -EPIPE;
 277                         break;
 278                 }
 279                 bufs = info->nrbufs;
 280                 if (bufs < PIPE_BUFFERS) {
 281                         int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS-1);
 282                         struct pipe_buffer *buf = info->bufs + newbuf;
 283                         struct page *page = info->tmp_page;
 284                         int error;
 285
 286                         if (!page) {
 287                                 page = alloc_page(GFP_HIGHUSER);
 288                                 if (unlikely(!page)) {
 289                                         ret = ret ? : -ENOMEM;
 290                                         break;
 291                                 }
 292                                 info->tmp_page = page;
 293                         }
 294                         /* Always wakeup, even if the copy fails. Otherwise
 295                          * we lock up (O_NONBLOCK-)readers that sleep due to
 296                          * syscall merging.
 297                          * FIXME! Is this really true?
 298                          */
 299                         do_wakeup = 1;
 300                         chars = PAGE_SIZE;
 301                         if (chars > total_len)
 302                                 chars = total_len;
 303
 304                         error = pipe_iov_copy_from_user(kmap(page), iov, chars);
 305                         kunmap(page);
 306                         if (unlikely(error)) {
 307                                 if (!ret) ret = -EFAULT;
 308                                 break;
 309                         }
 310                         ret += chars;
 311
 312                         /* Insert it into the buffer array */
 313                         buf->page = page;
 314                         buf->ops = &anon_pipe_buf_ops;
 315                         buf->offset = 0;
 316                         buf->len = chars;
 317                         info->nrbufs = ++bufs;
 318                         info->tmp_page = NULL;
 319
 320                         total_len -= chars;
 321                         if (!total_len)
 322                                 break;
 323                 }
 324                 if (bufs < PIPE_BUFFERS)
 325                         continue;
 326                 if (filp->f_flags & O_NONBLOCK) {
 327                         if (!ret) ret = -EAGAIN;
 328                         break;
 329                 }
 330                 if (signal_pending(current)) {
 331                         if (!ret) ret = -ERESTARTSYS;
 332                         break;
 333                 }
 334                 if (do_wakeup) {
 335                         wake_up_interruptible_sync(PIPE_WAIT(*inode));
 336                         kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
 337                         do_wakeup = 0;
 338                 }
 339                 PIPE_WAITING_WRITERS(*inode)++;
 340                 pipe_wait(inode);
 341                 PIPE_WAITING_WRITERS(*inode)--;
 342         }
 343 out:
 344         mutex_unlock(PIPE_MUTEX(*inode));
 345         if (do_wakeup) {
 346                 wake_up_interruptible(PIPE_WAIT(*inode));
 347                 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
 348         }
 349         if (ret > 0)
 350                 file_update_time(filp);
 351         return ret;
 352 }
 353
 354 static ssize_t
 355 pipe_write(struct file *filp, const char __user *buf,
 356            size_t count, loff_t *ppos)
 357 {
 358         struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = count };
 359         return pipe_writev(filp, &iov, 1, ppos);
 360 }
 361
 362 static ssize_t
 363 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 364 {
 365         return -EBADF;
 366 }
 367
 368 static ssize_t
 369 bad_pipe_w(struct file *filp, const char __user *buf, size_t count, loff_t *ppos)
 370 {
 371         return -EBADF;
 372 }
 373
 374 static int
 375 pipe_ioctl(struct inode *pino, struct file *filp,
 376            unsigned int cmd, unsigned long arg)
 377 {
 378         struct inode *inode = filp->f_dentry->d_inode;
 379         struct pipe_inode_info *info;
 380         int count, buf, nrbufs;
 381
 382         switch (cmd) {
 383                 case FIONREAD:
 384                         mutex_lock(PIPE_MUTEX(*inode));
 385                         info =  inode->i_pipe;
 386                         count = 0;
 387                         buf = info->curbuf;
 388                         nrbufs = info->nrbufs;
 389                         while (--nrbufs >= 0) {
 390                                 count += info->bufs[buf].len;
 391                                 buf = (buf+1) & (PIPE_BUFFERS-1);
 392                         }
 393                         mutex_unlock(PIPE_MUTEX(*inode));
 394                         return put_user(count, (int __user *)arg);
 395                 default:
 396                         return -EINVAL;
 397         }
 398 }
 399
 400 /* No kernel lock held - fine */
 401 static unsigned int
 402 pipe_poll(struct file *filp, poll_table *wait)
 403 {
 404         unsigned int mask;
 405         struct inode *inode = filp->f_dentry->d_inode;
 406         struct pipe_inode_info *info = inode->i_pipe;
 407         int nrbufs;
 408
 409         poll_wait(filp, PIPE_WAIT(*inode), wait);
 410
 411         /* Reading only -- no need for acquiring the semaphore.  */
 412         nrbufs = info->nrbufs;
 413         mask = 0;
 414         if (filp->f_mode & FMODE_READ) {
 415                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 416                 if (!PIPE_WRITERS(*inode) && filp->f_version != PIPE_WCOUNTER(*inode))
 417                         mask |= POLLHUP;
 418         }
 419
 420         if (filp->f_mode & FMODE_WRITE) {
 421                 mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
 422                 /*
 423                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 424                  * behave exactly like pipes for poll().
