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-size
  30  */
  31 unsigned int pipe_max_size = 1048576;
  32
  33 /*
  34  * Minimum pipe size, as required by POSIX
  35  */
  36 unsigned int pipe_min_size = PAGE_SIZE;
  37
  38 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
  39  * matches default values.
  40  */
  41 unsigned long pipe_user_pages_hard;
  42 unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  43
  44 /*
  45  * We use a start+len construction, which provides full use of the
  46  * allocated memory.
  47  * -- Florian Coosmann (FGC)
  48  *
  49  * Reads with count = 0 should always return 0.
  50  * -- Julian Bradfield 1999-06-07.
  51  *
  52  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  53  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  54  *
  55  * pipe_read & write cleanup
  56  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  57  */
  58
  59 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  60 {
  61         if (pipe->inode)
  62                 mutex_lock_nested(&pipe->inode->i_mutex, subclass);
  63 }
  64
  65 void pipe_lock(struct pipe_inode_info *pipe)
  66 {
  67         /*
  68          * pipe_lock() nests non-pipe inode locks (for writing to a file)
  69          */
  70         pipe_lock_nested(pipe, I_MUTEX_PARENT);
  71 }
  72 EXPORT_SYMBOL(pipe_lock);
  73
  74 void pipe_unlock(struct pipe_inode_info *pipe)
  75 {
  76         if (pipe->inode)
  77                 mutex_unlock(&pipe->inode->i_mutex);
  78 }
  79 EXPORT_SYMBOL(pipe_unlock);
  80
  81 void pipe_double_lock(struct pipe_inode_info *pipe1,
  82                       struct pipe_inode_info *pipe2)
  83 {
  84         BUG_ON(pipe1 == pipe2);
  85
  86         if (pipe1 < pipe2) {
  87                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
  88                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
  89         } else {
  90                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
  91                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
  92         }
  93 }
  94
  95 /* Drop the inode semaphore and wait for a pipe event, atomically */
  96 void pipe_wait(struct pipe_inode_info *pipe)
  97 {
  98         DEFINE_WAIT(wait);
  99
 100         /*
 101          * Pipes are system-local resources, so sleeping on them
 102          * is considered a noninteractive wait:
 103          */
 104         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
 105         pipe_unlock(pipe);
 106         schedule();
 107         finish_wait(&pipe->wait, &wait);
 108         pipe_lock(pipe);
 109 }
 110
 111 static int
 112 pipe_iov_copy_from_user(void *addr, int *offset, struct iovec *iov,
 113                         size_t *remaining, int atomic)
 114 {
 115         unsigned long copy;
 116
 117         while (*remaining > 0) {
 118                 while (!iov->iov_len)
 119                         iov++;
 120                 copy = min_t(unsigned long, *remaining, iov->iov_len);
 121
 122                 if (atomic) {
 123                         if (__copy_from_user_inatomic(addr + *offset,
 124                                                       iov->iov_base, copy))
 125                                 return -EFAULT;
 126                 } else {
 127                         if (copy_from_user(addr + *offset,
 128                                            iov->iov_base, copy))
 129                                 return -EFAULT;
 130                 }
 131                 *offset += copy;
 132                 *remaining -= copy;
 133                 iov->iov_base += copy;
 134                 iov->iov_len -= copy;
 135         }
 136         return 0;
 137 }
 138
 139 static int
 140 pipe_iov_copy_to_user(struct iovec *iov, void *addr, int *offset,
 141                       size_t *remaining, int atomic)
 142 {
 143         unsigned long copy;
 144
 145         while (*remaining > 0) {
 146                 while (!iov->iov_len)
 147                         iov++;
 148                 copy = min_t(unsigned long, *remaining, iov->iov_len);
 149
 150                 if (atomic) {
 151                         if (__copy_to_user_inatomic(iov->iov_base,
 152                                                     addr + *offset, copy))
 153                                 return -EFAULT;
 154                 } else {
 155                         if (copy_to_user(iov->iov_base,
 156                                          addr + *offset, copy))
 157                                 return -EFAULT;
 158                 }
 159                 *offset += copy;
 160                 *remaining -= copy;
 161                 iov->iov_base += copy;
 162                 iov->iov_len -= copy;
 163         }
 164         return 0;
 165 }
 166
 167 /*
 168  * Attempt to pre-fault in the user memory, so we can use atomic copies.
 169  * Returns the number of bytes not faulted in.
 170  */
 171 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
 172 {
 173         while (!iov->iov_len)
 174                 iov++;
 175
 176         while (len > 0) {
 177                 unsigned long this_len;
 178
 179                 this_len = min_t(unsigned long, len, iov->iov_len);
 180                 if (fault_in_pages_writeable(iov->iov_base, this_len))
 181                         break;
 182
 183                 len -= this_len;
 184                 iov++;
 185         }
 186
 187         return len;
 188 }
 189
 190 /*
 191  * Pre-fault in the user memory, so we can use atomic copies.
