SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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
 234 /**
 235  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
 236  * @pipe:       the pipe that the buffer belongs to
 237  * @buf:        the buffer that should be unmapped
 238  * @map_data:   the data that the mapping function returned
 239  *
 240  * Description:
 241  *      This function undoes the mapping that ->map() provided.
 242  */
 243 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 244                             struct pipe_buffer *buf, void *map_data)
 245 {
 246         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 247                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 248                 kunmap_atomic(map_data, KM_USER0);
 249         } else
 250                 kunmap(buf->page);
 251 }
 252
 253 /**
 254  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 255  * @pipe:       the pipe that the buffer belongs to
 256  * @buf:        the buffer to attempt to steal
 257  *
 258  * Description:
 259  *      This function attempts to steal the &struct page attached to
 260  *      @buf. If successful, this function returns 0 and returns with
 261  *      the page locked. The caller may then reuse the page for whatever
 262  *      he wishes; the typical use is insertion into a different file
 263  *      page cache.
 264  */
 265 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 266                            struct pipe_buffer *buf)
 267 {
 268         struct page *page = buf->page;
 269
 270         /*
 271          * A reference of one is golden, that means that the owner of this
 272          * page is the only one holding a reference to it. lock the page
 273          * and return OK.
 274          */
 275         if (page_count(page) == 1) {
 276                 lock_page(page);
 277                 return 0;
 278         }
 279
 280         return 1;
 281 }
 282
 283 /**
 284  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 285  * @pipe:       the pipe that the buffer belongs to
 286  * @buf:        the buffer to get a reference to
 287  *
 288  * Description:
 289  *      This function grabs an extra reference to @buf. It's used in
 290  *      in the tee() system call, when we duplicate the buffers in one
 291  *      pipe into another.
 292  */
 293 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 294 {
 295         page_cache_get(buf->page);
 296 }
 297
 298 /**
 299  * generic_pipe_buf_confirm - verify contents of the pipe buffer
 300  * @info:       the pipe that the buffer belongs to
 301  * @buf:        the buffer to confirm
 302  *
 303  * Description:
 304  *      This function does nothing, because the generic pipe code uses
 305  *      pages that are always good when inserted into the pipe.
 306  */
 307 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 308                              struct pipe_buffer *buf)
 309 {
 310         return 0;
 311 }
 312
 313 /**
 314  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 315  * @pipe:       the pipe that the buffer belongs to
 316  * @buf:        the buffer to put a reference to
 317  *
 318  * Description:
 319  *      This function releases a reference to @buf.
 320  */
 321 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 322                               struct pipe_buffer *buf)
 323 {
 324         page_cache_release(buf->page);
 325 }
 326
 327 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 328         .can_merge = 1,
 329         .map = generic_pipe_buf_map,
 330         .unmap = generic_pipe_buf_unmap,
 331         .confirm = generic_pipe_buf_confirm,
 332         .release = anon_pipe_buf_release,
 333         .steal = generic_pipe_buf_steal,
 334         .get = generic_pipe_buf_get,
 335 };
 336
 337 static ssize_t
 338 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 339            unsigned long nr_segs, loff_t pos)
 340 {
 341         struct file *filp = iocb->ki_filp;
 342         struct inode *inode = filp->f_path.dentry->d_inode;
 343         struct pipe_inode_info *pipe;
 344         int do_wakeup;
 345         ssize_t ret;
 346         struct iovec *iov = (struct iovec *)_iov;
 347         size_t total_len;
 348
 349         total_len = iov_length(iov, nr_segs);
 350         /* Null read succeeds. */
 351         if (unlikely(total_len == 0))
 352                 return 0;
 353
 354         do_wakeup = 0;
 355         ret = 0;
 356         mutex_lock(&inode->i_mutex);
 357         pipe = inode->i_pipe;
 358         for (;;) {
 359                 int bufs = pipe->nrbufs;
 360                 if (bufs) {
 361                         int curbuf = pipe->curbuf;
 362                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 363                         const struct pipe_buf_operations *ops = buf->ops;
 364                         void *addr;
 365                         size_t chars = buf->len;
 366                         int error, atomic;
 367
 368                         if (chars > total_len)
 369                                 chars = total_len;
 370
 371                         error = ops->confirm(pipe, buf);
 372                         if (error) {
 373                                 if (!ret)
 374                                         error = ret;
 375                                 break;
 376                         }
 377
 378                         atomic = !iov_fault_in_pages_write(iov, chars);
 379 redo:
 380                         addr = ops->map(pipe, buf, atomic);
 381                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
 382                         ops->unmap(pipe, buf, addr);
 383                         if (unlikely(error)) {
 384                                 /*
 385                                  * Just retry with the slow path if we failed.
