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 #include <linux/audit.h>
  20
  21 #include <asm/uaccess.h>
  22 #include <asm/ioctls.h>
  23
  24 /*
  25  * We use a start+len construction, which provides full use of the
  26  * allocated memory.
  27  * -- Florian Coosmann (FGC)
  28  *
  29  * Reads with count = 0 should always return 0.
  30  * -- Julian Bradfield 1999-06-07.
  31  *
  32  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  33  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  34  *
  35  * pipe_read & write cleanup
  36  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  37  */
  38
  39 /* Drop the inode semaphore and wait for a pipe event, atomically */
  40 void pipe_wait(struct pipe_inode_info *pipe)
  41 {
  42         DEFINE_WAIT(wait);
  43
  44         /*
  45          * Pipes are system-local resources, so sleeping on them
  46          * is considered a noninteractive wait:
  47          */
  48         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
  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                         int atomic)
  60 {
  61         unsigned long copy;
  62
  63         while (len > 0) {
  64                 while (!iov->iov_len)
  65                         iov++;
  66                 copy = min_t(unsigned long, len, iov->iov_len);
  67
  68                 if (atomic) {
  69                         if (__copy_from_user_inatomic(to, iov->iov_base, copy))
  70                                 return -EFAULT;
  71                 } else {
  72                         if (copy_from_user(to, iov->iov_base, copy))
  73                                 return -EFAULT;
  74                 }
  75                 to += copy;
  76                 len -= copy;
  77                 iov->iov_base += copy;
  78                 iov->iov_len -= copy;
  79         }
  80         return 0;
  81 }
  82
  83 static int
  84 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
  85                       int atomic)
  86 {
  87         unsigned long copy;
  88
  89         while (len > 0) {
  90                 while (!iov->iov_len)
  91                         iov++;
  92                 copy = min_t(unsigned long, len, iov->iov_len);
  93
  94                 if (atomic) {
  95                         if (__copy_to_user_inatomic(iov->iov_base, from, copy))
  96                                 return -EFAULT;
  97                 } else {
  98                         if (copy_to_user(iov->iov_base, from, copy))
  99                                 return -EFAULT;
 100                 }
 101                 from += copy;
 102                 len -= copy;
 103                 iov->iov_base += copy;
 104                 iov->iov_len -= copy;
 105         }
 106         return 0;
 107 }
 108
 109 /*
 110  * Attempt to pre-fault in the user memory, so we can use atomic copies.
 111  * Returns the number of bytes not faulted in.
 112  */
 113 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
 114 {
 115         while (!iov->iov_len)
 116                 iov++;
 117
 118         while (len > 0) {
 119                 unsigned long this_len;
 120
 121                 this_len = min_t(unsigned long, len, iov->iov_len);
 122                 if (fault_in_pages_writeable(iov->iov_base, this_len))
 123                         break;
 124
 125                 len -= this_len;
 126                 iov++;
 127         }
 128
 129         return len;
 130 }
 131
 132 /*
 133  * Pre-fault in the user memory, so we can use atomic copies.
 134  */
 135 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
 136 {
 137         while (!iov->iov_len)
 138                 iov++;
 139
 140         while (len > 0) {
 141                 unsigned long this_len;
 142
 143                 this_len = min_t(unsigned long, len, iov->iov_len);
 144                 fault_in_pages_readable(iov->iov_base, this_len);
 145                 len -= this_len;
 146                 iov++;
 147         }
 148 }
 149
 150 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 151                                   struct pipe_buffer *buf)
 152 {
 153         struct page *page = buf->page;
 154
 155         /*
 156          * If nobody else uses this page, and we don't already have a
 157          * temporary page, let's keep track of it as a one-deep
 158          * allocation cache. (Otherwise just release our reference to it)
 159          */
 160         if (page_count(page) == 1 && !pipe->tmp_page)
 161                 pipe->tmp_page = page;
 162         else
 163                 page_cache_release(page);
 164 }
 165
 166 /**
 167  * generic_pipe_buf_map - virtually map a pipe buffer
 168  * @pipe:       the pipe that the buffer belongs to
 169  * @buf:        the buffer that should be mapped
 170  * @atomic:     whether to use an atomic map
 171  *
 172  * Description:
 173  *      This function returns a kernel virtual address mapping for the
 174  *      passed in @pipe_buffer. If @atomic is set, an atomic map is provided
 175  *      and the caller has to be careful not to fault before calling
 176  *      the unmap function.
