fs/pipe.c

   1 /*
   2  *  linux/fs/pipe.c
   3  *
   4  *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
   5  */
   6
   7 #include <linux/mm.h>
   8 #include <linux/file.h>
   9 #include <linux/poll.h>
  10 #include <linux/slab.h>
  11 #include <linux/module.h>
  12 #include <linux/init.h>
  13 #include <linux/fs.h>
  14 #include <linux/mount.h>
  15 #include <linux/pipe_fs_i.h>
  16 #include <linux/uio.h>
  17 #include <linux/highmem.h>
  18 #include <linux/pagemap.h>
  19
  20 #include <asm/uaccess.h>
  21 #include <asm/ioctls.h>
  22
  23 /*
  24  * We use a start+len construction, which provides full use of the
  25  * allocated memory.
  26  * -- Florian Coosmann (FGC)
  27  *
  28  * Reads with count = 0 should always return 0.
  29  * -- Julian Bradfield 1999-06-07.
  30  *
  31  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  32  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  33  *
  34  * pipe_read & write cleanup
  35  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  36  */
  37
  38 /* Drop the inode semaphore and wait for a pipe event, atomically */
  39 void pipe_wait(struct pipe_inode_info *pipe)
  40 {
  41         DEFINE_WAIT(wait);
  42
  43         /*
  44          * Pipes are system-local resources, so sleeping on them
  45          * is considered a noninteractive wait:
  46          */
  47         prepare_to_wait(&pipe->wait, &wait,
  48                         TASK_INTERRUPTIBLE | TASK_NONINTERACTIVE);
  49         if (pipe->inode)
  50                 mutex_unlock(&pipe->inode->i_mutex);
  51         schedule();
  52         finish_wait(&pipe->wait, &wait);
  53         if (pipe->inode)
  54                 mutex_lock(&pipe->inode->i_mutex);
  55 }
  56
  57 static int
  58 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
  59                         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 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 167                            struct pipe_buffer *buf, int atomic)
 168 {
 169         if (atomic) {
 170                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 171                 return kmap_atomic(buf->page, KM_USER0);
 172         }
 173
 174         return kmap(buf->page);
 175 }
 176
 177 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 178                             struct pipe_buffer *buf, void *map_data)
 179 {
 180         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 181                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 182                 kunmap_atomic(map_data, KM_USER0);
 183         } else
 184                 kunmap(buf->page);
 185 }
 186
 187 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 188                            struct pipe_buffer *buf)
 189 {
 190         struct page *page = buf->page;
 191
 192         if (page_count(page) == 1) {
 193                 lock_page(page);
 194                 return 0;
 195         }
 196
 197         return 1;
 198 }
 199
 200 void generic_pipe_buf_get(struct pipe_inode_info *info, struct pipe_buffer *buf)
 201 {
 202         page_cache_get(buf->page);
 203 }
 204
 205 int generic_pipe_buf_pin(struct pipe_inode_info *info, struct pipe_buffer *buf)
 206 {
 207         return 0;
 208 }
 209
 210 static struct pipe_buf_operations anon_pipe_buf_ops = {
 211         .can_merge = 1,
 212         .map = generic_pipe_buf_map,
 213         .unmap = generic_pipe_buf_unmap,
 214         .pin = generic_pipe_buf_pin,
 215         .release = anon_pipe_buf_release,
 216         .steal = generic_pipe_buf_steal,
 217         .get = generic_pipe_buf_get,
 218 };
 219
 220 static ssize_t
 221 pipe_readv(struct file *filp, const struct iovec *_iov,
 222            unsigned long nr_segs, loff_t *ppos)
 223 {
 224         struct inode *inode = filp->f_dentry->d_inode;
 225         struct pipe_inode_info *pipe;
 226         int do_wakeup;
 227         ssize_t ret;
 228         struct iovec *iov = (struct iovec *)_iov;
 229         size_t total_len;
 230
 231         total_len = iov_length(iov, nr_segs);
 232         /* Null read succeeds. */
 233         if (unlikely(total_len == 0))
 234                 return 0;
 235
 236         do_wakeup = 0;
 237         ret = 0;
 238         mutex_lock(&inode->i_mutex);
 239         pipe = inode->i_pipe;
 240         for (;;) {
 241                 int bufs = pipe->nrbufs;
 242                 if (bufs) {
 243                         int curbuf = pipe->curbuf;
 244                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 245                         struct pipe_buf_operations *ops = buf->ops;
 246                         void *addr;
 247                         size_t chars = buf->len;
 248                         int error, atomic;
 249
 250                         if (chars > total_len)
 251                                 chars = total_len;
 252
 253                         error = ops->pin(pipe, buf);
 254                         if (error) {
 255                                 if (!ret)
 256                                         error = ret;
 257                                 break;
 258                         }
 259
 260                         atomic = !iov_fault_in_pages_write(iov, chars);
 261 redo:
 262                         addr = ops->map(pipe, buf, atomic);
 263                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
 264                         ops->unmap(pipe, buf, addr);
 265                         if (unlikely(error)) {
 266                                 /*
 267                                  * Just retry with the slow path if we failed.
