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/log2.h>
  15 #include <linux/mount.h>
  16 #include <linux/pipe_fs_i.h>
  17 #include <linux/uio.h>
  18 #include <linux/highmem.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/audit.h>
  21 #include <linux/syscalls.h>
  22 #include <linux/fcntl.h>
  23
  24 #include <asm/uaccess.h>
  25 #include <asm/ioctls.h>
  26
  27 /*
  28  * The max size that a non-root user is allowed to grow the pipe. Can
  29  * be set by root in /proc/sys/fs/pipe-max-pages
  30  */
  31 unsigned int pipe_max_pages = PIPE_DEF_BUFFERS * 16;
  32
  33 /*
  34  * We use a start+len construction, which provides full use of the
  35  * allocated memory.
  36  * -- Florian Coosmann (FGC)
  37  *
  38  * Reads with count = 0 should always return 0.
  39  * -- Julian Bradfield 1999-06-07.
  40  *
  41  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  42  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  43  *
  44  * pipe_read & write cleanup
  45  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  46  */
  47
  48 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  49 {
  50         if (pipe->inode)
  51                 mutex_lock_nested(&pipe->inode->i_mutex, subclass);
  52 }
  53
  54 void pipe_lock(struct pipe_inode_info *pipe)
  55 {
  56         /*
  57          * pipe_lock() nests non-pipe inode locks (for writing to a file)
  58          */
  59         pipe_lock_nested(pipe, I_MUTEX_PARENT);
  60 }
  61 EXPORT_SYMBOL(pipe_lock);
  62
  63 void pipe_unlock(struct pipe_inode_info *pipe)
  64 {
  65         if (pipe->inode)
  66                 mutex_unlock(&pipe->inode->i_mutex);
  67 }
  68 EXPORT_SYMBOL(pipe_unlock);
  69
  70 void pipe_double_lock(struct pipe_inode_info *pipe1,
  71                       struct pipe_inode_info *pipe2)
  72 {
  73         BUG_ON(pipe1 == pipe2);
  74
  75         if (pipe1 < pipe2) {
  76                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
  77                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
  78         } else {
  79                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
  80                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
  81         }
  82 }
  83
  84 /* Drop the inode semaphore and wait for a pipe event, atomically */
  85 void pipe_wait(struct pipe_inode_info *pipe)
  86 {
  87         DEFINE_WAIT(wait);
  88
  89         /*
  90          * Pipes are system-local resources, so sleeping on them
  91          * is considered a noninteractive wait:
  92          */
  93         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
  94         pipe_unlock(pipe);
  95         schedule();
  96         finish_wait(&pipe->wait, &wait);
  97         pipe_lock(pipe);
  98 }
  99
 100 static int
 101 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
 102                         int atomic)
 103 {
 104         unsigned long copy;
 105
 106         while (len > 0) {
 107                 while (!iov->iov_len)
 108                         iov++;
 109                 copy = min_t(unsigned long, len, iov->iov_len);
 110
 111                 if (atomic) {
 112                         if (__copy_from_user_inatomic(to, iov->iov_base, copy))
 113                                 return -EFAULT;
 114                 } else {
 115                         if (copy_from_user(to, iov->iov_base, copy))
 116                                 return -EFAULT;
 117                 }
 118                 to += copy;
 119                 len -= copy;
 120                 iov->iov_base += copy;
 121                 iov->iov_len -= copy;
 122         }
 123         return 0;
 124 }
 125
 126 static int
 127 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
 128                       int atomic)
 129 {
 130         unsigned long copy;
 131
 132         while (len > 0) {
 133                 while (!iov->iov_len)
 134                         iov++;
 135                 copy = min_t(unsigned long, len, iov->iov_len);
 136
 137                 if (atomic) {
 138                         if (__copy_to_user_inatomic(iov->iov_base, from, copy))
 139                                 return -EFAULT;
 140                 } else {
 141                         if (copy_to_user(iov->iov_base, from, copy))
 142                                 return -EFAULT;
 143                 }
 144                 from += copy;
 145                 len -= copy;
 146                 iov->iov_base += copy;
 147                 iov->iov_len -= copy;
 148         }
 149         return 0;
 150 }
 151
 152 /*
 153  * Attempt to pre-fault in the user memory, so we can use atomic copies.
 154  * Returns the number of bytes not faulted in.
 155  */
 156 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
 157 {
 158         while (!iov->iov_len)
 159                 iov++;
 160
 161         while (len > 0) {
 162                 unsigned long this_len;
 163
 164                 this_len = min_t(unsigned long, len, iov->iov_len);
 165                 if (fault_in_pages_writeable(iov->iov_base, this_len))
 166                         break;
 167
 168                 len -= this_len;
 169                 iov++;
 170         }
 171
 172         return len;
 173 }
 174
 175 /*
 176  * Pre-fault in the user memory, so we can use atomic copies.
