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                         int offset;
 405
 406                         if (chars > total_len)
 407                                 chars = total_len;
 408
 409                         error = ops->confirm(pipe, buf);
 410                         if (error) {
 411                                 if (!ret)
 412                                         ret = error;
 413                                 break;
 414                         }
 415
 416                         atomic = !iov_fault_in_pages_write(iov, chars);
 417                         remaining = chars;
 418                         offset = buf->offset;
 419 redo:
 420                         addr = ops->map(pipe, buf, atomic);
 421                         error = pipe_iov_copy_to_user(iov, addr, &offset,
 422                                                       &remaining, atomic);
 423                         ops->unmap(pipe, buf, addr);
 424                         if (unlikely(error)) {
 425                                 /*
 426                                  * Just retry with the slow path if we failed.
 427                                  */
 428                                 if (atomic) {
 429                                         atomic = 0;
 430                                         goto redo;
 431                                 }
 432                                 if (!ret)
 433                                         ret = error;
 434                                 break;
 435                         }
 436                         ret += chars;
 437                         buf->offset += chars;
 438                         buf->len -= chars;
 439
 440                         /* Was it a packet buffer? Clean up and exit */
 441                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 442                                 total_len = chars;
 443                                 buf->len = 0;
 444                         }
 445
 446                         if (!buf->len) {
 447                                 buf->ops = NULL;
 448                                 ops->release(pipe, buf);
 449                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
 450                                 pipe->curbuf = curbuf;
 451                                 pipe->nrbufs = --bufs;
 452                                 do_wakeup = 1;
 453                         }
 454                         total_len -= chars;
 455                         if (!total_len)
 456                                 break;  /* common path: read succeeded */
 457                 }
 458                 if (bufs)       /* More to do? */
 459                         continue;
 460                 if (!pipe->writers)
 461                         break;
 462                 if (!pipe->waiting_writers) {
 463                         /* syscall merging: Usually we must not sleep
 464                          * if O_NONBLOCK is set, or if we got some data.
 465                          * But if a writer sleeps in kernel space, then
 466                          * we can wait for that data without violating POSIX.
 467                          */
 468                         if (ret)
 469                                 break;
 470                         if (filp->f_flags & O_NONBLOCK) {
 471                                 ret = -EAGAIN;
 472                                 break;
 473                         }
 474                 }
 475                 if (signal_pending(current)) {
 476                         if (!ret)
 477                                 ret = -ERESTARTSYS;
 478                         break;
 479                 }
 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                 pipe_wait(pipe);
 485         }
 486         __pipe_unlock(pipe);
 487
 488         /* Signal writers asynchronously that there is more room. */
 489         if (do_wakeup) {
 490                 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 491                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 492         }
 493         if (ret > 0)
 494                 file_accessed(filp);
 495         return ret;
 496 }
 497
 498 static inline int is_packetized(struct file *file)
 499 {
 500         return (file->f_flags & O_DIRECT) != 0;
 501 }
 502
 503 static ssize_t
 504 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 505             unsigned long nr_segs, loff_t ppos)
 506 {
 507         struct file *filp = iocb->ki_filp;
 508         struct pipe_inode_info *pipe = filp->private_data;
 509         ssize_t ret;
 510         int do_wakeup;
 511         struct iovec *iov = (struct iovec *)_iov;
 512         size_t total_len;
 513         ssize_t chars;
 514
 515         total_len = iov_length(iov, nr_segs);
 516         /* Null write succeeds. */
 517         if (unlikely(total_len == 0))
 518                 return 0;
 519
 520         do_wakeup = 0;
 521         ret = 0;
 522         __pipe_lock(pipe);
 523
 524         if (!pipe->readers) {
 525                 send_sig(SIGPIPE, current, 0);
 526                 ret = -EPIPE;
 527                 goto out;
 528         }
 529
 530         /* We try to merge small writes */
 531         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 532         if (pipe->nrbufs && chars != 0) {
 533                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 534                                                         (pipe->buffers - 1);
 535                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 536                 const struct pipe_buf_operations *ops = buf->ops;
 537                 int offset = buf->offset + buf->len;
 538
 539                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 540                         int error, atomic = 1;
 541                         void *addr;
 542                         size_t remaining = chars;
 543
 544                         error = ops->confirm(pipe, buf);
 545                         if (error)
 546                                 goto out;
 547
 548                         iov_fault_in_pages_read(iov, chars);
 549 redo1:
 550                         addr = ops->map(pipe, buf, atomic);
 551                         error = pipe_iov_copy_from_user(addr, &offset, iov,
 552                                                         &remaining, atomic);
 553                         ops->unmap(pipe, buf, addr);
 554                         ret = error;
 555                         do_wakeup = 1;
 556                         if (error) {
 557                                 if (atomic) {
 558                                         atomic = 0;
 559                                         goto redo1;
 560                                 }
 561                                 goto out;
 562                         }
 563                         buf->len += chars;
 564                         total_len -= chars;
 565                         ret = chars;
