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 #include <linux/aio.h>
  25
  26 #include <asm/uaccess.h>
  27 #include <asm/ioctls.h>
  28
  29 #include "internal.h"
  30
  31 /*
  32  * The max size that a non-root user is allowed to grow the pipe. Can
  33  * be set by root in /proc/sys/fs/pipe-max-size
  34  */
  35 unsigned int pipe_max_size = 1048576;
  36
  37 /*
  38  * Minimum pipe size, as required by POSIX
  39  */
  40 unsigned int pipe_min_size = PAGE_SIZE;
  41
  42 /*
  43  * We use a start+len construction, which provides full use of the
  44  * allocated memory.
  45  * -- Florian Coosmann (FGC)
  46  *
  47  * Reads with count = 0 should always return 0.
  48  * -- Julian Bradfield 1999-06-07.
  49  *
  50  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  51  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  52  *
  53  * pipe_read & write cleanup
  54  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  55  */
  56
  57 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  58 {
  59         if (pipe->files)
  60                 mutex_lock_nested(&pipe->mutex, subclass);
  61 }
  62
  63 void pipe_lock(struct pipe_inode_info *pipe)
  64 {
  65         /*
  66          * pipe_lock() nests non-pipe inode locks (for writing to a file)
  67          */
  68         pipe_lock_nested(pipe, I_MUTEX_PARENT);
  69 }
  70 EXPORT_SYMBOL(pipe_lock);
  71
  72 void pipe_unlock(struct pipe_inode_info *pipe)
  73 {
  74         if (pipe->files)
  75                 mutex_unlock(&pipe->mutex);
  76 }
  77 EXPORT_SYMBOL(pipe_unlock);
  78
  79 static inline void __pipe_lock(struct pipe_inode_info *pipe)
  80 {
  81         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
  82 }
  83
  84 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
  85 {
  86         mutex_unlock(&pipe->mutex);
  87 }
  88
  89 void pipe_double_lock(struct pipe_inode_info *pipe1,
  90                       struct pipe_inode_info *pipe2)
  91 {
  92         BUG_ON(pipe1 == pipe2);
  93
  94         if (pipe1 < pipe2) {
  95                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
  96                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
  97         } else {
  98                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
  99                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
 100         }
 101 }
 102
 103 /* Drop the inode semaphore and wait for a pipe event, atomically */
 104 void pipe_wait(struct pipe_inode_info *pipe)
 105 {
 106         DEFINE_WAIT(wait);
 107
 108         /*
 109          * Pipes are system-local resources, so sleeping on them
 110          * is considered a noninteractive wait:
 111          */
 112         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
 113         pipe_unlock(pipe);
 114         schedule();
 115         finish_wait(&pipe->wait, &wait);
 116         pipe_lock(pipe);
 117 }
 118
 119 static int
 120 pipe_iov_copy_from_user(void *addr, int *offset, struct iovec *iov,
 121                         size_t *remaining, int atomic)
 122 {
 123         unsigned long copy;
 124
 125         while (*remaining > 0) {
 126                 while (!iov->iov_len)
 127                         iov++;
 128                 copy = min_t(unsigned long, *remaining, iov->iov_len);
 129
 130                 if (atomic) {
 131                         if (__copy_from_user_inatomic(addr + *offset,
 132                                                       iov->iov_base, copy))
 133                                 return -EFAULT;
 134                 } else {
 135                         if (copy_from_user(addr + *offset,
 136                                            iov->iov_base, copy))
 137                                 return -EFAULT;
 138                 }
 139                 *offset += copy;
 140                 *remaining -= copy;
 141                 iov->iov_base += copy;
 142                 iov->iov_len -= copy;
 143         }
 144         return 0;
 145 }
 146
 147 static int
 148 pipe_iov_copy_to_user(struct iovec *iov, void *addr, int *offset,
 149                       size_t *remaining, int atomic)
 150 {
 151         unsigned long copy;
 152
 153         while (*remaining > 0) {
 154                 while (!iov->iov_len)
 155                         iov++;
 156                 copy = min_t(unsigned long, *remaining, iov->iov_len);
 157
 158                 if (atomic) {
 159                         if (__copy_to_user_inatomic(iov->iov_base,
 160                                                     addr + *offset, copy))
 161                                 return -EFAULT;
 162                 } else {
 163                         if (copy_to_user(iov->iov_base,
 164                                          addr + *offset, copy))
 165                                 return -EFAULT;
 166                 }
 167                 *offset += copy;
 168                 *remaining -= copy;
 169                 iov->iov_base += copy;
 170                 iov->iov_len -= copy;
 171         }
 172         return 0;
 173 }
 174
 175 /*
 176  * Attempt to pre-fault in the user memory, so we can use atomic copies.
 177  * Returns the number of bytes not faulted in.