 177  */
 178 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
 179 {
 180         while (!iov->iov_len)
 181                 iov++;
 182
 183         while (len > 0) {
 184                 unsigned long this_len;
 185
 186                 this_len = min_t(unsigned long, len, iov->iov_len);
 187                 fault_in_pages_readable(iov->iov_base, this_len);
 188                 len -= this_len;
 189                 iov++;
 190         }
 191 }
 192
 193 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 194                                   struct pipe_buffer *buf)
 195 {
 196         struct page *page = buf->page;
 197
 198         /*
 199          * If nobody else uses this page, and we don't already have a
 200          * temporary page, let's keep track of it as a one-deep
 201          * allocation cache. (Otherwise just release our reference to it)
 202          */
 203         if (page_count(page) == 1 && !pipe->tmp_page)
 204                 pipe->tmp_page = page;
 205         else
 206                 page_cache_release(page);
 207 }
 208
 209 /**
 210  * generic_pipe_buf_map - virtually map a pipe buffer
 211  * @pipe:       the pipe that the buffer belongs to
 212  * @buf:        the buffer that should be mapped
 213  * @atomic:     whether to use an atomic map
 214  *
 215  * Description:
 216  *      This function returns a kernel virtual address mapping for the
 217  *      pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
 218  *      and the caller has to be careful not to fault before calling
 219  *      the unmap function.
 220  *
 221  *      Note that this function occupies KM_USER0 if @atomic != 0.
 222  */
 223 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 224                            struct pipe_buffer *buf, int atomic)
 225 {
 226         if (atomic) {
 227                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 228                 return kmap_atomic(buf->page, KM_USER0);
 229         }
 230
 231         return kmap(buf->page);
 232 }
 233 EXPORT_SYMBOL(generic_pipe_buf_map);
 234
 235 /**
 236  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
 237  * @pipe:       the pipe that the buffer belongs to
 238  * @buf:        the buffer that should be unmapped
 239  * @map_data:   the data that the mapping function returned
 240  *
 241  * Description:
 242  *      This function undoes the mapping that ->map() provided.
 243  */
 244 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 245                             struct pipe_buffer *buf, void *map_data)
 246 {
 247         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 248                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 249                 kunmap_atomic(map_data, KM_USER0);
 250         } else
 251                 kunmap(buf->page);
 252 }
 253 EXPORT_SYMBOL(generic_pipe_buf_unmap);
 254
 255 /**
 256  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 257  * @pipe:       the pipe that the buffer belongs to
 258  * @buf:        the buffer to attempt to steal
 259  *
 260  * Description:
 261  *      This function attempts to steal the &struct page attached to
 262  *      @buf. If successful, this function returns 0 and returns with
 263  *      the page locked. The caller may then reuse the page for whatever
 264  *      he wishes; the typical use is insertion into a different file
 265  *      page cache.
 266  */
 267 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 268                            struct pipe_buffer *buf)
 269 {
 270         struct page *page = buf->page;
 271
 272         /*
 273          * A reference of one is golden, that means that the owner of this
 274          * page is the only one holding a reference to it. lock the page
 275          * and return OK.
 276          */
 277         if (page_count(page) == 1) {
 278                 lock_page(page);
 279                 return 0;
 280         }
 281
 282         return 1;
 283 }
 284 EXPORT_SYMBOL(generic_pipe_buf_steal);
 285
 286 /**
 287  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 288  * @pipe:       the pipe that the buffer belongs to
 289  * @buf:        the buffer to get a reference to
 290  *
 291  * Description:
 292  *      This function grabs an extra reference to @buf. It's used in
 293  *      in the tee() system call, when we duplicate the buffers in one
 294  *      pipe into another.
 295  */
 296 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 297 {
 298         page_cache_get(buf->page);
 299 }
 300 EXPORT_SYMBOL(generic_pipe_buf_get);
 301
 302 /**
 303  * generic_pipe_buf_confirm - verify contents of the pipe buffer
 304  * @info:       the pipe that the buffer belongs to
 305  * @buf:        the buffer to confirm
 306  *
 307  * Description:
 308  *      This function does nothing, because the generic pipe code uses
 309  *      pages that are always good when inserted into the pipe.
 310  */
 311 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 312                              struct pipe_buffer *buf)
 313 {
 314         return 0;
 315 }
 316 EXPORT_SYMBOL(generic_pipe_buf_confirm);
 317
 318 /**
 319  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 320  * @pipe:       the pipe that the buffer belongs to
 321  * @buf:        the buffer to put a reference to
 322  *
 323  * Description:
 324  *      This function releases a reference to @buf.