 386                                  */
 387                                 if (atomic) {
 388                                         atomic = 0;
 389                                         goto redo;
 390                                 }
 391                                 if (!ret)
 392                                         ret = error;
 393                                 break;
 394                         }
 395                         ret += chars;
 396                         buf->offset += chars;
 397                         buf->len -= chars;
 398                         if (!buf->len) {
 399                                 buf->ops = NULL;
 400                                 ops->release(pipe, buf);
 401                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
 402                                 pipe->curbuf = curbuf;
 403                                 pipe->nrbufs = --bufs;
 404                                 do_wakeup = 1;
 405                         }
 406                         total_len -= chars;
 407                         if (!total_len)
 408                                 break;  /* common path: read succeeded */
 409                 }
 410                 if (bufs)       /* More to do? */
 411                         continue;
 412                 if (!pipe->writers)
 413                         break;
 414                 if (!pipe->waiting_writers) {
 415                         /* syscall merging: Usually we must not sleep
 416                          * if O_NONBLOCK is set, or if we got some data.
 417                          * But if a writer sleeps in kernel space, then
 418                          * we can wait for that data without violating POSIX.
 419                          */
 420                         if (ret)
 421                                 break;
 422                         if (filp->f_flags & O_NONBLOCK) {
 423                                 ret = -EAGAIN;
 424                                 break;
 425                         }
 426                 }
 427                 if (signal_pending(current)) {
 428                         if (!ret)
 429                                 ret = -ERESTARTSYS;
 430                         break;
 431                 }
 432                 if (do_wakeup) {
 433                         wake_up_interruptible_sync(&pipe->wait);
 434                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 435                 }
 436                 pipe_wait(pipe);
 437         }
 438         mutex_unlock(&inode->i_mutex);
 439
 440         /* Signal writers asynchronously that there is more room. */
 441         if (do_wakeup) {
 442                 wake_up_interruptible_sync(&pipe->wait);
 443                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 444         }
 445         if (ret > 0)
 446                 file_accessed(filp);
 447         return ret;
 448 }
 449
 450 static ssize_t
 451 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 452             unsigned long nr_segs, loff_t ppos)
 453 {
 454         struct file *filp = iocb->ki_filp;
 455         struct inode *inode = filp->f_path.dentry->d_inode;
 456         struct pipe_inode_info *pipe;
 457         ssize_t ret;
 458         int do_wakeup;
 459         struct iovec *iov = (struct iovec *)_iov;
 460         size_t total_len;
 461         ssize_t chars;
 462
 463         total_len = iov_length(iov, nr_segs);
 464         /* Null write succeeds. */
 465         if (unlikely(total_len == 0))
 466                 return 0;
 467
 468         do_wakeup = 0;
 469         ret = 0;
 470         mutex_lock(&inode->i_mutex);
 471         pipe = inode->i_pipe;
 472
 473         if (!pipe->readers) {
 474                 send_sig(SIGPIPE, current, 0);
 475                 ret = -EPIPE;
 476                 goto out;
 477         }
 478
 479         /* We try to merge small writes */
 480         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 481         if (pipe->nrbufs && chars != 0) {
 482                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 483                                                         (pipe->buffers - 1);
