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,
  49                         TASK_INTERRUPTIBLE | TASK_NONINTERACTIVE);
  50         if (pipe->inode)
  51                 mutex_unlock(&pipe->inode->i_mutex);
  52         schedule();
  53         finish_wait(&pipe->wait, &wait);
  54         if (pipe->inode)
  55                 mutex_lock(&pipe->inode->i_mutex);
  56 }
  57
  58 static int
  59 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
  60                         int atomic)
  61 {
  62         unsigned long copy;
  63
  64         while (len > 0) {
  65                 while (!iov->iov_len)
  66                         iov++;
  67                 copy = min_t(unsigned long, len, iov->iov_len);
  68
  69                 if (atomic) {
  70                         if (__copy_from_user_inatomic(to, iov->iov_base, copy))
  71                                 return -EFAULT;
  72                 } else {
  73                         if (copy_from_user(to, iov->iov_base, copy))
  74                                 return -EFAULT;
  75                 }
  76                 to += copy;
  77                 len -= copy;
  78                 iov->iov_base += copy;
  79                 iov->iov_len -= copy;
  80         }
  81         return 0;
  82 }
  83
  84 static int
  85 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
  86                       int atomic)
  87 {
  88         unsigned long copy;
  89
  90         while (len > 0) {
  91                 while (!iov->iov_len)
  92                         iov++;
  93                 copy = min_t(unsigned long, len, iov->iov_len);
  94
  95                 if (atomic) {
  96                         if (__copy_to_user_inatomic(iov->iov_base, from, copy))
  97                                 return -EFAULT;
  98                 } else {
  99                         if (copy_to_user(iov->iov_base, from, copy))
 100                                 return -EFAULT;
 101                 }
 102                 from += copy;
 103                 len -= copy;
 104                 iov->iov_base += copy;
 105                 iov->iov_len -= copy;
 106         }
 107         return 0;
 108 }
 109
 110 /*
 111  * Attempt to pre-fault in the user memory, so we can use atomic copies.
 112  * Returns the number of bytes not faulted in.
 113  */
 114 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
 115 {
 116         while (!iov->iov_len)
 117                 iov++;
 118
 119         while (len > 0) {
 120                 unsigned long this_len;
 121
 122                 this_len = min_t(unsigned long, len, iov->iov_len);
 123                 if (fault_in_pages_writeable(iov->iov_base, this_len))
 124                         break;
 125
 126                 len -= this_len;
 127                 iov++;
 128         }
 129
 130         return len;
 131 }
 132
 133 /*
 134  * Pre-fault in the user memory, so we can use atomic copies.
 135  */
 136 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
 137 {
 138         while (!iov->iov_len)
 139                 iov++;
 140
 141         while (len > 0) {
 142                 unsigned long this_len;
 143
 144                 this_len = min_t(unsigned long, len, iov->iov_len);
 145                 fault_in_pages_readable(iov->iov_base, this_len);
 146                 len -= this_len;
 147                 iov++;
 148         }
 149 }
 150
 151 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 152                                   struct pipe_buffer *buf)
 153 {
 154         struct page *page = buf->page;
 155
 156         /*
 157          * If nobody else uses this page, and we don't already have a
 158          * temporary page, let's keep track of it as a one-deep
 159          * allocation cache. (Otherwise just release our reference to it)
 160          */
 161         if (page_count(page) == 1 && !pipe->tmp_page)
 162                 pipe->tmp_page = page;
 163         else
 164                 page_cache_release(page);
 165 }
 166
 167 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 168                            struct pipe_buffer *buf, int atomic)
 169 {
 170         if (atomic) {
 171                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 172                 return kmap_atomic(buf->page, KM_USER0);
 173         }
 174
 175         return kmap(buf->page);
 176 }
 177
 178 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 179                             struct pipe_buffer *buf, void *map_data)
 180 {
 181         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 182                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 183                 kunmap_atomic(map_data, KM_USER0);
 184         } else
 185                 kunmap(buf->page);
