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/magic.h>
  17 #include <linux/pipe_fs_i.h>
  18 #include <linux/uio.h>
  19 #include <linux/highmem.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/audit.h>
  22 #include <linux/syscalls.h>
  23 #include <linux/fcntl.h>
  24
  25 #include <asm/uaccess.h>
  26 #include <asm/ioctls.h>
  27
  28 /*
  29  * The max size that a non-root user is allowed to grow the pipe. Can
  30  * be set by root in /proc/sys/fs/pipe-max-size
  31  */
  32 unsigned int pipe_max_size = 1048576;
  33
  34 /*
  35  * Minimum pipe size, as required by POSIX
  36  */
  37 unsigned int pipe_min_size = PAGE_SIZE;
  38
  39 /*
  40  * We use a start+len construction, which provides full use of the
  41  * allocated memory.
  42  * -- Florian Coosmann (FGC)
  43  *
  44  * Reads with count = 0 should always return 0.
  45  * -- Julian Bradfield 1999-06-07.
  46  *
  47  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  48  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  49  *
  50  * pipe_read & write cleanup
  51  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  52  */
  53
  54 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  55 {
  56         if (pipe->inode)
  57                 mutex_lock_nested(&pipe->inode->i_mutex, subclass);
  58 }
  59
  60 void pipe_lock(struct pipe_inode_info *pipe)
  61 {
  62         /*
  63          * pipe_lock() nests non-pipe inode locks (for writing to a file)
  64          */
  65         pipe_lock_nested(pipe, I_MUTEX_PARENT);
  66 }
  67 EXPORT_SYMBOL(pipe_lock);
  68
  69 void pipe_unlock(struct pipe_inode_info *pipe)
  70 {
  71         if (pipe->inode)
  72                 mutex_unlock(&pipe->inode->i_mutex);
  73 }
  74 EXPORT_SYMBOL(pipe_unlock);
  75
  76 void pipe_double_lock(struct pipe_inode_info *pipe1,
  77                       struct pipe_inode_info *pipe2)
  78 {
  79         BUG_ON(pipe1 == pipe2);
  80
  81         if (pipe1 < pipe2) {
  82                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
  83                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
  84         } else {
  85                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
  86                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
  87         }
  88 }
  89
  90 /* Drop the inode semaphore and wait for a pipe event, atomically */
  91 void pipe_wait(struct pipe_inode_info *pipe)
  92 {
  93         DEFINE_WAIT(wait);
  94
  95         /*
  96          * Pipes are system-local resources, so sleeping on them
  97          * is considered a noninteractive wait:
  98          */
  99         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
 100         pipe_unlock(pipe);
 101         schedule();
 102         finish_wait(&pipe->wait, &wait);
 103         pipe_lock(pipe);
 104 }
 105
 106 static int
 107 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
 108                         int atomic)
 109 {
 110         unsigned long copy;
 111
 112         while (len > 0) {
 113                 while (!iov->iov_len)
 114                         iov++;
 115                 copy = min_t(unsigned long, len, iov->iov_len);
 116
 117                 if (atomic) {
 118                         if (__copy_from_user_inatomic(to, iov->iov_base, copy))
 119                                 return -EFAULT;
 120                 } else {
 121                         if (copy_from_user(to, iov->iov_base, copy))
 122                                 return -EFAULT;
 123                 }
 124                 to += copy;
 125                 len -= copy;
 126                 iov->iov_base += copy;
 127                 iov->iov_len -= copy;
 128         }
 129         return 0;
 130 }
 131
 132 static int
 133 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
 134                       int atomic)
 135 {
 136         unsigned long copy;
 137
 138         while (len > 0) {
 139                 while (!iov->iov_len)
 140                         iov++;
 141                 copy = min_t(unsigned long, len, iov->iov_len);
 142
 143                 if (atomic) {
 144                         if (__copy_to_user_inatomic(iov->iov_base, from, copy))
 145                                 return -EFAULT;
 146                 } else {
 147                         if (copy_to_user(iov->iov_base, from, copy))
 148                                 return -EFAULT;
 149                 }
 150                 from += copy;
 151                 len -= copy;
 152                 iov->iov_base += copy;
 153                 iov->iov_len -= copy;
 154         }
 155         return 0;
 156 }
 157
 158 /*
 159  * Attempt to pre-fault in the user memory, so we can use atomic copies.
 160  * Returns the number of bytes not faulted in.
 161  */
 162 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
 163 {
 164         while (!iov->iov_len)
 165                 iov++;
 166
 167         while (len > 0) {
 168                 unsigned long this_len;
 169
 170                 this_len = min_t(unsigned long, len, iov->iov_len);
 171                 if (fault_in_pages_writeable(iov->iov_base, this_len))
 172                         break;
 173
 174                 len -= this_len;
 175                 iov++;
 176         }
 177
 178         return len;
 179 }
 180
 181 /*
 182  * Pre-fault in the user memory, so we can use atomic copies.