 484                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 485                 const struct pipe_buf_operations *ops = buf->ops;
 486                 int offset = buf->offset + buf->len;
 487
 488                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 489                         int error, atomic = 1;
 490                         void *addr;
 491
 492                         error = ops->confirm(pipe, buf);
 493                         if (error)
 494                                 goto out;
 495
 496                         iov_fault_in_pages_read(iov, chars);
 497 redo1:
 498                         addr = ops->map(pipe, buf, atomic);
 499                         error = pipe_iov_copy_from_user(offset + addr, iov,
 500                                                         chars, atomic);
 501                         ops->unmap(pipe, buf, addr);
 502                         ret = error;
 503                         do_wakeup = 1;
 504                         if (error) {
 505                                 if (atomic) {
 506                                         atomic = 0;
 507                                         goto redo1;
 508                                 }
 509                                 goto out;
 510                         }
 511                         buf->len += chars;
 512                         total_len -= chars;
 513                         ret = chars;
 514                         if (!total_len)
 515                                 goto out;
 516                 }
 517         }
 518
 519         for (;;) {
 520                 int bufs;
 521
 522                 if (!pipe->readers) {
 523                         send_sig(SIGPIPE, current, 0);
 524                         if (!ret)
 525                                 ret = -EPIPE;
 526                         break;
 527                 }
 528                 bufs = pipe->nrbufs;
 529                 if (bufs < pipe->buffers) {
 530                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 531                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 532                         struct page *page = pipe->tmp_page;
 533                         char *src;
 534                         int error, atomic = 1;
 535
 536                         if (!page) {
 537                                 page = alloc_page(GFP_HIGHUSER);
 538                                 if (unlikely(!page)) {
 539                                         ret = ret ? : -ENOMEM;
 540                                         break;
 541                                 }
 542                                 pipe->tmp_page = page;
 543                         }
 544                         /* Always wake up, even if the copy fails. Otherwise
 545                          * we lock up (O_NONBLOCK-)readers that sleep due to
 546                          * syscall merging.
 547                          * FIXME! Is this really true?
 548                          */
 549                         do_wakeup = 1;
 550                         chars = PAGE_SIZE;
 551                         if (chars > total_len)
 552                                 chars = total_len;
 553
 554                         iov_fault_in_pages_read(iov, chars);
 555 redo2:
 556                         if (atomic)
 557                                 src = kmap_atomic(page, KM_USER0);
 558                         else
 559                                 src = kmap(page);
 560
 561                         error = pipe_iov_copy_from_user(src, iov, chars,
 562                                                         atomic);
 563                         if (atomic)
 564                                 kunmap_atomic(src, KM_USER0);
 565                         else
 566                                 kunmap(page);
 567
 568                         if (unlikely(error)) {
 569                                 if (atomic) {
 570                                         atomic = 0;
 571                                         goto redo2;
 572                                 }
 573                                 if (!ret)
 574                                         ret = error;
 575                                 break;
 576                         }
 577                         ret += chars;
