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