SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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 #include <linux/pagemap.h>
  19
  20 #include <asm/uaccess.h>
  21 #include <asm/ioctls.h>
  22
  23 /*
  24  * We use a start+len construction, which provides full use of the
  25  * allocated memory.
  26  * -- Florian Coosmann (FGC)
  27  *
  28  * Reads with count = 0 should always return 0.
  29  * -- Julian Bradfield 1999-06-07.
  30  *
  31  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  32  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  33  *
  34  * pipe_read & write cleanup
  35  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  36  */
  37
  38 /* Drop the inode semaphore and wait for a pipe event, atomically */
  39 void pipe_wait(struct pipe_inode_info *pipe)
  40 {
  41         DEFINE_WAIT(wait);
  42
  43         /*
  44          * Pipes are system-local resources, so sleeping on them
  45          * is considered a noninteractive wait:
  46          */
  47         prepare_to_wait(&pipe->wait, &wait,
  48                         TASK_INTERRUPTIBLE | TASK_NONINTERACTIVE);
  49         if (pipe->inode)
  50                 mutex_unlock(&pipe->inode->i_mutex);
  51         schedule();
  52         finish_wait(&pipe->wait, &wait);
  53         if (pipe->inode)
  54                 mutex_lock(&pipe->inode->i_mutex);
  55 }
  56
  57 static int
  58 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len)
  59 {
  60         unsigned long copy;
  61
  62         while (len > 0) {
  63                 while (!iov->iov_len)
  64                         iov++;
  65                 copy = min_t(unsigned long, len, iov->iov_len);
  66
  67                 if (copy_from_user(to, iov->iov_base, copy))
  68                         return -EFAULT;
  69                 to += copy;
  70                 len -= copy;
  71                 iov->iov_base += copy;
  72                 iov->iov_len -= copy;
  73         }
  74         return 0;
  75 }
  76
  77 static int
  78 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len)
  79 {
  80         unsigned long copy;
  81
  82         while (len > 0) {
  83                 while (!iov->iov_len)
  84                         iov++;
  85                 copy = min_t(unsigned long, len, iov->iov_len);
  86
  87                 if (copy_to_user(iov->iov_base, from, copy))
  88                         return -EFAULT;
  89                 from += copy;
  90                 len -= copy;
  91                 iov->iov_base += copy;
  92                 iov->iov_len -= copy;
  93         }
  94         return 0;
  95 }
  96
  97 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
  98                                   struct pipe_buffer *buf)
  99 {
 100         struct page *page = buf->page;
 101
 102         /*
 103          * If nobody else uses this page, and we don't already have a
 104          * temporary page, let's keep track of it as a one-deep
 105          * allocation cache. (Otherwise just release our reference to it)
 106          */
 107         if (page_count(page) == 1 && !pipe->tmp_page)
 108                 pipe->tmp_page = page;
 109         else
 110                 page_cache_release(page);
 111 }
 112
 113 static void * anon_pipe_buf_map(struct file *file, struct pipe_inode_info *pipe,
 114                                 struct pipe_buffer *buf)
 115 {
 116         return kmap(buf->page);
 117 }
 118
 119 static void anon_pipe_buf_unmap(struct pipe_inode_info *pipe,
 120                                 struct pipe_buffer *buf)
 121 {
 122         kunmap(buf->page);
 123 }
 124
 125 static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
 126                                struct pipe_buffer *buf)
 127 {
 128         struct page *page = buf->page;
 129
 130         if (page_count(page) == 1) {
 131                 lock_page(page);
 132                 return 0;
 133         }
 134
 135         return 1;
 136 }
 137
 138 static void anon_pipe_buf_get(struct pipe_inode_info *info,
 139                               struct pipe_buffer *buf)
 140 {
 141         page_cache_get(buf->page);
 142 }
 143
 144 static struct pipe_buf_operations anon_pipe_buf_ops = {
 145         .can_merge = 1,
 146         .map = anon_pipe_buf_map,
 147         .unmap = anon_pipe_buf_unmap,
 148         .release = anon_pipe_buf_release,
 149         .steal = anon_pipe_buf_steal,
 150         .get = anon_pipe_buf_get,
 151 };
 152
 153 static ssize_t
 154 pipe_readv(struct file *filp, const struct iovec *_iov,