 578
 579                         /* Insert it into the buffer array */
 580                         buf->page = page;
 581                         buf->ops = &anon_pipe_buf_ops;
 582                         buf->offset = 0;
 583                         buf->len = chars;
 584                         pipe->nrbufs = ++bufs;
 585                         pipe->tmp_page = NULL;
 586
 587                         total_len -= chars;
 588                         if (!total_len)
 589                                 break;
 590                 }
 591                 if (bufs < pipe->buffers)
 592                         continue;
 593                 if (filp->f_flags & O_NONBLOCK) {
 594                         if (!ret)
 595                                 ret = -EAGAIN;
 596                         break;
 597                 }
 598                 if (signal_pending(current)) {
 599                         if (!ret)
 600                                 ret = -ERESTARTSYS;
 601                         break;
 602                 }
 603                 if (do_wakeup) {
 604                         wake_up_interruptible_sync(&pipe->wait);
 605                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 606                         do_wakeup = 0;
 607                 }
 608                 pipe->waiting_writers++;
 609                 pipe_wait(pipe);
 610                 pipe->waiting_writers--;
 611         }
 612 out:
 613         mutex_unlock(&inode->i_mutex);
 614         if (do_wakeup) {
 615                 wake_up_interruptible_sync(&pipe->wait);
 616                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 617         }
 618         if (ret > 0)
 619                 file_update_time(filp);
 620         return ret;
 621 }
 622
 623 static ssize_t
 624 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 625 {
 626         return -EBADF;
 627 }
 628
 629 static ssize_t
 630 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
 631            loff_t *ppos)
 632 {
 633         return -EBADF;
 634 }
 635
 636 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 637 {
 638         struct inode *inode = filp->f_path.dentry->d_inode;
 639         struct pipe_inode_info *pipe;
 640         int count, buf, nrbufs;
 641
 642         switch (cmd) {
 643                 case FIONREAD:
 644                         mutex_lock(&inode->i_mutex);
 645                         pipe = inode->i_pipe;
 646                         count = 0;
 647                         buf = pipe->curbuf;
 648                         nrbufs = pipe->nrbufs;
 649                         while (--nrbufs >= 0) {
 650                                 count += pipe->bufs[buf].len;
 651                                 buf = (buf+1) & (pipe->buffers - 1);
 652                         }
 653                         mutex_unlock(&inode->i_mutex);
 654
 655                         return put_user(count, (int __user *)arg);
 656                 default:
 657                         return -EINVAL;
 658         }
 659 }
 660
 661 /* No kernel lock held - fine */
 662 static unsigned int
 663 pipe_poll(struct file *filp, poll_table *wait)
 664 {
 665         unsigned int mask;
 666         struct inode *inode = filp->f_path.dentry->d_inode;
 667         struct pipe_inode_info *pipe = inode->i_pipe;
 668         int nrbufs;
 669
 670         poll_wait(filp, &pipe->wait, wait);
 671
 672         /* Reading only -- no need for acquiring the semaphore.  */
 673         nrbufs = pipe->nrbufs;
 674         mask = 0;
 675         if (filp->f_mode & FMODE_READ) {
 676                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 677                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 678                         mask |= POLLHUP;
 679         }
 680
 681         if (filp->f_mode & FMODE_WRITE) {
 682                 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 683                 /*
 684                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 685                  * behave exactly like pipes for poll().
 686                  */
 687                 if (!pipe->readers)
 688                         mask |= POLLERR;
 689         }
 690
 691         return mask;
 692 }
 693