 177  *
 178  *      Note that this function occupies KM_USER0 if @atomic != 0.
 179  */
 180 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 181                            struct pipe_buffer *buf, int atomic)
 182 {
 183         if (atomic) {
 184                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 185                 return kmap_atomic(buf->page, KM_USER0);
 186         }
 187
 188         return kmap(buf->page);
 189 }
 190
 191 /**
 192  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
 193  * @pipe:       the pipe that the buffer belongs to
 194  * @buf:        the buffer that should be unmapped
 195  * @map_data:   the data that the mapping function returned
 196  *
 197  * Description:
 198  *      This function undoes the mapping that ->map() provided.
 199  */
 200 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 201                             struct pipe_buffer *buf, void *map_data)
 202 {
 203         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 204                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 205                 kunmap_atomic(map_data, KM_USER0);
 206         } else
 207                 kunmap(buf->page);
 208 }
 209
 210 /**
 211  * generic_pipe_buf_steal - attempt to take ownership of a @pipe_buffer
 212  * @pipe:       the pipe that the buffer belongs to
 213  * @buf:        the buffer to attempt to steal
 214  *
 215  * Description:
 216  *      This function attempts to steal the @struct page attached to
 217  *      @buf. If successful, this function returns 0 and returns with
 218  *      the page locked. The caller may then reuse the page for whatever
 219  *      he wishes, the typical use is insertion into a different file
 220  *      page cache.
 221  */
 222 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 223                            struct pipe_buffer *buf)
 224 {
 225         struct page *page = buf->page;
 226
 227         /*
 228          * A reference of one is golden, that means that the owner of this
 229          * page is the only one holding a reference to it. lock the page
 230          * and return OK.
 231          */
 232         if (page_count(page) == 1) {
 233                 lock_page(page);
 234                 return 0;
 235         }
 236
 237         return 1;
 238 }
 239
 240 /**
 241  * generic_pipe_buf_get - get a reference to a @struct pipe_buffer
 242  * @pipe:       the pipe that the buffer belongs to
 243  * @buf:        the buffer to get a reference to
 244  *
 245  * Description:
 246  *      This function grabs an extra reference to @buf. It's used in
 247  *      in the tee() system call, when we duplicate the buffers in one
 248  *      pipe into another.
 249  */
 250 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 251 {
 252         page_cache_get(buf->page);
 253 }
 254
 255 /**
 256  * generic_pipe_buf_confirm - verify contents of the pipe buffer
 257  * @info:       the pipe that the buffer belongs to
 258  * @buf:        the buffer to confirm
 259  *
 260  * Description:
 261  *      This function does nothing, because the generic pipe code uses
 262  *      pages that are always good when inserted into the pipe.
 263  */
 264 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 265                              struct pipe_buffer *buf)
 266 {
 267         return 0;
 268 }
 269
 270 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 271         .can_merge = 1,
 272         .map = generic_pipe_buf_map,
 273         .unmap = generic_pipe_buf_unmap,
 274         .confirm = generic_pipe_buf_confirm,
 275         .release = anon_pipe_buf_release,
 276         .steal = generic_pipe_buf_steal,
 277         .get = generic_pipe_buf_get,
 278 };
 279
 280 static ssize_t
 281 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 282            unsigned long nr_segs, loff_t pos)
 283 {
 284         struct file *filp = iocb->ki_filp;
 285         struct inode *inode = filp->f_path.dentry->d_inode;
 286         struct pipe_inode_info *pipe;
 287         int do_wakeup;
 288         ssize_t ret;
 289         struct iovec *iov = (struct iovec *)_iov;
 290         size_t total_len;
 291
 292         total_len = iov_length(iov, nr_segs);
 293         /* Null read succeeds. */
 294         if (unlikely(total_len == 0))
 295                 return 0;
 296
 297         do_wakeup = 0;
 298         ret = 0;
 299         mutex_lock(&inode->i_mutex);
 300         pipe = inode->i_pipe;
 301         for (;;) {
 302                 int bufs = pipe->nrbufs;
 303                 if (bufs) {
 304                         int curbuf = pipe->curbuf;
 305                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 306                         const struct pipe_buf_operations *ops = buf->ops;
 307                         void *addr;
 308                         size_t chars = buf->len;
 309                         int error, atomic;
 310
 311                         if (chars > total_len)
 312                                 chars = total_len;
 313
 314                         error = ops->confirm(pipe, buf);
 315                         if (error) {
 316                                 if (!ret)
 317                                         error = ret;
 318                                 break;
 319                         }
 320
 321                         atomic = !iov_fault_in_pages_write(iov, chars);
 322 redo:
 323                         addr = ops->map(pipe, buf, atomic);
 324                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
 325                         ops->unmap(pipe, buf, addr);
 326                         if (unlikely(error)) {
 327                                 /*
 328                                  * Just retry with the slow path if we failed.