 183  */
 184 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
 185 {
 186         while (!iov->iov_len)
 187                 iov++;
 188
 189         while (len > 0) {
 190                 unsigned long this_len;
 191
 192                 this_len = min_t(unsigned long, len, iov->iov_len);
 193                 fault_in_pages_readable(iov->iov_base, this_len);
 194                 len -= this_len;
 195                 iov++;
 196         }
 197 }
 198
 199 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 200                                   struct pipe_buffer *buf)
 201 {
 202         struct page *page = buf->page;
 203
 204         /*
 205          * If nobody else uses this page, and we don't already have a
 206          * temporary page, let's keep track of it as a one-deep
 207          * allocation cache. (Otherwise just release our reference to it)
 208          */
 209         if (page_count(page) == 1 && !pipe->tmp_page)
 210                 pipe->tmp_page = page;
 211         else
 212                 page_cache_release(page);
 213 }
 214
 215 /**
 216  * generic_pipe_buf_map - virtually map a pipe buffer
 217  * @pipe:       the pipe that the buffer belongs to
 218  * @buf:        the buffer that should be mapped
 219  * @atomic:     whether to use an atomic map
 220  *
 221  * Description:
 222  *      This function returns a kernel virtual address mapping for the
 223  *      pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
 224  *      and the caller has to be careful not to fault before calling
 225  *      the unmap function.
 226  *
 227  *      Note that this function occupies KM_USER0 if @atomic != 0.
 228  */
 229 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 230                            struct pipe_buffer *buf, int atomic)
 231 {
 232         if (atomic) {
 233                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 234                 return kmap_atomic(buf->page);
 235         }
 236
 237         return kmap(buf->page);
 238 }
 239 EXPORT_SYMBOL(generic_pipe_buf_map);
 240
 241 /**
 242  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
 243  * @pipe:       the pipe that the buffer belongs to
 244  * @buf:        the buffer that should be unmapped
 245  * @map_data:   the data that the mapping function returned
 246  *
 247  * Description:
 248  *      This function undoes the mapping that ->map() provided.
 249  */
 250 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 251                             struct pipe_buffer *buf, void *map_data)
 252 {
 253         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 254                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 255                 kunmap_atomic(map_data);
 256         } else
 257                 kunmap(buf->page);
 258 }
 259 EXPORT_SYMBOL(generic_pipe_buf_unmap);
 260
 261 /**
 262  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 263  * @pipe:       the pipe that the buffer belongs to
 264  * @buf:        the buffer to attempt to steal
 265  *
 266  * Description:
 267  *      This function attempts to steal the &struct page attached to
 268  *      @buf. If successful, this function returns 0 and returns with
 269  *      the page locked. The caller may then reuse the page for whatever
 270  *      he wishes; the typical use is insertion into a different file
 271  *      page cache.
 272  */
 273 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 274                            struct pipe_buffer *buf)
 275 {
 276         struct page *page = buf->page;
 277
 278         /*
 279          * A reference of one is golden, that means that the owner of this
 280          * page is the only one holding a reference to it. lock the page
 281          * and return OK.
 282          */
 283         if (page_count(page) == 1) {
 284                 lock_page(page);
 285                 return 0;
 286         }
 287
 288         return 1;
 289 }
 290 EXPORT_SYMBOL(generic_pipe_buf_steal);
 291
 292 /**
 293  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 294  * @pipe:       the pipe that the buffer belongs to
 295  * @buf:        the buffer to get a reference to
 296  *
 297  * Description:
 298  *      This function grabs an extra reference to @buf. It's used in
 299  *      in the tee() system call, when we duplicate the buffers in one
 300  *      pipe into another.
 301  */
 302 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 303 {
 304         page_cache_get(buf->page);
 305 }
 306 EXPORT_SYMBOL(generic_pipe_buf_get);
 307
 308 /**
 309  * generic_pipe_buf_confirm - verify contents of the pipe buffer
 310  * @info:       the pipe that the buffer belongs to
 311  * @buf:        the buffer to confirm
 312  *
 313  * Description:
 314  *      This function does nothing, because the generic pipe code uses
 315  *      pages that are always good when inserted into the pipe.
 316  */
 317 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 318                              struct pipe_buffer *buf)
 319 {
 320         return 0;
 321 }
 322 EXPORT_SYMBOL(generic_pipe_buf_confirm);
 323
 324 /**
 325  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 326  * @pipe:       the pipe that the buffer belongs to
 327  * @buf:        the buffer to put a reference to
 328  *
 329  * Description:
 330  *      This function releases a reference to @buf.
