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 #include <linux/syscalls.h>
  21
  22 #include <asm/uaccess.h>
  23 #include <asm/ioctls.h>
  24
  25 /*
  26  * We use a start+len construction, which provides full use of the
  27  * allocated memory.
  28  * -- Florian Coosmann (FGC)
  29  *
  30  * Reads with count = 0 should always return 0.
  31  * -- Julian Bradfield 1999-06-07.
  32  *
  33  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  34  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  35  *
  36  * pipe_read & write cleanup
  37  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  38  */
  39
  40 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  41 {
  42         if (pipe->inode)
  43                 mutex_lock_nested(&pipe->inode->i_mutex, subclass);
  44 }
  45
  46 void pipe_lock(struct pipe_inode_info *pipe)
  47 {
  48         /*
  49          * pipe_lock() nests non-pipe inode locks (for writing to a file)
  50          */
  51         pipe_lock_nested(pipe, I_MUTEX_PARENT);
  52 }
  53 EXPORT_SYMBOL(pipe_lock);
  54
  55 void pipe_unlock(struct pipe_inode_info *pipe)
  56 {
  57         if (pipe->inode)
  58                 mutex_unlock(&pipe->inode->i_mutex);
  59 }
  60 EXPORT_SYMBOL(pipe_unlock);
  61
  62 void pipe_double_lock(struct pipe_inode_info *pipe1,
  63                       struct pipe_inode_info *pipe2)
  64 {
  65         BUG_ON(pipe1 == pipe2);
  66
  67         if (pipe1 < pipe2) {
  68                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
  69                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
  70         } else {
  71                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
  72                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
  73         }
  74 }
  75
  76 /* Drop the inode semaphore and wait for a pipe event, atomically */
  77 void pipe_wait(struct pipe_inode_info *pipe)
  78 {
  79         DEFINE_WAIT(wait);
  80
  81         /*
  82          * Pipes are system-local resources, so sleeping on them
  83          * is considered a noninteractive wait:
  84          */
  85         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
  86         pipe_unlock(pipe);
  87         schedule();
  88         finish_wait(&pipe->wait, &wait);
  89         pipe_lock(pipe);
  90 }
  91
  92 static int
  93 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
  94                         int atomic)
  95 {
  96         unsigned long copy;
  97
  98         while (len > 0) {
  99                 while (!iov->iov_len)
 100                         iov++;
 101                 copy = min_t(unsigned long, len, iov->iov_len);
 102
 103                 if (atomic) {
 104                         if (__copy_from_user_inatomic(to, iov->iov_base, copy))
 105                                 return -EFAULT;
 106                 } else {
 107                         if (copy_from_user(to, iov->iov_base, copy))
 108                                 return -EFAULT;
 109                 }
 110                 to += copy;
 111                 len -= copy;
 112                 iov->iov_base += copy;
 113                 iov->iov_len -= copy;
 114         }
 115         return 0;
 116 }
 117
 118 static int
 119 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
 120                       int atomic)
 121 {
 122         unsigned long copy;
 123
 124         while (len > 0) {
 125                 while (!iov->iov_len)
 126                         iov++;
 127                 copy = min_t(unsigned long, len, iov->iov_len);
 128
 129                 if (atomic) {
 130                         if (__copy_to_user_inatomic(iov->iov_base, from, copy))
 131                                 return -EFAULT;
 132                 } else {
 133                         if (copy_to_user(iov->iov_base, from, copy))
 134                                 return -EFAULT;
 135                 }
 136                 from += copy;
 137                 len -= copy;
 138                 iov->iov_base += copy;
 139                 iov->iov_len -= copy;
 140         }
 141         return 0;
 142 }
 143
 144 /*
 145  * Attempt to pre-fault in the user memory, so we can use atomic copies.
 146  * Returns the number of bytes not faulted in.
 147  */
 148 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
 149 {
 150         while (!iov->iov_len)
 151                 iov++;
 152
 153         while (len > 0) {
 154                 unsigned long this_len;
 155
 156                 this_len = min_t(unsigned long, len, iov->iov_len);
 157                 if (fault_in_pages_writeable(iov->iov_base, this_len))
 158                         break;
 159
 160                 len -= this_len;
 161                 iov++;
 162         }
 163
 164         return len;
 165 }
 166
 167 /*
 168  * Pre-fault in the user memory, so we can use atomic copies.