 566                         if (!total_len)
 567                                 goto out;
 568                 }
 569         }
 570
 571         for (;;) {
 572                 int bufs;
 573
 574                 if (!pipe->readers) {
 575                         send_sig(SIGPIPE, current, 0);
 576                         if (!ret)
 577                                 ret = -EPIPE;
 578                         break;
 579                 }
 580                 bufs = pipe->nrbufs;
 581                 if (bufs < pipe->buffers) {
 582                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 583                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 584                         struct page *page = pipe->tmp_page;
 585                         char *src;
 586                         int error, atomic = 1;
 587                         int offset = 0;
 588                         size_t remaining;
 589
 590                         if (!page) {
 591                                 page = alloc_page(GFP_HIGHUSER);
 592                                 if (unlikely(!page)) {
 593                                         ret = ret ? : -ENOMEM;
 594                                         break;
 595                                 }
 596                                 pipe->tmp_page = page;
 597                         }
 598                         /* Always wake up, even if the copy fails. Otherwise
 599                          * we lock up (O_NONBLOCK-)readers that sleep due to
 600                          * syscall merging.
 601                          * FIXME! Is this really true?
 602                          */
 603                         do_wakeup = 1;
 604                         chars = PAGE_SIZE;
 605                         if (chars > total_len)
 606                                 chars = total_len;
 607
 608                         iov_fault_in_pages_read(iov, chars);
 609                         remaining = chars;
 610 redo2:
 611                         if (atomic)
 612                                 src = kmap_atomic(page);
 613                         else
 614                                 src = kmap(page);
 615
 616                         error = pipe_iov_copy_from_user(src, &offset, iov,
 617                                                         &remaining, atomic);
 618                         if (atomic)
 619                                 kunmap_atomic(src);
 620                         else
 621                                 kunmap(page);
 622
 623                         if (unlikely(error)) {
 624                                 if (atomic) {
 625                                         atomic = 0;
 626                                         goto redo2;
 627                                 }
 628                                 if (!ret)
 629                                         ret = error;
 630                                 break;
 631                         }
 632                         ret += chars;
 633
 634                         /* Insert it into the buffer array */
 635                         buf->page = page;
 636                         buf->ops = &anon_pipe_buf_ops;
 637                         buf->offset = 0;
 638                         buf->len = chars;
 639                         buf->flags = 0;
 640                         if (is_packetized(filp)) {
 641                                 buf->ops = &packet_pipe_buf_ops;
 642                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 643                         }
 644                         pipe->nrbufs = ++bufs;
 645                         pipe->tmp_page = NULL;
 646
 647                         total_len -= chars;
 648                         if (!total_len)
 649                                 break;
 650                 }
 651                 if (bufs < pipe->buffers)
 652                         continue;
 653                 if (filp->f_flags & O_NONBLOCK) {
 654                         if (!ret)
 655                                 ret = -EAGAIN;
 656                         break;
 657                 }
 658                 if (signal_pending(current)) {
 659                         if (!ret)
 660                                 ret = -ERESTARTSYS;
 661                         break;
 662                 }
 663                 if (do_wakeup) {
 664                         wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 665                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 666                         do_wakeup = 0;
 667                 }
 668                 pipe->waiting_writers++;
 669                 pipe_wait(pipe);
 670                 pipe->waiting_writers--;
 671         }
 672 out:
 673         __pipe_unlock(pipe);
 674         if (do_wakeup) {
 675                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 676                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 677         }
 678         if (ret > 0) {
 679                 int err = file_update_time(filp);
 680                 if (err)
 681                         ret = err;
 682         }
 683         return ret;
 684 }
 685
 686 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 687 {
 688         struct pipe_inode_info *pipe = filp->private_data;
 689         int count, buf, nrbufs;
 690
 691         switch (cmd) {
 692                 case FIONREAD:
 693                         __pipe_lock(pipe);
 694                         count = 0;
 695                         buf = pipe->curbuf;
 696                         nrbufs = pipe->nrbufs;
 697                         while (--nrbufs >= 0) {
 698                                 count += pipe->bufs[buf].len;
 699                                 buf = (buf+1) & (pipe->buffers - 1);
 700                         }
 701                         __pipe_unlock(pipe);
 702
 703                         return put_user(count, (int __user *)arg);
 704                 default:
 705                         return -ENOIOCTLCMD;
 706         }
 707 }
 708
 709 /* No kernel lock held - fine */
 710 static unsigned int
 711 pipe_poll(struct file *filp, poll_table *wait)
 712 {
 713         unsigned int mask;
 714         struct pipe_inode_info *pipe = filp->private_data;
 715         int nrbufs;
 716
 717         poll_wait(filp, &pipe->wait, wait);
 718
 719         /* Reading only -- no need for acquiring the semaphore.  */
 720         nrbufs = pipe->nrbufs;
 721         mask = 0;
 722         if (filp->f_mode & FMODE_READ) {
 723                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 724                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 725                         mask |= POLLHUP;
 726         }
 727
 728         if (filp->f_mode & FMODE_WRITE) {
 729                 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 730                 /*
 731                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 732                  * behave exactly like pipes for poll().