 186 }
 187
 188 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 189                            struct pipe_buffer *buf)
 190 {
 191         struct page *page = buf->page;
 192
 193         if (page_count(page) == 1) {
 194                 lock_page(page);
 195                 return 0;
 196         }
 197
 198         return 1;
 199 }
 200
 201 void generic_pipe_buf_get(struct pipe_inode_info *info, struct pipe_buffer *buf)
 202 {
 203         page_cache_get(buf->page);
 204 }
 205
 206 int generic_pipe_buf_pin(struct pipe_inode_info *info, struct pipe_buffer *buf)
 207 {
 208         return 0;
 209 }
 210
 211 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 212         .can_merge = 1,
 213         .map = generic_pipe_buf_map,
 214         .unmap = generic_pipe_buf_unmap,
 215         .pin = generic_pipe_buf_pin,
 216         .release = anon_pipe_buf_release,
 217         .steal = generic_pipe_buf_steal,
 218         .get = generic_pipe_buf_get,
 219 };
 220
 221 static ssize_t
 222 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 223            unsigned long nr_segs, loff_t pos)
 224 {
 225         struct file *filp = iocb->ki_filp;
 226         struct inode *inode = filp->f_path.dentry->d_inode;
 227         struct pipe_inode_info *pipe;
 228         int do_wakeup;
 229         ssize_t ret;
 230         struct iovec *iov = (struct iovec *)_iov;
 231         size_t total_len;
 232
 233         total_len = iov_length(iov, nr_segs);
 234         /* Null read succeeds. */
 235         if (unlikely(total_len == 0))
 236                 return 0;
 237
 238         do_wakeup = 0;
 239         ret = 0;
 240         mutex_lock(&inode->i_mutex);
 241         pipe = inode->i_pipe;
 242         for (;;) {
 243                 int bufs = pipe->nrbufs;
 244                 if (bufs) {
 245                         int curbuf = pipe->curbuf;
 246                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 247                         const struct pipe_buf_operations *ops = buf->ops;
 248                         void *addr;
 249                         size_t chars = buf->len;
 250                         int error, atomic;
 251
 252                         if (chars > total_len)
 253                                 chars = total_len;
 254
 255                         error = ops->pin(pipe, buf);
 256                         if (error) {
 257                                 if (!ret)
 258                                         error = ret;
 259                                 break;
 260                         }
 261
 262                         atomic = !iov_fault_in_pages_write(iov, chars);
 263 redo:
 264                         addr = ops->map(pipe, buf, atomic);
 265                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
 266                         ops->unmap(pipe, buf, addr);
 267                         if (unlikely(error)) {
 268                                 /*
 269                                  * Just retry with the slow path if we failed.
 270                                  */
 271                                 if (atomic) {
 272                                         atomic = 0;
 273                                         goto redo;
 274                                 }
 275                                 if (!ret)
 276                                         ret = error;
 277                                 break;
 278                         }
 279                         ret += chars;
 280                         buf->offset += chars;
 281                         buf->len -= chars;
 282                         if (!buf->len) {
 283                                 buf->ops = NULL;
 284                                 ops->release(pipe, buf);
 285                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
 286                                 pipe->curbuf = curbuf;
 287                                 pipe->nrbufs = --bufs;
 288                                 do_wakeup = 1;
 289                         }
 290                         total_len -= chars;
 291                         if (!total_len)
 292                                 break;  /* common path: read succeeded */
 293                 }
 294                 if (bufs)       /* More to do? */
 295                         continue;
 296                 if (!pipe->writers)
 297                         break;
 298                 if (!pipe->waiting_writers) {
 299                         /* syscall merging: Usually we must not sleep
 300                          * if O_NONBLOCK is set, or if we got some data.
 301                          * But if a writer sleeps in kernel space, then
 302                          * we can wait for that data without violating POSIX.