 331  */
 332 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 333                               struct pipe_buffer *buf)
 334 {
 335         page_cache_release(buf->page);
 336 }
 337 EXPORT_SYMBOL(generic_pipe_buf_release);
 338
 339 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 340         .can_merge = 1,
 341         .map = generic_pipe_buf_map,
 342         .unmap = generic_pipe_buf_unmap,
 343         .confirm = generic_pipe_buf_confirm,
 344         .release = anon_pipe_buf_release,
 345         .steal = generic_pipe_buf_steal,
 346         .get = generic_pipe_buf_get,
 347 };
 348
 349 static const struct pipe_buf_operations packet_pipe_buf_ops = {
 350         .can_merge = 0,
 351         .map = generic_pipe_buf_map,
 352         .unmap = generic_pipe_buf_unmap,
 353         .confirm = generic_pipe_buf_confirm,
 354         .release = anon_pipe_buf_release,
 355         .steal = generic_pipe_buf_steal,
 356         .get = generic_pipe_buf_get,
 357 };
 358
 359 static ssize_t
 360 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 361            unsigned long nr_segs, loff_t pos)
 362 {
 363         struct file *filp = iocb->ki_filp;
 364         struct inode *inode = filp->f_path.dentry->d_inode;
 365         struct pipe_inode_info *pipe;
 366         int do_wakeup;
 367         ssize_t ret;
 368         struct iovec *iov = (struct iovec *)_iov;
 369         size_t total_len;
 370
 371         total_len = iov_length(iov, nr_segs);
 372         /* Null read succeeds. */
 373         if (unlikely(total_len == 0))
 374                 return 0;
 375
 376         do_wakeup = 0;
 377         ret = 0;
 378         mutex_lock(&inode->i_mutex);
 379         pipe = inode->i_pipe;
 380         for (;;) {
 381                 int bufs = pipe->nrbufs;
 382                 if (bufs) {
 383                         int curbuf = pipe->curbuf;
 384                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 385                         const struct pipe_buf_operations *ops = buf->ops;
 386                         void *addr;
 387                         size_t chars = buf->len;
 388                         int error, atomic;
 389
 390                         if (chars > total_len)
 391                                 chars = total_len;
 392
 393                         error = ops->confirm(pipe, buf);
 394                         if (error) {
 395                                 if (!ret)
 396                                         ret = error;
 397                                 break;
 398                         }
 399
 400                         atomic = !iov_fault_in_pages_write(iov, chars);
 401 redo:
 402                         addr = ops->map(pipe, buf, atomic);
 403                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
 404                         ops->unmap(pipe, buf, addr);
 405                         if (unlikely(error)) {
 406                                 /*
 407                                  * Just retry with the slow path if we failed.
 408                                  */
 409                                 if (atomic) {
 410                                         atomic = 0;
 411                                         goto redo;
 412                                 }
 413                                 if (!ret)
 414                                         ret = error;
 415                                 break;
 416                         }
 417                         ret += chars;
 418                         buf->offset += chars;
 419                         buf->len -= chars;
 420
 421                         /* Was it a packet buffer? Clean up and exit */
 422                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 423                                 total_len = chars;
 424                                 buf->len = 0;
 425                         }
 426
 427                         if (!buf->len) {
 428                                 buf->ops = NULL;
 429                                 ops->release(pipe, buf);
 430                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
 431                                 pipe->curbuf = curbuf;
 432                                 pipe->nrbufs = --bufs;
 433                                 do_wakeup = 1;
 434                         }
 435                         total_len -= chars;
 436                         if (!total_len)
 437                                 break;  /* common path: read succeeded */
 438                 }
 439                 if (bufs)       /* More to do? */
 440                         continue;
 441                 if (!pipe->writers)
 442                         break;
 443                 if (!pipe->waiting_writers) {
 444                         /* syscall merging: Usually we must not sleep
 445                          * if O_NONBLOCK is set, or if we got some data.
 446                          * But if a writer sleeps in kernel space, then
 447                          * we can wait for that data without violating POSIX.