 268                                  */
 269                                 if (atomic) {
 270                                         atomic = 0;
 271                                         goto redo;
 272                                 }
 273                                 if (!ret)
 274                                         ret = error;
 275                                 break;
 276                         }
 277                         ret += chars;
 278                         buf->offset += chars;
 279                         buf->len -= chars;
 280                         if (!buf->len) {
 281                                 buf->ops = NULL;
 282                                 ops->release(pipe, buf);
 283                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
 284                                 pipe->curbuf = curbuf;
 285                                 pipe->nrbufs = --bufs;
 286                                 do_wakeup = 1;
 287                         }
 288                         total_len -= chars;
 289                         if (!total_len)
 290                                 break;  /* common path: read succeeded */
 291                 }
 292                 if (bufs)       /* More to do? */
 293                         continue;
 294                 if (!pipe->writers)
 295                         break;
 296                 if (!pipe->waiting_writers) {
 297                         /* syscall merging: Usually we must not sleep
 298                          * if O_NONBLOCK is set, or if we got some data.
 299                          * But if a writer sleeps in kernel space, then
 300                          * we can wait for that data without violating POSIX.
 301                          */
 302                         if (ret)
 303                                 break;
 304                         if (filp->f_flags & O_NONBLOCK) {
 305                                 ret = -EAGAIN;
 306                                 break;
 307                         }
 308                 }
 309                 if (signal_pending(current)) {
 310                         if (!ret)
 311                                 ret = -ERESTARTSYS;
 312                         break;
 313                 }
 314                 if (do_wakeup) {
 315                         wake_up_interruptible_sync(&pipe->wait);
 316                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 317                 }
 318                 pipe_wait(pipe);
 319         }
 320         mutex_unlock(&inode->i_mutex);
 321
 322         /* Signal writers asynchronously that there is more room. */
 323         if (do_wakeup) {
 324                 wake_up_interruptible(&pipe->wait);
 325                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 326         }
 327         if (ret > 0)
 328                 file_accessed(filp);
 329         return ret;
 330 }
 331
 332 static ssize_t
 333 pipe_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 334 {
 335         struct iovec iov = { .iov_base = buf, .iov_len = count };
 336
 337         return pipe_readv(filp, &iov, 1, ppos);
 338 }
 339
 340 static ssize_t
 341 pipe_writev(struct file *filp, const struct iovec *_iov,
 342             unsigned long nr_segs, loff_t *ppos)
 343 {
 344         struct inode *inode = filp->f_dentry->d_inode;
 345         struct pipe_inode_info *pipe;
 346         ssize_t ret;
 347         int do_wakeup;
 348         struct iovec *iov = (struct iovec *)_iov;
 349         size_t total_len;
 350         ssize_t chars;
 351
 352         total_len = iov_length(iov, nr_segs);
 353         /* Null write succeeds. */
 354         if (unlikely(total_len == 0))
 355                 return 0;
 356
 357         do_wakeup = 0;
 358         ret = 0;
 359         mutex_lock(&inode->i_mutex);
 360         pipe = inode->i_pipe;
 361
 362         if (!pipe->readers) {
 363                 send_sig(SIGPIPE, current, 0);
 364                 ret = -EPIPE;
 365                 goto out;
 366         }
 367
 368         /* We try to merge small writes */
 369         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 370         if (pipe->nrbufs && chars != 0) {
 371                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 372                                                         (PIPE_BUFFERS-1);
 373                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 374                 struct pipe_buf_operations *ops = buf->ops;