 303                          */
 304                         if (ret)
 305                                 break;
 306                         if (filp->f_flags & O_NONBLOCK) {
 307                                 ret = -EAGAIN;
 308                                 break;
 309                         }
 310                 }
 311                 if (signal_pending(current)) {
 312                         if (!ret)
 313                                 ret = -ERESTARTSYS;
 314                         break;
 315                 }
 316                 if (do_wakeup) {
 317                         wake_up_interruptible_sync(&pipe->wait);
 318                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 319                 }
 320                 pipe_wait(pipe);
 321         }
 322         mutex_unlock(&inode->i_mutex);
 323
 324         /* Signal writers asynchronously that there is more room. */
 325         if (do_wakeup) {
 326                 wake_up_interruptible(&pipe->wait);
 327                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 328         }
 329         if (ret > 0)
 330                 file_accessed(filp);
 331         return ret;
 332 }
 333
 334 static ssize_t
 335 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 336             unsigned long nr_segs, loff_t ppos)
 337 {
 338         struct file *filp = iocb->ki_filp;
 339         struct inode *inode = filp->f_path.dentry->d_inode;
 340         struct pipe_inode_info *pipe;
 341         ssize_t ret;
 342         int do_wakeup;
 343         struct iovec *iov = (struct iovec *)_iov;
 344         size_t total_len;
 345         ssize_t chars;
 346
 347         total_len = iov_length(iov, nr_segs);
 348         /* Null write succeeds. */
 349         if (unlikely(total_len == 0))
 350                 return 0;
 351
 352         do_wakeup = 0;
 353         ret = 0;
 354         mutex_lock(&inode->i_mutex);
 355         pipe = inode->i_pipe;
 356
 357         if (!pipe->readers) {
 358                 send_sig(SIGPIPE, current, 0);
 359                 ret = -EPIPE;
 360                 goto out;
 361         }
 362
 363         /* We try to merge small writes */
 364         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 365         if (pipe->nrbufs && chars != 0) {
 366                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 367                                                         (PIPE_BUFFERS-1);
 368                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 369                 const struct pipe_buf_operations *ops = buf->ops;
 370                 int offset = buf->offset + buf->len;
 371
 372                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 373                         int error, atomic = 1;
 374                         void *addr;
 375
 376                         error = ops->pin(pipe, buf);
 377                         if (error)
 378                                 goto out;
 379
 380                         iov_fault_in_pages_read(iov, chars);
 381 redo1:
 382                         addr = ops->map(pipe, buf, atomic);
 383                         error = pipe_iov_copy_from_user(offset + addr, iov,
 384                                                         chars, atomic);
 385                         ops->unmap(pipe, buf, addr);
 386                         ret = error;
 387                         do_wakeup = 1;
 388                         if (error) {
 389                                 if (atomic) {
 390                                         atomic = 0;
 391                                         goto redo1;
 392                                 }
 393                                 goto out;
 394                         }
 395                         buf->len += chars;
 396                         total_len -= chars;
 397                         ret = chars;
 398                         if (!total_len)
 399                                 goto out;
 400                 }
 401         }
 402
 403         for (;;) {
 404                 int bufs;
 405
 406                 if (!pipe->readers) {
 407                         send_sig(SIGPIPE, current, 0);
 408                         if (!ret)
 409                                 ret = -EPIPE;
 410                         break;
 411                 }
 412                 bufs = pipe->nrbufs;
 413                 if (bufs < PIPE_BUFFERS) {
 414                         int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1);
 415                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 416                         struct page *page = pipe->tmp_page;
 417                         char *src;
 418                         int error, atomic = 1;
 419
 420                         if (!page) {
 421                                 page = alloc_page(GFP_HIGHUSER);
 422                                 if (unlikely(!page)) {
 423                                         ret = ret ? : -ENOMEM;
 424                                         break;
 425                                 }
 426                                 pipe->tmp_page = page;
 427                         }
 428                         /* Always wake up, even if the copy fails. Otherwise
 429                          * we lock up (O_NONBLOCK-)readers that sleep due to
 430                          * syscall merging.
 431                          * FIXME! Is this really true?