 192  */
 193 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
 194 {
 195         while (!iov->iov_len)
 196                 iov++;
 197
 198         while (len > 0) {
 199                 unsigned long this_len;
 200
 201                 this_len = min_t(unsigned long, len, iov->iov_len);
 202                 fault_in_pages_readable(iov->iov_base, this_len);
 203                 len -= this_len;
 204                 iov++;
 205         }
 206 }
 207
 208 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 209                                   struct pipe_buffer *buf)
 210 {
 211         struct page *page = buf->page;
 212
 213         /*
 214          * If nobody else uses this page, and we don't already have a
 215          * temporary page, let's keep track of it as a one-deep
 216          * allocation cache. (Otherwise just release our reference to it)
 217          */
 218         if (page_count(page) == 1 && !pipe->tmp_page)
 219                 pipe->tmp_page = page;
 220         else
 221                 page_cache_release(page);
 222 }
 223
 224 /**
 225  * generic_pipe_buf_map - virtually map a pipe buffer
 226  * @pipe:       the pipe that the buffer belongs to
 227  * @buf:        the buffer that should be mapped
 228  * @atomic:     whether to use an atomic map
 229  *
 230  * Description:
 231  *      This function returns a kernel virtual address mapping for the
 232  *      pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
 233  *      and the caller has to be careful not to fault before calling
 234  *      the unmap function.
 235  *
 236  *      Note that this function occupies KM_USER0 if @atomic != 0.
 237  */
 238 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 239                            struct pipe_buffer *buf, int atomic)
 240 {
 241         if (atomic) {
 242                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 243                 return kmap_atomic(buf->page, KM_USER0);
 244         }
 245
 246         return kmap(buf->page);
 247 }
 248 EXPORT_SYMBOL(generic_pipe_buf_map);
 249
 250 /**
 251  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
 252  * @pipe:       the pipe that the buffer belongs to
 253  * @buf:        the buffer that should be unmapped
 254  * @map_data:   the data that the mapping function returned
 255  *
 256  * Description:
 257  *      This function undoes the mapping that ->map() provided.
 258  */
 259 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 260                             struct pipe_buffer *buf, void *map_data)
 261 {
 262         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 263                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 264                 kunmap_atomic(map_data, KM_USER0);
 265         } else
 266                 kunmap(buf->page);
 267 }
 268 EXPORT_SYMBOL(generic_pipe_buf_unmap);
 269
 270 /**
 271  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 272  * @pipe:       the pipe that the buffer belongs to
 273  * @buf:        the buffer to attempt to steal
 274  *
 275  * Description:
 276  *      This function attempts to steal the &struct page attached to
 277  *      @buf. If successful, this function returns 0 and returns with
 278  *      the page locked. The caller may then reuse the page for whatever
 279  *      he wishes; the typical use is insertion into a different file
 280  *      page cache.
 281  */
 282 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 283                            struct pipe_buffer *buf)
 284 {
 285         struct page *page = buf->page;
 286
 287         /*
 288          * A reference of one is golden, that means that the owner of this
 289          * page is the only one holding a reference to it. lock the page
 290          * and return OK.
 291          */
 292         if (page_count(page) == 1) {
 293                 lock_page(page);
 294                 return 0;
 295         }
 296
 297         return 1;
 298 }
 299 EXPORT_SYMBOL(generic_pipe_buf_steal);
 300
 301 /**
 302  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 303  * @pipe:       the pipe that the buffer belongs to
 304  * @buf:        the buffer to get a reference to
 305  *
 306  * Description:
 307  *      This function grabs an extra reference to @buf. It's used in
 308  *      in the tee() system call, when we duplicate the buffers in one
 309  *      pipe into another.
 310  */
 311 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 312 {
 313         page_cache_get(buf->page);
 314 }
 315 EXPORT_SYMBOL(generic_pipe_buf_get);
 316
 317 /**
 318  * generic_pipe_buf_confirm - verify contents of the pipe buffer
 319  * @info:       the pipe that the buffer belongs to
 320  * @buf:        the buffer to confirm
 321  *
 322  * Description:
 323  *      This function does nothing, because the generic pipe code uses
 324  *      pages that are always good when inserted into the pipe.
 325  */
 326 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 327                              struct pipe_buffer *buf)
 328 {
 329         return 0;
 330 }
 331 EXPORT_SYMBOL(generic_pipe_buf_confirm);
 332
 333 /**
 334  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 335  * @pipe:       the pipe that the buffer belongs to
 336  * @buf:        the buffer to put a reference to
 337  *
 338  * Description:
 339  *      This function releases a reference to @buf.