 169  */
 170 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
 171 {
 172         while (!iov->iov_len)
 173                 iov++;
 174
 175         while (len > 0) {
 176                 unsigned long this_len;
 177
 178                 this_len = min_t(unsigned long, len, iov->iov_len);
 179                 fault_in_pages_readable(iov->iov_base, this_len);
 180                 len -= this_len;
 181                 iov++;
 182         }
 183 }
 184
 185 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 186                                   struct pipe_buffer *buf)
 187 {
 188         struct page *page = buf->page;
 189
 190         /*
 191          * If nobody else uses this page, and we don't already have a
 192          * temporary page, let's keep track of it as a one-deep
 193          * allocation cache. (Otherwise just release our reference to it)
 194          */
 195         if (page_count(page) == 1 && !pipe->tmp_page)
 196                 pipe->tmp_page = page;
 197         else
 198                 page_cache_release(page);
 199 }
 200
 201 /**
 202  * generic_pipe_buf_map - virtually map a pipe buffer
 203  * @pipe:       the pipe that the buffer belongs to
 204  * @buf:        the buffer that should be mapped
 205  * @atomic:     whether to use an atomic map
 206  *
 207  * Description:
 208  *      This function returns a kernel virtual address mapping for the
 209  *      pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
 210  *      and the caller has to be careful not to fault before calling
 211  *      the unmap function.
 212  *
 213  *      Note that this function occupies KM_USER0 if @atomic != 0.
 214  */
 215 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 216                            struct pipe_buffer *buf, int atomic)
 217 {
 218         if (atomic) {
 219                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 220                 return kmap_atomic(buf->page, KM_USER0);
 221         }
 222
 223         return kmap(buf->page);
 224 }
 225
 226 /**
 227  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
 228  * @pipe:       the pipe that the buffer belongs to
 229  * @buf:        the buffer that should be unmapped
 230  * @map_data:   the data that the mapping function returned
 231  *
 232  * Description:
 233  *      This function undoes the mapping that ->map() provided.
 234  */
 235 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 236                             struct pipe_buffer *buf, void *map_data)
 237 {
 238         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 239                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 240                 kunmap_atomic(map_data, KM_USER0);
 241         } else
 242                 kunmap(buf->page);
 243 }
 244
 245 /**
 246  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 247  * @pipe:       the pipe that the buffer belongs to
 248  * @buf:        the buffer to attempt to steal
 249  *
 250  * Description:
 251  *      This function attempts to steal the &struct page attached to
 252  *      @buf. If successful, this function returns 0 and returns with
 253  *      the page locked. The caller may then reuse the page for whatever
 254  *      he wishes; the typical use is insertion into a different file
 255  *      page cache.
 256  */
 257 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 258                            struct pipe_buffer *buf)
 259 {
 260         struct page *page = buf->page;
 261
 262         /*
 263          * A reference of one is golden, that means that the owner of this
 264          * page is the only one holding a reference to it. lock the page
 265          * and return OK.
 266          */
 267         if (page_count(page) == 1) {
 268                 lock_page(page);
 269                 return 0;
 270         }
 271
 272         return 1;
 273 }
 274
 275 /**
 276  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 277  * @pipe:       the pipe that the buffer belongs to
 278  * @buf:        the buffer to get a reference to
 279  *
 280  * Description:
 281  *      This function grabs an extra reference to @buf. It's used in
 282  *      in the tee() system call, when we duplicate the buffers in one
 283  *      pipe into another.
 284  */
 285 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 286 {
 287         page_cache_get(buf->page);
 288 }
 289
 290 /**
 291  * generic_pipe_buf_confirm - verify contents of the pipe buffer
 292  * @info:       the pipe that the buffer belongs to
 293  * @buf:        the buffer to confirm
 294  *
 295  * Description:
 296  *      This function does nothing, because the generic pipe code uses
 297  *      pages that are always good when inserted into the pipe.
 298  */
 299 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 300                              struct pipe_buffer *buf)
 301 {
 302         return 0;
 303 }
 304
 305 /**
 306  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 307  * @pipe:       the pipe that the buffer belongs to
 308  * @buf:        the buffer to put a reference to
 309  *
 310  * Description:
 311  *      This function releases a reference to @buf.