 329                                  */
 330                                 if (atomic) {
 331                                         atomic = 0;
 332                                         goto redo;
 333                                 }
 334                                 if (!ret)
 335                                         ret = error;
 336                                 break;
 337                         }
 338                         ret += chars;
 339                         buf->offset += chars;
 340                         buf->len -= chars;
 341                         if (!buf->len) {
 342                                 buf->ops = NULL;
 343                                 ops->release(pipe, buf);
 344                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
 345                                 pipe->curbuf = curbuf;
 346                                 pipe->nrbufs = --bufs;
 347                                 do_wakeup = 1;
 348                         }
 349                         total_len -= chars;
 350                         if (!total_len)
 351                                 break;  /* common path: read succeeded */
 352                 }
 353                 if (bufs)       /* More to do? */
 354                         continue;
 355                 if (!pipe->writers)
 356                         break;
 357                 if (!pipe->waiting_writers) {
 358                         /* syscall merging: Usually we must not sleep
 359                          * if O_NONBLOCK is set, or if we got some data.
 360                          * But if a writer sleeps in kernel space, then
 361                          * we can wait for that data without violating POSIX.
 362                          */
 363                         if (ret)
 364                                 break;
 365                         if (filp->f_flags & O_NONBLOCK) {
 366                                 ret = -EAGAIN;
 367                                 break;
 368                         }
 369                 }
 370                 if (signal_pending(current)) {
 371                         if (!ret)
 372                                 ret = -ERESTARTSYS;
 373                         break;
 374                 }
 375                 if (do_wakeup) {
 376                         wake_up_interruptible_sync(&pipe->wait);
 377                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 378                 }
 379                 pipe_wait(pipe);
 380         }
 381         mutex_unlock(&inode->i_mutex);
 382
 383         /* Signal writers asynchronously that there is more room. */
 384         if (do_wakeup) {
 385                 wake_up_interruptible_sync(&pipe->wait);
 386                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 387         }
 388         if (ret > 0)
 389                 file_accessed(filp);
 390         return ret;
 391 }
 392
 393 static ssize_t
 394 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 395             unsigned long nr_segs, loff_t ppos)
 396 {
 397         struct file *filp = iocb->ki_filp;
 398         struct inode *inode = filp->f_path.dentry->d_inode;
 399         struct pipe_inode_info *pipe;
 400         ssize_t ret;
 401         int do_wakeup;
 402         struct iovec *iov = (struct iovec *)_iov;
 403         size_t total_len;
 404         ssize_t chars;
 405
 406         total_len = iov_length(iov, nr_segs);
 407         /* Null write succeeds. */
 408         if (unlikely(total_len == 0))
 409                 return 0;
 410
 411         do_wakeup = 0;
 412         ret = 0;
 413         mutex_lock(&inode->i_mutex);
 414         pipe = inode->i_pipe;
 415
 416         if (!pipe->readers) {
 417                 send_sig(SIGPIPE, current, 0);
 418                 ret = -EPIPE;
 419                 goto out;
 420         }
 421
 422         /* We try to merge small writes */
 423         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 424         if (pipe->nrbufs && chars != 0) {
 425                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 426                                                         (PIPE_BUFFERS-1);
 427                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 428                 const struct pipe_buf_operations *ops = buf->ops;
 429                 int offset = buf->offset + buf->len;
 430
 431                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 432                         int error, atomic = 1;
 433                         void *addr;
 434
 435                         error = ops->confirm(pipe, buf);
 436                         if (error)
 437                                 goto out;
 438