 155            unsigned long nr_segs, loff_t *ppos)
 156 {
 157         struct inode *inode = filp->f_dentry->d_inode;
 158         struct pipe_inode_info *pipe;
 159         int do_wakeup;
 160         ssize_t ret;
 161         struct iovec *iov = (struct iovec *)_iov;
 162         size_t total_len;
 163
 164         total_len = iov_length(iov, nr_segs);
 165         /* Null read succeeds. */
 166         if (unlikely(total_len == 0))
 167                 return 0;
 168
 169         do_wakeup = 0;
 170         ret = 0;
 171         mutex_lock(&inode->i_mutex);
 172         pipe = inode->i_pipe;
 173         for (;;) {
 174                 int bufs = pipe->nrbufs;
 175                 if (bufs) {
 176                         int curbuf = pipe->curbuf;
 177                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 178                         struct pipe_buf_operations *ops = buf->ops;
 179                         void *addr;
 180                         size_t chars = buf->len;
 181                         int error;
 182
 183                         if (chars > total_len)
 184                                 chars = total_len;
 185
 186                         addr = ops->map(filp, pipe, buf);
 187                         if (IS_ERR(addr)) {
 188                                 if (!ret)
 189                                         ret = PTR_ERR(addr);
 190                                 break;
 191                         }
 192                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars);
 193                         ops->unmap(pipe, buf);
 194                         if (unlikely(error)) {
 195                                 if (!ret)
 196                                         ret = -EFAULT;
 197                                 break;
 198                         }
 199                         ret += chars;
 200                         buf->offset += chars;
 201                         buf->len -= chars;
 202                         if (!buf->len) {
 203                                 buf->ops = NULL;
 204                                 ops->release(pipe, buf);
 205                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
 206                                 pipe->curbuf = curbuf;
 207                                 pipe->nrbufs = --bufs;
 208                                 do_wakeup = 1;
 209                         }
 210                         total_len -= chars;
 211                         if (!total_len)
 212                                 break;  /* common path: read succeeded */
 213                 }
 214                 if (bufs)       /* More to do? */
 215                         continue;
 216                 if (!pipe->writers)
 217                         break;
 218                 if (!pipe->waiting_writers) {
 219                         /* syscall merging: Usually we must not sleep
 220                          * if O_NONBLOCK is set, or if we got some data.
 221                          * But if a writer sleeps in kernel space, then
 222                          * we can wait for that data without violating POSIX.
 223                          */
 224                         if (ret)
 225                                 break;
 226                         if (filp->f_flags & O_NONBLOCK) {
 227                                 ret = -EAGAIN;
 228                                 break;
 229                         }
 230                 }
 231                 if (signal_pending(current)) {
 232                         if (!ret)
 233                                 ret = -ERESTARTSYS;
 234                         break;
 235                 }
 236                 if (do_wakeup) {
 237                         wake_up_interruptible_sync(&pipe->wait);
 238                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 239                 }
 240                 pipe_wait(pipe);
 241         }
 242         mutex_unlock(&inode->i_mutex);
 243
 244         /* Signal writers asynchronously that there is more room. */
 245         if (do_wakeup) {
 246                 wake_up_interruptible(&pipe->wait);
 247                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 248         }
 249         if (ret > 0)
 250                 file_accessed(filp);
 251         return ret;
 252 }
 253
 254 static ssize_t
 255 pipe_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 256 {
 257         struct iovec iov = { .iov_base = buf, .iov_len = count };
 258