 425                  */
 426                 if (!PIPE_READERS(*inode))
 427                         mask |= POLLERR;
 428         }
 429
 430         return mask;
 431 }
 432
 433 static int
 434 pipe_release(struct inode *inode, int decr, int decw)
 435 {
 436         mutex_lock(PIPE_MUTEX(*inode));
 437         PIPE_READERS(*inode) -= decr;
 438         PIPE_WRITERS(*inode) -= decw;
 439         if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode)) {
 440                 free_pipe_info(inode);
 441         } else {
 442                 wake_up_interruptible(PIPE_WAIT(*inode));
 443                 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
 444                 kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
 445         }
 446         mutex_unlock(PIPE_MUTEX(*inode));
 447
 448         return 0;
 449 }
 450
 451 static int
 452 pipe_read_fasync(int fd, struct file *filp, int on)
 453 {
 454         struct inode *inode = filp->f_dentry->d_inode;
 455         int retval;
 456
 457         mutex_lock(PIPE_MUTEX(*inode));
 458         retval = fasync_helper(fd, filp, on, PIPE_FASYNC_READERS(*inode));
 459         mutex_unlock(PIPE_MUTEX(*inode));
 460
 461         if (retval < 0)
 462                 return retval;
 463
 464         return 0;
 465 }
 466
 467
 468 static int
 469 pipe_write_fasync(int fd, struct file *filp, int on)
 470 {
 471         struct inode *inode = filp->f_dentry->d_inode;
 472         int retval;
 473
 474         mutex_lock(PIPE_MUTEX(*inode));
 475         retval = fasync_helper(fd, filp, on, PIPE_FASYNC_WRITERS(*inode));
 476         mutex_unlock(PIPE_MUTEX(*inode));
 477
 478         if (retval < 0)
 479                 return retval;
 480
 481         return 0;
 482 }
 483
 484
 485 static int
 486 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 487 {
 488         struct inode *inode = filp->f_dentry->d_inode;
 489         int retval;
 490
 491         mutex_lock(PIPE_MUTEX(*inode));
 492
 493         retval = fasync_helper(fd, filp, on, PIPE_FASYNC_READERS(*inode));
 494
 495         if (retval >= 0)
 496                 retval = fasync_helper(fd, filp, on, PIPE_FASYNC_WRITERS(*inode));
 497
 498         mutex_unlock(PIPE_MUTEX(*inode));
 499
 500         if (retval < 0)
 501                 return retval;
 502
 503         return 0;
 504 }
 505
 506
 507 static int
 508 pipe_read_release(struct inode *inode, struct file *filp)
 509 {
 510         pipe_read_fasync(-1, filp, 0);
 511         return pipe_release(inode, 1, 0);
 512 }
 513
 514 static int
 515 pipe_write_release(struct inode *inode, struct file *filp)
 516 {
 517         pipe_write_fasync(-1, filp, 0);
 518         return pipe_release(inode, 0, 1);
 519 }
 520
 521 static int
 522 pipe_rdwr_release(struct inode *inode, struct file *filp)
 523 {
 524         int decr, decw;
 525
 526         pipe_rdwr_fasync(-1, filp, 0);
 527         decr = (filp->f_mode & FMODE_READ) != 0;
 528         decw = (filp->f_mode & FMODE_WRITE) != 0;
 529         return pipe_release(inode, decr, decw);
 530 }
 531
 532 static int
 533 pipe_read_open(struct inode *inode, struct file *filp)
 534 {
 535         /* We could have perhaps used atomic_t, but this and friends
 536            below are the only places.  So it doesn't seem worthwhile.  */
 537         mutex_lock(PIPE_MUTEX(*inode));
 538         PIPE_READERS(*inode)++;
 539         mutex_unlock(PIPE_MUTEX(*inode));
 540
 541         return 0;
 542 }
 543
 544 static int
 545 pipe_write_open(struct inode *inode, struct file *filp)
 546 {
 547         mutex_lock(PIPE_MUTEX(*inode));
 548         PIPE_WRITERS(*inode)++;
 549         mutex_unlock(PIPE_MUTEX(*inode));
 550
 551         return 0;
 552 }
 553
 554 static int
 555 pipe_rdwr_open(struct inode *inode, struct file *filp)
 556 {
 557         mutex_lock(PIPE_MUTEX(*inode));
 558         if (filp->f_mode & FMODE_READ)
 559                 PIPE_READERS(*inode)++;
 560         if (filp->f_mode & FMODE_WRITE)
 561                 PIPE_WRITERS(*inode)++;
 562         mutex_unlock(PIPE_MUTEX(*inode));
 563
 564         return 0;
 565 }
 566
 567 /*
 568  * The file_operations structs are not static because they
 569  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 570  */
 571 const struct file_operations read_fifo_fops = {
 572         .llseek         = no_llseek,
 573         .read           = pipe_read,
 574         .readv          = pipe_readv,
 575         .write          = bad_pipe_w,
 576         .poll           = pipe_poll,