 694 static int
 695 pipe_release(struct inode *inode, int decr, int decw)
 696 {
 697         struct pipe_inode_info *pipe;
 698
 699         mutex_lock(&inode->i_mutex);
 700         pipe = inode->i_pipe;
 701         pipe->readers -= decr;
 702         pipe->writers -= decw;
 703
 704         if (!pipe->readers && !pipe->writers) {
 705                 free_pipe_info(inode);
 706         } else {
 707                 wake_up_interruptible_sync(&pipe->wait);
 708                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 709                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 710         }
 711         mutex_unlock(&inode->i_mutex);
 712
 713         return 0;
 714 }
 715
 716 static int
 717 pipe_read_fasync(int fd, struct file *filp, int on)
 718 {
 719         struct inode *inode = filp->f_path.dentry->d_inode;
 720         int retval;
 721
 722         mutex_lock(&inode->i_mutex);
 723         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
 724         mutex_unlock(&inode->i_mutex);
 725
 726         return retval;
 727 }
 728
 729
 730 static int
 731 pipe_write_fasync(int fd, struct file *filp, int on)
 732 {
 733         struct inode *inode = filp->f_path.dentry->d_inode;
 734         int retval;
 735
 736         mutex_lock(&inode->i_mutex);
 737         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
 738         mutex_unlock(&inode->i_mutex);
 739
 740         return retval;
 741 }
 742
 743
 744 static int
 745 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 746 {
 747         struct inode *inode = filp->f_path.dentry->d_inode;
 748         struct pipe_inode_info *pipe = inode->i_pipe;
 749         int retval;
 750
 751         mutex_lock(&inode->i_mutex);
 752         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 753         if (retval >= 0) {
 754                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 755                 if (retval < 0) /* this can happen only if on == T */
 756                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 757         }
 758         mutex_unlock(&inode->i_mutex);
 759         return retval;
 760 }
 761
 762
 763 static int
 764 pipe_read_release(struct inode *inode, struct file *filp)
 765 {
 766         return pipe_release(inode, 1, 0);
 767 }
 768
 769 static int
 770 pipe_write_release(struct inode *inode, struct file *filp)
 771 {
 772         return pipe_release(inode, 0, 1);
 773 }
 774
 775 static int
 776 pipe_rdwr_release(struct inode *inode, struct file *filp)
 777 {
 778         int decr, decw;
 779
 780         decr = (filp->f_mode & FMODE_READ) != 0;
 781         decw = (filp->f_mode & FMODE_WRITE) != 0;
 782         return pipe_release(inode, decr, decw);
 783 }
 784
 785 static int
 786 pipe_read_open(struct inode *inode, struct file *filp)
 787 {
 788         int ret = -ENOENT;
 789
 790         mutex_lock(&inode->i_mutex);
 791
 792         if (inode->i_pipe) {
 793                 ret = 0;
 794                 inode->i_pipe->readers++;
 795         }
 796
 797         mutex_unlock(&inode->i_mutex);
 798
 799         return ret;
 800 }
 801
 802 static int
 803 pipe_write_open(struct inode *inode, struct file *filp)
 804 {
 805         int ret = -ENOENT;
 806
 807         mutex_lock(&inode->i_mutex);
 808
 809         if (inode->i_pipe) {
 810                 ret = 0;
 811                 inode->i_pipe->writers++;
 812         }
 813
 814         mutex_unlock(&inode->i_mutex);
 815
 816         return ret;
 817 }
 818
 819 static int
 820 pipe_rdwr_open(struct inode *inode, struct file *filp)
 821 {
 822         int ret = -ENOENT;
 823
 824         mutex_lock(&inode->i_mutex);
 825
 826         if (inode->i_pipe) {
 827                 ret = 0;
 828                 if (filp->f_mode & FMODE_READ)
 829                         inode->i_pipe->readers++;
 830                 if (filp->f_mode & FMODE_WRITE)
 831                         inode->i_pipe->writers++;
 832         }
 833
 834         mutex_unlock(&inode->i_mutex);
 835
 836         return ret;
 837 }
 838
 839 /*
 840  * The file_operations structs are not static because they
 841  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 842  *
 843  * Pipes reuse fifos' file_operations structs.