 448                          */
 449                         if (ret)
 450                                 break;
 451                         if (filp->f_flags & O_NONBLOCK) {
 452                                 ret = -EAGAIN;
 453                                 break;
 454                         }
 455                 }
 456                 if (signal_pending(current)) {
 457                         if (!ret)
 458                                 ret = -ERESTARTSYS;
 459                         break;
 460                 }
 461                 if (do_wakeup) {
 462                         wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 463                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 464                 }
 465                 pipe_wait(pipe);
 466         }
 467         mutex_unlock(&inode->i_mutex);
 468
 469         /* Signal writers asynchronously that there is more room. */
 470         if (do_wakeup) {
 471                 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 472                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 473         }
 474         if (ret > 0)
 475                 file_accessed(filp);
 476         return ret;
 477 }
 478
 479 static inline int is_packetized(struct file *file)
 480 {
 481         return (file->f_flags & O_DIRECT) != 0;
 482 }
 483
 484 static ssize_t
 485 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 486             unsigned long nr_segs, loff_t ppos)
 487 {
 488         struct file *filp = iocb->ki_filp;
 489         struct inode *inode = filp->f_path.dentry->d_inode;
 490         struct pipe_inode_info *pipe;
 491         ssize_t ret;
 492         int do_wakeup;
 493         struct iovec *iov = (struct iovec *)_iov;
 494         size_t total_len;
 495         ssize_t chars;
 496
 497         total_len = iov_length(iov, nr_segs);
 498         /* Null write succeeds. */
 499         if (unlikely(total_len == 0))
 500                 return 0;
 501
 502         do_wakeup = 0;
 503         ret = 0;
 504         mutex_lock(&inode->i_mutex);
 505         pipe = inode->i_pipe;
 506
 507         if (!pipe->readers) {
 508                 send_sig(SIGPIPE, current, 0);
 509                 ret = -EPIPE;
 510                 goto out;
 511         }
 512
 513         /* We try to merge small writes */
 514         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 515         if (pipe->nrbufs && chars != 0) {
 516                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 517                                                         (pipe->buffers - 1);
 518                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 519                 const struct pipe_buf_operations *ops = buf->ops;
 520                 int offset = buf->offset + buf->len;
 521
 522                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 523                         int error, atomic = 1;
 524                         void *addr;
 525
 526                         error = ops->confirm(pipe, buf);
 527                         if (error)
 528                                 goto out;
 529
 530                         iov_fault_in_pages_read(iov, chars);
 531 redo1:
 532                         addr = ops->map(pipe, buf, atomic);
 533                         error = pipe_iov_copy_from_user(offset + addr, iov,
 534                                                         chars, atomic);
 535                         ops->unmap(pipe, buf, addr);
 536                         ret = error;
 537                         do_wakeup = 1;
 538                         if (error) {
 539                                 if (atomic) {
 540                                         atomic = 0;
 541                                         goto redo1;
 542                                 }
 543                                 goto out;
 544                         }
 545                         buf->len += chars;
 546                         total_len -= chars;
 547                         ret = chars;
 548                         if (!total_len)
 549                                 goto out;
 550                 }
 551         }
 552
 553         for (;;) {
 554                 int bufs;
 555
 556                 if (!pipe->readers) {
 557                         send_sig(SIGPIPE, current, 0);
 558                         if (!ret)
 559                                 ret = -EPIPE;
 560                         break;
 561                 }
 562                 bufs = pipe->nrbufs;
 563                 if (bufs < pipe->buffers) {
 564                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 565                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 566                         struct page *page = pipe->tmp_page;
 567                         char *src;
 568                         int error, atomic = 1;
 569
 570                         if (!page) {
 571                                 page = alloc_page(GFP_HIGHUSER);
 572                                 if (unlikely(!page)) {
 573                                         ret = ret ? : -ENOMEM;
 574                                         break;
 575                                 }
 576                                 pipe->tmp_page = page;
 577                         }
 578                         /* Always wake up, even if the copy fails. Otherwise
 579                          * we lock up (O_NONBLOCK-)readers that sleep due to
 580                          * syscall merging.
 581                          * FIXME! Is this really true?
 582                          */
 583                         do_wakeup = 1;
 584                         chars = PAGE_SIZE;
 585                         if (chars > total_len)
 586                                 chars = total_len;
 587
 588                         iov_fault_in_pages_read(iov, chars);
 589 redo2:
 590                         if (atomic)
 591                                 src = kmap_atomic(page);
 592                         else
 593                                 src = kmap(page);
 594
 595                         error = pipe_iov_copy_from_user(src, iov, chars,
 596                                                         atomic);