 733                  */
 734                 if (!pipe->readers)
 735                         mask |= POLLERR;
 736         }
 737
 738         return mask;
 739 }
 740
 741 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 742 {
 743         int kill = 0;
 744
 745         spin_lock(&inode->i_lock);
 746         if (!--pipe->files) {
 747                 inode->i_pipe = NULL;
 748                 kill = 1;
 749         }
 750         spin_unlock(&inode->i_lock);
 751
 752         if (kill)
 753                 free_pipe_info(pipe);
 754 }
 755
 756 static int
 757 pipe_release(struct inode *inode, struct file *file)
 758 {
 759         struct pipe_inode_info *pipe = file->private_data;
 760
 761         __pipe_lock(pipe);
 762         if (file->f_mode & FMODE_READ)
 763                 pipe->readers--;
 764         if (file->f_mode & FMODE_WRITE)
 765                 pipe->writers--;
 766
 767         if (pipe->readers || pipe->writers) {
 768                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
 769                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 770                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 771         }
 772         __pipe_unlock(pipe);
 773
 774         put_pipe_info(inode, pipe);
 775         return 0;
 776 }
 777
 778 static int
 779 pipe_fasync(int fd, struct file *filp, int on)
 780 {
 781         struct pipe_inode_info *pipe = filp->private_data;
 782         int retval = 0;
 783
 784         __pipe_lock(pipe);
 785         if (filp->f_mode & FMODE_READ)
 786                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 787         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 788                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 789                 if (retval < 0 && (filp->f_mode & FMODE_READ))
 790                         /* this can happen only if on == T */
 791                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 792         }
 793         __pipe_unlock(pipe);
 794         return retval;
 795 }
 796
 797 struct pipe_inode_info *alloc_pipe_info(void)
 798 {
 799         struct pipe_inode_info *pipe;
 800
 801         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 802         if (pipe) {
 803                 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
 804                 if (pipe->bufs) {
 805                         init_waitqueue_head(&pipe->wait);
 806                         pipe->r_counter = pipe->w_counter = 1;
 807                         pipe->buffers = PIPE_DEF_BUFFERS;
 808                         mutex_init(&pipe->mutex);
 809                         return pipe;
 810                 }
 811                 kfree(pipe);
 812         }
 813
 814         return NULL;
 815 }
 816
 817 void free_pipe_info(struct pipe_inode_info *pipe)
 818 {
 819         int i;
 820
 821         for (i = 0; i < pipe->buffers; i++) {
 822                 struct pipe_buffer *buf = pipe->bufs + i;
 823                 if (buf->ops)
 824                         buf->ops->release(pipe, buf);
 825         }
 826         if (pipe->tmp_page)
 827                 __free_page(pipe->tmp_page);
 828         kfree(pipe->bufs);
 829         kfree(pipe);
 830 }
 831
 832 static struct vfsmount *pipe_mnt __read_mostly;
 833
 834 /*
 835  * pipefs_dname() is called from d_path().