 312  */
 313 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 314                               struct pipe_buffer *buf)
 315 {
 316         page_cache_release(buf->page);
 317 }
 318
 319 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 320         .can_merge = 1,
 321         .map = generic_pipe_buf_map,
 322         .unmap = generic_pipe_buf_unmap,
 323         .confirm = generic_pipe_buf_confirm,
 324         .release = anon_pipe_buf_release,
 325         .steal = generic_pipe_buf_steal,
 326         .get = generic_pipe_buf_get,
 327 };
 328
 329 static ssize_t
 330 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 331            unsigned long nr_segs, loff_t pos)
 332 {
 333         struct file *filp = iocb->ki_filp;
 334         struct inode *inode = filp->f_path.dentry->d_inode;
 335         struct pipe_inode_info *pipe;
 336         int do_wakeup;
 337         ssize_t ret;
 338         struct iovec *iov = (struct iovec *)_iov;
 339         size_t total_len;
 340
 341         total_len = iov_length(iov, nr_segs);
 342         /* Null read succeeds. */
 343         if (unlikely(total_len == 0))
 344                 return 0;
 345
 346         do_wakeup = 0;
 347         ret = 0;
 348         mutex_lock(&inode->i_mutex);
 349         pipe = inode->i_pipe;
 350         for (;;) {
 351                 int bufs = pipe->nrbufs;
 352                 if (bufs) {
 353                         int curbuf = pipe->curbuf;
 354                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 355                         const struct pipe_buf_operations *ops = buf->ops;
 356                         void *addr;
 357                         size_t chars = buf->len;
 358                         int error, atomic;
 359
 360                         if (chars > total_len)
 361                                 chars = total_len;
 362
 363                         error = ops->confirm(pipe, buf);
 364                         if (error) {
 365                                 if (!ret)
 366                                         error = ret;
 367                                 break;
 368                         }
 369
 370                         atomic = !iov_fault_in_pages_write(iov, chars);
 371 redo:
 372                         addr = ops->map(pipe, buf, atomic);
 373                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
 374                         ops->unmap(pipe, buf, addr);
 375                         if (unlikely(error)) {
 376                                 /*
 377                                  * Just retry with the slow path if we failed.
 378                                  */
 379                                 if (atomic) {
 380                                         atomic = 0;
 381                                         goto redo;
 382                                 }
 383                                 if (!ret)
 384                                         ret = error;
 385                                 break;
 386                         }
 387                         ret += chars;
 388                         buf->offset += chars;
 389                         buf->len -= chars;
 390                         if (!buf->len) {
 391                                 buf->ops = NULL;
 392                                 ops->release(pipe, buf);
 393                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
 394                                 pipe->curbuf = curbuf;
 395                                 pipe->nrbufs = --bufs;
 396                                 do_wakeup = 1;
 397                         }
 398                         total_len -= chars;
 399                         if (!total_len)
 400                                 break;  /* common path: read succeeded */
 401                 }
 402                 if (bufs)       /* More to do? */
 403                         continue;
 404                 if (!pipe->writers)
 405                         break;
 406                 if (!pipe->waiting_writers) {
 407                         /* syscall merging: Usually we must not sleep
 408                          * if O_NONBLOCK is set, or if we got some data.
 409                          * But if a writer sleeps in kernel space, then
 410                          * we can wait for that data without violating POSIX.