 340  */
 341 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 342                               struct pipe_buffer *buf)
 343 {
 344         page_cache_release(buf->page);
 345 }
 346 EXPORT_SYMBOL(generic_pipe_buf_release);
 347
 348 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 349         .can_merge = 1,
 350         .map = generic_pipe_buf_map,
 351         .unmap = generic_pipe_buf_unmap,
 352         .confirm = generic_pipe_buf_confirm,
 353         .release = anon_pipe_buf_release,
 354         .steal = generic_pipe_buf_steal,
 355         .get = generic_pipe_buf_get,
 356 };
 357
 358 static const struct pipe_buf_operations packet_pipe_buf_ops = {
 359         .can_merge = 0,
 360         .map = generic_pipe_buf_map,
 361         .unmap = generic_pipe_buf_unmap,
 362         .confirm = generic_pipe_buf_confirm,
 363         .release = anon_pipe_buf_release,
 364         .steal = generic_pipe_buf_steal,
 365         .get = generic_pipe_buf_get,
 366 };
 367
 368 static ssize_t
 369 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 370            unsigned long nr_segs, loff_t pos)
 371 {
 372         struct file *filp = iocb->ki_filp;
 373         struct inode *inode = filp->f_path.dentry->d_inode;
 374         struct pipe_inode_info *pipe;
 375         int do_wakeup;
 376         ssize_t ret;
 377         struct iovec *iov = (struct iovec *)_iov;
 378         size_t total_len;
 379
 380         total_len = iov_length(iov, nr_segs);
 381         /* Null read succeeds. */
 382         if (unlikely(total_len == 0))
 383                 return 0;
 384
 385         do_wakeup = 0;
 386         ret = 0;
 387         mutex_lock(&inode->i_mutex);
 388         pipe = inode->i_pipe;
 389         for (;;) {
 390                 int bufs = pipe->nrbufs;
 391                 if (bufs) {
 392                         int curbuf = pipe->curbuf;
 393                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 394                         const struct pipe_buf_operations *ops = buf->ops;
 395                         void *addr;
 396                         size_t chars = buf->len, remaining;
 397                         int error, atomic;
 398
 399                         if (chars > total_len)
 400                                 chars = total_len;
 401
 402                         error = ops->confirm(pipe, buf);
 403                         if (error) {
 404                                 if (!ret)
 405                                         ret = error;
 406                                 break;
 407                         }
 408
 409                         atomic = !iov_fault_in_pages_write(iov, chars);
 410                         remaining = chars;
 411 redo:
 412                         addr = ops->map(pipe, buf, atomic);
 413                         error = pipe_iov_copy_to_user(iov, addr, &buf->offset,
 414                                                       &remaining, atomic);
 415                         ops->unmap(pipe, buf, addr);
 416                         if (unlikely(error)) {
 417                                 /*
 418                                  * Just retry with the slow path if we failed.
 419                                  */
 420                                 if (atomic) {
 421                                         atomic = 0;
 422                                         goto redo;
 423                                 }
 424                                 if (!ret)
 425                                         ret = error;
 426                                 break;
 427                         }
 428                         ret += chars;
 429                         buf->len -= chars;
 430
 431                         /* Was it a packet buffer? Clean up and exit */
 432                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 433                                 total_len = chars;
 434                                 buf->len = 0;
 435                         }
 436
 437                         if (!buf->len) {
 438                                 buf->ops = NULL;
 439                                 ops->release(pipe, buf);
 440                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
 441                                 pipe->curbuf = curbuf;
 442                                 pipe->nrbufs = --bufs;
 443                                 do_wakeup = 1;
 444                         }
 445                         total_len -= chars;
 446                         if (!total_len)
 447                                 break;  /* common path: read succeeded */
 448                 }
 449                 if (bufs)       /* More to do? */
 450                         continue;
 451                 if (!pipe->writers)
 452                         break;
 453                 if (!pipe->waiting_writers) {
 454                         /* syscall merging: Usually we must not sleep
 455                          * if O_NONBLOCK is set, or if we got some data.
 456                          * But if a writer sleeps in kernel space, then
 457                          * we can wait for that data without violating POSIX.
 458                          */
 459                         if (ret)
 460                                 break;
 461                         if (filp->f_flags & O_NONBLOCK) {
 462                                 ret = -EAGAIN;
 463                                 break;
 464                         }
 465                 }
 466                 if (signal_pending(current)) {
 467                         if (!ret)
 468                                 ret = -ERESTARTSYS;
 469                         break;
 470                 }
 471                 if (do_wakeup) {
 472                         wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 473                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 474                 }
 475                 pipe_wait(pipe);
 476         }
 477         mutex_unlock(&inode->i_mutex);
 478
 479         /* Signal writers asynchronously that there is more room. */
 480         if (do_wakeup) {
 481                 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 482                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 483         }
 484         if (ret > 0)
 485                 file_accessed(filp);
 486         return ret;
 487 }
 488
 489 static inline int is_packetized(struct file *file)
 490 {
 491         return (file->f_flags & O_DIRECT) != 0;
 492 }
 493
 494 static ssize_t
 495 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 496             unsigned long nr_segs, loff_t ppos)
 497 {
 498         struct file *filp = iocb->ki_filp;
 499         struct inode *inode = filp->f_path.dentry->d_inode;
 500         struct pipe_inode_info *pipe;
 501         ssize_t ret;
 502         int do_wakeup;
 503         struct iovec *iov = (struct iovec *)_iov;
 504         size_t total_len;
 505         ssize_t chars;
 506