 432                          */
 433                         do_wakeup = 1;
 434                         chars = PAGE_SIZE;
 435                         if (chars > total_len)
 436                                 chars = total_len;
 437
 438                         iov_fault_in_pages_read(iov, chars);
 439 redo2:
 440                         if (atomic)
 441                                 src = kmap_atomic(page, KM_USER0);
 442                         else
 443                                 src = kmap(page);
 444
 445                         error = pipe_iov_copy_from_user(src, iov, chars,
 446                                                         atomic);
 447                         if (atomic)
 448                                 kunmap_atomic(src, KM_USER0);
 449                         else
 450                                 kunmap(page);
 451
 452                         if (unlikely(error)) {
 453                                 if (atomic) {
 454                                         atomic = 0;
 455                                         goto redo2;
 456                                 }
 457                                 if (!ret)
 458                                         ret = error;
 459                                 break;
 460                         }
 461                         ret += chars;
 462
 463                         /* Insert it into the buffer array */
 464                         buf->page = page;
 465                         buf->ops = &anon_pipe_buf_ops;
 466                         buf->offset = 0;
 467                         buf->len = chars;
 468                         pipe->nrbufs = ++bufs;
 469                         pipe->tmp_page = NULL;
 470
 471                         total_len -= chars;
 472                         if (!total_len)
 473                                 break;
 474                 }
 475                 if (bufs < PIPE_BUFFERS)
 476                         continue;
 477                 if (filp->f_flags & O_NONBLOCK) {
 478                         if (!ret)
 479                                 ret = -EAGAIN;
 480                         break;
 481                 }
 482                 if (signal_pending(current)) {
 483                         if (!ret)
 484                                 ret = -ERESTARTSYS;
 485                         break;
 486                 }
 487                 if (do_wakeup) {
 488                         wake_up_interruptible_sync(&pipe->wait);
 489                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 490                         do_wakeup = 0;
 491                 }
 492                 pipe->waiting_writers++;
 493                 pipe_wait(pipe);
 494                 pipe->waiting_writers--;
 495         }
 496 out:
 497         mutex_unlock(&inode->i_mutex);
 498         if (do_wakeup) {
 499                 wake_up_interruptible(&pipe->wait);
 500                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 501         }
 502         if (ret > 0)
 503                 file_update_time(filp);
 504         return ret;
 505 }
 506
 507 static ssize_t
 508 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 509 {
 510         return -EBADF;
 511 }
 512
 513 static ssize_t
 514 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
 515            loff_t *ppos)
 516 {
 517         return -EBADF;
 518 }
 519
 520 static int
 521 pipe_ioctl(struct inode *pino, struct file *filp,
 522            unsigned int cmd, unsigned long arg)
 523 {
 524         struct inode *inode = filp->f_path.dentry->d_inode;
 525         struct pipe_inode_info *pipe;
 526         int count, buf, nrbufs;
 527
 528         switch (cmd) {
 529                 case FIONREAD:
 530                         mutex_lock(&inode->i_mutex);
 531                         pipe = inode->i_pipe;
 532                         count = 0;
 533                         buf = pipe->curbuf;
 534                         nrbufs = pipe->nrbufs;
 535                         while (--nrbufs >= 0) {
 536                                 count += pipe->bufs[buf].len;
 537                                 buf = (buf+1) & (PIPE_BUFFERS-1);
 538                         }
 539                         mutex_unlock(&inode->i_mutex);
 540
 541                         return put_user(count, (int __user *)arg);
 542                 default:
 543                         return -EINVAL;
 544         }
 545 }
 546
 547 /* No kernel lock held - fine */
 548 static unsigned int
 549 pipe_poll(struct file *filp, poll_table *wait)
 550 {
 551         unsigned int mask;
 552         struct inode *inode = filp->f_path.dentry->d_inode;
 553         struct pipe_inode_info *pipe = inode->i_pipe;
 554         int nrbufs;
 555
 556         poll_wait(filp, &pipe->wait, wait);
 557
 558         /* Reading only -- no need for acquiring the semaphore.  */
 559         nrbufs = pipe->nrbufs;
 560         mask = 0;
 561         if (filp->f_mode & FMODE_READ) {
 562                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 563                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 564                         mask |= POLLHUP;
 565         }
 566
 567         if (filp->f_mode & FMODE_WRITE) {
 568                 mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
 569                 /*
 570                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 571                  * behave exactly like pipes for poll().