 439                         iov_fault_in_pages_read(iov, chars);
 440 redo1:
 441                         addr = ops->map(pipe, buf, atomic);
 442                         error = pipe_iov_copy_from_user(offset + addr, iov,
 443                                                         chars, atomic);
 444                         ops->unmap(pipe, buf, addr);
 445                         ret = error;
 446                         do_wakeup = 1;
 447                         if (error) {
 448                                 if (atomic) {
 449                                         atomic = 0;
 450                                         goto redo1;
 451                                 }
 452                                 goto out;
 453                         }
 454                         buf->len += chars;
 455                         total_len -= chars;
 456                         ret = chars;
 457                         if (!total_len)
 458                                 goto out;
 459                 }
 460         }
 461
 462         for (;;) {
 463                 int bufs;
 464
 465                 if (!pipe->readers) {
 466                         send_sig(SIGPIPE, current, 0);
 467                         if (!ret)
 468                                 ret = -EPIPE;
 469                         break;
 470                 }
 471                 bufs = pipe->nrbufs;
 472                 if (bufs < PIPE_BUFFERS) {
 473                         int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1);
 474                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 475                         struct page *page = pipe->tmp_page;
 476                         char *src;
 477                         int error, atomic = 1;
 478
 479                         if (!page) {
 480                                 page = alloc_page(GFP_HIGHUSER);
 481                                 if (unlikely(!page)) {
 482                                         ret = ret ? : -ENOMEM;
 483                                         break;
 484                                 }
 485                                 pipe->tmp_page = page;
 486                         }
 487                         /* Always wake up, even if the copy fails. Otherwise
 488                          * we lock up (O_NONBLOCK-)readers that sleep due to
 489                          * syscall merging.
 490                          * FIXME! Is this really true?
 491                          */
 492                         do_wakeup = 1;
 493                         chars = PAGE_SIZE;
 494                         if (chars > total_len)
 495                                 chars = total_len;
 496
 497                         iov_fault_in_pages_read(iov, chars);
 498 redo2:
 499                         if (atomic)
 500                                 src = kmap_atomic(page, KM_USER0);
 501                         else
 502                                 src = kmap(page);
 503
 504                         error = pipe_iov_copy_from_user(src, iov, chars,
 505                                                         atomic);
 506                         if (atomic)
 507                                 kunmap_atomic(src, KM_USER0);
 508                         else
 509                                 kunmap(page);
 510
 511                         if (unlikely(error)) {
 512                                 if (atomic) {
 513                                         atomic = 0;
 514                                         goto redo2;
 515                                 }
 516                                 if (!ret)
 517                                         ret = error;
 518                                 break;
 519                         }
 520                         ret += chars;
 521
 522                         /* Insert it into the buffer array */
 523                         buf->page = page;
 524                         buf->ops = &anon_pipe_buf_ops;
 525                         buf->offset = 0;
 526                         buf->len = chars;
 527                         pipe->nrbufs = ++bufs;
 528                         pipe->tmp_page = NULL;
 529
 530                         total_len -= chars;
 531                         if (!total_len)
 532                                 break;
 533                 }
 534                 if (bufs < PIPE_BUFFERS)
 535                         continue;
 536                 if (filp->f_flags & O_NONBLOCK) {
 537                         if (!ret)
 538                                 ret = -EAGAIN;
 539                         break;
 540                 }
 541                 if (signal_pending(current)) {
 542                         if (!ret)
 543                                 ret = -ERESTARTSYS;