 507         total_len = iov_length(iov, nr_segs);
 508         /* Null write succeeds. */
 509         if (unlikely(total_len == 0))
 510                 return 0;
 511
 512         do_wakeup = 0;
 513         ret = 0;
 514         mutex_lock(&inode->i_mutex);
 515         pipe = inode->i_pipe;
 516
 517         if (!pipe->readers) {
 518                 send_sig(SIGPIPE, current, 0);
 519                 ret = -EPIPE;
 520                 goto out;
 521         }
 522
 523         /* We try to merge small writes */
 524         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 525         if (pipe->nrbufs && chars != 0) {
 526                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 527                                                         (pipe->buffers - 1);
 528                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 529                 const struct pipe_buf_operations *ops = buf->ops;
 530                 int offset = buf->offset + buf->len;
 531
 532                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 533                         int error, atomic = 1;
 534                         void *addr;
 535                         size_t remaining = chars;
 536
 537                         error = ops->confirm(pipe, buf);
 538                         if (error)
 539                                 goto out;
 540
 541                         iov_fault_in_pages_read(iov, chars);
 542 redo1:
 543                         addr = ops->map(pipe, buf, atomic);
 544                         error = pipe_iov_copy_from_user(addr, &offset, iov,
 545                                                         &remaining, atomic);
 546                         ops->unmap(pipe, buf, addr);
 547                         ret = error;
 548                         do_wakeup = 1;
 549                         if (error) {
 550                                 if (atomic) {
 551                                         atomic = 0;
 552                                         goto redo1;
 553                                 }
 554                                 goto out;
 555                         }
 556                         buf->len += chars;
 557                         total_len -= chars;
 558                         ret = chars;
 559                         if (!total_len)
 560                                 goto out;
 561                 }
 562         }
 563
 564         for (;;) {
 565                 int bufs;
 566
 567                 if (!pipe->readers) {
 568                         send_sig(SIGPIPE, current, 0);
 569                         if (!ret)
 570                                 ret = -EPIPE;
 571                         break;
 572                 }
 573                 bufs = pipe->nrbufs;
 574                 if (bufs < pipe->buffers) {
 575                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 576                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 577                         struct page *page = pipe->tmp_page;
 578                         char *src;
 579                         int error, atomic = 1;
 580                         int offset = 0;
 581                         size_t remaining;
 582
 583                         if (!page) {
 584                                 page = alloc_page(GFP_HIGHUSER);
 585                                 if (unlikely(!page)) {
 586                                         ret = ret ? : -ENOMEM;
 587                                         break;
 588                                 }
 589                                 pipe->tmp_page = page;
 590                         }
 591                         /* Always wake up, even if the copy fails. Otherwise
 592                          * we lock up (O_NONBLOCK-)readers that sleep due to
 593                          * syscall merging.
 594                          * FIXME! Is this really true?
 595                          */
 596                         do_wakeup = 1;
 597                         chars = PAGE_SIZE;
 598                         if (chars > total_len)
 599                                 chars = total_len;
 600
 601                         iov_fault_in_pages_read(iov, chars);
 602                         remaining = chars;
 603 redo2:
 604                         if (atomic)
 605                                 src = kmap_atomic(page, KM_USER0);
 606                         else
 607                                 src = kmap(page);
 608
 609                         error = pipe_iov_copy_from_user(src, &offset, iov,
 610                                                         &remaining, atomic);
 611                         if (atomic)
 612                                 kunmap_atomic(src, KM_USER0);
 613                         else
 614                                 kunmap(page);
 615
 616                         if (unlikely(error)) {
 617                                 if (atomic) {
 618                                         atomic = 0;
 619                                         goto redo2;
 620                                 }
 621                                 if (!ret)
 622                                         ret = error;
 623                                 break;
 624                         }
 625                         ret += chars;
 626
 627                         /* Insert it into the buffer array */
 628                         buf->page = page;
 629                         buf->ops = &anon_pipe_buf_ops;
 630                         buf->offset = 0;
 631                         buf->len = chars;
 632                         buf->flags = 0;
 633                         if (is_packetized(filp)) {
 634                                 buf->ops = &packet_pipe_buf_ops;
 635                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 636                         }
 637                         pipe->nrbufs = ++bufs;
 638                         pipe->tmp_page = NULL;
 639
 640                         total_len -= chars;
 641                         if (!total_len)
 642                                 break;
 643                 }
 644                 if (bufs < pipe->buffers)
 645                         continue;
 646                 if (filp->f_flags & O_NONBLOCK) {
 647                         if (!ret)
 648                                 ret = -EAGAIN;
 649                         break;
 650                 }
 651                 if (signal_pending(current)) {
 652                         if (!ret)
 653                                 ret = -ERESTARTSYS;
 654                         break;
 655                 }
 656                 if (do_wakeup) {
 657                         wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 658                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 659                         do_wakeup = 0;
 660                 }
 661                 pipe->waiting_writers++;
 662                 pipe_wait(pipe);
 663                 pipe->waiting_writers--;
 664         }