 375                 int offset = buf->offset + buf->len;
 376
 377                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 378                         int error, atomic = 1;
 379                         void *addr;
 380
 381                         error = ops->pin(pipe, buf);
 382                         if (error)
 383                                 goto out;
 384
 385                         iov_fault_in_pages_read(iov, chars);
 386 redo1:
 387                         addr = ops->map(pipe, buf, atomic);
 388                         error = pipe_iov_copy_from_user(offset + addr, iov,
 389                                                         chars, atomic);
 390                         ops->unmap(pipe, buf, addr);
 391                         ret = error;
 392                         do_wakeup = 1;
 393                         if (error) {
 394                                 if (atomic) {
 395                                         atomic = 0;
 396                                         goto redo1;
 397                                 }
 398                                 goto out;
 399                         }
 400                         buf->len += chars;
 401                         total_len -= chars;
 402                         ret = chars;
 403                         if (!total_len)
 404                                 goto out;
 405                 }
 406         }
 407
 408         for (;;) {
 409                 int bufs;
 410
 411                 if (!pipe->readers) {
 412                         send_sig(SIGPIPE, current, 0);
 413                         if (!ret)
 414                                 ret = -EPIPE;
 415                         break;
 416                 }
 417                 bufs = pipe->nrbufs;
 418                 if (bufs < PIPE_BUFFERS) {
 419                         int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1);
 420                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 421                         struct page *page = pipe->tmp_page;
 422                         char *src;
 423                         int error, atomic = 1;
 424
 425                         if (!page) {
 426                                 page = alloc_page(GFP_HIGHUSER);
 427                                 if (unlikely(!page)) {
 428                                         ret = ret ? : -ENOMEM;
 429                                         break;
 430                                 }
 431                                 pipe->tmp_page = page;
 432                         }
 433                         /* Always wake up, even if the copy fails. Otherwise
 434                          * we lock up (O_NONBLOCK-)readers that sleep due to
 435                          * syscall merging.
 436                          * FIXME! Is this really true?
 437                          */
 438                         do_wakeup = 1;
 439                         chars = PAGE_SIZE;
 440                         if (chars > total_len)
 441                                 chars = total_len;
 442
 443                         iov_fault_in_pages_read(iov, chars);
 444 redo2:
 445                         if (atomic)
 446                                 src = kmap_atomic(page, KM_USER0);
 447                         else
 448                                 src = kmap(page);
 449
 450                         error = pipe_iov_copy_from_user(src, iov, chars,
 451                                                         atomic);
 452                         if (atomic)
 453                                 kunmap_atomic(src, KM_USER0);
 454                         else
 455                                 kunmap(page);
 456
 457                         if (unlikely(error)) {
 458                                 if (atomic) {
 459                                         atomic = 0;
 460                                         goto redo2;
 461                                 }
 462                                 if (!ret)
 463                                         ret = error;
 464                                 break;
 465                         }
 466                         ret += chars;
 467
 468                         /* Insert it into the buffer array */
 469                         buf->page = page;
 470                         buf->ops = &anon_pipe_buf_ops;
 471                         buf->offset = 0;