 259         return pipe_readv(filp, &iov, 1, ppos);
 260 }
 261
 262 static ssize_t
 263 pipe_writev(struct file *filp, const struct iovec *_iov,
 264             unsigned long nr_segs, loff_t *ppos)
 265 {
 266         struct inode *inode = filp->f_dentry->d_inode;
 267         struct pipe_inode_info *pipe;
 268         ssize_t ret;
 269         int do_wakeup;
 270         struct iovec *iov = (struct iovec *)_iov;
 271         size_t total_len;
 272         ssize_t chars;
 273
 274         total_len = iov_length(iov, nr_segs);
 275         /* Null write succeeds. */
 276         if (unlikely(total_len == 0))
 277                 return 0;
 278
 279         do_wakeup = 0;
 280         ret = 0;
 281         mutex_lock(&inode->i_mutex);
 282         pipe = inode->i_pipe;
 283
 284         if (!pipe->readers) {
 285                 send_sig(SIGPIPE, current, 0);
 286                 ret = -EPIPE;
 287                 goto out;
 288         }
 289
 290         /* We try to merge small writes */
 291         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 292         if (pipe->nrbufs && chars != 0) {
 293                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 294                                                         (PIPE_BUFFERS-1);
 295                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 296                 struct pipe_buf_operations *ops = buf->ops;
 297                 int offset = buf->offset + buf->len;
 298
 299                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 300                         void *addr;
 301                         int error;
 302
 303                         addr = ops->map(filp, pipe, buf);
 304                         if (IS_ERR(addr)) {
 305                                 error = PTR_ERR(addr);
 306                                 goto out;
 307                         }
 308                         error = pipe_iov_copy_from_user(offset + addr, iov,
 309                                                         chars);
 310                         ops->unmap(pipe, buf);
 311                         ret = error;
 312                         do_wakeup = 1;
 313                         if (error)
 314                                 goto out;
 315                         buf->len += chars;
 316                         total_len -= chars;
 317                         ret = chars;
 318                         if (!total_len)
 319                                 goto out;
 320                 }
 321         }
 322
 323         for (;;) {
 324                 int bufs;
 325
 326                 if (!pipe->readers) {
 327                         send_sig(SIGPIPE, current, 0);
 328                         if (!ret)
 329                                 ret = -EPIPE;
 330                         break;
 331                 }
 332                 bufs = pipe->nrbufs;
 333                 if (bufs < PIPE_BUFFERS) {
 334                         int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1);
 335                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 336                         struct page *page = pipe->tmp_page;
 337                         int error;
 338
 339                         if (!page) {
 340                                 page = alloc_page(GFP_HIGHUSER);
 341                                 if (unlikely(!page)) {
 342                                         ret = ret ? : -ENOMEM;
 343                                         break;
 344                                 }
 345                                 pipe->tmp_page = page;
 346                         }
 347                         /* Always wake up, even if the copy fails. Otherwise
 348                          * we lock up (O_NONBLOCK-)readers that sleep due to
 349                          * syscall merging.
 350                          * FIXME! Is this really true?
 351                          */
 352                         do_wakeup = 1;
 353                         chars = PAGE_SIZE;
 354                         if (chars > total_len)
 355                                 chars = total_len;
 356
 357                         error = pipe_iov_copy_from_user(kmap(page), iov, chars);
 358                         kunmap(page);
 359                         if (unlikely(error)) {
 360                                 if (!ret)
 361                                         ret = -EFAULT;
 362                                 break;
 363                         }
 364                         ret += chars;
