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