 844  */
 845 const struct file_operations read_pipefifo_fops = {
 846         .llseek         = no_llseek,
 847         .read           = do_sync_read,
 848         .aio_read       = pipe_read,
 849         .write          = bad_pipe_w,
 850         .poll           = pipe_poll,
 851         .unlocked_ioctl = pipe_ioctl,
 852         .open           = pipe_read_open,
 853         .release        = pipe_read_release,
 854         .fasync         = pipe_read_fasync,
 855 };
 856
 857 const struct file_operations write_pipefifo_fops = {
 858         .llseek         = no_llseek,
 859         .read           = bad_pipe_r,
 860         .write          = do_sync_write,
 861         .aio_write      = pipe_write,
 862         .poll           = pipe_poll,
 863         .unlocked_ioctl = pipe_ioctl,
 864         .open           = pipe_write_open,
 865         .release        = pipe_write_release,
 866         .fasync         = pipe_write_fasync,
 867 };
 868
 869 const struct file_operations rdwr_pipefifo_fops = {
 870         .llseek         = no_llseek,
 871         .read           = do_sync_read,
 872         .aio_read       = pipe_read,
 873         .write          = do_sync_write,
 874         .aio_write      = pipe_write,
 875         .poll           = pipe_poll,
 876         .unlocked_ioctl = pipe_ioctl,
 877         .open           = pipe_rdwr_open,
 878         .release        = pipe_rdwr_release,
 879         .fasync         = pipe_rdwr_fasync,
 880 };
 881
 882 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
 883 {
 884         struct pipe_inode_info *pipe;
 885
 886         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 887         if (pipe) {
 888                 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
 889                 if (pipe->bufs) {
 890                         init_waitqueue_head(&pipe->wait);
 891                         pipe->r_counter = pipe->w_counter = 1;
 892                         pipe->inode = inode;
 893                         pipe->buffers = PIPE_DEF_BUFFERS;
 894                         return pipe;
 895                 }
 896                 kfree(pipe);
 897         }
 898
 899         return NULL;
 900 }
 901
 902 void __free_pipe_info(struct pipe_inode_info *pipe)
 903 {
 904         int i;
 905
 906         for (i = 0; i < pipe->buffers; i++) {
 907                 struct pipe_buffer *buf = pipe->bufs + i;
 908                 if (buf->ops)
 909                         buf->ops->release(pipe, buf);
 910         }
 911         if (pipe->tmp_page)
 912                 __free_page(pipe->tmp_page);
 913         kfree(pipe->bufs);
 914         kfree(pipe);
 915 }
 916
 917 void free_pipe_info(struct inode *inode)
 918 {
 919         __free_pipe_info(inode->i_pipe);
 920         inode->i_pipe = NULL;
 921 }
 922
 923 static struct vfsmount *pipe_mnt __read_mostly;
 924
 925 /*
 926  * pipefs_dname() is called from d_path().
 927  */
 928 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 929 {
 930         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 931                                 dentry->d_inode->i_ino);
 932 }
 933
 934 static const struct dentry_operations pipefs_dentry_operations = {
 935         .d_dname        = pipefs_dname,
 936 };
 937
 938 static struct inode * get_pipe_inode(void)
 939 {
 940         struct inode *inode = new_inode(pipe_mnt->mnt_sb);
 941         struct pipe_inode_info *pipe;
 942
 943         if (!inode)
 944                 goto fail_inode;
 945
 946         pipe = alloc_pipe_info(inode);
 947         if (!pipe)
 948                 goto fail_iput;
 949         inode->i_pipe = pipe;
 950
 951         pipe->readers = pipe->writers = 1;
 952         inode->i_fop = &rdwr_pipefifo_fops;
 953
 954         /*
 955          * Mark the inode dirty from the very beginning,
 956          * that way it will never be moved to the dirty
 957          * list because "mark_inode_dirty()" will think
 958          * that it already _is_ on the dirty list.