 365
 366                         /* Insert it into the buffer array */
 367                         buf->page = page;
 368                         buf->ops = &anon_pipe_buf_ops;
 369                         buf->offset = 0;
 370                         buf->len = chars;
 371                         pipe->nrbufs = ++bufs;
 372                         pipe->tmp_page = NULL;
 373
 374                         total_len -= chars;
 375                         if (!total_len)
 376                                 break;
 377                 }
 378                 if (bufs < PIPE_BUFFERS)
 379                         continue;
 380                 if (filp->f_flags & O_NONBLOCK) {
 381                         if (!ret)
 382                                 ret = -EAGAIN;
 383                         break;
 384                 }
 385                 if (signal_pending(current)) {
 386                         if (!ret)
 387                                 ret = -ERESTARTSYS;
 388                         break;
 389                 }
 390                 if (do_wakeup) {
 391                         wake_up_interruptible_sync(&pipe->wait);
 392                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 393                         do_wakeup = 0;
 394                 }
 395                 pipe->waiting_writers++;
 396                 pipe_wait(pipe);
 397                 pipe->waiting_writers--;
 398         }
 399 out:
 400         mutex_unlock(&inode->i_mutex);
 401         if (do_wakeup) {
 402                 wake_up_interruptible(&pipe->wait);
 403                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 404         }
 405         if (ret > 0)
 406                 file_update_time(filp);
 407         return ret;
 408 }
 409
 410 static ssize_t
 411 pipe_write(struct file *filp, const char __user *buf,
 412            size_t count, loff_t *ppos)
 413 {
 414         struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = count };
 415
 416         return pipe_writev(filp, &iov, 1, ppos);
 417 }
 418
 419 static ssize_t
 420 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 421 {
 422         return -EBADF;
 423 }
 424
 425 static ssize_t
 426 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
 427            loff_t *ppos)
 428 {
 429         return -EBADF;
 430 }
 431
 432 static int
 433 pipe_ioctl(struct inode *pino, struct file *filp,
 434            unsigned int cmd, unsigned long arg)
 435 {
 436         struct inode *inode = filp->f_dentry->d_inode;
 437         struct pipe_inode_info *pipe;
 438         int count, buf, nrbufs;
 439
 440         switch (cmd) {
 441                 case FIONREAD:
 442                         mutex_lock(&inode->i_mutex);
 443                         pipe = inode->i_pipe;
 444                         count = 0;
 445                         buf = pipe->curbuf;
 446                         nrbufs = pipe->nrbufs;
 447                         while (--nrbufs >= 0) {
 448                                 count += pipe->bufs[buf].len;
 449                                 buf = (buf+1) & (PIPE_BUFFERS-1);
 450                         }
 451                         mutex_unlock(&inode->i_mutex);
 452
 453                         return put_user(count, (int __user *)arg);
 454                 default:
 455                         return -EINVAL;
 456         }
 457 }
 458
 459 /* No kernel lock held - fine */
 460 static unsigned int
 461 pipe_poll(struct file *filp, poll_table *wait)
 462 {
 463         unsigned int mask;
 464         struct inode *inode = filp->f_dentry->d_inode;
 465         struct pipe_inode_info *pipe = inode->i_pipe;
 466         int nrbufs;
 467
 468         poll_wait(filp, &pipe->wait, wait);
 469
 470         /* Reading only -- no need for acquiring the semaphore.  */
 471         nrbufs = pipe->nrbufs;
 472         mask = 0;
 473         if (filp->f_mode & FMODE_READ) {
 474                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 475                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 476                         mask |= POLLHUP;
 477         }
 478
 479         if (filp->f_mode & FMODE_WRITE) {
 480                 mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
 481                 /*
 482                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 483                  * behave exactly like pipes for poll().
 484                  */
 485                 if (!pipe->readers)
 486                         mask |= POLLERR;
 487         }