 472                         buf->len = chars;
 473                         pipe->nrbufs = ++bufs;
 474                         pipe->tmp_page = NULL;
 475
 476                         total_len -= chars;
 477                         if (!total_len)
 478                                 break;
 479                 }
 480                 if (bufs < PIPE_BUFFERS)
 481                         continue;
 482                 if (filp->f_flags & O_NONBLOCK) {
 483                         if (!ret)
 484                                 ret = -EAGAIN;
 485                         break;
 486                 }
 487                 if (signal_pending(current)) {
 488                         if (!ret)
 489                                 ret = -ERESTARTSYS;
 490                         break;
 491                 }
 492                 if (do_wakeup) {
 493                         wake_up_interruptible_sync(&pipe->wait);
 494                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 495                         do_wakeup = 0;
 496                 }
 497                 pipe->waiting_writers++;
 498                 pipe_wait(pipe);
 499                 pipe->waiting_writers--;
 500         }
 501 out:
 502         mutex_unlock(&inode->i_mutex);
 503         if (do_wakeup) {
 504                 wake_up_interruptible(&pipe->wait);
 505                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 506         }
 507         if (ret > 0)
 508                 file_update_time(filp);
 509         return ret;
 510 }
 511
 512 static ssize_t
 513 pipe_write(struct file *filp, const char __user *buf,
 514            size_t count, loff_t *ppos)
 515 {
 516         struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = count };
 517
 518         return pipe_writev(filp, &iov, 1, ppos);
 519 }
 520
 521 static ssize_t
 522 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 523 {
 524         return -EBADF;
 525 }
 526
 527 static ssize_t
 528 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
 529            loff_t *ppos)
 530 {
 531         return -EBADF;
 532 }
 533
 534 static int
 535 pipe_ioctl(struct inode *pino, struct file *filp,
 536            unsigned int cmd, unsigned long arg)
 537 {
 538         struct inode *inode = filp->f_dentry->d_inode;
 539         struct pipe_inode_info *pipe;
 540         int count, buf, nrbufs;
 541
 542         switch (cmd) {
 543                 case FIONREAD:
 544                         mutex_lock(&inode->i_mutex);
 545                         pipe = inode->i_pipe;
 546                         count = 0;
 547                         buf = pipe->curbuf;
 548                         nrbufs = pipe->nrbufs;
 549                         while (--nrbufs >= 0) {
 550                                 count += pipe->bufs[buf].len;
 551                                 buf = (buf+1) & (PIPE_BUFFERS-1);
 552                         }
 553                         mutex_unlock(&inode->i_mutex);
 554
 555                         return put_user(count, (int __user *)arg);
 556                 default:
 557                         return -EINVAL;
 558         }
 559 }
 560
 561 /* No kernel lock held - fine */
 562 static unsigned int
 563 pipe_poll(struct file *filp, poll_table *wait)
 564 {
 565         unsigned int mask;
 566         struct inode *inode = filp->f_dentry->d_inode;
 567         struct pipe_inode_info *pipe = inode->i_pipe;
 568         int nrbufs;
 569
 570         poll_wait(filp, &pipe->wait, wait);
 571
 572         /* Reading only -- no need for acquiring the semaphore.  */
 573         nrbufs = pipe->nrbufs;
 574         mask = 0;
 575         if (filp->f_mode & FMODE_READ) {
 576                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 577                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 578                         mask |= POLLHUP;
 579         }
 580
 581         if (filp->f_mode & FMODE_WRITE) {
 582                 mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
 583                 /*
 584                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 585                  * behave exactly like pipes for poll().
 586                  */
 587                 if (!pipe->readers)
 588                         mask |= POLLERR;
 589         }
 590
 591         return mask;
 592 }
 593
 594 static int
 595 pipe_release(struct inode *inode, int decr, int decw)
 596 {