 325  */
 326 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 327                               struct pipe_buffer *buf)
 328 {
 329         page_cache_release(buf->page);
 330 }
 331 EXPORT_SYMBOL(generic_pipe_buf_release);
 332
 333 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 334         .can_merge = 1,
 335         .map = generic_pipe_buf_map,
 336         .unmap = generic_pipe_buf_unmap,
 337         .confirm = generic_pipe_buf_confirm,
 338         .release = anon_pipe_buf_release,
 339         .steal = generic_pipe_buf_steal,
 340         .get = generic_pipe_buf_get,
 341 };
 342
 343 static ssize_t
 344 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 345            unsigned long nr_segs, loff_t pos)
 346 {
 347         struct file *filp = iocb->ki_filp;
 348         struct inode *inode = filp->f_path.dentry->d_inode;
 349         struct pipe_inode_info *pipe;
 350         int do_wakeup;
 351         ssize_t ret;
 352         struct iovec *iov = (struct iovec *)_iov;
 353         size_t total_len;
 354
 355         total_len = iov_length(iov, nr_segs);
 356         /* Null read succeeds. */
 357         if (unlikely(total_len == 0))
 358                 return 0;
 359
 360         do_wakeup = 0;
 361         ret = 0;
 362         mutex_lock(&inode->i_mutex);
 363         pipe = inode->i_pipe;
 364         for (;;) {
 365                 int bufs = pipe->nrbufs;
 366                 if (bufs) {
 367                         int curbuf = pipe->curbuf;
 368                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 369                         const struct pipe_buf_operations *ops = buf->ops;
 370                         void *addr;
 371                         size_t chars = buf->len;
 372                         int error, atomic;
 373
 374                         if (chars > total_len)
 375                                 chars = total_len;
 376
 377                         error = ops->confirm(pipe, buf);
 378                         if (error) {
 379                                 if (!ret)
 380                                         error = ret;
 381                                 break;
 382                         }
 383
 384                         atomic = !iov_fault_in_pages_write(iov, chars);
 385 redo:
 386                         addr = ops->map(pipe, buf, atomic);
 387                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
 388                         ops->unmap(pipe, buf, addr);
 389                         if (unlikely(error)) {
 390                                 /*
 391                                  * Just retry with the slow path if we failed.
 392                                  */
 393                                 if (atomic) {
 394                                         atomic = 0;
 395                                         goto redo;
 396                                 }
 397                                 if (!ret)
 398                                         ret = error;
 399                                 break;
 400                         }
 401                         ret += chars;
 402                         buf->offset += chars;
 403                         buf->len -= chars;
 404                         if (!buf->len) {
 405                                 buf->ops = NULL;
 406                                 ops->release(pipe, buf);
 407                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
 408                                 pipe->curbuf = curbuf;
 409                                 pipe->nrbufs = --bufs;
 410                                 do_wakeup = 1;
 411                         }
 412                         total_len -= chars;
 413                         if (!total_len)
 414                                 break;  /* common path: read succeeded */
 415                 }
 416                 if (bufs)       /* More to do? */
 417                         continue;
 418                 if (!pipe->writers)
 419                         break;
 420                 if (!pipe->waiting_writers) {
 421                         /* syscall merging: Usually we must not sleep
 422                          * if O_NONBLOCK is set, or if we got some data.
 423                          * But if a writer sleeps in kernel space, then
 424                          * we can wait for that data without violating POSIX.