 665 out:
 666         mutex_unlock(&inode->i_mutex);
 667         if (do_wakeup) {
 668                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 669                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 670         }
 671         if (ret > 0)
 672                 file_update_time(filp);
 673         return ret;
 674 }
 675
 676 static ssize_t
 677 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 678 {
 679         return -EBADF;
 680 }
 681
 682 static ssize_t
 683 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
 684            loff_t *ppos)
 685 {
 686         return -EBADF;
 687 }
 688
 689 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 690 {
 691         struct inode *inode = filp->f_path.dentry->d_inode;
 692         struct pipe_inode_info *pipe;
 693         int count, buf, nrbufs;
 694
 695         switch (cmd) {
 696                 case FIONREAD:
 697                         mutex_lock(&inode->i_mutex);
 698                         pipe = inode->i_pipe;
 699                         count = 0;
 700                         buf = pipe->curbuf;
 701                         nrbufs = pipe->nrbufs;
 702                         while (--nrbufs >= 0) {
 703                                 count += pipe->bufs[buf].len;
 704                                 buf = (buf+1) & (pipe->buffers - 1);
 705                         }
 706                         mutex_unlock(&inode->i_mutex);
 707
 708                         return put_user(count, (int __user *)arg);
 709                 default:
 710                         return -EINVAL;
 711         }
 712 }
 713
 714 /* No kernel lock held - fine */
 715 static unsigned int
 716 pipe_poll(struct file *filp, poll_table *wait)
 717 {
 718         unsigned int mask;
 719         struct inode *inode = filp->f_path.dentry->d_inode;
 720         struct pipe_inode_info *pipe = inode->i_pipe;
 721         int nrbufs;
 722
 723         poll_wait(filp, &pipe->wait, wait);
 724
 725         /* Reading only -- no need for acquiring the semaphore.  */
 726         nrbufs = pipe->nrbufs;
 727         mask = 0;
 728         if (filp->f_mode & FMODE_READ) {
 729                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 730                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 731                         mask |= POLLHUP;
 732         }
 733
 734         if (filp->f_mode & FMODE_WRITE) {
 735                 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 736                 /*
 737                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 738                  * behave exactly like pipes for poll().
 739                  */
 740                 if (!pipe->readers)
 741                         mask |= POLLERR;
 742         }
 743
 744         return mask;
 745 }
 746
 747 static int
 748 pipe_release(struct inode *inode, int decr, int decw)
 749 {
 750         struct pipe_inode_info *pipe;
 751
 752         mutex_lock(&inode->i_mutex);
 753         pipe = inode->i_pipe;
 754         pipe->readers -= decr;
 755         pipe->writers -= decw;
 756
 757         if (!pipe->readers && !pipe->writers) {
 758                 free_pipe_info(inode);
 759         } else {
 760                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
 761                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 762                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 763         }
 764         mutex_unlock(&inode->i_mutex);
 765
 766         return 0;
 767 }
 768
 769 static int
 770 pipe_read_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_readers);
 777         mutex_unlock(&inode->i_mutex);
 778
 779         return retval;
 780 }
 781
 782
 783 static int
 784 pipe_write_fasync(int fd, struct file *filp, int on)
 785 {
 786         struct inode *inode = filp->f_path.dentry->d_inode;
 787         int retval;
 788
 789         mutex_lock(&inode->i_mutex);
 790         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
 791         mutex_unlock(&inode->i_mutex);
 792
 793         return retval;
 794 }
 795
 796
 797 static int
 798 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 799 {
 800         struct inode *inode = filp->f_path.dentry->d_inode;
 801         struct pipe_inode_info *pipe = inode->i_pipe;
 802         int retval;
 803
 804         mutex_lock(&inode->i_mutex);
 805         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 806         if (retval >= 0) {
 807                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 808                 if (retval < 0) /* this can happen only if on == T */
 809                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 810         }
 811         mutex_unlock(&inode->i_mutex);
 812         return retval;
 813 }
 814
 815
 816 static int
 817 pipe_read_release(struct inode *inode, struct file *filp)
 818 {
 819         return pipe_release(inode, 1, 0);
 820 }
 821
 822 static int
 823 pipe_write_release(struct inode *inode, struct file *filp)
 824 {
 825         return pipe_release(inode, 0, 1);
 826 }
 827
 828 static int
 829 pipe_rdwr_release(struct inode *inode, struct file *filp)
 830 {
 831         int decr, decw;
 832
 833         decr = (filp->f_mode & FMODE_READ) != 0;
 834         decw = (filp->f_mode & FMODE_WRITE) != 0;
 835         return pipe_release(inode, decr, decw);
 836 }
 837
 838 static int
 839 pipe_read_open(struct inode *inode, struct file *filp)
 840 {
 841         int ret = -ENOENT;
 842
 843         mutex_lock(&inode->i_mutex);
 844
 845         if (inode->i_pipe) {
 846                 ret = 0;
 847                 inode->i_pipe->readers++;
 848         }
 849
 850         mutex_unlock(&inode->i_mutex);
 851
 852         return ret;
 853 }
 854
 855 static int
 856 pipe_write_open(struct inode *inode, struct file *filp)
 857 {
 858         int ret = -ENOENT;
 859
 860         mutex_lock(&inode->i_mutex);
 861
 862         if (inode->i_pipe) {
 863                 ret = 0;
 864                 inode->i_pipe->writers++;
 865         }
 866
 867         mutex_unlock(&inode->i_mutex);
 868
 869         return ret;
 870 }
 871
 872 static int
 873 pipe_rdwr_open(struct inode *inode, struct file *filp)
 874 {
 875         int ret = -ENOENT;
 876
 877         if (!(filp->f_mode & (FMODE_READ|FMODE_WRITE)))
 878                 return -EINVAL;
 879
 880         mutex_lock(&inode->i_mutex);
 881
 882         if (inode->i_pipe) {
 883                 ret = 0;
 884                 if (filp->f_mode & FMODE_READ)
 885                         inode->i_pipe->readers++;
 886                 if (filp->f_mode & FMODE_WRITE)
 887                         inode->i_pipe->writers++;
 888         }
 889
 890         mutex_unlock(&inode->i_mutex);
 891
 892         return ret;
 893 }
 894
 895 /*
 896  * The file_operations structs are not static because they
 897  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 898  *
 899  * Pipes reuse fifos' file_operations structs.