 572                  */
 573                 if (!pipe->readers)
 574                         mask |= POLLERR;
 575         }
 576
 577         return mask;
 578 }
 579
 580 static int
 581 pipe_release(struct inode *inode, int decr, int decw)
 582 {
 583         struct pipe_inode_info *pipe;
 584
 585         mutex_lock(&inode->i_mutex);
 586         pipe = inode->i_pipe;
 587         pipe->readers -= decr;
 588         pipe->writers -= decw;
 589
 590         if (!pipe->readers && !pipe->writers) {
 591                 free_pipe_info(inode);
 592         } else {
 593                 wake_up_interruptible(&pipe->wait);
 594                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 595                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 596         }
 597         mutex_unlock(&inode->i_mutex);
 598
 599         return 0;
 600 }
 601
 602 static int
 603 pipe_read_fasync(int fd, struct file *filp, int on)
 604 {
 605         struct inode *inode = filp->f_path.dentry->d_inode;
 606         int retval;
 607
 608         mutex_lock(&inode->i_mutex);
 609         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
 610         mutex_unlock(&inode->i_mutex);
 611
 612         if (retval < 0)
 613                 return retval;
 614
 615         return 0;
 616 }
 617
 618
 619 static int
 620 pipe_write_fasync(int fd, struct file *filp, int on)
 621 {
 622         struct inode *inode = filp->f_path.dentry->d_inode;
 623         int retval;
 624
 625         mutex_lock(&inode->i_mutex);
 626         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
 627         mutex_unlock(&inode->i_mutex);
 628
 629         if (retval < 0)
 630                 return retval;
 631
 632         return 0;
 633 }
 634
 635
 636 static int
 637 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 638 {
 639         struct inode *inode = filp->f_path.dentry->d_inode;
 640         struct pipe_inode_info *pipe = inode->i_pipe;
 641         int retval;
 642
 643         mutex_lock(&inode->i_mutex);
 644
 645         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 646
 647         if (retval >= 0)
 648                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 649
 650         mutex_unlock(&inode->i_mutex);
 651
 652         if (retval < 0)
 653                 return retval;
 654
 655         return 0;
 656 }
 657
 658
 659 static int
 660 pipe_read_release(struct inode *inode, struct file *filp)
 661 {
 662         pipe_read_fasync(-1, filp, 0);
 663         return pipe_release(inode, 1, 0);
 664 }
 665
 666 static int
 667 pipe_write_release(struct inode *inode, struct file *filp)
 668 {
 669         pipe_write_fasync(-1, filp, 0);
 670         return pipe_release(inode, 0, 1);
 671 }
 672
 673 static int
 674 pipe_rdwr_release(struct inode *inode, struct file *filp)
 675 {
 676         int decr, decw;
 677
 678         pipe_rdwr_fasync(-1, filp, 0);
 679         decr = (filp->f_mode & FMODE_READ) != 0;
 680         decw = (filp->f_mode & FMODE_WRITE) != 0;
 681         return pipe_release(inode, decr, decw);
 682 }
 683
 684 static int
 685 pipe_read_open(struct inode *inode, struct file *filp)
 686 {
 687         /* We could have perhaps used atomic_t, but this and friends
 688            below are the only places.  So it doesn't seem worthwhile.  */
 689         mutex_lock(&inode->i_mutex);
 690         inode->i_pipe->readers++;
 691         mutex_unlock(&inode->i_mutex);
 692
 693         return 0;
 694 }
 695
 696 static int
 697 pipe_write_open(struct inode *inode, struct file *filp)
 698 {
 699         mutex_lock(&inode->i_mutex);
 700         inode->i_pipe->writers++;
 701         mutex_unlock(&inode->i_mutex);
 702
 703         return 0;
 704 }
 705
 706 static int
 707 pipe_rdwr_open(struct inode *inode, struct file *filp)
 708 {
 709         mutex_lock(&inode->i_mutex);
 710         if (filp->f_mode & FMODE_READ)
 711                 inode->i_pipe->readers++;
 712         if (filp->f_mode & FMODE_WRITE)
 713                 inode->i_pipe->writers++;
 714         mutex_unlock(&inode->i_mutex);
 715
 716         return 0;
 717 }
 718
 719 /*
 720  * The file_operations structs are not static because they
 721  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 722  */