 425                          */
 426                         if (ret)
 427                                 break;
 428                         if (filp->f_flags & O_NONBLOCK) {
 429                                 ret = -EAGAIN;
 430                                 break;
 431                         }
 432                 }
 433                 if (signal_pending(current)) {
 434                         if (!ret)
 435                                 ret = -ERESTARTSYS;
 436                         break;
 437                 }
 438                 if (do_wakeup) {
 439                         wake_up_interruptible_sync(&pipe->wait);
 440                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 441                 }
 442                 pipe_wait(pipe);
 443         }
 444         mutex_unlock(&inode->i_mutex);
 445
 446         /* Signal writers asynchronously that there is more room. */
 447         if (do_wakeup) {
 448                 wake_up_interruptible_sync(&pipe->wait);
 449                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 450         }
 451         if (ret > 0)
 452                 file_accessed(filp);
 453         return ret;
 454 }
 455
 456 static ssize_t
 457 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 458             unsigned long nr_segs, loff_t ppos)
 459 {
 460         struct file *filp = iocb->ki_filp;
 461         struct inode *inode = filp->f_path.dentry->d_inode;
 462         struct pipe_inode_info *pipe;
 463         ssize_t ret;
 464         int do_wakeup;
 465         struct iovec *iov = (struct iovec *)_iov;
 466         size_t total_len;
 467         ssize_t chars;
 468
 469         total_len = iov_length(iov, nr_segs);
 470         /* Null write succeeds. */
 471         if (unlikely(total_len == 0))
 472                 return 0;
 473
 474         do_wakeup = 0;
 475         ret = 0;
 476         mutex_lock(&inode->i_mutex);
 477         pipe = inode->i_pipe;
 478
 479         if (!pipe->readers) {
 480                 send_sig(SIGPIPE, current, 0);
 481                 ret = -EPIPE;
 482                 goto out;
 483         }
 484
 485         /* We try to merge small writes */
 486         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 487         if (pipe->nrbufs && chars != 0) {
 488                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 489                                                         (pipe->buffers - 1);
 490                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 491                 const struct pipe_buf_operations *ops = buf->ops;
 492                 int offset = buf->offset + buf->len;
 493
 494                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 495                         int error, atomic = 1;
 496                         void *addr;
 497
 498                         error = ops->confirm(pipe, buf);
 499                         if (error)
 500                                 goto out;
 501
 502                         iov_fault_in_pages_read(iov, chars);
 503 redo1:
 504                         addr = ops->map(pipe, buf, atomic);
 505                         error = pipe_iov_copy_from_user(offset + addr, iov,
 506                                                         chars, atomic);
 507                         ops->unmap(pipe, buf, addr);
 508                         ret = error;
 509                         do_wakeup = 1;
 510                         if (error) {
 511                                 if (atomic) {
 512                                         atomic = 0;
 513                                         goto redo1;
 514                                 }
 515                                 goto out;
 516                         }
 517                         buf->len += chars;
 518                         total_len -= chars;
 519                         ret = chars;
 520                         if (!total_len)
 521                                 goto out;
 522                 }
 523         }
 524
 525         for (;;) {
 526                 int bufs;
 527
 528                 if (!pipe->readers) {
 529                         send_sig(SIGPIPE, current, 0);
 530                         if (!ret)
 531                                 ret = -EPIPE;
 532                         break;
 533                 }
 534                 bufs = pipe->nrbufs;
 535                 if (bufs < pipe->buffers) {
 536                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 537                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 538                         struct page *page = pipe->tmp_page;
 539                         char *src;
 540                         int error, atomic = 1;
 541
 542                         if (!page) {
 543                                 page = alloc_page(GFP_HIGHUSER);
 544                                 if (unlikely(!page)) {
 545                                         ret = ret ? : -ENOMEM;
 546                                         break;
 547                                 }
 548                                 pipe->tmp_page = page;
 549                         }
 550                         /* Always wake up, even if the copy fails. Otherwise
 551                          * we lock up (O_NONBLOCK-)readers that sleep due to
 552                          * syscall merging.
 553                          * FIXME! Is this really true?
 554                          */
 555                         do_wakeup = 1;
 556                         chars = PAGE_SIZE;
 557                         if (chars > total_len)
 558                                 chars = total_len;
 559
 560                         iov_fault_in_pages_read(iov, chars);
 561 redo2:
 562                         if (atomic)
 563                                 src = kmap_atomic(page, KM_USER0);
 564                         else
 565                                 src = kmap(page);
 566
 567                         error = pipe_iov_copy_from_user(src, iov, chars,