 597                         if (atomic)
 598                                 kunmap_atomic(src);
 599                         else
 600                                 kunmap(page);
 601
 602                         if (unlikely(error)) {
 603                                 if (atomic) {
 604                                         atomic = 0;
 605                                         goto redo2;
 606                                 }
 607                                 if (!ret)
 608                                         ret = error;
 609                                 break;
 610                         }
 611                         ret += chars;
 612
 613                         /* Insert it into the buffer array */
 614                         buf->page = page;
 615                         buf->ops = &anon_pipe_buf_ops;
 616                         buf->offset = 0;
 617                         buf->len = chars;
 618                         buf->flags = 0;
 619                         if (is_packetized(filp)) {
 620                                 buf->ops = &packet_pipe_buf_ops;
 621                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 622                         }
 623                         pipe->nrbufs = ++bufs;
 624                         pipe->tmp_page = NULL;
 625
 626                         total_len -= chars;
 627                         if (!total_len)
 628                                 break;
 629                 }
 630                 if (bufs < pipe->buffers)
 631                         continue;
 632                 if (filp->f_flags & O_NONBLOCK) {
 633                         if (!ret)
 634                                 ret = -EAGAIN;
 635                         break;
 636                 }
 637                 if (signal_pending(current)) {
 638                         if (!ret)
 639                                 ret = -ERESTARTSYS;
 640                         break;
 641                 }
 642                 if (do_wakeup) {
 643                         wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 644                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 645                         do_wakeup = 0;
 646                 }
 647                 pipe->waiting_writers++;
 648                 pipe_wait(pipe);
 649                 pipe->waiting_writers--;
 650         }
 651 out:
 652         mutex_unlock(&inode->i_mutex);
 653         if (do_wakeup) {
 654                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 655                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 656         }
 657         if (ret > 0)
 658                 file_update_time(filp);
 659         return ret;
 660 }
 661
 662 static ssize_t
 663 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 664 {
 665         return -EBADF;
 666 }
 667
 668 static ssize_t
 669 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
 670            loff_t *ppos)
 671 {
 672         return -EBADF;
 673 }
 674
 675 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 676 {
 677         struct inode *inode = filp->f_path.dentry->d_inode;
 678         struct pipe_inode_info *pipe;
 679         int count, buf, nrbufs;
 680
 681         switch (cmd) {
 682                 case FIONREAD:
 683                         mutex_lock(&inode->i_mutex);
 684                         pipe = inode->i_pipe;
 685                         count = 0;
 686                         buf = pipe->curbuf;
 687                         nrbufs = pipe->nrbufs;
 688                         while (--nrbufs >= 0) {
 689                                 count += pipe->bufs[buf].len;
 690                                 buf = (buf+1) & (pipe->buffers - 1);
 691                         }
 692                         mutex_unlock(&inode->i_mutex);
 693
 694                         return put_user(count, (int __user *)arg);
 695                 default:
 696                         return -EINVAL;
 697         }
 698 }
 699
 700 /* No kernel lock held - fine */
 701 static unsigned int
 702 pipe_poll(struct file *filp, poll_table *wait)
 703 {
 704         unsigned int mask;
 705         struct inode *inode = filp->f_path.dentry->d_inode;
 706         struct pipe_inode_info *pipe = inode->i_pipe;
 707         int nrbufs;
 708
 709         poll_wait(filp, &pipe->wait, wait);
 710
 711         /* Reading only -- no need for acquiring the semaphore.  */
 712         nrbufs = pipe->nrbufs;
 713         mask = 0;
 714         if (filp->f_mode & FMODE_READ) {
 715                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 716                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 717                         mask |= POLLHUP;
 718         }
 719
 720         if (filp->f_mode & FMODE_WRITE) {
 721                 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 722                 /*
 723                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 724                  * behave exactly like pipes for poll().
 725                  */
 726                 if (!pipe->readers)
 727                         mask |= POLLERR;
 728         }
 729
 730         return mask;
 731 }
 732
 733 static int
 734 pipe_release(struct inode *inode, int decr, int decw)
 735 {
 736         struct pipe_inode_info *pipe;
 737
 738         mutex_lock(&inode->i_mutex);
 739         pipe = inode->i_pipe;
 740         pipe->readers -= decr;
 741         pipe->writers -= decw;
 742
 743         if (!pipe->readers && !pipe->writers) {
 744                 free_pipe_info(inode);
 745         } else {
 746                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
 747                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 748                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 749         }
 750         mutex_unlock(&inode->i_mutex);
 751
 752         return 0;
 753 }
 754
 755 static int
 756 pipe_read_fasync(int fd, struct file *filp, int on)
 757 {
 758         struct inode *inode = filp->f_path.dentry->d_inode;
 759         int retval;
 760
 761         mutex_lock(&inode->i_mutex);
 762         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