 411                          */
 412                         if (ret)
 413                                 break;
 414                         if (filp->f_flags & O_NONBLOCK) {
 415                                 ret = -EAGAIN;
 416                                 break;
 417                         }
 418                 }
 419                 if (signal_pending(current)) {
 420                         if (!ret)
 421                                 ret = -ERESTARTSYS;
 422                         break;
 423                 }
 424                 if (do_wakeup) {
 425                         wake_up_interruptible_sync(&pipe->wait);
 426                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 427                 }
 428                 pipe_wait(pipe);
 429         }
 430         mutex_unlock(&inode->i_mutex);
 431
 432         /* Signal writers asynchronously that there is more room. */
 433         if (do_wakeup) {
 434                 wake_up_interruptible_sync(&pipe->wait);
 435                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 436         }
 437         if (ret > 0)
 438                 file_accessed(filp);
 439         return ret;
 440 }
 441
 442 static ssize_t
 443 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 444             unsigned long nr_segs, loff_t ppos)
 445 {
 446         struct file *filp = iocb->ki_filp;
 447         struct inode *inode = filp->f_path.dentry->d_inode;
 448         struct pipe_inode_info *pipe;
 449         ssize_t ret;
 450         int do_wakeup;
 451         struct iovec *iov = (struct iovec *)_iov;
 452         size_t total_len;
 453         ssize_t chars;
 454
 455         total_len = iov_length(iov, nr_segs);
 456         /* Null write succeeds. */
 457         if (unlikely(total_len == 0))
 458                 return 0;
 459
 460         do_wakeup = 0;
 461         ret = 0;
 462         mutex_lock(&inode->i_mutex);
 463         pipe = inode->i_pipe;
 464
 465         if (!pipe->readers) {
 466                 send_sig(SIGPIPE, current, 0);
 467                 ret = -EPIPE;
 468                 goto out;
 469         }
 470
 471         /* We try to merge small writes */
 472         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 473         if (pipe->nrbufs && chars != 0) {
 474                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 475                                                         (PIPE_BUFFERS-1);
 476                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 477                 const struct pipe_buf_operations *ops = buf->ops;
 478                 int offset = buf->offset + buf->len;
 479
 480                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 481                         int error, atomic = 1;
 482                         void *addr;
 483
 484                         error = ops->confirm(pipe, buf);
 485                         if (error)
 486                                 goto out;
 487
 488                         iov_fault_in_pages_read(iov, chars);
 489 redo1:
 490                         addr = ops->map(pipe, buf, atomic);
 491                         error = pipe_iov_copy_from_user(offset + addr, iov,
 492                                                         chars, atomic);
 493                         ops->unmap(pipe, buf, addr);
 494                         ret = error;
 495                         do_wakeup = 1;
 496                         if (error) {
 497                                 if (atomic) {
 498                                         atomic = 0;
 499                                         goto redo1;
 500                                 }
 501                                 goto out;
 502                         }
 503                         buf->len += chars;
 504                         total_len -= chars;
 505                         ret = chars;
 506                         if (!total_len)
 507                                 goto out;
 508                 }
 509         }
 510
 511         for (;;) {
 512                 int bufs;
 513
 514                 if (!pipe->readers) {
 515                         send_sig(SIGPIPE, current, 0);
 516                         if (!ret)
 517                                 ret = -EPIPE;
 518                         break;
 519                 }
 520                 bufs = pipe->nrbufs;
 521                 if (bufs < PIPE_BUFFERS) {
 522                         int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1);
 523                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 524                         struct page *page = pipe->tmp_page;
 525                         char *src;
 526                         int error, atomic = 1;
 527
 528                         if (!page) {
 529                                 page = alloc_page(GFP_HIGHUSER);
 530                                 if (unlikely(!page)) {
 531                                         ret = ret ? : -ENOMEM;
 532                                         break;
 533                                 }
 534                                 pipe->tmp_page = page;
 535                         }
 536                         /* Always wake up, even if the copy fails. Otherwise
 537                          * we lock up (O_NONBLOCK-)readers that sleep due to
 538                          * syscall merging.
 539                          * FIXME! Is this really true?