 597         struct pipe_inode_info *pipe;
 598
 599         mutex_lock(&inode->i_mutex);
 600         pipe = inode->i_pipe;
 601         pipe->readers -= decr;
 602         pipe->writers -= decw;
 603
 604         if (!pipe->readers && !pipe->writers) {
 605                 free_pipe_info(inode);
 606         } else {
 607                 wake_up_interruptible(&pipe->wait);
 608                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 609                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 610         }
 611         mutex_unlock(&inode->i_mutex);
 612
 613         return 0;
 614 }
 615
 616 static int
 617 pipe_read_fasync(int fd, struct file *filp, int on)
 618 {
 619         struct inode *inode = filp->f_dentry->d_inode;
 620         int retval;
 621
 622         mutex_lock(&inode->i_mutex);
 623         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
 624         mutex_unlock(&inode->i_mutex);
 625
 626         if (retval < 0)
 627                 return retval;
 628
 629         return 0;
 630 }
 631
 632
 633 static int
 634 pipe_write_fasync(int fd, struct file *filp, int on)
 635 {
 636         struct inode *inode = filp->f_dentry->d_inode;
 637         int retval;
 638
 639         mutex_lock(&inode->i_mutex);
 640         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
 641         mutex_unlock(&inode->i_mutex);
 642
 643         if (retval < 0)
 644                 return retval;
 645
 646         return 0;
 647 }
 648
 649
 650 static int
 651 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 652 {
 653         struct inode *inode = filp->f_dentry->d_inode;
 654         struct pipe_inode_info *pipe = inode->i_pipe;
 655         int retval;
 656
 657         mutex_lock(&inode->i_mutex);
 658
 659         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 660
 661         if (retval >= 0)
 662                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 663
 664         mutex_unlock(&inode->i_mutex);
 665
 666         if (retval < 0)
 667                 return retval;
 668
 669         return 0;
 670 }
 671
 672
 673 static int
 674 pipe_read_release(struct inode *inode, struct file *filp)
 675 {
 676         pipe_read_fasync(-1, filp, 0);
 677         return pipe_release(inode, 1, 0);
 678 }
 679
 680 static int
 681 pipe_write_release(struct inode *inode, struct file *filp)
 682 {
 683         pipe_write_fasync(-1, filp, 0);
 684         return pipe_release(inode, 0, 1);
 685 }
 686
 687 static int
 688 pipe_rdwr_release(struct inode *inode, struct file *filp)
 689 {
 690         int decr, decw;
 691
 692         pipe_rdwr_fasync(-1, filp, 0);
 693         decr = (filp->f_mode & FMODE_READ) != 0;
 694         decw = (filp->f_mode & FMODE_WRITE) != 0;
 695         return pipe_release(inode, decr, decw);
 696 }
 697
 698 static int
 699 pipe_read_open(struct inode *inode, struct file *filp)
 700 {
 701         /* We could have perhaps used atomic_t, but this and friends
 702            below are the only places.  So it doesn't seem worthwhile.  */
 703         mutex_lock(&inode->i_mutex);
 704         inode->i_pipe->readers++;
 705         mutex_unlock(&inode->i_mutex);
 706
 707         return 0;
 708 }
 709
 710 static int
 711 pipe_write_open(struct inode *inode, struct file *filp)
 712 {
 713         mutex_lock(&inode->i_mutex);
 714         inode->i_pipe->writers++;
 715         mutex_unlock(&inode->i_mutex);
 716
 717         return 0;
 718 }
 719
 720 static int
 721 pipe_rdwr_open(struct inode *inode, struct file *filp)
 722 {
 723         mutex_lock(&inode->i_mutex);
 724         if (filp->f_mode & FMODE_READ)
 725                 inode->i_pipe->readers++;
 726         if (filp->f_mode & FMODE_WRITE)
 727                 inode->i_pipe->writers++;
 728         mutex_unlock(&inode->i_mutex);
 729
 730         return 0;
 731 }
 732
 733 /*
 734  * The file_operations structs are not static because they
 735  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 736  */
 737 const struct file_operations read_fifo_fops = {
 738         .llseek         = no_llseek,
 739         .read           = pipe_read,
 740         .readv          = pipe_readv,
 741         .write          = bad_pipe_w,
 742         .poll           = pipe_poll,
 743         .ioctl          = pipe_ioctl,
 744         .open           = pipe_read_open,
 745         .release        = pipe_read_release,
 746         .fasync         = pipe_read_fasync,
 747 };