 178  */
 179 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
 180 {
 181         while (!iov->iov_len)
 182                 iov++;
 183
 184         while (len > 0) {
 185                 unsigned long this_len;
 186
 187                 this_len = min_t(unsigned long, len, iov->iov_len);
 188                 if (fault_in_pages_writeable(iov->iov_base, this_len))
 189                         break;
 190
 191                 len -= this_len;
 192                 iov++;
 193         }
 194
 195         return len;
 196 }
 197
 198 /*
 199  * Pre-fault in the user memory, so we can use atomic copies.
 200  */
 201 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
 202 {
 203         while (!iov->iov_len)
 204                 iov++;
 205
 206         while (len > 0) {
 207                 unsigned long this_len;
 208
 209                 this_len = min_t(unsigned long, len, iov->iov_len);
 210                 fault_in_pages_readable(iov->iov_base, this_len);
 211                 len -= this_len;
 212                 iov++;
 213         }
 214 }
 215
 216 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 217                                   struct pipe_buffer *buf)
 218 {
 219         struct page *page = buf->page;
 220
 221         /*
 222          * If nobody else uses this page, and we don't already have a
 223          * temporary page, let's keep track of it as a one-deep
 224          * allocation cache. (Otherwise just release our reference to it)
 225          */
 226         if (page_count(page) == 1 && !pipe->tmp_page)
 227                 pipe->tmp_page = page;
 228         else
 229                 page_cache_release(page);
 230 }
 231
 232 /**
 233  * generic_pipe_buf_map - virtually map a pipe buffer
 234  * @pipe:       the pipe that the buffer belongs to
 235  * @buf:        the buffer that should be mapped
 236  * @atomic:     whether to use an atomic map
 237  *
 238  * Description:
 239  *      This function returns a kernel virtual address mapping for the
 240  *      pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
 241  *      and the caller has to be careful not to fault before calling
 242  *      the unmap function.
 243  *
 244  *      Note that this function calls kmap_atomic() if @atomic != 0.
 245  */
 246 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 247                            struct pipe_buffer *buf, int atomic)
 248 {
 249         if (atomic) {
 250                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 251                 return kmap_atomic(buf->page);
 252         }
 253
 254         return kmap(buf->page);
 255 }
 256 EXPORT_SYMBOL(generic_pipe_buf_map);
 257
 258 /**
 259  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
 260  * @pipe:       the pipe that the buffer belongs to
 261  * @buf:        the buffer that should be unmapped
 262  * @map_data:   the data that the mapping function returned
 263  *
 264  * Description:
 265  *      This function undoes the mapping that ->map() provided.
 266  */
 267 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 268                             struct pipe_buffer *buf, void *map_data)
 269 {
 270         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 271                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 272                 kunmap_atomic(map_data);
 273         } else
 274                 kunmap(buf->page);
 275 }
 276 EXPORT_SYMBOL(generic_pipe_buf_unmap);
 277
 278 /**
 279  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 280  * @pipe:       the pipe that the buffer belongs to
 281  * @buf:        the buffer to attempt to steal
 282  *
 283  * Description:
 284  *      This function attempts to steal the &struct page attached to
 285  *      @buf. If successful, this function returns 0 and returns with
 286  *      the page locked. The caller may then reuse the page for whatever
 287  *      he wishes; the typical use is insertion into a different file
 288  *      page cache.
 289  */
 290 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 291                            struct pipe_buffer *buf)
 292 {
 293         struct page *page = buf->page;
 294
 295         /*
 296          * A reference of one is golden, that means that the owner of this
 297          * page is the only one holding a reference to it. lock the page
 298          * and return OK.
 299          */
 300         if (page_count(page) == 1) {
 301                 lock_page(page);
 302                 return 0;
 303         }
 304
 305         return 1;
 306 }
 307 EXPORT_SYMBOL(generic_pipe_buf_steal);
 308
 309 /**
 310  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 311  * @pipe:       the pipe that the buffer belongs to
 312  * @buf:        the buffer to get a reference to
 313  *
 314  * Description:
 315  *      This function grabs an extra reference to @buf. It's used in
 316  *      in the tee() system call, when we duplicate the buffers in one
 317  *      pipe into another.
 318  */
 319 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 320 {
 321         page_cache_get(buf->page);
 322 }
 323 EXPORT_SYMBOL(generic_pipe_buf_get);
 324
 325 /**
 326  * generic_pipe_buf_confirm - verify contents of the pipe buffer
 327  * @info:       the pipe that the buffer belongs to
 328  * @buf:        the buffer to confirm
 329  *
 330  * Description:
 331  *      This function does nothing, because the generic pipe code uses
 332  *      pages that are always good when inserted into the pipe.
 333  */
 334 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 335                              struct pipe_buffer *buf)
 336 {
 337         return 0;
 338 }
 339 EXPORT_SYMBOL(generic_pipe_buf_confirm);
 340
 341 /**
 342  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 343  * @pipe:       the pipe that the buffer belongs to
 344  * @buf:        the buffer to put a reference to
 345  *
 346  * Description:
 347  *      This function releases a reference to @buf.