 900  */
 901 const struct file_operations read_pipefifo_fops = {
 902         .llseek         = no_llseek,
 903         .read           = do_sync_read,
 904         .aio_read       = pipe_read,
 905         .write          = bad_pipe_w,
 906         .poll           = pipe_poll,
 907         .unlocked_ioctl = pipe_ioctl,
 908         .open           = pipe_read_open,
 909         .release        = pipe_read_release,
 910         .fasync         = pipe_read_fasync,
 911 };
 912
 913 const struct file_operations write_pipefifo_fops = {
 914         .llseek         = no_llseek,
 915         .read           = bad_pipe_r,
 916         .write          = do_sync_write,
 917         .aio_write      = pipe_write,
 918         .poll           = pipe_poll,
 919         .unlocked_ioctl = pipe_ioctl,
 920         .open           = pipe_write_open,
 921         .release        = pipe_write_release,
 922         .fasync         = pipe_write_fasync,
 923 };
 924
 925 const struct file_operations rdwr_pipefifo_fops = {
 926         .llseek         = no_llseek,
 927         .read           = do_sync_read,
 928         .aio_read       = pipe_read,
 929         .write          = do_sync_write,
 930         .aio_write      = pipe_write,
 931         .poll           = pipe_poll,
 932         .unlocked_ioctl = pipe_ioctl,
 933         .open           = pipe_rdwr_open,
 934         .release        = pipe_rdwr_release,
 935         .fasync         = pipe_rdwr_fasync,
 936 };
 937
 938 static void account_pipe_buffers(struct pipe_inode_info *pipe,
 939                                  unsigned long old, unsigned long new)
 940 {
 941         atomic_long_add(new - old, &pipe->user->pipe_bufs);
 942 }
 943
 944 static bool too_many_pipe_buffers_soft(struct user_struct *user)
 945 {
 946         return pipe_user_pages_soft &&
 947                atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_soft;
 948 }
 949
 950 static bool too_many_pipe_buffers_hard(struct user_struct *user)
 951 {
 952         return pipe_user_pages_hard &&
 953                atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_hard;
 954 }
 955
 956 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
 957 {
 958         struct pipe_inode_info *pipe;
 959
 960         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 961         if (pipe) {
 962                 unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 963                 struct user_struct *user = get_current_user();
 964
 965                 if (!too_many_pipe_buffers_hard(user)) {
 966                         if (too_many_pipe_buffers_soft(user))
 967                                 pipe_bufs = 1;
 968                         pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * pipe_bufs, GFP_KERNEL);
 969                 }
 970
 971                 if (pipe->bufs) {
 972                         init_waitqueue_head(&pipe->wait);
 973                         pipe->r_counter = pipe->w_counter = 1;
 974                         pipe->inode = inode;
 975                         pipe->buffers = pipe_bufs;
 976                         pipe->user = user;
 977                         account_pipe_buffers(pipe, 0, pipe_bufs);
 978                         return pipe;
 979                 }
 980                 free_uid(user);
 981                 kfree(pipe);
 982         }
 983
 984         return NULL;
 985 }
 986
 987 void __free_pipe_info(struct pipe_inode_info *pipe)
 988 {
 989         int i;
 990
 991         account_pipe_buffers(pipe, pipe->buffers, 0);
 992         free_uid(pipe->user);
 993         for (i = 0; i < pipe->buffers; i++) {
 994                 struct pipe_buffer *buf = pipe->bufs + i;
 995                 if (buf->ops)
 996                         buf->ops->release(pipe, buf);
 997         }
 998         if (pipe->tmp_page)
 999                 __free_page(pipe->tmp_page);
1000         kfree(pipe->bufs);
1001         kfree(pipe);
1002 }
1003
1004 void free_pipe_info(struct inode *inode)
1005 {
1006         __free_pipe_info(inode->i_pipe);
1007         inode->i_pipe = NULL;
1008 }
1009
1010 static struct vfsmount *pipe_mnt __read_mostly;
1011
1012 /*
1013  * pipefs_dname() is called from d_path().