 544                         break;
 545                 }
 546                 if (do_wakeup) {
 547                         wake_up_interruptible_sync(&pipe->wait);
 548                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 549                         do_wakeup = 0;
 550                 }
 551                 pipe->waiting_writers++;
 552                 pipe_wait(pipe);
 553                 pipe->waiting_writers--;
 554         }
 555 out:
 556         mutex_unlock(&inode->i_mutex);
 557         if (do_wakeup) {
 558                 wake_up_interruptible_sync(&pipe->wait);
 559                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 560         }
 561         if (ret > 0)
 562                 file_update_time(filp);
 563         return ret;
 564 }
 565
 566 static ssize_t
 567 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 568 {
 569         return -EBADF;
 570 }
 571
 572 static ssize_t
 573 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
 574            loff_t *ppos)
 575 {
 576         return -EBADF;
 577 }
 578
 579 static int
 580 pipe_ioctl(struct inode *pino, struct file *filp,
 581            unsigned int cmd, unsigned long arg)
 582 {
 583         struct inode *inode = filp->f_path.dentry->d_inode;
 584         struct pipe_inode_info *pipe;
 585         int count, buf, nrbufs;
 586
 587         switch (cmd) {
 588                 case FIONREAD:
 589                         mutex_lock(&inode->i_mutex);
 590                         pipe = inode->i_pipe;
 591                         count = 0;
 592                         buf = pipe->curbuf;
 593                         nrbufs = pipe->nrbufs;
 594                         while (--nrbufs >= 0) {
 595                                 count += pipe->bufs[buf].len;
 596                                 buf = (buf+1) & (PIPE_BUFFERS-1);
 597                         }
 598                         mutex_unlock(&inode->i_mutex);
 599
 600                         return put_user(count, (int __user *)arg);
 601                 default:
 602                         return -EINVAL;
 603         }
 604 }
 605
 606 /* No kernel lock held - fine */
 607 static unsigned int
 608 pipe_poll(struct file *filp, poll_table *wait)
 609 {
 610         unsigned int mask;
 611         struct inode *inode = filp->f_path.dentry->d_inode;
 612         struct pipe_inode_info *pipe = inode->i_pipe;
 613         int nrbufs;
 614
 615         poll_wait(filp, &pipe->wait, wait);
 616
 617         /* Reading only -- no need for acquiring the semaphore.  */
 618         nrbufs = pipe->nrbufs;
 619         mask = 0;
 620         if (filp->f_mode & FMODE_READ) {
 621                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 622                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 623                         mask |= POLLHUP;
 624         }
 625
 626         if (filp->f_mode & FMODE_WRITE) {
 627                 mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
 628                 /*
 629                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 630                  * behave exactly like pipes for poll().
 631                  */
 632                 if (!pipe->readers)
 633                         mask |= POLLERR;
 634         }
 635
 636         return mask;
 637 }
 638
 639 static int
 640 pipe_release(struct inode *inode, int decr, int decw)
 641 {
 642         struct pipe_inode_info *pipe;
 643
 644         mutex_lock(&inode->i_mutex);
 645         pipe = inode->i_pipe;
 646         pipe->readers -= decr;
 647         pipe->writers -= decw;
 648
 649         if (!pipe->readers && !pipe->writers) {
 650                 free_pipe_info(inode);
 651         } else {
 652                 wake_up_interruptible_sync(&pipe->wait);
 653                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 654                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 655         }
 656         mutex_unlock(&inode->i_mutex);
 657
 658         return 0;
 659 }
 660
 661 static int
 662 pipe_read_fasync(int fd, struct file *filp, int on)
 663 {
 664         struct inode *inode = filp->f_path.dentry->d_inode;
 665         int retval;
 666
 667         mutex_lock(&inode->i_mutex);
 668         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
 669         mutex_unlock(&inode->i_mutex);
 670
 671         if (retval < 0)
 672                 return retval;
 673
 674         return 0;
 675 }
 676
 677
 678 static int
 679 pipe_write_fasync(int fd, struct file *filp, int on)
 680 {
 681         struct inode *inode = filp->f_path.dentry->d_inode;
 682         int retval;
 683
 684         mutex_lock(&inode->i_mutex);
 685         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