 836  */
 837 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 838 {
 839         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 840                                 dentry->d_inode->i_ino);
 841 }
 842
 843 static const struct dentry_operations pipefs_dentry_operations = {
 844         .d_dname        = pipefs_dname,
 845 };
 846
 847 static struct inode * get_pipe_inode(void)
 848 {
 849         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 850         struct pipe_inode_info *pipe;
 851
 852         if (!inode)
 853                 goto fail_inode;
 854
 855         inode->i_ino = get_next_ino();
 856
 857         pipe = alloc_pipe_info();
 858         if (!pipe)
 859                 goto fail_iput;
 860
 861         inode->i_pipe = pipe;
 862         pipe->files = 2;
 863         pipe->readers = pipe->writers = 1;
 864         inode->i_fop = &pipefifo_fops;
 865
 866         /*
 867          * Mark the inode dirty from the very beginning,
 868          * that way it will never be moved to the dirty
 869          * list because "mark_inode_dirty()" will think
 870          * that it already _is_ on the dirty list.
 871          */
 872         inode->i_state = I_DIRTY;
 873         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 874         inode->i_uid = current_fsuid();
 875         inode->i_gid = current_fsgid();
 876         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 877
 878         return inode;
 879
 880 fail_iput:
 881         iput(inode);
 882
 883 fail_inode:
 884         return NULL;
 885 }
 886
 887 int create_pipe_files(struct file **res, int flags)
 888 {
 889         int err;
 890         struct inode *inode = get_pipe_inode();
 891         struct file *f;
 892         struct path path;
 893         static struct qstr name = { .name = "" };
 894
 895         if (!inode)
 896                 return -ENFILE;
 897
 898         err = -ENOMEM;
 899         path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
 900         if (!path.dentry)
 901                 goto err_inode;
 902         path.mnt = mntget(pipe_mnt);
 903
 904         d_instantiate(path.dentry, inode);
 905
 906         err = -ENFILE;
 907         f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
 908         if (IS_ERR(f))
 909                 goto err_dentry;
 910
 911         f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
 912         f->private_data = inode->i_pipe;
 913
 914         res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
 915         if (IS_ERR(res[0]))
 916                 goto err_file;
 917
 918         path_get(&path);
 919         res[0]->private_data = inode->i_pipe;
 920         res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
 921         res[1] = f;
 922         return 0;
 923
 924 err_file:
 925         put_filp(f);
 926 err_dentry:
 927         free_pipe_info(inode->i_pipe);
 928         path_put(&path);
 929         return err;
 930
 931 err_inode:
 932         free_pipe_info(inode->i_pipe);
 933         iput(inode);
 934         return err;
 935 }
 936
 937 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 938 {
 939         int error;
 940         int fdw, fdr;
 941
 942         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
 943                 return -EINVAL;
 944
 945         error = create_pipe_files(files, flags);
 946         if (error)
 947                 return error;
 948
 949         error = get_unused_fd_flags(flags);
 950         if (error < 0)
 951                 goto err_read_pipe;
 952         fdr = error;
 953
 954         error = get_unused_fd_flags(flags);
 955         if (error < 0)
 956                 goto err_fdr;
 957         fdw = error;
 958
 959         audit_fd_pair(fdr, fdw);
 960         fd[0] = fdr;
 961         fd[1] = fdw;
 962         return 0;
 963
 964  err_fdr:
 965         put_unused_fd(fdr);
 966  err_read_pipe:
 967         fput(files[0]);
 968         fput(files[1]);
 969         return error;
 970 }
 971
 972 int do_pipe_flags(int *fd, int flags)
 973 {
 974         struct file *files[2];
 975         int error = __do_pipe_flags(fd, files, flags);
 976         if (!error) {
 977                 fd_install(fd[0], files[0]);
 978                 fd_install(fd[1], files[1]);
 979         }
 980         return error;
 981 }
 982
 983 /*
 984  * sys_pipe() is the normal C calling standard for creating
 985  * a pipe. It's not the way Unix traditionally does this, though.