 348  */
 349 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 350                               struct pipe_buffer *buf)
 351 {
 352         page_cache_release(buf->page);
 353 }
 354 EXPORT_SYMBOL(generic_pipe_buf_release);
 355
 356 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 357         .can_merge = 1,
 358         .map = generic_pipe_buf_map,
 359         .unmap = generic_pipe_buf_unmap,
 360         .confirm = generic_pipe_buf_confirm,
 361         .release = anon_pipe_buf_release,
 362         .steal = generic_pipe_buf_steal,
 363         .get = generic_pipe_buf_get,
 364 };
 365
 366 static const struct pipe_buf_operations packet_pipe_buf_ops = {
 367         .can_merge = 0,
 368         .map = generic_pipe_buf_map,
 369         .unmap = generic_pipe_buf_unmap,
 370         .confirm = generic_pipe_buf_confirm,
 371         .release = anon_pipe_buf_release,
 372         .steal = generic_pipe_buf_steal,
 373         .get = generic_pipe_buf_get,
 374 };
 375
 376 static ssize_t
 377 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 378            unsigned long nr_segs, loff_t pos)
 379 {
 380         struct file *filp = iocb->ki_filp;
 381         struct pipe_inode_info *pipe = filp->private_data;
 382         int do_wakeup;
 383         ssize_t ret;
 384         struct iovec *iov = (struct iovec *)_iov;
 385         size_t total_len;
 386
 387         total_len = iov_length(iov, nr_segs);
 388         /* Null read succeeds. */
 389         if (unlikely(total_len == 0))
 390                 return 0;
 391
 392         do_wakeup = 0;
 393         ret = 0;
 394         __pipe_lock(pipe);
 395         for (;;) {
 396                 int bufs = pipe->nrbufs;
 397                 if (bufs) {
 398                         int curbuf = pipe->curbuf;
 399                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 400                         const struct pipe_buf_operations *ops = buf->ops;
 401                         void *addr;
 402                         size_t chars = buf->len, remaining;
 403                         int error, atomic;
 404
 405                         if (chars > total_len)
 406                                 chars = total_len;
 407
 408                         error = ops->confirm(pipe, buf);
 409                         if (error) {
 410                                 if (!ret)
 411                                         ret = error;
 412                                 break;
 413                         }
 414
 415                         atomic = !iov_fault_in_pages_write(iov, chars);
 416                         remaining = chars;
 417 redo:
 418                         addr = ops->map(pipe, buf, atomic);
 419                         error = pipe_iov_copy_to_user(iov, addr, &buf->offset,
 420                                                       &remaining, atomic);
 421                         ops->unmap(pipe, buf, addr);
 422                         if (unlikely(error)) {
 423                                 /*
 424                                  * Just retry with the slow path if we failed.
 425                                  */
 426                                 if (atomic) {
 427                                         atomic = 0;
 428                                         goto redo;
 429                                 }
 430                                 if (!ret)
 431                                         ret = error;
 432                                 break;
 433                         }
 434                         ret += chars;
 435                         buf->len -= chars;
 436
 437                         /* Was it a packet buffer? Clean up and exit */
 438                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 439                                 total_len = chars;
 440                                 buf->len = 0;
 441                         }
 442
 443                         if (!buf->len) {
 444                                 buf->ops = NULL;
 445                                 ops->release(pipe, buf);
 446                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
 447                                 pipe->curbuf = curbuf;
 448                                 pipe->nrbufs = --bufs;
 449                                 do_wakeup = 1;
 450                         }
 451                         total_len -= chars;
 452                         if (!total_len)
 453                                 break;  /* common path: read succeeded */
 454                 }
 455                 if (bufs)       /* More to do? */
 456                         continue;
 457                 if (!pipe->writers)
 458                         break;
 459                 if (!pipe->waiting_writers) {
 460                         /* syscall merging: Usually we must not sleep
 461                          * if O_NONBLOCK is set, or if we got some data.
 462                          * But if a writer sleeps in kernel space, then
 463                          * we can wait for that data without violating POSIX.