 723 const struct file_operations read_fifo_fops = {
 724         .llseek         = no_llseek,
 725         .read           = do_sync_read,
 726         .aio_read       = pipe_read,
 727         .write          = bad_pipe_w,
 728         .poll           = pipe_poll,
 729         .ioctl          = pipe_ioctl,
 730         .open           = pipe_read_open,
 731         .release        = pipe_read_release,
 732         .fasync         = pipe_read_fasync,
 733 };
 734
 735 const struct file_operations write_fifo_fops = {
 736         .llseek         = no_llseek,
 737         .read           = bad_pipe_r,
 738         .write          = do_sync_write,
 739         .aio_write      = pipe_write,
 740         .poll           = pipe_poll,
 741         .ioctl          = pipe_ioctl,
 742         .open           = pipe_write_open,
 743         .release        = pipe_write_release,
 744         .fasync         = pipe_write_fasync,
 745 };
 746
 747 const struct file_operations rdwr_fifo_fops = {
 748         .llseek         = no_llseek,
 749         .read           = do_sync_read,
 750         .aio_read       = pipe_read,
 751         .write          = do_sync_write,
 752         .aio_write      = pipe_write,
 753         .poll           = pipe_poll,
 754         .ioctl          = pipe_ioctl,
 755         .open           = pipe_rdwr_open,
 756         .release        = pipe_rdwr_release,
 757         .fasync         = pipe_rdwr_fasync,
 758 };
 759
 760 static const struct file_operations read_pipe_fops = {
 761         .llseek         = no_llseek,
 762         .read           = do_sync_read,
 763         .aio_read       = pipe_read,
 764         .write          = bad_pipe_w,
 765         .poll           = pipe_poll,
 766         .ioctl          = pipe_ioctl,
 767         .open           = pipe_read_open,
 768         .release        = pipe_read_release,
 769         .fasync         = pipe_read_fasync,
 770 };
 771
 772 static const struct file_operations write_pipe_fops = {
 773         .llseek         = no_llseek,
 774         .read           = bad_pipe_r,
 775         .write          = do_sync_write,
 776         .aio_write      = pipe_write,
 777         .poll           = pipe_poll,
 778         .ioctl          = pipe_ioctl,
 779         .open           = pipe_write_open,
 780         .release        = pipe_write_release,
 781         .fasync         = pipe_write_fasync,
 782 };
 783
 784 static const struct file_operations rdwr_pipe_fops = {
 785         .llseek         = no_llseek,
 786         .read           = do_sync_read,
 787         .aio_read       = pipe_read,
 788         .write          = do_sync_write,
 789         .aio_write      = pipe_write,
 790         .poll           = pipe_poll,
 791         .ioctl          = pipe_ioctl,
 792         .open           = pipe_rdwr_open,
 793         .release        = pipe_rdwr_release,
 794         .fasync         = pipe_rdwr_fasync,
 795 };
 796
 797 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
 798 {
 799         struct pipe_inode_info *pipe;
 800
 801         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 802         if (pipe) {
 803                 init_waitqueue_head(&pipe->wait);
 804                 pipe->r_counter = pipe->w_counter = 1;
 805                 pipe->inode = inode;
 806         }
 807
 808         return pipe;
 809 }
 810
 811 void __free_pipe_info(struct pipe_inode_info *pipe)
 812 {
 813         int i;
 814
 815         for (i = 0; i < PIPE_BUFFERS; i++) {
 816                 struct pipe_buffer *buf = pipe->bufs + i;
 817                 if (buf->ops)
 818                         buf->ops->release(pipe, buf);
 819         }
 820         if (pipe->tmp_page)
 821                 __free_page(pipe->tmp_page);
 822         kfree(pipe);
 823 }
 824
 825 void free_pipe_info(struct inode *inode)
 826 {
 827         __free_pipe_info(inode->i_pipe);
 828         inode->i_pipe = NULL;
 829 }
 830
 831 static struct vfsmount *pipe_mnt __read_mostly;
 832 static int pipefs_delete_dentry(struct dentry *dentry)
 833 {
 834         /*
 835          * At creation time, we pretended this dentry was hashed
 836          * (by clearing DCACHE_UNHASHED bit in d_flags)
 837          * At delete time, we restore the truth : not hashed.