 540                          */
 541                         do_wakeup = 1;
 542                         chars = PAGE_SIZE;
 543                         if (chars > total_len)
 544                                 chars = total_len;
 545
 546                         iov_fault_in_pages_read(iov, chars);
 547 redo2:
 548                         if (atomic)
 549                                 src = kmap_atomic(page, KM_USER0);
 550                         else
 551                                 src = kmap(page);
 552
 553                         error = pipe_iov_copy_from_user(src, iov, chars,
 554                                                         atomic);
 555                         if (atomic)
 556                                 kunmap_atomic(src, KM_USER0);
 557                         else
 558                                 kunmap(page);
 559
 560                         if (unlikely(error)) {
 561                                 if (atomic) {
 562                                         atomic = 0;
 563                                         goto redo2;
 564                                 }
 565                                 if (!ret)
 566                                         ret = error;
 567                                 break;
 568                         }
 569                         ret += chars;
 570
 571                         /* Insert it into the buffer array */
 572                         buf->page = page;
 573                         buf->ops = &anon_pipe_buf_ops;
 574                         buf->offset = 0;
 575                         buf->len = chars;
 576                         pipe->nrbufs = ++bufs;
 577                         pipe->tmp_page = NULL;
 578
 579                         total_len -= chars;
 580                         if (!total_len)
 581                                 break;
 582                 }
 583                 if (bufs < PIPE_BUFFERS)
 584                         continue;
 585                 if (filp->f_flags & O_NONBLOCK) {
 586                         if (!ret)
 587                                 ret = -EAGAIN;
 588                         break;
 589                 }
 590                 if (signal_pending(current)) {
 591                         if (!ret)
 592                                 ret = -ERESTARTSYS;
 593                         break;
 594                 }
 595                 if (do_wakeup) {
 596                         wake_up_interruptible_sync(&pipe->wait);
 597                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 598                         do_wakeup = 0;
 599                 }
 600                 pipe->waiting_writers++;
 601                 pipe_wait(pipe);
 602                 pipe->waiting_writers--;
 603         }
 604 out:
 605         mutex_unlock(&inode->i_mutex);
 606         if (do_wakeup) {
 607                 wake_up_interruptible_sync(&pipe->wait);
 608                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 609         }
 610         if (ret > 0)
 611                 file_update_time(filp);
 612         return ret;
 613 }
 614
 615 static ssize_t
 616 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 617 {
 618         return -EBADF;
 619 }
 620
 621 static ssize_t
 622 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
 623            loff_t *ppos)
 624 {
 625         return -EBADF;
 626 }
 627
 628 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 629 {
 630         struct inode *inode = filp->f_path.dentry->d_inode;
 631         struct pipe_inode_info *pipe;
 632         int count, buf, nrbufs;
 633
 634         switch (cmd) {
 635                 case FIONREAD:
 636                         mutex_lock(&inode->i_mutex);
 637                         pipe = inode->i_pipe;
 638                         count = 0;
 639                         buf = pipe->curbuf;
 640                         nrbufs = pipe->nrbufs;
 641                         while (--nrbufs >= 0) {
 642                                 count += pipe->bufs[buf].len;
 643                                 buf = (buf+1) & (PIPE_BUFFERS-1);
 644                         }
 645                         mutex_unlock(&inode->i_mutex);
 646
 647                         return put_user(count, (int __user *)arg);
 648                 default:
 649                         return -EINVAL;
 650         }
 651 }
 652
 653 /* No kernel lock held - fine */
 654 static unsigned int
 655 pipe_poll(struct file *filp, poll_table *wait)
 656 {
 657         unsigned int mask;
 658         struct inode *inode = filp->f_path.dentry->d_inode;
 659         struct pipe_inode_info *pipe = inode->i_pipe;
 660         int nrbufs;
 661
 662         poll_wait(filp, &pipe->wait, wait);
 663
 664         /* Reading only -- no need for acquiring the semaphore.  */
 665         nrbufs = pipe->nrbufs;
 666         mask = 0;
 667         if (filp->f_mode & FMODE_READ) {
 668                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 669                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 670                         mask |= POLLHUP;
 671         }
 672
 673         if (filp->f_mode & FMODE_WRITE) {
 674                 mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
 675                 /*
 676                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 677                  * behave exactly like pipes for poll().