 568                                                         atomic);
 569                         if (atomic)
 570                                 kunmap_atomic(src, KM_USER0);
 571                         else
 572                                 kunmap(page);
 573
 574                         if (unlikely(error)) {
 575                                 if (atomic) {
 576                                         atomic = 0;
 577                                         goto redo2;
 578                                 }
 579                                 if (!ret)
 580                                         ret = error;
 581                                 break;
 582                         }
 583                         ret += chars;
 584
 585                         /* Insert it into the buffer array */
 586                         buf->page = page;
 587                         buf->ops = &anon_pipe_buf_ops;
 588                         buf->offset = 0;
 589                         buf->len = chars;
 590                         pipe->nrbufs = ++bufs;
 591                         pipe->tmp_page = NULL;
 592
 593                         total_len -= chars;
 594                         if (!total_len)
 595                                 break;
 596                 }
 597                 if (bufs < pipe->buffers)
 598                         continue;
 599                 if (filp->f_flags & O_NONBLOCK) {
 600                         if (!ret)
 601                                 ret = -EAGAIN;
 602                         break;
 603                 }
 604                 if (signal_pending(current)) {
 605                         if (!ret)
 606                                 ret = -ERESTARTSYS;
 607                         break;
 608                 }
 609                 if (do_wakeup) {
 610                         wake_up_interruptible_sync(&pipe->wait);
 611                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 612                         do_wakeup = 0;
 613                 }
 614                 pipe->waiting_writers++;
 615                 pipe_wait(pipe);
 616                 pipe->waiting_writers--;
 617         }
 618 out:
 619         mutex_unlock(&inode->i_mutex);
 620         if (do_wakeup) {
 621                 wake_up_interruptible_sync(&pipe->wait);
 622                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 623         }
 624         if (ret > 0)
 625                 file_update_time(filp);
 626         return ret;
 627 }
 628
 629 static ssize_t
 630 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 631 {
 632         return -EBADF;
 633 }
 634
 635 static ssize_t
 636 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
 637            loff_t *ppos)
 638 {
 639         return -EBADF;
 640 }
 641
 642 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 643 {
 644         struct inode *inode = filp->f_path.dentry->d_inode;
 645         struct pipe_inode_info *pipe;
 646         int count, buf, nrbufs;
 647
 648         switch (cmd) {
 649                 case FIONREAD:
 650                         mutex_lock(&inode->i_mutex);
 651                         pipe = inode->i_pipe;
 652                         count = 0;
 653                         buf = pipe->curbuf;
 654                         nrbufs = pipe->nrbufs;
 655                         while (--nrbufs >= 0) {
 656                                 count += pipe->bufs[buf].len;
 657                                 buf = (buf+1) & (pipe->buffers - 1);
 658                         }
 659                         mutex_unlock(&inode->i_mutex);
 660
 661                         return put_user(count, (int __user *)arg);
 662                 default:
 663                         return -EINVAL;
 664         }
 665 }
 666
 667 /* No kernel lock held - fine */
 668 static unsigned int
 669 pipe_poll(struct file *filp, poll_table *wait)
 670 {
 671         unsigned int mask;
 672         struct inode *inode = filp->f_path.dentry->d_inode;
 673         struct pipe_inode_info *pipe = inode->i_pipe;
 674         int nrbufs;
 675
 676         poll_wait(filp, &pipe->wait, wait);
 677
 678         /* Reading only -- no need for acquiring the semaphore.  */
 679         nrbufs = pipe->nrbufs;
 680         mask = 0;
 681         if (filp->f_mode & FMODE_READ) {
 682                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 683                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 684                         mask |= POLLHUP;
 685         }
 686
 687         if (filp->f_mode & FMODE_WRITE) {
 688                 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 689                 /*
 690                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 691                  * behave exactly like pipes for poll().
 692                  */
 693                 if (!pipe->readers)
 694                         mask |= POLLERR;
 695         }
 696
 697         return mask;
 698 }
 699
 700 static int
 701 pipe_release(struct inode *inode, int decr, int decw)
 702 {
 703         struct pipe_inode_info *pipe;
 704
 705         mutex_lock(&inode->i_mutex);
 706         pipe = inode->i_pipe;
 707         pipe->readers -= decr;
 708         pipe->writers -= decw;
 709
 710         if (!pipe->readers && !pipe->writers) {
 711                 free_pipe_info(inode);
 712         } else {
 713                 wake_up_interruptible_sync(&pipe->wait);
 714                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 715                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 716         }
 717         mutex_unlock(&inode->i_mutex);
 718
 719         return 0;
 720 }
 721
 722 static int
 723 pipe_read_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_readers);
 730         mutex_unlock(&inode->i_mutex);
 731
 732         return retval;
 733 }
 734
 735
 736 static int
 737 pipe_write_fasync(int fd, struct file *filp, int on)
 738 {