 838          * (so that dput() can proceed correctly)
 839          */
 840         dentry->d_flags |= DCACHE_UNHASHED;
 841         return 0;
 842 }
 843
 844 /*
 845  * pipefs_dname() is called from d_path().
 846  */
 847 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 848 {
 849         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 850                                 dentry->d_inode->i_ino);
 851 }
 852
 853 static struct dentry_operations pipefs_dentry_operations = {
 854         .d_delete       = pipefs_delete_dentry,
 855         .d_dname        = pipefs_dname,
 856 };
 857
 858 static struct inode * get_pipe_inode(void)
 859 {
 860         struct inode *inode = new_inode(pipe_mnt->mnt_sb);
 861         struct pipe_inode_info *pipe;
 862
 863         if (!inode)
 864                 goto fail_inode;
 865
 866         pipe = alloc_pipe_info(inode);
 867         if (!pipe)
 868                 goto fail_iput;
 869         inode->i_pipe = pipe;
 870
 871         pipe->readers = pipe->writers = 1;
 872         inode->i_fop = &rdwr_pipe_fops;
 873
 874         /*
 875          * Mark the inode dirty from the very beginning,
 876          * that way it will never be moved to the dirty
 877          * list because "mark_inode_dirty()" will think
 878          * that it already _is_ on the dirty list.
 879          */
 880         inode->i_state = I_DIRTY;
 881         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 882         inode->i_uid = current->fsuid;
 883         inode->i_gid = current->fsgid;
 884         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 885
 886         return inode;
 887
 888 fail_iput:
 889         iput(inode);
 890
 891 fail_inode:
 892         return NULL;
 893 }
 894
 895 struct file *create_write_pipe(void)
 896 {
 897         int err;
 898         struct inode *inode;
 899         struct file *f;
 900         struct dentry *dentry;
 901         struct qstr name = { .name = "" };
 902
 903         f = get_empty_filp();
 904         if (!f)
 905                 return ERR_PTR(-ENFILE);
 906         err = -ENFILE;
 907         inode = get_pipe_inode();
 908         if (!inode)
 909                 goto err_file;
 910
 911         err = -ENOMEM;
 912         dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
 913         if (!dentry)
 914                 goto err_inode;
 915
 916         dentry->d_op = &pipefs_dentry_operations;
 917         /*
 918          * We dont want to publish this dentry into global dentry hash table.