 488
 489         return mask;
 490 }
 491
 492 static int
 493 pipe_release(struct inode *inode, int decr, int decw)
 494 {
 495         struct pipe_inode_info *pipe;
 496
 497         mutex_lock(&inode->i_mutex);
 498         pipe = inode->i_pipe;
 499         pipe->readers -= decr;
 500         pipe->writers -= decw;
 501
 502         if (!pipe->readers && !pipe->writers) {
 503                 free_pipe_info(inode);
 504         } else {
 505                 wake_up_interruptible(&pipe->wait);
 506                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 507                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 508         }
 509         mutex_unlock(&inode->i_mutex);
 510
 511         return 0;
 512 }
 513
 514 static int
 515 pipe_read_fasync(int fd, struct file *filp, int on)
 516 {
 517         struct inode *inode = filp->f_dentry->d_inode;
 518         int retval;
 519
 520         mutex_lock(&inode->i_mutex);
 521         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
 522         mutex_unlock(&inode->i_mutex);
 523
 524         if (retval < 0)
 525                 return retval;
 526
 527         return 0;
 528 }
 529
 530
 531 static int
 532 pipe_write_fasync(int fd, struct file *filp, int on)
 533 {
 534         struct inode *inode = filp->f_dentry->d_inode;
 535         int retval;
 536
 537         mutex_lock(&inode->i_mutex);
 538         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
 539         mutex_unlock(&inode->i_mutex);
 540
 541         if (retval < 0)
 542                 return retval;
 543
 544         return 0;
 545 }
 546
 547
 548 static int
 549 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 550 {
 551         struct inode *inode = filp->f_dentry->d_inode;
 552         struct pipe_inode_info *pipe = inode->i_pipe;
 553         int retval;
 554
 555         mutex_lock(&inode->i_mutex);
 556
 557         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 558
 559         if (retval >= 0)
 560                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 561
 562         mutex_unlock(&inode->i_mutex);
 563
 564         if (retval < 0)
 565                 return retval;
 566
 567         return 0;
 568 }
 569
 570
 571 static int
 572 pipe_read_release(struct inode *inode, struct file *filp)
 573 {
 574         pipe_read_fasync(-1, filp, 0);
 575         return pipe_release(inode, 1, 0);
 576 }
 577
 578 static int
 579 pipe_write_release(struct inode *inode, struct file *filp)
 580 {
 581         pipe_write_fasync(-1, filp, 0);
 582         return pipe_release(inode, 0, 1);
 583 }
 584
 585 static int
 586 pipe_rdwr_release(struct inode *inode, struct file *filp)
 587 {
 588         int decr, decw;
 589
 590         pipe_rdwr_fasync(-1, filp, 0);
 591         decr = (filp->f_mode & FMODE_READ) != 0;
 592         decw = (filp->f_mode & FMODE_WRITE) != 0;
 593         return pipe_release(inode, decr, decw);
 594 }
 595
 596 static int
 597 pipe_read_open(struct inode *inode, struct file *filp)
 598 {
 599         /* We could have perhaps used atomic_t, but this and friends
 600            below are the only places.  So it doesn't seem worthwhile.  */
 601         mutex_lock(&inode->i_mutex);
 602         inode->i_pipe->readers++;
 603         mutex_unlock(&inode->i_mutex);
 604
 605         return 0;
 606 }
 607
 608 static int
 609 pipe_write_open(struct inode *inode, struct file *filp)
 610 {
 611         mutex_lock(&inode->i_mutex);
 612         inode->i_pipe->writers++;
 613         mutex_unlock(&inode->i_mutex);
 614
 615         return 0;
 616 }
 617
 618 static int
 619 pipe_rdwr_open(struct inode *inode, struct file *filp)
 620 {
 621         mutex_lock(&inode->i_mutex);
 622         if (filp->f_mode & FMODE_READ)
 623                 inode->i_pipe->readers++;
 624         if (filp->f_mode & FMODE_WRITE)
 625                 inode->i_pipe->writers++;
 626         mutex_unlock(&inode->i_mutex);
 627
 628         return 0;
 629 }
 630
 631 /*
 632  * The file_operations structs are not static because they
 633  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 634  */
 635 const struct file_operations read_fifo_fops = {
 636         .llseek         = no_llseek,
 637         .read           = pipe_read,
 638         .readv          = pipe_readv,
 639         .write          = bad_pipe_w,
 640         .poll           = pipe_poll,
 641         .ioctl          = pipe_ioctl,
 642         .open           = pipe_read_open,
 643         .release        = pipe_read_release,