 678                  */
 679                 if (!pipe->readers)
 680                         mask |= POLLERR;
 681         }
 682
 683         return mask;
 684 }
 685
 686 static int
 687 pipe_release(struct inode *inode, int decr, int decw)
 688 {
 689         struct pipe_inode_info *pipe;
 690
 691         mutex_lock(&inode->i_mutex);
 692         pipe = inode->i_pipe;
 693         pipe->readers -= decr;
 694         pipe->writers -= decw;
 695
 696         if (!pipe->readers && !pipe->writers) {
 697                 free_pipe_info(inode);
 698         } else {
 699                 wake_up_interruptible_sync(&pipe->wait);
 700                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 701                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 702         }
 703         mutex_unlock(&inode->i_mutex);
 704
 705         return 0;
 706 }
 707
 708 static int
 709 pipe_read_fasync(int fd, struct file *filp, int on)
 710 {
 711         struct inode *inode = filp->f_path.dentry->d_inode;
 712         int retval;
 713
 714         mutex_lock(&inode->i_mutex);
 715         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
 716         mutex_unlock(&inode->i_mutex);
 717
 718         return retval;
 719 }
 720
 721
 722 static int
 723 pipe_write_fasync(int fd, struct file *filp, int on)
 724 {
 725         struct inode *inode = filp->f_path.dentry->d_inode;
 726         int retval;
 727
 728         mutex_lock(&inode->i_mutex);
 729         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
 730         mutex_unlock(&inode->i_mutex);
 731
 732         return retval;
 733 }
 734
 735
 736 static int
 737 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 738 {
 739         struct inode *inode = filp->f_path.dentry->d_inode;
 740         struct pipe_inode_info *pipe = inode->i_pipe;
 741         int retval;
 742
 743         mutex_lock(&inode->i_mutex);
 744         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 745         if (retval >= 0) {
 746                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 747                 if (retval < 0) /* this can happen only if on == T */
 748                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 749         }
 750         mutex_unlock(&inode->i_mutex);
 751         return retval;
 752 }
 753
 754
 755 static int
 756 pipe_read_release(struct inode *inode, struct file *filp)
 757 {
 758         return pipe_release(inode, 1, 0);
 759 }
 760
 761 static int
 762 pipe_write_release(struct inode *inode, struct file *filp)
 763 {
 764         return pipe_release(inode, 0, 1);
 765 }
 766
 767 static int
 768 pipe_rdwr_release(struct inode *inode, struct file *filp)
 769 {
 770         int decr, decw;
 771
 772         decr = (filp->f_mode & FMODE_READ) != 0;
 773         decw = (filp->f_mode & FMODE_WRITE) != 0;
 774         return pipe_release(inode, decr, decw);
 775 }
 776
 777 static int
 778 pipe_read_open(struct inode *inode, struct file *filp)
 779 {
 780         /* We could have perhaps used atomic_t, but this and friends
 781            below are the only places.  So it doesn't seem worthwhile.  */
 782         mutex_lock(&inode->i_mutex);
 783         inode->i_pipe->readers++;
 784         mutex_unlock(&inode->i_mutex);
 785
 786         return 0;
 787 }
 788
 789 static int
 790 pipe_write_open(struct inode *inode, struct file *filp)
 791 {
 792         mutex_lock(&inode->i_mutex);
 793         inode->i_pipe->writers++;
 794         mutex_unlock(&inode->i_mutex);
 795
 796         return 0;
 797 }
 798
 799 static int
 800 pipe_rdwr_open(struct inode *inode, struct file *filp)
 801 {
 802         mutex_lock(&inode->i_mutex);
 803         if (filp->f_mode & FMODE_READ)
 804                 inode->i_pipe->readers++;
 805         if (filp->f_mode & FMODE_WRITE)
 806                 inode->i_pipe->writers++;
 807         mutex_unlock(&inode->i_mutex);
 808
 809         return 0;
 810 }
 811
 812 /*
 813  * The file_operations structs are not static because they
 814  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 815  *
 816  * Pipes reuse fifos' file_operations structs.
 817  */
 818 const struct file_operations read_pipefifo_fops = {
 819         .llseek         = no_llseek,
 820         .read           = do_sync_read,
 821         .aio_read       = pipe_read,
 822         .write          = bad_pipe_w,
 823         .poll           = pipe_poll,
 824         .unlocked_ioctl = pipe_ioctl,
 825         .open           = pipe_read_open,
 826         .release        = pipe_read_release,
 827         .fasync         = pipe_read_fasync,
 828 };
 829
 830 const struct file_operations write_pipefifo_fops = {