1014  */
1015 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
1016 {
1017         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
1018                                 dentry->d_inode->i_ino);
1019 }
1020
1021 static const struct dentry_operations pipefs_dentry_operations = {
1022         .d_dname        = pipefs_dname,
1023 };
1024
1025 static struct inode * get_pipe_inode(void)
1026 {
1027         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
1028         struct pipe_inode_info *pipe;
1029
1030         if (!inode)
1031                 goto fail_inode;
1032
1033         inode->i_ino = get_next_ino();
1034
1035         pipe = alloc_pipe_info(inode);
1036         if (!pipe)
1037                 goto fail_iput;
1038         inode->i_pipe = pipe;
1039
1040         pipe->readers = pipe->writers = 1;
1041         inode->i_fop = &rdwr_pipefifo_fops;
1042
1043         /*
1044          * Mark the inode dirty from the very beginning,
1045          * that way it will never be moved to the dirty
1046          * list because "mark_inode_dirty()" will think
1047          * that it already _is_ on the dirty list.
1048          */
1049         inode->i_state = I_DIRTY;
1050         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
1051         inode->i_uid = current_fsuid();
1052         inode->i_gid = current_fsgid();
1053         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1054
1055         return inode;
1056
1057 fail_iput:
1058         iput(inode);
1059
1060 fail_inode:
1061         return NULL;
1062 }
1063
1064 struct file *create_write_pipe(int flags)
1065 {
1066         int err;
1067         struct inode *inode;
1068         struct file *f;
1069         struct path path;
1070         struct qstr name = { .name = "" };
1071
1072         err = -ENFILE;
1073         inode = get_pipe_inode();
1074         if (!inode)
1075                 goto err;
1076
1077         err = -ENOMEM;
1078         path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
1079         if (!path.dentry)
1080                 goto err_inode;
1081         path.mnt = mntget(pipe_mnt);
1082
1083         d_instantiate(path.dentry, inode);
1084
1085         err = -ENFILE;
1086         f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
1087         if (!f)
1088                 goto err_dentry;
1089         f->f_mapping = inode->i_mapping;
1090
1091         f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
1092         f->f_version = 0;
1093
1094         return f;
1095
1096  err_dentry:
1097         free_pipe_info(inode);
1098         path_put(&path);
1099         return ERR_PTR(err);
1100
1101  err_inode:
1102         free_pipe_info(inode);
1103         iput(inode);
1104  err:
1105         return ERR_PTR(err);
1106 }
1107
1108 void free_write_pipe(struct file *f)
1109 {
1110         free_pipe_info(f->f_dentry->d_inode);
1111         path_put(&f->f_path);
1112         put_filp(f);
1113 }
1114
1115 struct file *create_read_pipe(struct file *wrf, int flags)
1116 {
1117         /* Grab pipe from the writer */
1118         struct file *f = alloc_file(&wrf->f_path, FMODE_READ,
1119                                     &read_pipefifo_fops);
1120         if (!f)
1121                 return ERR_PTR(-ENFILE);
1122
1123         path_get(&wrf->f_path);
1124         f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
1125
1126         return f;
1127 }
1128
1129 int do_pipe_flags(int *fd, int flags)
1130 {
1131         struct file *fw, *fr;
1132         int error;
1133         int fdw, fdr;
1134
1135         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
1136                 return -EINVAL;
1137
1138         fw = create_write_pipe(flags);
1139         if (IS_ERR(fw))
1140                 return PTR_ERR(fw);
1141         fr = create_read_pipe(fw, flags);
1142         error = PTR_ERR(fr);
1143         if (IS_ERR(fr))
1144                 goto err_write_pipe;
1145
1146         error = get_unused_fd_flags(flags);
1147         if (error < 0)
1148                 goto err_read_pipe;
1149         fdr = error;
1150
1151         error = get_unused_fd_flags(flags);
1152         if (error < 0)
1153                 goto err_fdr;
1154         fdw = error;
1155
1156         audit_fd_pair(fdr, fdw);
1157         fd_install(fdr, fr);
1158         fd_install(fdw, fw);
1159         fd[0] = fdr;
1160         fd[1] = fdw;
1161
1162         return 0;
1163
1164  err_fdr:
1165         put_unused_fd(fdr);
1166  err_read_pipe:
1167         path_put(&fr->f_path);
1168         put_filp(fr);
1169  err_write_pipe:
1170         free_write_pipe(fw);
1171         return error;
1172 }
1173
1174 /*
1175  * sys_pipe() is the normal C calling standard for creating
1176  * a pipe. It's not the way Unix traditionally does this, though.
1177  */
1178 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1179 {
1180         int fd[2];
1181         int error;
1182
1183         error = do_pipe_flags(fd, flags);
1184         if (!error) {
1185                 if (copy_to_user(fildes, fd, sizeof(fd))) {
1186                         sys_close(fd[0]);
1187                         sys_close(fd[1]);
1188                         error = -EFAULT;
1189                 }
1190         }
1191         return error;
1192 }
1193
1194 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1195 {
1196         return sys_pipe2(fildes, 0);
1197 }
1198
1199 /*
1200  * Allocate a new array of pipe buffers and copy the info over. Returns the
1201  * pipe size if successful, or return -ERROR on error.
1202  */
1203 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1204 {
1205         struct pipe_buffer *bufs;
1206
1207         /*
1208          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1209          * expect a lot of shrink+grow operations, just free and allocate
1210          * again like we would do for growing. If the pipe currently
1211          * contains more buffers than arg, then return busy.