 959          */
 960         inode->i_state = I_DIRTY;
 961         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 962         inode->i_uid = current_fsuid();
 963         inode->i_gid = current_fsgid();
 964         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 965
 966         return inode;
 967
 968 fail_iput:
 969         iput(inode);
 970
 971 fail_inode:
 972         return NULL;
 973 }
 974
 975 struct file *create_write_pipe(int flags)
 976 {
 977         int err;
 978         struct inode *inode;
 979         struct file *f;
 980         struct path path;
 981         struct qstr name = { .name = "" };
 982
 983         err = -ENFILE;
 984         inode = get_pipe_inode();
 985         if (!inode)
 986                 goto err;
 987
 988         err = -ENOMEM;
 989         path.dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
 990         if (!path.dentry)
 991                 goto err_inode;
 992         path.mnt = mntget(pipe_mnt);
 993
 994         path.dentry->d_op = &pipefs_dentry_operations;
 995         d_instantiate(path.dentry, inode);
 996
 997         err = -ENFILE;
 998         f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
 999         if (!f)
1000                 goto err_dentry;
1001         f->f_mapping = inode->i_mapping;
1002
1003         f->f_flags = O_WRONLY | (flags & O_NONBLOCK);
1004         f->f_version = 0;
1005
1006         return f;
1007
1008  err_dentry:
1009         free_pipe_info(inode);
1010         path_put(&path);
1011         return ERR_PTR(err);
1012
1013  err_inode:
1014         free_pipe_info(inode);
1015         iput(inode);
1016  err:
1017         return ERR_PTR(err);
1018 }
1019
1020 void free_write_pipe(struct file *f)
1021 {
1022         free_pipe_info(f->f_dentry->d_inode);
1023         path_put(&f->f_path);
1024         put_filp(f);
1025 }
1026
1027 struct file *create_read_pipe(struct file *wrf, int flags)
1028 {
1029         /* Grab pipe from the writer */
1030         struct file *f = alloc_file(&wrf->f_path, FMODE_READ,
1031                                     &read_pipefifo_fops);
1032         if (!f)
1033                 return ERR_PTR(-ENFILE);
1034
1035         path_get(&wrf->f_path);
1036         f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
1037
1038         return f;
1039 }
1040
1041 int do_pipe_flags(int *fd, int flags)
1042 {
1043         struct file *fw, *fr;
1044         int error;
1045         int fdw, fdr;
1046
1047         if (flags & ~(O_CLOEXEC | O_NONBLOCK))
1048                 return -EINVAL;
1049
1050         fw = create_write_pipe(flags);
1051         if (IS_ERR(fw))
1052                 return PTR_ERR(fw);
1053         fr = create_read_pipe(fw, flags);
1054         error = PTR_ERR(fr);
1055         if (IS_ERR(fr))
1056                 goto err_write_pipe;
1057
1058         error = get_unused_fd_flags(flags);
1059         if (error < 0)
1060                 goto err_read_pipe;
1061         fdr = error;
1062
1063         error = get_unused_fd_flags(flags);
1064         if (error < 0)
1065                 goto err_fdr;
1066         fdw = error;
1067
1068         audit_fd_pair(fdr, fdw);
1069         fd_install(fdr, fr);
1070         fd_install(fdw, fw);
1071         fd[0] = fdr;
1072         fd[1] = fdw;
1073
1074         return 0;
1075
1076  err_fdr:
1077         put_unused_fd(fdr);
1078  err_read_pipe:
1079         path_put(&fr->f_path);
1080         put_filp(fr);
1081  err_write_pipe:
1082         free_write_pipe(fw);
1083         return error;
1084 }
1085
1086 /*
1087  * sys_pipe() is the normal C calling standard for creating
1088  * a pipe. It's not the way Unix traditionally does this, though.
1089  */
1090 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1091 {
1092         int fd[2];
1093         int error;
1094
1095         error = do_pipe_flags(fd, flags);
1096         if (!error) {
1097                 if (copy_to_user(fildes, fd, sizeof(fd))) {
1098                         sys_close(fd[0]);
1099                         sys_close(fd[1]);
1100                         error = -EFAULT;
1101                 }
1102         }
1103         return error;
1104 }
1105
1106 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1107 {
1108         return sys_pipe2(fildes, 0);
1109 }
1110
1111 /*
1112  * Allocate a new array of pipe buffers and copy the info over. Returns the
1113  * pipe size if successful, or return -ERROR on error.