 831         .llseek         = no_llseek,
 832         .read           = bad_pipe_r,
 833         .write          = do_sync_write,
 834         .aio_write      = pipe_write,
 835         .poll           = pipe_poll,
 836         .unlocked_ioctl = pipe_ioctl,
 837         .open           = pipe_write_open,
 838         .release        = pipe_write_release,
 839         .fasync         = pipe_write_fasync,
 840 };
 841
 842 const struct file_operations rdwr_pipefifo_fops = {
 843         .llseek         = no_llseek,
 844         .read           = do_sync_read,
 845         .aio_read       = pipe_read,
 846         .write          = do_sync_write,
 847         .aio_write      = pipe_write,
 848         .poll           = pipe_poll,
 849         .unlocked_ioctl = pipe_ioctl,
 850         .open           = pipe_rdwr_open,
 851         .release        = pipe_rdwr_release,
 852         .fasync         = pipe_rdwr_fasync,
 853 };
 854
 855 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
 856 {
 857         struct pipe_inode_info *pipe;
 858
 859         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 860         if (pipe) {
 861                 init_waitqueue_head(&pipe->wait);
 862                 pipe->r_counter = pipe->w_counter = 1;
 863                 pipe->inode = inode;
 864         }
 865
 866         return pipe;
 867 }
 868
 869 void __free_pipe_info(struct pipe_inode_info *pipe)
 870 {
 871         int i;
 872
 873         for (i = 0; i < PIPE_BUFFERS; i++) {
 874                 struct pipe_buffer *buf = pipe->bufs + i;
 875                 if (buf->ops)
 876                         buf->ops->release(pipe, buf);
 877         }
 878         if (pipe->tmp_page)
 879                 __free_page(pipe->tmp_page);
 880         kfree(pipe);
 881 }
 882
 883 void free_pipe_info(struct inode *inode)
 884 {
 885         __free_pipe_info(inode->i_pipe);
 886         inode->i_pipe = NULL;
 887 }
 888
 889 static struct vfsmount *pipe_mnt __read_mostly;
 890 static int pipefs_delete_dentry(struct dentry *dentry)
 891 {
 892         /*
 893          * At creation time, we pretended this dentry was hashed
 894          * (by clearing DCACHE_UNHASHED bit in d_flags)
 895          * At delete time, we restore the truth : not hashed.
 896          * (so that dput() can proceed correctly)
 897          */
 898         dentry->d_flags |= DCACHE_UNHASHED;
 899         return 0;
 900 }
 901
 902 /*
 903  * pipefs_dname() is called from d_path().
 904  */
 905 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 906 {
 907         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 908                                 dentry->d_inode->i_ino);
 909 }
 910
 911 static const struct dentry_operations pipefs_dentry_operations = {
 912         .d_delete       = pipefs_delete_dentry,
 913         .d_dname        = pipefs_dname,
 914 };
 915
 916 static struct inode * get_pipe_inode(void)
 917 {
 918         struct inode *inode = new_inode(pipe_mnt->mnt_sb);
 919         struct pipe_inode_info *pipe;
 920
 921         if (!inode)
 922                 goto fail_inode;
 923
 924         pipe = alloc_pipe_info(inode);
 925         if (!pipe)
 926                 goto fail_iput;
 927         inode->i_pipe = pipe;
 928
 929         pipe->readers = pipe->writers = 1;
 930         inode->i_fop = &rdwr_pipefifo_fops;
 931
 932         /*
 933          * Mark the inode dirty from the very beginning,
 934          * that way it will never be moved to the dirty
 935          * list because "mark_inode_dirty()" will think
 936          * that it already _is_ on the dirty list.
 937          */
 938         inode->i_state = I_DIRTY;
 939         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 940         inode->i_uid = current_fsuid();
 941         inode->i_gid = current_fsgid();
 942         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 943
 944         return inode;
 945
 946 fail_iput:
 947         iput(inode);
 948
 949 fail_inode:
 950         return NULL;
 951 }
 952
 953 struct file *create_write_pipe(int flags)
 954 {
 955         int err;
 956         struct inode *inode;
 957         struct file *f;
 958         struct dentry *dentry;
 959         struct qstr name = { .name = "" };
 960
 961         err = -ENFILE;
 962         inode = get_pipe_inode();
 963         if (!inode)
 964                 goto err;
 965
 966         err = -ENOMEM;
 967         dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
 968         if (!dentry)
 969                 goto err_inode;
 970
 971         dentry->d_op = &pipefs_dentry_operations;
 972         /*
 973          * We dont want to publish this dentry into global dentry hash table.