 763         mutex_unlock(&inode->i_mutex);
 764
 765         return retval;
 766 }
 767
 768
 769 static int
 770 pipe_write_fasync(int fd, struct file *filp, int on)
 771 {
 772         struct inode *inode = filp->f_path.dentry->d_inode;
 773         int retval;
 774
 775         mutex_lock(&inode->i_mutex);
 776         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
 777         mutex_unlock(&inode->i_mutex);
 778
 779         return retval;
 780 }
 781
 782
 783 static int
 784 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 785 {
 786         struct inode *inode = filp->f_path.dentry->d_inode;
 787         struct pipe_inode_info *pipe = inode->i_pipe;
 788         int retval;
 789
 790         mutex_lock(&inode->i_mutex);
 791         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 792         if (retval >= 0) {
 793                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 794                 if (retval < 0) /* this can happen only if on == T */
 795                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 796         }
 797         mutex_unlock(&inode->i_mutex);
 798         return retval;
 799 }
 800
 801
 802 static int
 803 pipe_read_release(struct inode *inode, struct file *filp)
 804 {
 805         return pipe_release(inode, 1, 0);
 806 }
 807
 808 static int
 809 pipe_write_release(struct inode *inode, struct file *filp)
 810 {
 811         return pipe_release(inode, 0, 1);
 812 }
 813
 814 static int
 815 pipe_rdwr_release(struct inode *inode, struct file *filp)
 816 {
 817         int decr, decw;
 818
 819         decr = (filp->f_mode & FMODE_READ) != 0;
 820         decw = (filp->f_mode & FMODE_WRITE) != 0;
 821         return pipe_release(inode, decr, decw);
 822 }
 823
 824 static int
 825 pipe_read_open(struct inode *inode, struct file *filp)
 826 {
 827         int ret = -ENOENT;
 828
 829         mutex_lock(&inode->i_mutex);
 830
 831         if (inode->i_pipe) {
 832                 ret = 0;
 833                 inode->i_pipe->readers++;
 834         }
 835
 836         mutex_unlock(&inode->i_mutex);
 837
 838         return ret;
 839 }
 840
 841 static int
 842 pipe_write_open(struct inode *inode, struct file *filp)
 843 {
 844         int ret = -ENOENT;
 845
 846         mutex_lock(&inode->i_mutex);
 847
 848         if (inode->i_pipe) {
 849                 ret = 0;
 850                 inode->i_pipe->writers++;
 851         }
 852
 853         mutex_unlock(&inode->i_mutex);
 854
 855         return ret;
 856 }
 857
 858 static int
 859 pipe_rdwr_open(struct inode *inode, struct file *filp)
 860 {
 861         int ret = -ENOENT;
 862
 863         mutex_lock(&inode->i_mutex);
 864
 865         if (inode->i_pipe) {
 866                 ret = 0;
 867                 if (filp->f_mode & FMODE_READ)
 868                         inode->i_pipe->readers++;
 869                 if (filp->f_mode & FMODE_WRITE)
 870                         inode->i_pipe->writers++;
 871         }
 872
 873         mutex_unlock(&inode->i_mutex);
 874
 875         return ret;
 876 }
 877
 878 /*
 879  * The file_operations structs are not static because they
 880  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 881  *
 882  * Pipes reuse fifos' file_operations structs.
 883  */
 884 const struct file_operations read_pipefifo_fops = {
 885         .llseek         = no_llseek,
 886         .read           = do_sync_read,
 887         .aio_read       = pipe_read,
 888         .write          = bad_pipe_w,
 889         .poll           = pipe_poll,
 890         .unlocked_ioctl = pipe_ioctl,
 891         .open           = pipe_read_open,
 892         .release        = pipe_read_release,
 893         .fasync         = pipe_read_fasync,
 894 };
 895
 896 const struct file_operations write_pipefifo_fops = {
 897         .llseek         = no_llseek,
 898         .read           = bad_pipe_r,
 899         .write          = do_sync_write,
 900         .aio_write      = pipe_write,
 901         .poll           = pipe_poll,
 902         .unlocked_ioctl = pipe_ioctl,
 903         .open           = pipe_write_open,
 904         .release        = pipe_write_release,
 905         .fasync         = pipe_write_fasync,
 906 };
 907
 908 const struct file_operations rdwr_pipefifo_fops = {
 909         .llseek         = no_llseek,
 910         .read           = do_sync_read,
 911         .aio_read       = pipe_read,
 912         .write          = do_sync_write,
 913         .aio_write      = pipe_write,
 914         .poll           = pipe_poll,
 915         .unlocked_ioctl = pipe_ioctl,
 916         .open           = pipe_rdwr_open,
 917         .release        = pipe_rdwr_release,
 918         .fasync         = pipe_rdwr_fasync,
 919 };
 920
 921 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
 922 {
 923         struct pipe_inode_info *pipe;
 924
 925         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 926         if (pipe) {
 927                 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
 928                 if (pipe->bufs) {
 929                         init_waitqueue_head(&pipe->wait);
 930                         pipe->r_counter = pipe->w_counter = 1;
 931                         pipe->inode = inode;
 932                         pipe->buffers = PIPE_DEF_BUFFERS;
 933                         return pipe;
 934                 }
 935                 kfree(pipe);
 936         }
 937
 938         return NULL;
 939 }
 940
 941 void __free_pipe_info(struct pipe_inode_info *pipe)
 942 {
 943         int i;
 944
 945         for (i = 0; i < pipe->buffers; i++) {
 946                 struct pipe_buffer *buf = pipe->bufs + i;
 947                 if (buf->ops)
 948                         buf->ops->release(pipe, buf);
 949         }
 950         if (pipe->tmp_page)
 951                 __free_page(pipe->tmp_page);
 952         kfree(pipe->bufs);
 953         kfree(pipe);
 954 }
 955
 956 void free_pipe_info(struct inode *inode)
 957 {
 958         __free_pipe_info(inode->i_pipe);
 959         inode->i_pipe = NULL;
 960 }
 961
 962 static struct vfsmount *pipe_mnt __read_mostly;
 963
 964 /*
 965  * pipefs_dname() is called from d_path().