 464                          */
 465                         if (ret)
 466                                 break;
 467                         if (filp->f_flags & O_NONBLOCK) {
 468                                 ret = -EAGAIN;
 469                                 break;
 470                         }
 471                 }
 472                 if (signal_pending(current)) {
 473                         if (!ret)
 474                                 ret = -ERESTARTSYS;
 475                         break;
 476                 }
 477                 if (do_wakeup) {
 478                         wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 479                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 480                 }
 481                 pipe_wait(pipe);
 482         }
 483         __pipe_unlock(pipe);
 484
 485         /* Signal writers asynchronously that there is more room. */
 486         if (do_wakeup) {
 487                 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 488                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 489         }
 490         if (ret > 0)
 491                 file_accessed(filp);
 492         return ret;
 493 }
 494
 495 static inline int is_packetized(struct file *file)
 496 {
 497         return (file->f_flags & O_DIRECT) != 0;
 498 }
 499
 500 static ssize_t
 501 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 502             unsigned long nr_segs, loff_t ppos)
 503 {
 504         struct file *filp = iocb->ki_filp;
 505         struct pipe_inode_info *pipe = filp->private_data;
 506         ssize_t ret;
 507         int do_wakeup;
 508         struct iovec *iov = (struct iovec *)_iov;
 509         size_t total_len;
 510         ssize_t chars;
 511
 512         total_len = iov_length(iov, nr_segs);
 513         /* Null write succeeds. */
 514         if (unlikely(total_len == 0))
 515                 return 0;
 516
 517         do_wakeup = 0;
 518         ret = 0;
 519         __pipe_lock(pipe);
 520
 521         if (!pipe->readers) {
 522                 send_sig(SIGPIPE, current, 0);
 523                 ret = -EPIPE;
 524                 goto out;
 525         }
 526
 527         /* We try to merge small writes */
 528         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 529         if (pipe->nrbufs && chars != 0) {
 530                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 531                                                         (pipe->buffers - 1);
 532                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 533                 const struct pipe_buf_operations *ops = buf->ops;
 534                 int offset = buf->offset + buf->len;
 535
 536                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 537                         int error, atomic = 1;
 538                         void *addr;
 539                         size_t remaining = chars;
 540
 541                         error = ops->confirm(pipe, buf);
 542                         if (error)
 543                                 goto out;
 544
 545                         iov_fault_in_pages_read(iov, chars);
 546 redo1:
 547                         addr = ops->map(pipe, buf, atomic);
 548                         error = pipe_iov_copy_from_user(addr, &offset, iov,
 549                                                         &remaining, atomic);
 550                         ops->unmap(pipe, buf, addr);
 551                         ret = error;
 552                         do_wakeup = 1;
 553                         if (error) {
 554                                 if (atomic) {
 555                                         atomic = 0;
 556                                         goto redo1;
 557                                 }
 558                                 goto out;
 559                         }
 560                         buf->len += chars;
 561                         total_len -= chars;
 562                         ret = chars;
 563                         if (!total_len)
 564                                 goto out;
 565                 }
 566         }
 567
 568         for (;;) {
 569                 int bufs;
 570
 571                 if (!pipe->readers) {
 572                         send_sig(SIGPIPE, current, 0);
 573                         if (!ret)
 574                                 ret = -EPIPE;
 575                         break;
 576                 }
 577                 bufs = pipe->nrbufs;
 578                 if (bufs < pipe->buffers) {
 579                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 580                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 581                         struct page *page = pipe->tmp_page;
 582                         char *src;
 583                         int error, atomic = 1;
 584                         int offset = 0;
 585                         size_t remaining;
 586
 587                         if (!page) {
 588                                 page = alloc_page(GFP_HIGHUSER);
 589                                 if (unlikely(!page)) {
 590                                         ret = ret ? : -ENOMEM;
 591                                         break;
 592                                 }
 593                                 pipe->tmp_page = page;
 594                         }
 595                         /* Always wake up, even if the copy fails. Otherwise
 596                          * we lock up (O_NONBLOCK-)readers that sleep due to
 597                          * syscall merging.
 598                          * FIXME! Is this really true?
 599                          */
 600                         do_wakeup = 1;
 601                         chars = PAGE_SIZE;
 602                         if (chars > total_len)
 603                                 chars = total_len;
 604
 605                         iov_fault_in_pages_read(iov, chars);
 606                         remaining = chars;
 607 redo2:
 608                         if (atomic)
 609                                 src = kmap_atomic(page);
 610                         else
 611                                 src = kmap(page);
 612
 613                         error = pipe_iov_copy_from_user(src, &offset, iov,
 614                                                         &remaining, atomic);
 615                         if (atomic)
 616                                 kunmap_atomic(src);
 617                         else
 618                                 kunmap(page);
 619
 620                         if (unlikely(error)) {
 621                                 if (atomic) {
 622                                         atomic = 0;
 623                                         goto redo2;
 624                                 }
 625                                 if (!ret)
 626                                         ret = error;
 627                                 break;
 628                         }
 629                         ret += chars;
 630
 631                         /* Insert it into the buffer array */
 632                         buf->page = page;
 633                         buf->ops = &anon_pipe_buf_ops;