 739         struct inode *inode = filp->f_path.dentry->d_inode;
 740         int retval;
 741
 742         mutex_lock(&inode->i_mutex);
 743         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
 744         mutex_unlock(&inode->i_mutex);
 745
 746         return retval;
 747 }
 748
 749
 750 static int
 751 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 752 {
 753         struct inode *inode = filp->f_path.dentry->d_inode;
 754         struct pipe_inode_info *pipe = inode->i_pipe;
 755         int retval;
 756
 757         mutex_lock(&inode->i_mutex);
 758         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 759         if (retval >= 0) {
 760                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 761                 if (retval < 0) /* this can happen only if on == T */
 762                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 763         }
 764         mutex_unlock(&inode->i_mutex);
 765         return retval;
 766 }
 767
 768
 769 static int
 770 pipe_read_release(struct inode *inode, struct file *filp)
 771 {
 772         return pipe_release(inode, 1, 0);
 773 }
 774
 775 static int
 776 pipe_write_release(struct inode *inode, struct file *filp)
 777 {
 778         return pipe_release(inode, 0, 1);
 779 }
 780
 781 static int
 782 pipe_rdwr_release(struct inode *inode, struct file *filp)
 783 {
 784         int decr, decw;
 785
 786         decr = (filp->f_mode & FMODE_READ) != 0;
 787         decw = (filp->f_mode & FMODE_WRITE) != 0;
 788         return pipe_release(inode, decr, decw);
 789 }
 790
 791 static int
 792 pipe_read_open(struct inode *inode, struct file *filp)
 793 {
 794         int ret = -ENOENT;
 795
 796         mutex_lock(&inode->i_mutex);
 797
 798         if (inode->i_pipe) {
 799                 ret = 0;
 800                 inode->i_pipe->readers++;
 801         }
 802
 803         mutex_unlock(&inode->i_mutex);
 804
 805         return ret;
 806 }
 807
 808 static int
 809 pipe_write_open(struct inode *inode, struct file *filp)
 810 {
 811         int ret = -ENOENT;
 812
 813         mutex_lock(&inode->i_mutex);
 814
 815         if (inode->i_pipe) {
 816                 ret = 0;
 817                 inode->i_pipe->writers++;
 818         }
 819
 820         mutex_unlock(&inode->i_mutex);
 821
 822         return ret;
 823 }
 824
 825 static int
 826 pipe_rdwr_open(struct inode *inode, struct file *filp)
 827 {
 828         int ret = -ENOENT;
 829
 830         mutex_lock(&inode->i_mutex);
 831
 832         if (inode->i_pipe) {
 833                 ret = 0;
 834                 if (filp->f_mode & FMODE_READ)
 835                         inode->i_pipe->readers++;
 836                 if (filp->f_mode & FMODE_WRITE)
 837                         inode->i_pipe->writers++;
 838         }
 839
 840         mutex_unlock(&inode->i_mutex);
 841
 842         return ret;
 843 }
 844
 845 /*
 846  * The file_operations structs are not static because they
 847  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 848  *
 849  * Pipes reuse fifos' file_operations structs.
 850  */
 851 const struct file_operations read_pipefifo_fops = {
 852         .llseek         = no_llseek,
 853         .read           = do_sync_read,
 854         .aio_read       = pipe_read,
 855         .write          = bad_pipe_w,
 856         .poll           = pipe_poll,
 857         .unlocked_ioctl = pipe_ioctl,
 858         .open           = pipe_read_open,
 859         .release        = pipe_read_release,
 860         .fasync         = pipe_read_fasync,
 861 };
 862
 863 const struct file_operations write_pipefifo_fops = {
 864         .llseek         = no_llseek,
 865         .read           = bad_pipe_r,
 866         .write          = do_sync_write,
 867         .aio_write      = pipe_write,
 868         .poll           = pipe_poll,
 869         .unlocked_ioctl = pipe_ioctl,
 870         .open           = pipe_write_open,
 871         .release        = pipe_write_release,
 872         .fasync         = pipe_write_fasync,
 873 };
 874
 875 const struct file_operations rdwr_pipefifo_fops = {
 876         .llseek         = no_llseek,
 877         .read           = do_sync_read,
 878         .aio_read       = pipe_read,
 879         .write          = do_sync_write,
 880         .aio_write      = pipe_write,
 881         .poll           = pipe_poll,
 882         .unlocked_ioctl = pipe_ioctl,
 883         .open           = pipe_rdwr_open,
 884         .release        = pipe_rdwr_release,
 885         .fasync         = pipe_rdwr_fasync,
 886 };
 887
 888 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
 889 {
 890         struct pipe_inode_info *pipe;
 891
 892         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 893         if (pipe) {
 894                 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
 895                 if (pipe->bufs) {
 896                         init_waitqueue_head(&pipe->wait);
 897                         pipe->r_counter = pipe->w_counter = 1;
 898                         pipe->inode = inode;
 899                         pipe->buffers = PIPE_DEF_BUFFERS;
 900                         return pipe;
 901                 }
 902                 kfree(pipe);
 903         }
 904
 905         return NULL;
 906 }
 907
 908 void __free_pipe_info(struct pipe_inode_info *pipe)
 909 {
 910         int i;
 911
 912         for (i = 0; i < pipe->buffers; i++) {
 913                 struct pipe_buffer *buf = pipe->bufs + i;
 914                 if (buf->ops)
 915                         buf->ops->release(pipe, buf);
 916         }
 917         if (pipe->tmp_page)
 918                 __free_page(pipe->tmp_page);
 919         kfree(pipe->bufs);
 920         kfree(pipe);
 921 }
 922
 923 void free_pipe_info(struct inode *inode)
 924 {
 925         __free_pipe_info(inode->i_pipe);
 926         inode->i_pipe = NULL;
 927 }
 928
 929 static struct vfsmount *pipe_mnt __read_mostly;
 930
 931 /*
 932  * pipefs_dname() is called from d_path().