 577         .ioctl          = pipe_ioctl,
 578         .open           = pipe_read_open,
 579         .release        = pipe_read_release,
 580         .fasync         = pipe_read_fasync,
 581 };
 582
 583 const struct file_operations write_fifo_fops = {
 584         .llseek         = no_llseek,
 585         .read           = bad_pipe_r,
 586         .write          = pipe_write,
 587         .writev         = pipe_writev,
 588         .poll           = pipe_poll,
 589         .ioctl          = pipe_ioctl,
 590         .open           = pipe_write_open,
 591         .release        = pipe_write_release,
 592         .fasync         = pipe_write_fasync,
 593 };
 594
 595 const struct file_operations rdwr_fifo_fops = {
 596         .llseek         = no_llseek,
 597         .read           = pipe_read,
 598         .readv          = pipe_readv,
 599         .write          = pipe_write,
 600         .writev         = pipe_writev,
 601         .poll           = pipe_poll,
 602         .ioctl          = pipe_ioctl,
 603         .open           = pipe_rdwr_open,
 604         .release        = pipe_rdwr_release,
 605         .fasync         = pipe_rdwr_fasync,
 606 };
 607
 608 static struct file_operations read_pipe_fops = {
 609         .llseek         = no_llseek,
 610         .read           = pipe_read,
 611         .readv          = pipe_readv,
 612         .write          = bad_pipe_w,
 613         .poll           = pipe_poll,
 614         .ioctl          = pipe_ioctl,
 615         .open           = pipe_read_open,
 616         .release        = pipe_read_release,
 617         .fasync         = pipe_read_fasync,
 618 };
 619
 620 static struct file_operations write_pipe_fops = {
 621         .llseek         = no_llseek,
 622         .read           = bad_pipe_r,
 623         .write          = pipe_write,
 624         .writev         = pipe_writev,
 625         .poll           = pipe_poll,
 626         .ioctl          = pipe_ioctl,
 627         .open           = pipe_write_open,
 628         .release        = pipe_write_release,
 629         .fasync         = pipe_write_fasync,
 630 };
 631
 632 static struct file_operations rdwr_pipe_fops = {
 633         .llseek         = no_llseek,
 634         .read           = pipe_read,
 635         .readv          = pipe_readv,
 636         .write          = pipe_write,
 637         .writev         = pipe_writev,
 638         .poll           = pipe_poll,
 639         .ioctl          = pipe_ioctl,
 640         .open           = pipe_rdwr_open,
 641         .release        = pipe_rdwr_release,
 642         .fasync         = pipe_rdwr_fasync,
 643 };
 644
 645 void free_pipe_info(struct inode *inode)
 646 {
 647         int i;
 648         struct pipe_inode_info *info = inode->i_pipe;
 649
 650         inode->i_pipe = NULL;
 651         for (i = 0; i < PIPE_BUFFERS; i++) {
 652                 struct pipe_buffer *buf = info->bufs + i;
 653                 if (buf->ops)
 654                         buf->ops->release(info, buf);
 655         }
 656         if (info->tmp_page)
 657                 __free_page(info->tmp_page);
 658         kfree(info);
 659 }
 660
 661 struct inode* pipe_new(struct inode* inode)
 662 {
 663         struct pipe_inode_info *info;
 664
 665         info = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 666         if (!info)
 667                 goto fail_page;
 668         inode->i_pipe = info;
 669
 670         init_waitqueue_head(PIPE_WAIT(*inode));
 671         PIPE_RCOUNTER(*inode) = PIPE_WCOUNTER(*inode) = 1;
 672
 673         return inode;
 674 fail_page:
 675         return NULL;
 676 }
 677
 678 static struct vfsmount *pipe_mnt __read_mostly;
 679 static int pipefs_delete_dentry(struct dentry *dentry)
 680 {
 681         return 1;
 682 }
 683 static struct dentry_operations pipefs_dentry_operations = {
 684         .d_delete       = pipefs_delete_dentry,
 685 };
 686
 687 static struct inode * get_pipe_inode(void)
 688 {
 689         struct inode *inode = new_inode(pipe_mnt->mnt_sb);
 690
 691         if (!inode)
 692                 goto fail_inode;
 693
 694         if(!pipe_new(inode))
 695                 goto fail_iput;
 696         PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 1;
 697         inode->i_fop = &rdwr_pipe_fops;
 698
 699         /*
 700          * Mark the inode dirty from the very beginning,
 701          * that way it will never be moved to the dirty
 702          * list because "mark_inode_dirty()" will think
 703          * that it already _is_ on the dirty list.