 634                         buf->offset = 0;
 635                         buf->len = chars;
 636                         buf->flags = 0;
 637                         if (is_packetized(filp)) {
 638                                 buf->ops = &packet_pipe_buf_ops;
 639                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 640                         }
 641                         pipe->nrbufs = ++bufs;
 642                         pipe->tmp_page = NULL;
 643
 644                         total_len -= chars;
 645                         if (!total_len)
 646                                 break;
 647                 }
 648                 if (bufs < pipe->buffers)
 649                         continue;
 650                 if (filp->f_flags & O_NONBLOCK) {
 651                         if (!ret)
 652                                 ret = -EAGAIN;
 653                         break;
 654                 }
 655                 if (signal_pending(current)) {
 656                         if (!ret)
 657                                 ret = -ERESTARTSYS;
 658                         break;
 659                 }
 660                 if (do_wakeup) {
 661                         wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 662                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 663                         do_wakeup = 0;
 664                 }
 665                 pipe->waiting_writers++;
 666                 pipe_wait(pipe);
 667                 pipe->waiting_writers--;
 668         }
 669 out:
 670         __pipe_unlock(pipe);
 671         if (do_wakeup) {
 672                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 673                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 674         }
 675         if (ret > 0) {
 676                 int err = file_update_time(filp);
 677                 if (err)
 678                         ret = err;
 679         }
 680         return ret;
 681 }
 682
 683 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 684 {
 685         struct pipe_inode_info *pipe = filp->private_data;
 686         int count, buf, nrbufs;
 687
 688         switch (cmd) {
 689                 case FIONREAD:
 690                         __pipe_lock(pipe);
 691                         count = 0;
 692                         buf = pipe->curbuf;
 693                         nrbufs = pipe->nrbufs;
 694                         while (--nrbufs >= 0) {
 695                                 count += pipe->bufs[buf].len;
 696                                 buf = (buf+1) & (pipe->buffers - 1);
 697                         }
 698                         __pipe_unlock(pipe);
 699
 700                         return put_user(count, (int __user *)arg);
 701                 default:
 702                         return -ENOIOCTLCMD;
 703         }
 704 }
 705
 706 /* No kernel lock held - fine */
 707 static unsigned int
 708 pipe_poll(struct file *filp, poll_table *wait)
 709 {
 710         unsigned int mask;
 711         struct pipe_inode_info *pipe = filp->private_data;
 712         int nrbufs;
 713
 714         poll_wait(filp, &pipe->wait, wait);
 715
 716         /* Reading only -- no need for acquiring the semaphore.  */
 717         nrbufs = pipe->nrbufs;
 718         mask = 0;
 719         if (filp->f_mode & FMODE_READ) {
 720                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 721                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 722                         mask |= POLLHUP;
 723         }
 724
 725         if (filp->f_mode & FMODE_WRITE) {
 726                 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 727                 /*
 728                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 729                  * behave exactly like pipes for poll().
 730                  */
 731                 if (!pipe->readers)
 732                         mask |= POLLERR;
 733         }
 734
 735         return mask;
 736 }
 737
 738 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 739 {
 740         int kill = 0;
 741
 742         spin_lock(&inode->i_lock);
 743         if (!--pipe->files) {
 744                 inode->i_pipe = NULL;
 745                 kill = 1;
 746         }
 747         spin_unlock(&inode->i_lock);
 748
 749         if (kill)
 750                 free_pipe_info(pipe);
 751 }
 752
 753 static int
 754 pipe_release(struct inode *inode, struct file *file)
 755 {
 756         struct pipe_inode_info *pipe = file->private_data;
 757
 758         __pipe_lock(pipe);
 759         if (file->f_mode & FMODE_READ)
 760                 pipe->readers--;
 761         if (file->f_mode & FMODE_WRITE)
 762                 pipe->writers--;
 763
 764         if (pipe->readers || pipe->writers) {
 765                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
 766                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 767                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 768         }
 769         __pipe_unlock(pipe);
 770
 771         put_pipe_info(inode, pipe);
 772         return 0;
 773 }
 774
 775 static int
 776 pipe_fasync(int fd, struct file *filp, int on)
 777 {
 778         struct pipe_inode_info *pipe = filp->private_data;
 779         int retval = 0;
 780
 781         __pipe_lock(pipe);
 782         if (filp->f_mode & FMODE_READ)
 783                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 784         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 785                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 786                 if (retval < 0 && (filp->f_mode & FMODE_READ))
 787                         /* this can happen only if on == T */
 788                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 789         }
 790         __pipe_unlock(pipe);
 791         return retval;
 792 }
 793
 794 struct pipe_inode_info *alloc_pipe_info(void)
 795 {
 796         struct pipe_inode_info *pipe;
 797
 798         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 799         if (pipe) {
 800                 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
 801                 if (pipe->bufs) {
 802                         init_waitqueue_head(&pipe->wait);
 803                         pipe->r_counter = pipe->w_counter = 1;
 804                         pipe->buffers = PIPE_DEF_BUFFERS;
 805                         mutex_init(&pipe->mutex);
 806                         return pipe;
 807                 }
 808                 kfree(pipe);
 809         }
 810
 811         return NULL;
 812 }
 813
 814 void free_pipe_info(struct pipe_inode_info *pipe)
 815 {
 816         int i;
 817
 818         for (i = 0; i < pipe->buffers; i++) {
 819                 struct pipe_buffer *buf = pipe->bufs + i;
 820                 if (buf->ops)
 821                         buf->ops->release(pipe, buf);
 822         }
 823         if (pipe->tmp_page)
 824                 __free_page(pipe->tmp_page);
 825         kfree(pipe->bufs);
 826         kfree(pipe);
 827 }
 828
 829 static struct vfsmount *pipe_mnt __read_mostly;
 830
 831 /*
 832  * pipefs_dname() is called from d_path().