 966  */
 967 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 968 {
 969         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 970                                 dentry->d_inode->i_ino);
 971 }
 972
 973 static const struct dentry_operations pipefs_dentry_operations = {
 974         .d_dname        = pipefs_dname,
 975 };
 976
 977 static struct inode * get_pipe_inode(void)
 978 {
 979         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 980         struct pipe_inode_info *pipe;
 981
 982         if (!inode)
 983                 goto fail_inode;
 984
 985         inode->i_ino = get_next_ino();
 986
 987         pipe = alloc_pipe_info(inode);
 988         if (!pipe)
 989                 goto fail_iput;
 990         inode->i_pipe = pipe;
 991
 992         pipe->readers = pipe->writers = 1;
 993         inode->i_fop = &rdwr_pipefifo_fops;
 994
 995         /*
 996          * Mark the inode dirty from the very beginning,
 997          * that way it will never be moved to the dirty
 998          * list because "mark_inode_dirty()" will think
 999          * that it already _is_ on the dirty list.
1000          */
1001         inode->i_state = I_DIRTY;
1002         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
1003         inode->i_uid = current_fsuid();
1004         inode->i_gid = current_fsgid();
1005         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1006
1007         return inode;
1008
1009 fail_iput:
1010         iput(inode);
1011
1012 fail_inode:
1013         return NULL;
1014 }
1015
1016 struct file *create_write_pipe(int flags)
1017 {
1018         int err;
1019         struct inode *inode;
1020         struct file *f;
1021         struct path path;
1022         struct qstr name = { .name = "" };
1023
1024         err = -ENFILE;
1025         inode = get_pipe_inode();
1026         if (!inode)
1027                 goto err;
1028
1029         err = -ENOMEM;
1030         path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
1031         if (!path.dentry)
1032                 goto err_inode;
1033         path.mnt = mntget(pipe_mnt);
1034
1035         d_instantiate(path.dentry, inode);
1036
1037         err = -ENFILE;
1038         f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
1039         if (!f)
1040                 goto err_dentry;
1041         f->f_mapping = inode->i_mapping;
1042
1043         f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
1044         f->f_version = 0;
1045
1046         return f;
1047
1048  err_dentry:
1049         free_pipe_info(inode);
1050         path_put(&path);
1051         return ERR_PTR(err);
1052
1053  err_inode:
1054         free_pipe_info(inode);
1055         iput(inode);
1056  err:
1057         return ERR_PTR(err);
1058 }
1059
1060 void free_write_pipe(struct file *f)
1061 {
1062         free_pipe_info(f->f_dentry->d_inode);
1063         path_put(&f->f_path);
1064         put_filp(f);
1065 }
1066
1067 struct file *create_read_pipe(struct file *wrf, int flags)
1068 {
1069         /* Grab pipe from the writer */
1070         struct file *f = alloc_file(&wrf->f_path, FMODE_READ,
1071                                     &read_pipefifo_fops);
1072         if (!f)
1073                 return ERR_PTR(-ENFILE);
1074
1075         path_get(&wrf->f_path);
1076         f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
1077
1078         return f;
1079 }
1080
1081 int do_pipe_flags(int *fd, int flags)
1082 {
1083         struct file *fw, *fr;
1084         int error;
1085         int fdw, fdr;
1086
1087         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
1088                 return -EINVAL;
1089
1090         fw = create_write_pipe(flags);
1091         if (IS_ERR(fw))
1092                 return PTR_ERR(fw);
1093         fr = create_read_pipe(fw, flags);
1094         error = PTR_ERR(fr);
1095         if (IS_ERR(fr))
1096                 goto err_write_pipe;
1097
1098         error = get_unused_fd_flags(flags);
1099         if (error < 0)
1100                 goto err_read_pipe;
1101         fdr = error;
1102
1103         error = get_unused_fd_flags(flags);
1104         if (error < 0)
1105                 goto err_fdr;
1106         fdw = error;
1107
1108         audit_fd_pair(fdr, fdw);
1109         fd_install(fdr, fr);
1110         fd_install(fdw, fw);
1111         fd[0] = fdr;
1112         fd[1] = fdw;
1113
1114         return 0;
1115
1116  err_fdr:
1117         put_unused_fd(fdr);
1118  err_read_pipe:
1119         path_put(&fr->f_path);
1120         put_filp(fr);
1121  err_write_pipe:
1122         free_write_pipe(fw);
1123         return error;
1124 }
1125
1126 /*
1127  * sys_pipe() is the normal C calling standard for creating
1128  * a pipe. It's not the way Unix traditionally does this, though.
1129  */
1130 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1131 {
1132         int fd[2];
1133         int error;
1134
1135         error = do_pipe_flags(fd, flags);
1136         if (!error) {
1137                 if (copy_to_user(fildes, fd, sizeof(fd))) {
1138                         sys_close(fd[0]);
1139                         sys_close(fd[1]);
1140                         error = -EFAULT;
1141                 }
1142         }
1143         return error;
1144 }
1145
1146 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1147 {
1148         return sys_pipe2(fildes, 0);
1149 }
1150
1151 /*
1152  * Allocate a new array of pipe buffers and copy the info over. Returns the
1153  * pipe size if successful, or return -ERROR on error.