1114  */
1115 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1116 {
1117         struct pipe_buffer *bufs;
1118
1119         /*
1120          * Must be a power-of-2 currently
1121          */
1122         if (!is_power_of_2(arg))
1123                 return -EINVAL;
1124
1125         /*
1126          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1127          * expect a lot of shrink+grow operations, just free and allocate
1128          * again like we would do for growing. If the pipe currently
1129          * contains more buffers than arg, then return busy.
1130          */
1131         if (arg < pipe->nrbufs)
1132                 return -EBUSY;
1133
1134         bufs = kcalloc(arg, sizeof(struct pipe_buffer), GFP_KERNEL);
1135         if (unlikely(!bufs))
1136                 return -ENOMEM;
1137
1138         /*
1139          * The pipe array wraps around, so just start the new one at zero
1140          * and adjust the indexes.
1141          */
1142         if (pipe->nrbufs) {
1143                 const unsigned int tail = pipe->nrbufs & (pipe->buffers - 1);
1144                 const unsigned int head = pipe->nrbufs - tail;
1145
1146                 if (head)
1147                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1148                 if (tail)
1149                         memcpy(bufs + head, pipe->bufs + pipe->curbuf, tail * sizeof(struct pipe_buffer));
1150         }
1151
1152         pipe->curbuf = 0;
1153         kfree(pipe->bufs);
1154         pipe->bufs = bufs;
1155         pipe->buffers = arg;
1156         return arg;
1157 }
1158
1159 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1160 {
1161         struct pipe_inode_info *pipe;
1162         long ret;
1163
1164         pipe = file->f_path.dentry->d_inode->i_pipe;
1165         if (!pipe)
1166                 return -EBADF;
1167
1168         mutex_lock(&pipe->inode->i_mutex);
1169
1170         switch (cmd) {
1171         case F_SETPIPE_SZ:
1172                 if (!capable(CAP_SYS_ADMIN) && arg > pipe_max_pages) {
1173                         ret = -EINVAL;
1174                         goto out;
1175                 }
1176                 /*
1177                  * The pipe needs to be at least 2 pages large to
1178                  * guarantee POSIX behaviour.
1179                  */
1180                 if (arg < 2) {
1181                         ret = -EINVAL;
1182                         goto out;
1183                 }
1184                 ret = pipe_set_size(pipe, arg);
1185                 break;
1186         case F_GETPIPE_SZ:
1187                 ret = pipe->buffers;
1188                 break;
1189         default:
1190                 ret = -EINVAL;
1191                 break;
1192         }
1193
1194 out:
1195         mutex_unlock(&pipe->inode->i_mutex);
1196         return ret;
1197 }
1198
1199 /*
1200  * pipefs should _never_ be mounted by userland - too much of security hassle,
1201  * no real gain from having the whole whorehouse mounted. So we don't need
1202  * any operations on the root directory. However, we need a non-trivial
1203  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1204  */
1205 static int pipefs_get_sb(struct file_system_type *fs_type,
1206                          int flags, const char *dev_name, void *data,
1207                          struct vfsmount *mnt)
1208 {
1209         return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
1210 }
1211
1212 static struct file_system_type pipe_fs_type = {
1213         .name           = "pipefs",
1214         .get_sb         = pipefs_get_sb,
1215         .kill_sb        = kill_anon_super,
1216 };
1217
1218 static int __init init_pipe_fs(void)
1219 {
1220         int err = register_filesystem(&pipe_fs_type);
1221
1222         if (!err) {
1223                 pipe_mnt = kern_mount(&pipe_fs_type);
1224                 if (IS_ERR(pipe_mnt)) {
1225                         err = PTR_ERR(pipe_mnt);
1226                         unregister_filesystem(&pipe_fs_type);
1227                 }
1228         }
1229         return err;
1230 }
1231
1232 static void __exit exit_pipe_fs(void)
1233 {
1234         unregister_filesystem(&pipe_fs_type);
1235         mntput(pipe_mnt);
1236 }
1237
1238 fs_initcall(init_pipe_fs);
1239 module_exit(exit_pipe_fs);