 686         mutex_unlock(&inode->i_mutex);
 687
 688         if (retval < 0)
 689                 return retval;
 690
 691         return 0;
 692 }
 693
 694
 695 static int
 696 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 697 {
 698         struct inode *inode = filp->f_path.dentry->d_inode;
 699         struct pipe_inode_info *pipe = inode->i_pipe;
 700         int retval;
 701
 702         mutex_lock(&inode->i_mutex);
 703
 704         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 705
 706         if (retval >= 0)
 707                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 708
 709         mutex_unlock(&inode->i_mutex);
 710
 711         if (retval < 0)
 712                 return retval;
 713
 714         return 0;
 715 }
 716
 717
 718 static int
 719 pipe_read_release(struct inode *inode, struct file *filp)
 720 {
 721         pipe_read_fasync(-1, filp, 0);
 722         return pipe_release(inode, 1, 0);
 723 }
 724
 725 static int
 726 pipe_write_release(struct inode *inode, struct file *filp)
 727 {
 728         pipe_write_fasync(-1, filp, 0);
 729         return pipe_release(inode, 0, 1);
 730 }
 731
 732 static int
 733 pipe_rdwr_release(struct inode *inode, struct file *filp)
 734 {
 735         int decr, decw;
 736
 737         pipe_rdwr_fasync(-1, filp, 0);
 738         decr = (filp->f_mode & FMODE_READ) != 0;
 739         decw = (filp->f_mode & FMODE_WRITE) != 0;
 740         return pipe_release(inode, decr, decw);
 741 }
 742
 743 static int
 744 pipe_read_open(struct inode *inode, struct file *filp)
 745 {
 746         /* We could have perhaps used atomic_t, but this and friends
 747            below are the only places.  So it doesn't seem worthwhile.  */
 748         mutex_lock(&inode->i_mutex);
 749         inode->i_pipe->readers++;
 750         mutex_unlock(&inode->i_mutex);
 751
 752         return 0;
 753 }
 754
 755 static int
 756 pipe_write_open(struct inode *inode, struct file *filp)
 757 {
 758         mutex_lock(&inode->i_mutex);
 759         inode->i_pipe->writers++;
 760         mutex_unlock(&inode->i_mutex);
 761
 762         return 0;
 763 }
 764
 765 static int
 766 pipe_rdwr_open(struct inode *inode, struct file *filp)
 767 {
 768         mutex_lock(&inode->i_mutex);
 769         if (filp->f_mode & FMODE_READ)
 770                 inode->i_pipe->readers++;
 771         if (filp->f_mode & FMODE_WRITE)
 772                 inode->i_pipe->writers++;
 773         mutex_unlock(&inode->i_mutex);
 774
 775         return 0;
 776 }
 777
 778 /*
 779  * The file_operations structs are not static because they
 780  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 781  */
 782 const struct file_operations read_fifo_fops = {
 783         .llseek         = no_llseek,
 784         .read           = do_sync_read,
 785         .aio_read       = pipe_read,
 786         .write          = bad_pipe_w,
 787         .poll           = pipe_poll,
 788         .ioctl          = pipe_ioctl,
 789         .open           = pipe_read_open,
 790         .release        = pipe_read_release,
 791         .fasync         = pipe_read_fasync,
 792 };
 793
 794 const struct file_operations write_fifo_fops = {
 795         .llseek         = no_llseek,
 796         .read           = bad_pipe_r,
 797         .write          = do_sync_write,
 798         .aio_write      = pipe_write,
 799         .poll           = pipe_poll,
 800         .ioctl          = pipe_ioctl,
 801         .open           = pipe_write_open,
 802         .release        = pipe_write_release,
 803         .fasync         = pipe_write_fasync,
 804 };
 805
 806 const struct file_operations rdwr_fifo_fops = {
 807         .llseek         = no_llseek,
 808         .read           = do_sync_read,
 809         .aio_read       = pipe_read,
 810         .write          = do_sync_write,
 811         .aio_write      = pipe_write,
 812         .poll           = pipe_poll,
 813         .ioctl          = pipe_ioctl,
 814         .open           = pipe_rdwr_open,
 815         .release        = pipe_rdwr_release,
 816         .fasync         = pipe_rdwr_fasync,
 817 };
 818
 819 static const struct file_operations read_pipe_fops = {
 820         .llseek         = no_llseek,
 821         .read           = do_sync_read,
 822         .aio_read       = pipe_read,
 823         .write          = bad_pipe_w,
 824         .poll           = pipe_poll,
 825         .ioctl          = pipe_ioctl,
 826         .open           = pipe_read_open,
 827         .release        = pipe_read_release,
 828         .fasync         = pipe_read_fasync,
 829 };
 830
 831 static const struct file_operations write_pipe_fops = {
 832         .llseek         = no_llseek,