1154  */
1155 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1156 {
1157         struct pipe_buffer *bufs;
1158
1159         /*
1160          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1161          * expect a lot of shrink+grow operations, just free and allocate
1162          * again like we would do for growing. If the pipe currently
1163          * contains more buffers than arg, then return busy.
1164          */
1165         if (nr_pages < pipe->nrbufs)
1166                 return -EBUSY;
1167
1168         bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
1169         if (unlikely(!bufs))
1170                 return -ENOMEM;
1171
1172         /*
1173          * The pipe array wraps around, so just start the new one at zero
1174          * and adjust the indexes.
1175          */
1176         if (pipe->nrbufs) {
1177                 unsigned int tail;
1178                 unsigned int head;
1179
1180                 tail = pipe->curbuf + pipe->nrbufs;
1181                 if (tail < pipe->buffers)
1182                         tail = 0;
1183                 else
1184                         tail &= (pipe->buffers - 1);
1185
1186                 head = pipe->nrbufs - tail;
1187                 if (head)
1188                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1189                 if (tail)
1190                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1191         }
1192
1193         pipe->curbuf = 0;
1194         kfree(pipe->bufs);
1195         pipe->bufs = bufs;
1196         pipe->buffers = nr_pages;
1197         return nr_pages * PAGE_SIZE;
1198 }
1199
1200 /*
1201  * Currently we rely on the pipe array holding a power-of-2 number
1202  * of pages.
1203  */
1204 static inline unsigned int round_pipe_size(unsigned int size)
1205 {
1206         unsigned long nr_pages;
1207
1208         nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1209         return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1210 }
1211
1212 /*
1213  * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1214  * will return an error.
1215  */
1216 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1217                  size_t *lenp, loff_t *ppos)
1218 {
1219         int ret;
1220
1221         ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1222         if (ret < 0 || !write)
1223                 return ret;
1224
1225         pipe_max_size = round_pipe_size(pipe_max_size);
1226         return ret;
1227 }
1228
1229 /*
1230  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1231  * location, so checking ->i_pipe is not enough to verify that this is a
1232  * pipe.
1233  */
1234 struct pipe_inode_info *get_pipe_info(struct file *file)
1235 {
1236         struct inode *i = file->f_path.dentry->d_inode;
1237
1238         return S_ISFIFO(i->i_mode) ? i->i_pipe : NULL;
1239 }
1240
1241 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1242 {
1243         struct pipe_inode_info *pipe;
1244         long ret;
1245
1246         pipe = get_pipe_info(file);
1247         if (!pipe)
1248                 return -EBADF;
1249
1250         mutex_lock(&pipe->inode->i_mutex);
1251
1252         switch (cmd) {
1253         case F_SETPIPE_SZ: {
1254                 unsigned int size, nr_pages;
1255
1256                 size = round_pipe_size(arg);
1257                 nr_pages = size >> PAGE_SHIFT;
1258
1259                 ret = -EINVAL;
1260                 if (!nr_pages)
1261                         goto out;
1262
1263                 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1264                         ret = -EPERM;
1265                         goto out;
1266                 }
1267                 ret = pipe_set_size(pipe, nr_pages);
1268                 break;
1269                 }
1270         case F_GETPIPE_SZ:
1271                 ret = pipe->buffers * PAGE_SIZE;
1272                 break;
1273         default:
1274                 ret = -EINVAL;
1275                 break;
1276         }
1277
1278 out:
1279         mutex_unlock(&pipe->inode->i_mutex);
1280         return ret;
1281 }
1282
1283 static const struct super_operations pipefs_ops = {
1284         .destroy_inode = free_inode_nonrcu,
1285         .statfs = simple_statfs,
1286 };
1287
1288 /*
1289  * pipefs should _never_ be mounted by userland - too much of security hassle,
1290  * no real gain from having the whole whorehouse mounted. So we don't need
1291  * any operations on the root directory. However, we need a non-trivial
1292  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1293  */
1294 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1295                          int flags, const char *dev_name, void *data)
1296 {
1297         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1298                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1299 }
1300
1301 static struct file_system_type pipe_fs_type = {
1302         .name           = "pipefs",
1303         .mount          = pipefs_mount,
1304         .kill_sb        = kill_anon_super,
1305 };
1306
1307 static int __init init_pipe_fs(void)
1308 {
1309         int err = register_filesystem(&pipe_fs_type);
1310
1311         if (!err) {
1312                 pipe_mnt = kern_mount(&pipe_fs_type);
1313                 if (IS_ERR(pipe_mnt)) {
1314                         err = PTR_ERR(pipe_mnt);
1315                         unregister_filesystem(&pipe_fs_type);
1316                 }
1317         }
1318         return err;
1319 }
1320
1321 fs_initcall(init_pipe_fs);