 833  */
 834 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 835 {
 836         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 837                                 dentry->d_inode->i_ino);
 838 }
 839
 840 static const struct dentry_operations pipefs_dentry_operations = {
 841         .d_dname        = pipefs_dname,
 842 };
 843
 844 static struct inode * get_pipe_inode(void)
 845 {
 846         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 847         struct pipe_inode_info *pipe;
 848
 849         if (!inode)
 850                 goto fail_inode;
 851
 852         inode->i_ino = get_next_ino();
 853
 854         pipe = alloc_pipe_info();
 855         if (!pipe)
 856                 goto fail_iput;
 857
 858         inode->i_pipe = pipe;
 859         pipe->files = 2;
 860         pipe->readers = pipe->writers = 1;
 861         inode->i_fop = &pipefifo_fops;
 862
 863         /*
 864          * Mark the inode dirty from the very beginning,
 865          * that way it will never be moved to the dirty
 866          * list because "mark_inode_dirty()" will think
 867          * that it already _is_ on the dirty list.
 868          */
 869         inode->i_state = I_DIRTY;
 870         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 871         inode->i_uid = current_fsuid();
 872         inode->i_gid = current_fsgid();
 873         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 874
 875         return inode;
 876
 877 fail_iput:
 878         iput(inode);
 879
 880 fail_inode:
 881         return NULL;
 882 }
 883
 884 int create_pipe_files(struct file **res, int flags)
 885 {
 886         int err;
 887         struct inode *inode = get_pipe_inode();
 888         struct file *f;
 889         struct path path;
 890         static struct qstr name = { .name = "" };
 891
 892         if (!inode)
 893                 return -ENFILE;
 894
 895         err = -ENOMEM;
 896         path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
 897         if (!path.dentry)
 898                 goto err_inode;
 899         path.mnt = mntget(pipe_mnt);
 900
 901         d_instantiate(path.dentry, inode);
 902
 903         err = -ENFILE;
 904         f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
 905         if (IS_ERR(f))
 906                 goto err_dentry;
 907
 908         f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
 909         f->private_data = inode->i_pipe;
 910
 911         res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
 912         if (IS_ERR(res[0]))
 913                 goto err_file;
 914
 915         path_get(&path);
 916         res[0]->private_data = inode->i_pipe;
 917         res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
 918         res[1] = f;
 919         return 0;
 920
 921 err_file:
 922         put_filp(f);
 923 err_dentry:
 924         free_pipe_info(inode->i_pipe);
 925         path_put(&path);
 926         return err;
 927
 928 err_inode:
 929         free_pipe_info(inode->i_pipe);
 930         iput(inode);
 931         return err;
 932 }
 933
 934 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 935 {
 936         int error;
 937         int fdw, fdr;
 938
 939         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
 940                 return -EINVAL;
 941
 942         error = create_pipe_files(files, flags);
 943         if (error)
 944                 return error;
 945
 946         error = get_unused_fd_flags(flags);
 947         if (error < 0)
 948                 goto err_read_pipe;
 949         fdr = error;
 950
 951         error = get_unused_fd_flags(flags);
 952         if (error < 0)
 953                 goto err_fdr;
 954         fdw = error;
 955
 956         audit_fd_pair(fdr, fdw);
 957         fd[0] = fdr;
 958         fd[1] = fdw;
 959         return 0;
 960
 961  err_fdr:
 962         put_unused_fd(fdr);
 963  err_read_pipe:
 964         fput(files[0]);
 965         fput(files[1]);
 966         return error;
 967 }
 968
 969 int do_pipe_flags(int *fd, int flags)
 970 {
 971         struct file *files[2];
 972         int error = __do_pipe_flags(fd, files, flags);
 973         if (!error) {
 974                 fd_install(fd[0], files[0]);
 975                 fd_install(fd[1], files[1]);
 976         }
 977         return error;
 978 }
 979
 980 /*
 981  * sys_pipe() is the normal C calling standard for creating
 982  * a pipe. It's not the way Unix traditionally does this, though.