 644         .fasync         = pipe_read_fasync,
 645 };
 646
 647 const struct file_operations write_fifo_fops = {
 648         .llseek         = no_llseek,
 649         .read           = bad_pipe_r,
 650         .write          = pipe_write,
 651         .writev         = pipe_writev,
 652         .poll           = pipe_poll,
 653         .ioctl          = pipe_ioctl,
 654         .open           = pipe_write_open,
 655         .release        = pipe_write_release,
 656         .fasync         = pipe_write_fasync,
 657 };
 658
 659 const struct file_operations rdwr_fifo_fops = {
 660         .llseek         = no_llseek,
 661         .read           = pipe_read,
 662         .readv          = pipe_readv,
 663         .write          = pipe_write,
 664         .writev         = pipe_writev,
 665         .poll           = pipe_poll,
 666         .ioctl          = pipe_ioctl,
 667         .open           = pipe_rdwr_open,
 668         .release        = pipe_rdwr_release,
 669         .fasync         = pipe_rdwr_fasync,
 670 };
 671
 672 static struct file_operations read_pipe_fops = {
 673         .llseek         = no_llseek,
 674         .read           = pipe_read,
 675         .readv          = pipe_readv,
 676         .write          = bad_pipe_w,
 677         .poll           = pipe_poll,
 678         .ioctl          = pipe_ioctl,
 679         .open           = pipe_read_open,
 680         .release        = pipe_read_release,
 681         .fasync         = pipe_read_fasync,
 682 };
 683
 684 static struct file_operations write_pipe_fops = {
 685         .llseek         = no_llseek,
 686         .read           = bad_pipe_r,
 687         .write          = pipe_write,
 688         .writev         = pipe_writev,
 689         .poll           = pipe_poll,
 690         .ioctl          = pipe_ioctl,
 691         .open           = pipe_write_open,
 692         .release        = pipe_write_release,
 693         .fasync         = pipe_write_fasync,
 694 };
 695
 696 static struct file_operations rdwr_pipe_fops = {
 697         .llseek         = no_llseek,
 698         .read           = pipe_read,
 699         .readv          = pipe_readv,
 700         .write          = pipe_write,
 701         .writev         = pipe_writev,
 702         .poll           = pipe_poll,
 703         .ioctl          = pipe_ioctl,
 704         .open           = pipe_rdwr_open,
 705         .release        = pipe_rdwr_release,
 706         .fasync         = pipe_rdwr_fasync,
 707 };
 708
 709 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
 710 {
 711         struct pipe_inode_info *pipe;
 712
 713         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 714         if (pipe) {
 715                 init_waitqueue_head(&pipe->wait);
 716                 pipe->r_counter = pipe->w_counter = 1;
 717                 pipe->inode = inode;
 718         }
 719
 720         return pipe;
 721 }
 722
 723 void __free_pipe_info(struct pipe_inode_info *pipe)
 724 {
 725         int i;
 726
 727         for (i = 0; i < PIPE_BUFFERS; i++) {
 728                 struct pipe_buffer *buf = pipe->bufs + i;
 729                 if (buf->ops)
 730                         buf->ops->release(pipe, buf);
 731         }
 732         if (pipe->tmp_page)
 733                 __free_page(pipe->tmp_page);
 734         kfree(pipe);
 735 }
 736
 737 void free_pipe_info(struct inode *inode)
 738 {
 739         __free_pipe_info(inode->i_pipe);
 740         inode->i_pipe = NULL;
 741 }
 742
 743 static struct vfsmount *pipe_mnt __read_mostly;
 744 static int pipefs_delete_dentry(struct dentry *dentry)
 745 {
 746         return 1;
 747 }
 748
 749 static struct dentry_operations pipefs_dentry_operations = {
 750         .d_delete       = pipefs_delete_dentry,
 751 };
 752
 753 static struct inode * get_pipe_inode(void)
 754 {
 755         struct inode *inode = new_inode(pipe_mnt->mnt_sb);
 756         struct pipe_inode_info *pipe;
 757
 758         if (!inode)
 759                 goto fail_inode;
 760
 761         pipe = alloc_pipe_info(inode);
 762         if (!pipe)
 763                 goto fail_iput;
 764         inode->i_pipe = pipe;
 765
 766         pipe->readers = pipe->writers = 1;
 767         inode->i_fop = &rdwr_pipe_fops;
 768
 769         /*
 770          * Mark the inode dirty from the very beginning,
 771          * that way it will never be moved to the dirty
 772          * list because "mark_inode_dirty()" will think
 773          * that it already _is_ on the dirty list.