 833         .read           = bad_pipe_r,
 834         .write          = do_sync_write,
 835         .aio_write      = pipe_write,
 836         .poll           = pipe_poll,
 837         .ioctl          = pipe_ioctl,
 838         .open           = pipe_write_open,
 839         .release        = pipe_write_release,
 840         .fasync         = pipe_write_fasync,
 841 };
 842
 843 static const struct file_operations rdwr_pipe_fops = {
 844         .llseek         = no_llseek,
 845         .read           = do_sync_read,
 846         .aio_read       = pipe_read,
 847         .write          = do_sync_write,
 848         .aio_write      = pipe_write,
 849         .poll           = pipe_poll,
 850         .ioctl          = pipe_ioctl,
 851         .open           = pipe_rdwr_open,
 852         .release        = pipe_rdwr_release,
 853         .fasync         = pipe_rdwr_fasync,
 854 };
 855
 856 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
 857 {
 858         struct pipe_inode_info *pipe;
 859
 860         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 861         if (pipe) {
 862                 init_waitqueue_head(&pipe->wait);
 863                 pipe->r_counter = pipe->w_counter = 1;
 864                 pipe->inode = inode;
 865         }
 866
 867         return pipe;
 868 }
 869
 870 void __free_pipe_info(struct pipe_inode_info *pipe)
 871 {
 872         int i;
 873
 874         for (i = 0; i < PIPE_BUFFERS; i++) {
 875                 struct pipe_buffer *buf = pipe->bufs + i;
 876                 if (buf->ops)
 877                         buf->ops->release(pipe, buf);
 878         }
 879         if (pipe->tmp_page)
 880                 __free_page(pipe->tmp_page);
 881         kfree(pipe);
 882 }
 883
 884 void free_pipe_info(struct inode *inode)
 885 {
 886         __free_pipe_info(inode->i_pipe);
 887         inode->i_pipe = NULL;
 888 }
 889
 890 static struct vfsmount *pipe_mnt __read_mostly;
 891 static int pipefs_delete_dentry(struct dentry *dentry)
 892 {
 893         /*
 894          * At creation time, we pretended this dentry was hashed
 895          * (by clearing DCACHE_UNHASHED bit in d_flags)
 896          * At delete time, we restore the truth : not hashed.
 897          * (so that dput() can proceed correctly)
 898          */
 899         dentry->d_flags |= DCACHE_UNHASHED;
 900         return 0;
 901 }
 902
 903 /*
 904  * pipefs_dname() is called from d_path().
 905  */
 906 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 907 {
 908         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 909                                 dentry->d_inode->i_ino);
 910 }
 911
 912 static struct dentry_operations pipefs_dentry_operations = {
 913         .d_delete       = pipefs_delete_dentry,
 914         .d_dname        = pipefs_dname,
 915 };
 916
 917 static struct inode * get_pipe_inode(void)
 918 {
 919         struct inode *inode = new_inode(pipe_mnt->mnt_sb);
 920         struct pipe_inode_info *pipe;
 921
 922         if (!inode)
 923                 goto fail_inode;
 924
 925         pipe = alloc_pipe_info(inode);
 926         if (!pipe)
 927                 goto fail_iput;
 928         inode->i_pipe = pipe;
 929
 930         pipe->readers = pipe->writers = 1;
 931         inode->i_fop = &rdwr_pipe_fops;
 932
 933         /*
 934          * Mark the inode dirty from the very beginning,
 935          * that way it will never be moved to the dirty
 936          * list because "mark_inode_dirty()" will think
 937          * that it already _is_ on the dirty list.
 938          */
 939         inode->i_state = I_DIRTY;
 940         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 941         inode->i_uid = current->fsuid;
 942         inode->i_gid = current->fsgid;
 943         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 944
 945         return inode;
 946
 947 fail_iput:
 948         iput(inode);
 949
 950 fail_inode:
 951         return NULL;
 952 }
 953
 954 struct file *create_write_pipe(void)
 955 {
 956         int err;
 957         struct inode *inode;
 958         struct file *f;
 959         struct dentry *dentry;
 960         struct qstr name = { .name = "" };
 961
 962         f = get_empty_filp();
 963         if (!f)
 964                 return ERR_PTR(-ENFILE);
 965         err = -ENFILE;
 966         inode = get_pipe_inode();
 967         if (!inode)
 968                 goto err_file;
 969
 970         err = -ENOMEM;
 971         dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
 972         if (!dentry)
 973                 goto err_inode;
 974
 975         dentry->d_op = &pipefs_dentry_operations;
 976         /*
 977          * We dont want to publish this dentry into global dentry hash table.