 983  */
 984 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
 985 {
 986         struct file *files[2];
 987         int fd[2];
 988         int error;
 989
 990         error = __do_pipe_flags(fd, files, flags);
 991         if (!error) {
 992                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
 993                         fput(files[0]);
 994                         fput(files[1]);
 995                         put_unused_fd(fd[0]);
 996                         put_unused_fd(fd[1]);
 997                         error = -EFAULT;
 998                 } else {
 999                         fd_install(fd[0], files[0]);
1000                         fd_install(fd[1], files[1]);
1001                 }
1002         }
1003         return error;
1004 }
1005
1006 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1007 {
1008         return sys_pipe2(fildes, 0);
1009 }
1010
1011 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1012 {
1013         int cur = *cnt;
1014
1015         while (cur == *cnt) {
1016                 pipe_wait(pipe);
1017                 if (signal_pending(current))
1018                         break;
1019         }
1020         return cur == *cnt ? -ERESTARTSYS : 0;
1021 }
1022
1023 static void wake_up_partner(struct pipe_inode_info *pipe)
1024 {
1025         wake_up_interruptible(&pipe->wait);
1026 }
1027
1028 static int fifo_open(struct inode *inode, struct file *filp)
1029 {
1030         struct pipe_inode_info *pipe;
1031         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1032         int ret;
1033
1034         filp->f_version = 0;
1035
1036         spin_lock(&inode->i_lock);
1037         if (inode->i_pipe) {
1038                 pipe = inode->i_pipe;
1039                 pipe->files++;
1040                 spin_unlock(&inode->i_lock);
1041         } else {
1042                 spin_unlock(&inode->i_lock);
1043                 pipe = alloc_pipe_info();
1044                 if (!pipe)
1045                         return -ENOMEM;
1046                 pipe->files = 1;
1047                 spin_lock(&inode->i_lock);
1048                 if (unlikely(inode->i_pipe)) {
1049                         inode->i_pipe->files++;
1050                         spin_unlock(&inode->i_lock);
1051                         free_pipe_info(pipe);
1052                         pipe = inode->i_pipe;
1053                 } else {
1054                         inode->i_pipe = pipe;
1055                         spin_unlock(&inode->i_lock);
1056                 }
1057         }
1058         filp->private_data = pipe;
1059         /* OK, we have a pipe and it's pinned down */
1060
1061         __pipe_lock(pipe);
1062
1063         /* We can only do regular read/write on fifos */
1064         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
1065
1066         switch (filp->f_mode) {
1067         case FMODE_READ:
1068         /*
1069          *  O_RDONLY
1070          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1071          *  opened, even when there is no process writing the FIFO.
1072          */
1073                 pipe->r_counter++;
1074                 if (pipe->readers++ == 0)
1075                         wake_up_partner(pipe);
1076
1077                 if (!is_pipe && !pipe->writers) {
1078                         if ((filp->f_flags & O_NONBLOCK)) {
1079                                 /* suppress POLLHUP until we have
1080                                  * seen a writer */
1081                                 filp->f_version = pipe->w_counter;
1082                         } else {
1083                                 if (wait_for_partner(pipe, &pipe->w_counter))
1084                                         goto err_rd;
1085                         }
1086                 }
1087                 break;
1088
1089         case FMODE_WRITE:
1090         /*
1091          *  O_WRONLY
1092          *  POSIX.1 says that O_NONBLOCK means return -1 with
1093          *  errno=ENXIO when there is no process reading the FIFO.
1094          */
1095                 ret = -ENXIO;
1096                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1097                         goto err;
1098
1099                 pipe->w_counter++;
1100                 if (!pipe->writers++)
1101                         wake_up_partner(pipe);
1102
1103                 if (!is_pipe && !pipe->readers) {
1104                         if (wait_for_partner(pipe, &pipe->r_counter))
1105                                 goto err_wr;
1106                 }
1107                 break;
1108
1109         case FMODE_READ | FMODE_WRITE:
1110         /*
1111          *  O_RDWR
1112          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1113          *  This implementation will NEVER block on a O_RDWR open, since
1114          *  the process can at least talk to itself.
1115          */
1116
1117                 pipe->readers++;
1118                 pipe->writers++;
1119                 pipe->r_counter++;
1120                 pipe->w_counter++;
1121                 if (pipe->readers == 1 || pipe->writers == 1)
1122                         wake_up_partner(pipe);
1123                 break;
1124
1125         default:
1126                 ret = -EINVAL;
1127                 goto err;
1128         }
1129
1130         /* Ok! */
1131         __pipe_unlock(pipe);
1132         return 0;
1133
1134 err_rd:
1135         if (!--pipe->readers)
1136                 wake_up_interruptible(&pipe->wait);
1137         ret = -ERESTARTSYS;
1138         goto err;
1139
1140 err_wr:
1141         if (!--pipe->writers)
1142                 wake_up_interruptible(&pipe->wait);
1143         ret = -ERESTARTSYS;
1144         goto err;
1145
1146 err:
1147         __pipe_unlock(pipe);
1148
1149         put_pipe_info(inode, pipe);
1150         return ret;
1151 }
1152
1153 const struct file_operations pipefifo_fops = {
1154         .open           = fifo_open,
1155         .llseek         = no_llseek,
1156         .read           = do_sync_read,
1157         .aio_read       = pipe_read,
1158         .write          = do_sync_write,
1159         .aio_write      = pipe_write,
1160         .poll           = pipe_poll,
1161         .unlocked_ioctl = pipe_ioctl,
1162         .release        = pipe_release,
1163         .fasync         = pipe_fasync,
1164 };
1165
1166 /*
1167  * Allocate a new array of pipe buffers and copy the info over. Returns the
1168  * pipe size if successful, or return -ERROR on error.