 933  */
 934 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 935 {
 936         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 937                                 dentry->d_inode->i_ino);
 938 }
 939
 940 static const struct dentry_operations pipefs_dentry_operations = {
 941         .d_dname        = pipefs_dname,
 942 };
 943
 944 static struct inode * get_pipe_inode(void)
 945 {
 946         struct inode *inode = new_inode(pipe_mnt->mnt_sb);
 947         struct pipe_inode_info *pipe;
 948
 949         if (!inode)
 950                 goto fail_inode;
 951
 952         pipe = alloc_pipe_info(inode);
 953         if (!pipe)
 954                 goto fail_iput;
 955         inode->i_pipe = pipe;
 956
 957         pipe->readers = pipe->writers = 1;
 958         inode->i_fop = &rdwr_pipefifo_fops;
 959
 960         /*
 961          * Mark the inode dirty from the very beginning,
 962          * that way it will never be moved to the dirty
 963          * list because "mark_inode_dirty()" will think
 964          * that it already _is_ on the dirty list.
 965          */
 966         inode->i_state = I_DIRTY;
 967         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 968         inode->i_uid = current_fsuid();
 969         inode->i_gid = current_fsgid();
 970         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 971
 972         return inode;
 973
 974 fail_iput:
 975         iput(inode);
 976
 977 fail_inode:
 978         return NULL;
 979 }
 980
 981 struct file *create_write_pipe(int flags)
 982 {
 983         int err;
 984         struct inode *inode;
 985         struct file *f;
 986         struct path path;
 987         struct qstr name = { .name = "" };
 988
 989         err = -ENFILE;
 990         inode = get_pipe_inode();
 991         if (!inode)
 992                 goto err;
 993
 994         err = -ENOMEM;
 995         path.dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
 996         if (!path.dentry)
 997                 goto err_inode;
 998         path.mnt = mntget(pipe_mnt);
 999
1000         path.dentry->d_op = &pipefs_dentry_operations;
1001         d_instantiate(path.dentry, inode);
1002
1003         err = -ENFILE;
1004         f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
1005         if (!f)
1006                 goto err_dentry;
1007         f->f_mapping = inode->i_mapping;
1008
1009         f->f_flags = O_WRONLY | (flags & O_NONBLOCK);
1010         f->f_version = 0;
1011
1012         return f;
1013
1014  err_dentry:
1015         free_pipe_info(inode);
1016         path_put(&path);
1017         return ERR_PTR(err);
1018
1019  err_inode:
1020         free_pipe_info(inode);
1021         iput(inode);
1022  err:
1023         return ERR_PTR(err);
1024 }
1025
1026 void free_write_pipe(struct file *f)
1027 {
1028         free_pipe_info(f->f_dentry->d_inode);
1029         path_put(&f->f_path);
1030         put_filp(f);
1031 }
1032
1033 struct file *create_read_pipe(struct file *wrf, int flags)
1034 {
1035         /* Grab pipe from the writer */
1036         struct file *f = alloc_file(&wrf->f_path, FMODE_READ,
1037                                     &read_pipefifo_fops);
1038         if (!f)
1039                 return ERR_PTR(-ENFILE);
1040
1041         path_get(&wrf->f_path);
1042         f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
1043
1044         return f;
1045 }
1046
1047 int do_pipe_flags(int *fd, int flags)
1048 {
1049         struct file *fw, *fr;
1050         int error;
1051         int fdw, fdr;
1052
1053         if (flags & ~(O_CLOEXEC | O_NONBLOCK))
1054                 return -EINVAL;
1055
1056         fw = create_write_pipe(flags);
1057         if (IS_ERR(fw))
1058                 return PTR_ERR(fw);
1059         fr = create_read_pipe(fw, flags);
1060         error = PTR_ERR(fr);
1061         if (IS_ERR(fr))
1062                 goto err_write_pipe;
1063
1064         error = get_unused_fd_flags(flags);
1065         if (error < 0)
1066                 goto err_read_pipe;
1067         fdr = error;
1068
1069         error = get_unused_fd_flags(flags);
1070         if (error < 0)
1071                 goto err_fdr;
1072         fdw = error;
1073
1074         audit_fd_pair(fdr, fdw);
1075         fd_install(fdr, fr);
1076         fd_install(fdw, fw);
1077         fd[0] = fdr;
1078         fd[1] = fdw;
1079
1080         return 0;
1081
1082  err_fdr:
1083         put_unused_fd(fdr);
1084  err_read_pipe:
1085         path_put(&fr->f_path);
1086         put_filp(fr);
1087  err_write_pipe:
1088         free_write_pipe(fw);
1089         return error;
1090 }
1091
1092 /*
1093  * sys_pipe() is the normal C calling standard for creating
1094  * a pipe. It's not the way Unix traditionally does this, though.