1212          */
1213         if (nr_pages < pipe->nrbufs)
1214                 return -EBUSY;
1215
1216         bufs = kcalloc(nr_pages, sizeof(struct pipe_buffer), GFP_KERNEL);
1217         if (unlikely(!bufs))
1218                 return -ENOMEM;
1219
1220         /*
1221          * The pipe array wraps around, so just start the new one at zero
1222          * and adjust the indexes.
1223          */
1224         if (pipe->nrbufs) {
1225                 unsigned int tail;
1226                 unsigned int head;
1227
1228                 tail = pipe->curbuf + pipe->nrbufs;
1229                 if (tail < pipe->buffers)
1230                         tail = 0;
1231                 else
1232                         tail &= (pipe->buffers - 1);
1233
1234                 head = pipe->nrbufs - tail;
1235                 if (head)
1236                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1237                 if (tail)
1238                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1239         }
1240
1241         account_pipe_buffers(pipe, pipe->buffers, nr_pages);
1242         pipe->curbuf = 0;
1243         kfree(pipe->bufs);
1244         pipe->bufs = bufs;
1245         pipe->buffers = nr_pages;
1246         return nr_pages * PAGE_SIZE;
1247 }
1248
1249 /*
1250  * Currently we rely on the pipe array holding a power-of-2 number
1251  * of pages.
1252  */
1253 static inline unsigned int round_pipe_size(unsigned int size)
1254 {
1255         unsigned long nr_pages;
1256
1257         nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1258         return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1259 }
1260
1261 /*
1262  * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1263  * will return an error.
1264  */
1265 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1266                  size_t *lenp, loff_t *ppos)
1267 {
1268         int ret;
1269
1270         ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1271         if (ret < 0 || !write)
1272                 return ret;
1273
1274         pipe_max_size = round_pipe_size(pipe_max_size);
1275         return ret;
1276 }
1277
1278 /*
1279  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1280  * location, so checking ->i_pipe is not enough to verify that this is a
1281  * pipe.
1282  */
1283 struct pipe_inode_info *get_pipe_info(struct file *file)
1284 {
1285         struct inode *i = file->f_path.dentry->d_inode;
1286
1287         return S_ISFIFO(i->i_mode) ? i->i_pipe : NULL;
1288 }
1289
1290 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1291 {
1292         struct pipe_inode_info *pipe;
1293         long ret;
1294
1295         pipe = get_pipe_info(file);
1296         if (!pipe)
1297                 return -EBADF;
1298
1299         mutex_lock(&pipe->inode->i_mutex);
1300
1301         switch (cmd) {
1302         case F_SETPIPE_SZ: {
1303                 unsigned int size, nr_pages;
1304
1305                 size = round_pipe_size(arg);
1306                 nr_pages = size >> PAGE_SHIFT;
1307
1308                 ret = -EINVAL;
1309                 if (!nr_pages)
1310                         goto out;
1311
1312                 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1313                         ret = -EPERM;
1314                         goto out;
1315                 } else if ((too_many_pipe_buffers_hard(pipe->user) ||
1316                             too_many_pipe_buffers_soft(pipe->user)) &&
1317                            !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
1318                         ret = -EPERM;
1319                         goto out;
1320                 }
1321                 ret = pipe_set_size(pipe, nr_pages);
1322                 break;
1323                 }
1324         case F_GETPIPE_SZ:
1325                 ret = pipe->buffers * PAGE_SIZE;
1326                 break;
1327         default:
1328                 ret = -EINVAL;
1329                 break;
1330         }
1331
1332 out:
1333         mutex_unlock(&pipe->inode->i_mutex);
1334         return ret;
1335 }
1336
1337 static const struct super_operations pipefs_ops = {
1338         .destroy_inode = free_inode_nonrcu,
1339         .statfs = simple_statfs,
1340 };
1341
1342 /*
1343  * pipefs should _never_ be mounted by userland - too much of security hassle,
1344  * no real gain from having the whole whorehouse mounted. So we don't need
1345  * any operations on the root directory. However, we need a non-trivial
1346  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1347  */
1348 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1349                          int flags, const char *dev_name, void *data)
1350 {
1351         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1352                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1353 }
1354
1355 static struct file_system_type pipe_fs_type = {
1356         .name           = "pipefs",
1357         .mount          = pipefs_mount,
1358         .kill_sb        = kill_anon_super,
1359 };
1360
1361 static int __init init_pipe_fs(void)
1362 {
1363         int err = register_filesystem(&pipe_fs_type);
1364
1365         if (!err) {
1366                 pipe_mnt = kern_mount(&pipe_fs_type);
1367                 if (IS_ERR(pipe_mnt)) {
1368                         err = PTR_ERR(pipe_mnt);
1369                         unregister_filesystem(&pipe_fs_type);
1370                 }
1371         }
1372         return err;
1373 }
1374
1375 static void __exit exit_pipe_fs(void)
1376 {
1377         kern_unmount(pipe_mnt);
1378         unregister_filesystem(&pipe_fs_type);
1379 }
1380
1381 fs_initcall(init_pipe_fs);
1382 module_exit(exit_pipe_fs);