 974          * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
 975          * This permits a working /proc/$pid/fd/XXX on pipes
 976          */
 977         dentry->d_flags &= ~DCACHE_UNHASHED;
 978         d_instantiate(dentry, inode);
 979
 980         err = -ENFILE;
 981         f = alloc_file(pipe_mnt, dentry, FMODE_WRITE, &write_pipefifo_fops);
 982         if (!f)
 983                 goto err_dentry;
 984         f->f_mapping = inode->i_mapping;
 985
 986         f->f_flags = O_WRONLY | (flags & O_NONBLOCK);
 987         f->f_version = 0;
 988
 989         return f;
 990
 991  err_dentry:
 992         free_pipe_info(inode);
 993         dput(dentry);
 994         return ERR_PTR(err);
 995
 996  err_inode:
 997         free_pipe_info(inode);
 998         iput(inode);
 999  err:
1000         return ERR_PTR(err);
1001 }
1002
1003 void free_write_pipe(struct file *f)
1004 {
1005         free_pipe_info(f->f_dentry->d_inode);
1006         path_put(&f->f_path);
1007         put_filp(f);
1008 }
1009
1010 struct file *create_read_pipe(struct file *wrf, int flags)
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 = wrf->f_path;
1018         path_get(&wrf->f_path);
1019         f->f_mapping = wrf->f_path.dentry->d_inode->i_mapping;
1020
1021         f->f_pos = 0;
1022         f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
1023         f->f_op = &read_pipefifo_fops;
1024         f->f_mode = FMODE_READ;
1025         f->f_version = 0;
1026
1027         return f;
1028 }
1029
1030 int do_pipe_flags(int *fd, int flags)
1031 {
1032         struct file *fw, *fr;
1033         int error;
1034         int fdw, fdr;
1035
1036         if (flags & ~(O_CLOEXEC | O_NONBLOCK))
1037                 return -EINVAL;
1038
1039         fw = create_write_pipe(flags);
1040         if (IS_ERR(fw))
1041                 return PTR_ERR(fw);
1042         fr = create_read_pipe(fw, flags);
1043         error = PTR_ERR(fr);
1044         if (IS_ERR(fr))
1045                 goto err_write_pipe;
1046
1047         error = get_unused_fd_flags(flags);
1048         if (error < 0)
1049                 goto err_read_pipe;
1050         fdr = error;
1051
1052         error = get_unused_fd_flags(flags);
1053         if (error < 0)
1054                 goto err_fdr;
1055         fdw = error;
1056
1057         audit_fd_pair(fdr, fdw);
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_fdr:
1066         put_unused_fd(fdr);
1067  err_read_pipe:
1068         path_put(&fr->f_path);
1069         put_filp(fr);
1070  err_write_pipe:
1071         free_write_pipe(fw);
1072         return error;
1073 }
1074
1075 /*
1076  * sys_pipe() is the normal C calling standard for creating
1077  * a pipe. It's not the way Unix traditionally does this, though.
1078  */
1079 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1080 {
1081         int fd[2];
1082         int error;
1083
1084         error = do_pipe_flags(fd, flags);
1085         if (!error) {
1086                 if (copy_to_user(fildes, fd, sizeof(fd))) {
1087                         sys_close(fd[0]);
1088                         sys_close(fd[1]);
1089                         error = -EFAULT;
1090                 }
1091         }
1092         return error;
1093 }
1094
1095 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1096 {
1097         return sys_pipe2(fildes, 0);
1098 }
1099
1100 /*
1101  * pipefs should _never_ be mounted by userland - too much of security hassle,
1102  * no real gain from having the whole whorehouse mounted. So we don't need
1103  * any operations on the root directory. However, we need a non-trivial
1104  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1105  */
1106 static int pipefs_get_sb(struct file_system_type *fs_type,
1107                          int flags, const char *dev_name, void *data,
1108                          struct vfsmount *mnt)
1109 {
1110         return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
1111 }
1112
1113 static struct file_system_type pipe_fs_type = {
1114         .name           = "pipefs",
1115         .get_sb         = pipefs_get_sb,
1116         .kill_sb        = kill_anon_super,
1117 };
1118
1119 static int __init init_pipe_fs(void)
1120 {
1121         int err = register_filesystem(&pipe_fs_type);
1122
1123         if (!err) {
1124                 pipe_mnt = kern_mount(&pipe_fs_type);
1125                 if (IS_ERR(pipe_mnt)) {
1126                         err = PTR_ERR(pipe_mnt);
1127                         unregister_filesystem(&pipe_fs_type);
1128                 }
1129         }
1130         return err;
1131 }
1132
1133 static void __exit exit_pipe_fs(void)
1134 {
1135         unregister_filesystem(&pipe_fs_type);
1136         mntput(pipe_mnt);
1137 }
1138
1139 fs_initcall(init_pipe_fs);
1140 module_exit(exit_pipe_fs);