 748
 749 const struct file_operations write_fifo_fops = {
 750         .llseek         = no_llseek,
 751         .read           = bad_pipe_r,
 752         .write          = pipe_write,
 753         .writev         = pipe_writev,
 754         .poll           = pipe_poll,
 755         .ioctl          = pipe_ioctl,
 756         .open           = pipe_write_open,
 757         .release        = pipe_write_release,
 758         .fasync         = pipe_write_fasync,
 759 };
 760
 761 const struct file_operations rdwr_fifo_fops = {
 762         .llseek         = no_llseek,
 763         .read           = pipe_read,
 764         .readv          = pipe_readv,
 765         .write          = pipe_write,
 766         .writev         = pipe_writev,
 767         .poll           = pipe_poll,
 768         .ioctl          = pipe_ioctl,
 769         .open           = pipe_rdwr_open,
 770         .release        = pipe_rdwr_release,
 771         .fasync         = pipe_rdwr_fasync,
 772 };
 773
 774 static struct file_operations read_pipe_fops = {
 775         .llseek         = no_llseek,
 776         .read           = pipe_read,
 777         .readv          = pipe_readv,
 778         .write          = bad_pipe_w,
 779         .poll           = pipe_poll,
 780         .ioctl          = pipe_ioctl,
 781         .open           = pipe_read_open,
 782         .release        = pipe_read_release,
 783         .fasync         = pipe_read_fasync,
 784 };
 785
 786 static struct file_operations write_pipe_fops = {
 787         .llseek         = no_llseek,
 788         .read           = bad_pipe_r,
 789         .write          = pipe_write,
 790         .writev         = pipe_writev,
 791         .poll           = pipe_poll,
 792         .ioctl          = pipe_ioctl,
 793         .open           = pipe_write_open,
 794         .release        = pipe_write_release,
 795         .fasync         = pipe_write_fasync,
 796 };
 797
 798 static struct file_operations rdwr_pipe_fops = {
 799         .llseek         = no_llseek,
 800         .read           = pipe_read,
 801         .readv          = pipe_readv,
 802         .write          = pipe_write,
 803         .writev         = pipe_writev,
 804         .poll           = pipe_poll,
 805         .ioctl          = pipe_ioctl,
 806         .open           = pipe_rdwr_open,
 807         .release        = pipe_rdwr_release,
 808         .fasync         = pipe_rdwr_fasync,
 809 };
 810
 811 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
 812 {
 813         struct pipe_inode_info *pipe;
 814
 815         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 816         if (pipe) {
 817                 init_waitqueue_head(&pipe->wait);
 818                 pipe->r_counter = pipe->w_counter = 1;
 819                 pipe->inode = inode;
 820         }
 821
 822         return pipe;
 823 }
 824
 825 void __free_pipe_info(struct pipe_inode_info *pipe)
 826 {
 827         int i;
 828
 829         for (i = 0; i < PIPE_BUFFERS; i++) {
 830                 struct pipe_buffer *buf = pipe->bufs + i;
 831                 if (buf->ops)
 832                         buf->ops->release(pipe, buf);
 833         }
 834         if (pipe->tmp_page)
 835                 __free_page(pipe->tmp_page);
 836         kfree(pipe);
 837 }
 838
 839 void free_pipe_info(struct inode *inode)
 840 {
 841         __free_pipe_info(inode->i_pipe);
 842         inode->i_pipe = NULL;
 843 }
 844
 845 static struct vfsmount *pipe_mnt __read_mostly;
 846 static int pipefs_delete_dentry(struct dentry *dentry)
 847 {
 848         return 1;
 849 }
 850
 851 static struct dentry_operations pipefs_dentry_operations = {
 852         .d_delete       = pipefs_delete_dentry,
 853 };
 854
 855 static struct inode * get_pipe_inode(void)
 856 {
 857         struct inode *inode = new_inode(pipe_mnt->mnt_sb);
 858         struct pipe_inode_info *pipe;
 859
 860         if (!inode)
 861                 goto fail_inode;
 862
 863         pipe = alloc_pipe_info(inode);
 864         if (!pipe)
 865                 goto fail_iput;
 866         inode->i_pipe = pipe;
 867
 868         pipe->readers = pipe->writers = 1;
 869         inode->i_fop = &rdwr_pipe_fops;
 870
 871         /*
 872          * Mark the inode dirty from the very beginning,
 873          * that way it will never be moved to the dirty
 874          * list because "mark_inode_dirty()" will think
 875          * that it already _is_ on the dirty list.