 919          * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
 920          * This permits a working /proc/$pid/fd/XXX on pipes
 921          */
 922         dentry->d_flags &= ~DCACHE_UNHASHED;
 923         d_instantiate(dentry, inode);
 924         f->f_path.mnt = mntget(pipe_mnt);
 925         f->f_path.dentry = dentry;
 926         f->f_mapping = inode->i_mapping;
 927
 928         f->f_flags = O_WRONLY;
 929         f->f_op = &write_pipe_fops;
 930         f->f_mode = FMODE_WRITE;
 931         f->f_version = 0;
 932
 933         return f;
 934
 935  err_inode:
 936         free_pipe_info(inode);
 937         iput(inode);
 938  err_file:
 939         put_filp(f);
 940         return ERR_PTR(err);
 941 }
 942
 943 void free_write_pipe(struct file *f)
 944 {
 945         free_pipe_info(f->f_dentry->d_inode);
 946         dput(f->f_path.dentry);
 947         mntput(f->f_path.mnt);
 948         put_filp(f);
 949 }
 950
 951 struct file *create_read_pipe(struct file *wrf)
 952 {
 953         struct file *f = get_empty_filp();
 954         if (!f)
 955                 return ERR_PTR(-ENFILE);
 956
 957         /* Grab pipe from the writer */
 958         f->f_path.mnt = mntget(wrf->f_path.mnt);
 959         f->f_path.dentry = dget(wrf->f_path.dentry);
 960         f->f_mapping = wrf->f_path.dentry->d_inode->i_mapping;
 961
 962         f->f_pos = 0;
 963         f->f_flags = O_RDONLY;
 964         f->f_op = &read_pipe_fops;
 965         f->f_mode = FMODE_READ;
 966         f->f_version = 0;
 967
 968         return f;
 969 }
 970
 971 int do_pipe(int *fd)
 972 {
 973         struct file *fw, *fr;
 974         int error;
 975         int fdw, fdr;
 976
 977         fw = create_write_pipe();
 978         if (IS_ERR(fw))
 979                 return PTR_ERR(fw);
 980         fr = create_read_pipe(fw);
 981         error = PTR_ERR(fr);
 982         if (IS_ERR(fr))
 983                 goto err_write_pipe;
 984
 985         error = get_unused_fd();
 986         if (error < 0)
 987                 goto err_read_pipe;
 988         fdr = error;
 989
 990         error = get_unused_fd();
 991         if (error < 0)
 992                 goto err_fdr;
 993         fdw = error;
 994
 995         error = audit_fd_pair(fdr, fdw);
 996         if (error < 0)
 997                 goto err_fdw;
 998
 999         fd_install(fdr, fr);
1000         fd_install(fdw, fw);
1001         fd[0] = fdr;
1002         fd[1] = fdw;
1003
1004         return 0;
1005
1006  err_fdw:
1007         put_unused_fd(fdw);
1008  err_fdr:
1009         put_unused_fd(fdr);
1010  err_read_pipe:
1011         dput(fr->f_dentry);
1012         mntput(fr->f_vfsmnt);
1013         put_filp(fr);
1014  err_write_pipe:
1015         free_write_pipe(fw);
1016         return error;
1017 }
1018
1019 /*
1020  * pipefs should _never_ be mounted by userland - too much of security hassle,
1021  * no real gain from having the whole whorehouse mounted. So we don't need
1022  * any operations on the root directory. However, we need a non-trivial
1023  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1024  */
1025 static int pipefs_get_sb(struct file_system_type *fs_type,
1026                          int flags, const char *dev_name, void *data,
1027                          struct vfsmount *mnt)
1028 {
1029         return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
1030 }
1031
1032 static struct file_system_type pipe_fs_type = {
1033         .name           = "pipefs",
1034         .get_sb         = pipefs_get_sb,
1035         .kill_sb        = kill_anon_super,
1036 };
1037
1038 static int __init init_pipe_fs(void)
1039 {
1040         int err = register_filesystem(&pipe_fs_type);
1041
1042         if (!err) {
1043                 pipe_mnt = kern_mount(&pipe_fs_type);
1044                 if (IS_ERR(pipe_mnt)) {
1045                         err = PTR_ERR(pipe_mnt);
1046                         unregister_filesystem(&pipe_fs_type);
1047                 }
1048         }
1049         return err;
1050 }
1051
1052 static void __exit exit_pipe_fs(void)
1053 {
1054         unregister_filesystem(&pipe_fs_type);
1055         mntput(pipe_mnt);
1056 }
1057
1058 fs_initcall(init_pipe_fs);
1059 module_exit(exit_pipe_fs);