 986  */
 987 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
 988 {
 989         struct file *files[2];
 990         int fd[2];
 991         int error;
 992
 993         error = __do_pipe_flags(fd, files, flags);
 994         if (!error) {
 995                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
 996                         fput(files[0]);
 997                         fput(files[1]);
 998                         put_unused_fd(fd[0]);
 999                         put_unused_fd(fd[1]);
1000                         error = -EFAULT;
1001                 } else {
1002                         fd_install(fd[0], files[0]);
1003                         fd_install(fd[1], files[1]);
1004                 }
1005         }
1006         return error;
1007 }
1008
1009 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1010 {
1011         return sys_pipe2(fildes, 0);
1012 }
1013
1014 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1015 {
1016         int cur = *cnt;
1017
1018         while (cur == *cnt) {
1019                 pipe_wait(pipe);
1020                 if (signal_pending(current))
1021                         break;
1022         }
1023         return cur == *cnt ? -ERESTARTSYS : 0;
1024 }
1025
1026 static void wake_up_partner(struct pipe_inode_info *pipe)
1027 {
1028         wake_up_interruptible(&pipe->wait);
1029 }
1030
1031 static int fifo_open(struct inode *inode, struct file *filp)
1032 {
1033         struct pipe_inode_info *pipe;
1034         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1035         int ret;
1036
1037         filp->f_version = 0;
1038
1039         spin_lock(&inode->i_lock);
1040         if (inode->i_pipe) {
1041                 pipe = inode->i_pipe;
1042                 pipe->files++;
1043                 spin_unlock(&inode->i_lock);
1044         } else {
1045                 spin_unlock(&inode->i_lock);
1046                 pipe = alloc_pipe_info();
1047                 if (!pipe)
1048                         return -ENOMEM;
1049                 pipe->files = 1;
1050                 spin_lock(&inode->i_lock);
1051                 if (unlikely(inode->i_pipe)) {
1052                         inode->i_pipe->files++;
1053                         spin_unlock(&inode->i_lock);
1054                         free_pipe_info(pipe);
1055                         pipe = inode->i_pipe;
1056                 } else {
1057                         inode->i_pipe = pipe;
1058                         spin_unlock(&inode->i_lock);
1059                 }
1060         }
1061         filp->private_data = pipe;
1062         /* OK, we have a pipe and it's pinned down */
1063
1064         __pipe_lock(pipe);
1065
1066         /* We can only do regular read/write on fifos */
1067         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
1068
1069         switch (filp->f_mode) {
1070         case FMODE_READ:
1071         /*
1072          *  O_RDONLY
1073          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1074          *  opened, even when there is no process writing the FIFO.
1075          */
1076                 pipe->r_counter++;
1077                 if (pipe->readers++ == 0)
1078                         wake_up_partner(pipe);
1079
1080                 if (!is_pipe && !pipe->writers) {
1081                         if ((filp->f_flags & O_NONBLOCK)) {
1082                                 /* suppress POLLHUP until we have
1083                                  * seen a writer */
1084                                 filp->f_version = pipe->w_counter;
1085                         } else {
1086                                 if (wait_for_partner(pipe, &pipe->w_counter))
1087                                         goto err_rd;
1088                         }
1089                 }
1090                 break;
1091
1092         case FMODE_WRITE:
1093         /*
1094          *  O_WRONLY
1095          *  POSIX.1 says that O_NONBLOCK means return -1 with
1096          *  errno=ENXIO when there is no process reading the FIFO.
1097          */
1098                 ret = -ENXIO;
1099                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1100                         goto err;
1101
1102                 pipe->w_counter++;
1103                 if (!pipe->writers++)
1104                         wake_up_partner(pipe);
1105
1106                 if (!is_pipe && !pipe->readers) {
1107                         if (wait_for_partner(pipe, &pipe->r_counter))
1108                                 goto err_wr;
1109                 }
1110                 break;
1111
1112         case FMODE_READ | FMODE_WRITE:
1113         /*
1114          *  O_RDWR
1115          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1116          *  This implementation will NEVER block on a O_RDWR open, since
1117          *  the process can at least talk to itself.