 876          */
 877         inode->i_state = I_DIRTY;
 878         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 879         inode->i_uid = current->fsuid;
 880         inode->i_gid = current->fsgid;
 881         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 882         inode->i_blksize = PAGE_SIZE;
 883
 884         return inode;
 885
 886 fail_iput:
 887         iput(inode);
 888
 889 fail_inode:
 890         return NULL;
 891 }
 892
 893 int do_pipe(int *fd)
 894 {
 895         struct qstr this;
 896         char name[32];
 897         struct dentry *dentry;
 898         struct inode * inode;
 899         struct file *f1, *f2;
 900         int error;
 901         int i, j;
 902
 903         error = -ENFILE;
 904         f1 = get_empty_filp();
 905         if (!f1)
 906                 goto no_files;
 907
 908         f2 = get_empty_filp();
 909         if (!f2)
 910                 goto close_f1;
 911
 912         inode = get_pipe_inode();
 913         if (!inode)
 914                 goto close_f12;
 915
 916         error = get_unused_fd();
 917         if (error < 0)
 918                 goto close_f12_inode;
 919         i = error;
 920
 921         error = get_unused_fd();
 922         if (error < 0)
 923                 goto close_f12_inode_i;
 924         j = error;
 925
 926         error = -ENOMEM;
 927         sprintf(name, "[%lu]", inode->i_ino);
 928         this.name = name;
 929         this.len = strlen(name);
 930         this.hash = inode->i_ino; /* will go */
 931         dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this);
 932         if (!dentry)
 933                 goto close_f12_inode_i_j;
 934
 935         dentry->d_op = &pipefs_dentry_operations;
 936         d_add(dentry, inode);
 937         f1->f_vfsmnt = f2->f_vfsmnt = mntget(mntget(pipe_mnt));
 938         f1->f_dentry = f2->f_dentry = dget(dentry);
 939         f1->f_mapping = f2->f_mapping = inode->i_mapping;
 940
 941         /* read file */
 942         f1->f_pos = f2->f_pos = 0;
 943         f1->f_flags = O_RDONLY;
 944         f1->f_op = &read_pipe_fops;
 945         f1->f_mode = FMODE_READ;
 946         f1->f_version = 0;
 947
 948         /* write file */
 949         f2->f_flags = O_WRONLY;
 950         f2->f_op = &write_pipe_fops;
 951         f2->f_mode = FMODE_WRITE;
 952         f2->f_version = 0;
 953
 954         fd_install(i, f1);
 955         fd_install(j, f2);
 956         fd[0] = i;
 957         fd[1] = j;
 958
 959         return 0;
 960
 961 close_f12_inode_i_j:
 962         put_unused_fd(j);
 963 close_f12_inode_i:
 964         put_unused_fd(i);
 965 close_f12_inode:
 966         free_pipe_info(inode);
 967         iput(inode);
 968 close_f12:
 969         put_filp(f2);
 970 close_f1:
 971         put_filp(f1);
 972 no_files:
 973         return error;
 974 }
 975
 976 /*
 977  * pipefs should _never_ be mounted by userland - too much of security hassle,
 978  * no real gain from having the whole whorehouse mounted. So we don't need
 979  * any operations on the root directory. However, we need a non-trivial
 980  * d_name - pipe: will go nicely and kill the special-casing in procfs.
 981  */
 982
 983 static struct super_block *
 984 pipefs_get_sb(struct file_system_type *fs_type, int flags,
 985               const char *dev_name, void *data)
 986 {
 987         return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC);
 988 }
 989
 990 static struct file_system_type pipe_fs_type = {
 991         .name           = "pipefs",
 992         .get_sb         = pipefs_get_sb,
 993         .kill_sb        = kill_anon_super,
 994 };
 995
 996 static int __init init_pipe_fs(void)
 997 {
 998         int err = register_filesystem(&pipe_fs_type);
 999
1000         if (!err) {
1001                 pipe_mnt = kern_mount(&pipe_fs_type);
1002                 if (IS_ERR(pipe_mnt)) {
1003                         err = PTR_ERR(pipe_mnt);
1004                         unregister_filesystem(&pipe_fs_type);
1005                 }
1006         }
1007         return err;
1008 }
1009
1010 static void __exit exit_pipe_fs(void)
1011 {
1012         unregister_filesystem(&pipe_fs_type);
1013         mntput(pipe_mnt);
1014 }
1015
1016 fs_initcall(init_pipe_fs);
1017 module_exit(exit_pipe_fs);