1169  */
1170 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1171 {
1172         struct pipe_buffer *bufs;
1173
1174         /*
1175          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1176          * expect a lot of shrink+grow operations, just free and allocate
1177          * again like we would do for growing. If the pipe currently
1178          * contains more buffers than arg, then return busy.
1179          */
1180         if (nr_pages < pipe->nrbufs)
1181                 return -EBUSY;
1182
1183         bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
1184         if (unlikely(!bufs))
1185                 return -ENOMEM;
1186
1187         /*
1188          * The pipe array wraps around, so just start the new one at zero
1189          * and adjust the indexes.
1190          */
1191         if (pipe->nrbufs) {
1192                 unsigned int tail;
1193                 unsigned int head;
1194
1195                 tail = pipe->curbuf + pipe->nrbufs;
1196                 if (tail < pipe->buffers)
1197                         tail = 0;
1198                 else
1199                         tail &= (pipe->buffers - 1);
1200
1201                 head = pipe->nrbufs - tail;
1202                 if (head)
1203                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1204                 if (tail)
1205                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1206         }
1207
1208         pipe->curbuf = 0;
1209         kfree(pipe->bufs);
1210         pipe->bufs = bufs;
1211         pipe->buffers = nr_pages;
1212         return nr_pages * PAGE_SIZE;
1213 }
1214
1215 /*
1216  * Currently we rely on the pipe array holding a power-of-2 number
1217  * of pages.
1218  */
1219 static inline unsigned int round_pipe_size(unsigned int size)
1220 {
1221         unsigned long nr_pages;
1222
1223         nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1224         return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1225 }
1226
1227 /*
1228  * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1229  * will return an error.
1230  */
1231 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1232                  size_t *lenp, loff_t *ppos)
1233 {
1234         int ret;
1235
1236         ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1237         if (ret < 0 || !write)
1238                 return ret;
1239
1240         pipe_max_size = round_pipe_size(pipe_max_size);
1241         return ret;
1242 }
1243
1244 /*
1245  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1246  * location, so checking ->i_pipe is not enough to verify that this is a
1247  * pipe.
1248  */
1249 struct pipe_inode_info *get_pipe_info(struct file *file)
1250 {
1251         return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1252 }
1253
1254 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1255 {
1256         struct pipe_inode_info *pipe;
1257         long ret;
1258
1259         pipe = get_pipe_info(file);
1260         if (!pipe)
1261                 return -EBADF;
1262
1263         __pipe_lock(pipe);
1264
1265         switch (cmd) {
1266         case F_SETPIPE_SZ: {
1267                 unsigned int size, nr_pages;
1268
1269                 size = round_pipe_size(arg);
1270                 nr_pages = size >> PAGE_SHIFT;
1271
1272                 ret = -EINVAL;
1273                 if (!nr_pages)
1274                         goto out;
1275
1276                 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1277                         ret = -EPERM;
1278                         goto out;
1279                 }
1280                 ret = pipe_set_size(pipe, nr_pages);
1281                 break;
1282                 }
1283         case F_GETPIPE_SZ:
1284                 ret = pipe->buffers * PAGE_SIZE;
1285                 break;
1286         default:
1287                 ret = -EINVAL;
1288                 break;
1289         }
1290
1291 out:
1292         __pipe_unlock(pipe);
1293         return ret;
1294 }
1295
1296 static const struct super_operations pipefs_ops = {
1297         .destroy_inode = free_inode_nonrcu,
1298         .statfs = simple_statfs,
1299 };
1300
1301 /*
1302  * pipefs should _never_ be mounted by userland - too much of security hassle,
1303  * no real gain from having the whole whorehouse mounted. So we don't need
1304  * any operations on the root directory. However, we need a non-trivial
1305  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1306  */
1307 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1308                          int flags, const char *dev_name, void *data)
1309 {
1310         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1311                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1312 }
1313
1314 static struct file_system_type pipe_fs_type = {
1315         .name           = "pipefs",
1316         .mount          = pipefs_mount,
1317         .kill_sb        = kill_anon_super,
1318 };
1319
1320 static int __init init_pipe_fs(void)
1321 {
1322         int err = register_filesystem(&pipe_fs_type);
1323
1324         if (!err) {
1325                 pipe_mnt = kern_mount(&pipe_fs_type);
1326                 if (IS_ERR(pipe_mnt)) {
1327                         err = PTR_ERR(pipe_mnt);
1328                         unregister_filesystem(&pipe_fs_type);
1329                 }
1330         }
1331         return err;
1332 }
1333
1334 fs_initcall(init_pipe_fs);