1095  */
1096 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1097 {
1098         int fd[2];
1099         int error;
1100
1101         error = do_pipe_flags(fd, flags);
1102         if (!error) {
1103                 if (copy_to_user(fildes, fd, sizeof(fd))) {
1104                         sys_close(fd[0]);
1105                         sys_close(fd[1]);
1106                         error = -EFAULT;
1107                 }
1108         }
1109         return error;
1110 }
1111
1112 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1113 {
1114         return sys_pipe2(fildes, 0);
1115 }
1116
1117 /*
1118  * Allocate a new array of pipe buffers and copy the info over. Returns the
1119  * pipe size if successful, or return -ERROR on error.
1120  */
1121 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1122 {
1123         struct pipe_buffer *bufs;
1124
1125         /*
1126          * Must be a power-of-2 currently
1127          */
1128         if (!is_power_of_2(arg))
1129                 return -EINVAL;
1130
1131         /*
1132          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1133          * expect a lot of shrink+grow operations, just free and allocate
1134          * again like we would do for growing. If the pipe currently
1135          * contains more buffers than arg, then return busy.
1136          */
1137         if (arg < pipe->nrbufs)
1138                 return -EBUSY;
1139
1140         bufs = kcalloc(arg, sizeof(struct pipe_buffer), GFP_KERNEL);
1141         if (unlikely(!bufs))
1142                 return -ENOMEM;
1143
1144         /*
1145          * The pipe array wraps around, so just start the new one at zero
1146          * and adjust the indexes.
1147          */
1148         if (pipe->nrbufs) {
1149                 const unsigned int tail = pipe->nrbufs & (pipe->buffers - 1);
1150                 const unsigned int head = pipe->nrbufs - tail;
1151
1152                 if (head)
1153                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1154                 if (tail)
1155                         memcpy(bufs + head, pipe->bufs + pipe->curbuf, tail * sizeof(struct pipe_buffer));
1156         }
1157
1158         pipe->curbuf = 0;
1159         kfree(pipe->bufs);
1160         pipe->bufs = bufs;
1161         pipe->buffers = arg;
1162         return arg;
1163 }
1164
1165 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1166 {
1167         struct pipe_inode_info *pipe;
1168         long ret;
1169
1170         pipe = file->f_path.dentry->d_inode->i_pipe;
1171         if (!pipe)
1172                 return -EBADF;
1173
1174         mutex_lock(&pipe->inode->i_mutex);
1175
1176         switch (cmd) {
1177         case F_SETPIPE_SZ:
1178                 if (!capable(CAP_SYS_ADMIN) && arg > pipe_max_pages) {
1179                         ret = -EINVAL;
1180                         goto out;
1181                 }
1182                 /*
1183                  * The pipe needs to be at least 2 pages large to
1184                  * guarantee POSIX behaviour.
1185                  */
1186                 if (arg < 2) {
1187                         ret = -EINVAL;
1188                         goto out;
1189                 }
1190                 ret = pipe_set_size(pipe, arg);
1191                 break;
1192         case F_GETPIPE_SZ:
1193                 ret = pipe->buffers;
1194                 break;
1195         default:
1196                 ret = -EINVAL;
1197                 break;
1198         }
1199
1200 out:
1201         mutex_unlock(&pipe->inode->i_mutex);
1202         return ret;
1203 }
1204
1205 /*
1206  * pipefs should _never_ be mounted by userland - too much of security hassle,
1207  * no real gain from having the whole whorehouse mounted. So we don't need
1208  * any operations on the root directory. However, we need a non-trivial
1209  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1210  */
1211 static int pipefs_get_sb(struct file_system_type *fs_type,
1212                          int flags, const char *dev_name, void *data,
1213                          struct vfsmount *mnt)
1214 {
1215         return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
1216 }
1217
1218 static struct file_system_type pipe_fs_type = {
1219         .name           = "pipefs",
1220         .get_sb         = pipefs_get_sb,
1221         .kill_sb        = kill_anon_super,
1222 };
1223
1224 static int __init init_pipe_fs(void)
1225 {
1226         int err = register_filesystem(&pipe_fs_type);
1227
1228         if (!err) {
1229                 pipe_mnt = kern_mount(&pipe_fs_type);
1230                 if (IS_ERR(pipe_mnt)) {
1231                         err = PTR_ERR(pipe_mnt);
1232                         unregister_filesystem(&pipe_fs_type);
1233                 }
1234         }
1235         return err;
1236 }
1237
1238 static void __exit exit_pipe_fs(void)
1239 {
1240         unregister_filesystem(&pipe_fs_type);
1241         mntput(pipe_mnt);
1242 }
1243
1244 fs_initcall(init_pipe_fs);
1245 module_exit(exit_pipe_fs);