 774          */
 775         inode->i_state = I_DIRTY;
 776         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 777         inode->i_uid = current->fsuid;
 778         inode->i_gid = current->fsgid;
 779         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 780         inode->i_blksize = PAGE_SIZE;
 781
 782         return inode;
 783
 784 fail_iput:
 785         iput(inode);
 786
 787 fail_inode:
 788         return NULL;
 789 }
 790
 791 int do_pipe(int *fd)
 792 {
 793         struct qstr this;
 794         char name[32];
 795         struct dentry *dentry;
 796         struct inode * inode;
 797         struct file *f1, *f2;
 798         int error;
 799         int i, j;
 800
 801         error = -ENFILE;
 802         f1 = get_empty_filp();
 803         if (!f1)
 804                 goto no_files;
 805
 806         f2 = get_empty_filp();
 807         if (!f2)
 808                 goto close_f1;
 809
 810         inode = get_pipe_inode();
 811         if (!inode)
 812                 goto close_f12;
 813
 814         error = get_unused_fd();
 815         if (error < 0)
 816                 goto close_f12_inode;
 817         i = error;
 818
 819         error = get_unused_fd();
 820         if (error < 0)
 821                 goto close_f12_inode_i;
 822         j = error;
 823
 824         error = -ENOMEM;
 825         sprintf(name, "[%lu]", inode->i_ino);
 826         this.name = name;
 827         this.len = strlen(name);
 828         this.hash = inode->i_ino; /* will go */
 829         dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this);
 830         if (!dentry)
 831                 goto close_f12_inode_i_j;
 832
 833         dentry->d_op = &pipefs_dentry_operations;
 834         d_add(dentry, inode);
 835         f1->f_vfsmnt = f2->f_vfsmnt = mntget(mntget(pipe_mnt));
 836         f1->f_dentry = f2->f_dentry = dget(dentry);
 837         f1->f_mapping = f2->f_mapping = inode->i_mapping;
 838
 839         /* read file */
 840         f1->f_pos = f2->f_pos = 0;
 841         f1->f_flags = O_RDONLY;
 842         f1->f_op = &read_pipe_fops;
 843         f1->f_mode = FMODE_READ;
 844         f1->f_version = 0;
 845
 846         /* write file */
 847         f2->f_flags = O_WRONLY;
 848         f2->f_op = &write_pipe_fops;
 849         f2->f_mode = FMODE_WRITE;
 850         f2->f_version = 0;
 851
 852         fd_install(i, f1);
 853         fd_install(j, f2);
 854         fd[0] = i;
 855         fd[1] = j;
 856
 857         return 0;
 858
 859 close_f12_inode_i_j:
 860         put_unused_fd(j);
 861 close_f12_inode_i:
 862         put_unused_fd(i);
 863 close_f12_inode:
 864         free_pipe_info(inode);
 865         iput(inode);
 866 close_f12:
 867         put_filp(f2);
 868 close_f1:
 869         put_filp(f1);
 870 no_files:
 871         return error;
 872 }
 873
 874 /*
 875  * pipefs should _never_ be mounted by userland - too much of security hassle,
 876  * no real gain from having the whole whorehouse mounted. So we don't need
 877  * any operations on the root directory. However, we need a non-trivial
 878  * d_name - pipe: will go nicely and kill the special-casing in procfs.
 879  */
 880
 881 static struct super_block *
 882 pipefs_get_sb(struct file_system_type *fs_type, int flags,
 883               const char *dev_name, void *data)
 884 {
 885         return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC);
 886 }
 887
 888 static struct file_system_type pipe_fs_type = {
 889         .name           = "pipefs",
 890         .get_sb         = pipefs_get_sb,
 891         .kill_sb        = kill_anon_super,
 892 };
 893
 894 static int __init init_pipe_fs(void)
 895 {
 896         int err = register_filesystem(&pipe_fs_type);
 897
 898         if (!err) {
 899                 pipe_mnt = kern_mount(&pipe_fs_type);
 900                 if (IS_ERR(pipe_mnt)) {
 901                         err = PTR_ERR(pipe_mnt);
 902                         unregister_filesystem(&pipe_fs_type);
 903                 }
 904         }
 905         return err;
 906 }
 907
 908 static void __exit exit_pipe_fs(void)
 909 {
 910         unregister_filesystem(&pipe_fs_type);
 911         mntput(pipe_mnt);
 912 }
 913
 914 fs_initcall(init_pipe_fs);
 915 module_exit(exit_pipe_fs);