 978          * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
 979          * This permits a working /proc/$pid/fd/XXX on pipes
 980          */
 981         dentry->d_flags &= ~DCACHE_UNHASHED;
 982         d_instantiate(dentry, inode);
 983         f->f_path.mnt = mntget(pipe_mnt);
 984         f->f_path.dentry = dentry;
 985         f->f_mapping = inode->i_mapping;
 986
 987         f->f_flags = O_WRONLY;
 988         f->f_op = &write_pipe_fops;
 989         f->f_mode = FMODE_WRITE;
 990         f->f_version = 0;
 991
 992         return f;
 993
 994  err_inode:
 995         free_pipe_info(inode);
 996         iput(inode);
 997  err_file:
 998         put_filp(f);
 999         return ERR_PTR(err);
1000 }
1001
1002 void free_write_pipe(struct file *f)
1003 {
1004         free_pipe_info(f->f_dentry->d_inode);
1005         dput(f->f_path.dentry);
1006         mntput(f->f_path.mnt);
1007         put_filp(f);
1008 }
1009
1010 struct file *create_read_pipe(struct file *wrf)
1011 {
1012         struct file *f = get_empty_filp();
1013         if (!f)
1014                 return ERR_PTR(-ENFILE);
1015
1016         /* Grab pipe from the writer */
1017         f->f_path.mnt = mntget(wrf->f_path.mnt);
1018         f->f_path.dentry = dget(wrf->f_path.dentry);
1019         f->f_mapping = wrf->f_path.dentry->d_inode->i_mapping;
1020
1021         f->f_pos = 0;
1022         f->f_flags = O_RDONLY;
1023         f->f_op = &read_pipe_fops;
1024         f->f_mode = FMODE_READ;
1025         f->f_version = 0;
1026
1027         return f;
1028 }
1029
1030 int do_pipe(int *fd)
1031 {
1032         struct file *fw, *fr;
1033         int error;
1034         int fdw, fdr;
1035
1036         fw = create_write_pipe();
1037         if (IS_ERR(fw))
1038                 return PTR_ERR(fw);
1039         fr = create_read_pipe(fw);
1040         error = PTR_ERR(fr);
1041         if (IS_ERR(fr))
1042                 goto err_write_pipe;
1043
1044         error = get_unused_fd();
1045         if (error < 0)
1046                 goto err_read_pipe;
1047         fdr = error;
1048
1049         error = get_unused_fd();
1050         if (error < 0)
1051                 goto err_fdr;
1052         fdw = error;
1053
1054         error = audit_fd_pair(fdr, fdw);
1055         if (error < 0)
1056                 goto err_fdw;
1057
1058         fd_install(fdr, fr);
1059         fd_install(fdw, fw);
1060         fd[0] = fdr;
1061         fd[1] = fdw;
1062
1063         return 0;
1064
1065  err_fdw:
1066         put_unused_fd(fdw);
1067  err_fdr:
1068         put_unused_fd(fdr);
1069  err_read_pipe:
1070         dput(fr->f_dentry);
1071         mntput(fr->f_vfsmnt);
1072         put_filp(fr);
1073  err_write_pipe:
1074         free_write_pipe(fw);
1075         return error;
1076 }
1077
1078 /*
1079  * pipefs should _never_ be mounted by userland - too much of security hassle,
1080  * no real gain from having the whole whorehouse mounted. So we don't need
1081  * any operations on the root directory. However, we need a non-trivial
1082  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1083  */
1084 static int pipefs_get_sb(struct file_system_type *fs_type,
1085                          int flags, const char *dev_name, void *data,
1086                          struct vfsmount *mnt)
1087 {
1088         return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
1089 }
1090
1091 static struct file_system_type pipe_fs_type = {
1092         .name           = "pipefs",
1093         .get_sb         = pipefs_get_sb,
1094         .kill_sb        = kill_anon_super,
1095 };
1096
1097 static int __init init_pipe_fs(void)
1098 {
1099         int err = register_filesystem(&pipe_fs_type);
1100
1101         if (!err) {
1102                 pipe_mnt = kern_mount(&pipe_fs_type);
1103                 if (IS_ERR(pipe_mnt)) {
1104                         err = PTR_ERR(pipe_mnt);
1105                         unregister_filesystem(&pipe_fs_type);
1106                 }
1107         }
1108         return err;
1109 }
1110
1111 static void __exit exit_pipe_fs(void)
1112 {
1113         unregister_filesystem(&pipe_fs_type);
1114         mntput(pipe_mnt);
1115 }
1116
1117 fs_initcall(init_pipe_fs);
1118 module_exit(exit_pipe_fs);