 704          */
 705         inode->i_state = I_DIRTY;
 706         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 707         inode->i_uid = current->fsuid;
 708         inode->i_gid = current->fsgid;
 709         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 710         inode->i_blksize = PAGE_SIZE;
 711         return inode;
 712
 713 fail_iput:
 714         iput(inode);
 715 fail_inode:
 716         return NULL;
 717 }
 718
 719 int do_pipe(int *fd)
 720 {
 721         struct qstr this;
 722         char name[32];
 723         struct dentry *dentry;
 724         struct inode * inode;
 725         struct file *f1, *f2;
 726         int error;
 727         int i,j;
 728
 729         error = -ENFILE;
 730         f1 = get_empty_filp();
 731         if (!f1)
 732                 goto no_files;
 733
 734         f2 = get_empty_filp();
 735         if (!f2)
 736                 goto close_f1;
 737
 738         inode = get_pipe_inode();
 739         if (!inode)
 740                 goto close_f12;
 741
 742         error = get_unused_fd();
 743         if (error < 0)
 744                 goto close_f12_inode;
 745         i = error;
 746
 747         error = get_unused_fd();
 748         if (error < 0)
 749                 goto close_f12_inode_i;
 750         j = error;
 751
 752         error = -ENOMEM;
 753         sprintf(name, "[%lu]", inode->i_ino);
 754         this.name = name;
 755         this.len = strlen(name);
 756         this.hash = inode->i_ino; /* will go */
 757         dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this);
 758         if (!dentry)
 759                 goto close_f12_inode_i_j;
 760         dentry->d_op = &pipefs_dentry_operations;
 761         d_add(dentry, inode);
 762         f1->f_vfsmnt = f2->f_vfsmnt = mntget(mntget(pipe_mnt));
 763         f1->f_dentry = f2->f_dentry = dget(dentry);
 764         f1->f_mapping = f2->f_mapping = inode->i_mapping;
 765
 766         /* read file */
 767         f1->f_pos = f2->f_pos = 0;
 768         f1->f_flags = O_RDONLY;
 769         f1->f_op = &read_pipe_fops;
 770         f1->f_mode = FMODE_READ;
 771         f1->f_version = 0;
 772
 773         /* write file */
 774         f2->f_flags = O_WRONLY;
 775         f2->f_op = &write_pipe_fops;
 776         f2->f_mode = FMODE_WRITE;
 777         f2->f_version = 0;
 778
 779         fd_install(i, f1);
 780         fd_install(j, f2);
 781         fd[0] = i;
 782         fd[1] = j;
 783         return 0;
 784
 785 close_f12_inode_i_j:
 786         put_unused_fd(j);
 787 close_f12_inode_i:
 788         put_unused_fd(i);
 789 close_f12_inode:
 790         free_pipe_info(inode);
 791         iput(inode);
 792 close_f12:
 793         put_filp(f2);
 794 close_f1:
 795         put_filp(f1);
 796 no_files:
 797         return error;
 798 }
 799
 800 /*
 801  * pipefs should _never_ be mounted by userland - too much of security hassle,
 802  * no real gain from having the whole whorehouse mounted. So we don't need
 803  * any operations on the root directory. However, we need a non-trivial
 804  * d_name - pipe: will go nicely and kill the special-casing in procfs.
 805  */
 806
 807 static struct super_block *pipefs_get_sb(struct file_system_type *fs_type,
 808         int flags, const char *dev_name, void *data)
 809 {
 810         return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC);
 811 }
 812
 813 static struct file_system_type pipe_fs_type = {
 814         .name           = "pipefs",
 815         .get_sb         = pipefs_get_sb,
 816         .kill_sb        = kill_anon_super,
 817 };
 818
 819 static int __init init_pipe_fs(void)
 820 {
 821         int err = register_filesystem(&pipe_fs_type);
 822         if (!err) {
 823                 pipe_mnt = kern_mount(&pipe_fs_type);
 824                 if (IS_ERR(pipe_mnt)) {
 825                         err = PTR_ERR(pipe_mnt);
 826                         unregister_filesystem(&pipe_fs_type);
 827                 }
 828         }
 829         return err;
 830 }
 831
 832 static void __exit exit_pipe_fs(void)
 833 {
 834         unregister_filesystem(&pipe_fs_type);
 835         mntput(pipe_mnt);
 836 }
 837
 838 fs_initcall(init_pipe_fs);
 839 module_exit(exit_pipe_fs);