1118          */
1119
1120                 pipe->readers++;
1121                 pipe->writers++;
1122                 pipe->r_counter++;
1123                 pipe->w_counter++;
1124                 if (pipe->readers == 1 || pipe->writers == 1)
1125                         wake_up_partner(pipe);
1126                 break;
1127
1128         default:
1129                 ret = -EINVAL;
1130                 goto err;
1131         }
1132
1133         /* Ok! */
1134         __pipe_unlock(pipe);
1135         return 0;
1136
1137 err_rd:
1138         if (!--pipe->readers)
1139                 wake_up_interruptible(&pipe->wait);
1140         ret = -ERESTARTSYS;
1141         goto err;
1142
1143 err_wr:
1144         if (!--pipe->writers)
1145                 wake_up_interruptible(&pipe->wait);
1146         ret = -ERESTARTSYS;
1147         goto err;
1148
1149 err:
1150         __pipe_unlock(pipe);
1151
1152         put_pipe_info(inode, pipe);
1153         return ret;
1154 }
1155
1156 const struct file_operations pipefifo_fops = {
1157         .open           = fifo_open,
1158         .llseek         = no_llseek,
1159         .read           = do_sync_read,
1160         .aio_read       = pipe_read,
1161         .write          = do_sync_write,
1162         .aio_write      = pipe_write,
1163         .poll           = pipe_poll,
1164         .unlocked_ioctl = pipe_ioctl,
1165         .release        = pipe_release,
1166         .fasync         = pipe_fasync,
1167 };
1168
1169 /*
1170  * Allocate a new array of pipe buffers and copy the info over. Returns the
1171  * pipe size if successful, or return -ERROR on error.
1172  */
1173 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1174 {
1175         struct pipe_buffer *bufs;
1176
1177         /*
1178          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1179          * expect a lot of shrink+grow operations, just free and allocate
1180          * again like we would do for growing. If the pipe currently
1181          * contains more buffers than arg, then return busy.
1182          */
1183         if (nr_pages < pipe->nrbufs)
1184                 return -EBUSY;
1185
1186         bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
1187         if (unlikely(!bufs))
1188                 return -ENOMEM;
1189
1190         /*
1191          * The pipe array wraps around, so just start the new one at zero
1192          * and adjust the indexes.
1193          */
1194         if (pipe->nrbufs) {
1195                 unsigned int tail;
1196                 unsigned int head;
1197
1198                 tail = pipe->curbuf + pipe->nrbufs;
1199                 if (tail < pipe->buffers)
1200                         tail = 0;
1201                 else
1202                         tail &= (pipe->buffers - 1);
1203
1204                 head = pipe->nrbufs - tail;
1205                 if (head)
1206                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1207                 if (tail)
1208                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1209         }
1210
1211         pipe->curbuf = 0;
1212         kfree(pipe->bufs);
1213         pipe->bufs = bufs;
1214         pipe->buffers = nr_pages;
1215         return nr_pages * PAGE_SIZE;
1216 }
1217
1218 /*
1219  * Currently we rely on the pipe array holding a power-of-2 number
1220  * of pages.
1221  */
1222 static inline unsigned int round_pipe_size(unsigned int size)
1223 {
1224         unsigned long nr_pages;
1225
1226         nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1227         return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1228 }
1229
1230 /*
1231  * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1232  * will return an error.
1233  */
1234 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1235                  size_t *lenp, loff_t *ppos)
1236 {
1237         int ret;
1238
1239         ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1240         if (ret < 0 || !write)
1241                 return ret;
1242
1243         pipe_max_size = round_pipe_size(pipe_max_size);
1244         return ret;
1245 }
1246
1247 /*
1248  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1249  * location, so checking ->i_pipe is not enough to verify that this is a
1250  * pipe.
1251  */
1252 struct pipe_inode_info *get_pipe_info(struct file *file)
1253 {
1254         return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1255 }
1256
1257 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1258 {
1259         struct pipe_inode_info *pipe;
1260         long ret;
1261
1262         pipe = get_pipe_info(file);
1263         if (!pipe)
1264                 return -EBADF;
1265
1266         __pipe_lock(pipe);
1267
1268         switch (cmd) {
1269         case F_SETPIPE_SZ: {
1270                 unsigned int size, nr_pages;
1271
1272                 size = round_pipe_size(arg);
1273                 nr_pages = size >> PAGE_SHIFT;
1274
1275                 ret = -EINVAL;
1276                 if (!nr_pages)
1277                         goto out;
1278
1279                 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1280                         ret = -EPERM;
1281                         goto out;
1282                 }
1283                 ret = pipe_set_size(pipe, nr_pages);
1284                 break;
1285                 }
1286         case F_GETPIPE_SZ:
1287                 ret = pipe->buffers * PAGE_SIZE;
1288                 break;
1289         default:
1290                 ret = -EINVAL;
1291                 break;
1292         }
1293
1294 out:
1295         __pipe_unlock(pipe);
1296         return ret;
1297 }
1298
1299 static const struct super_operations pipefs_ops = {
1300         .destroy_inode = free_inode_nonrcu,
1301         .statfs = simple_statfs,
1302 };
1303
1304 /*
1305  * pipefs should _never_ be mounted by userland - too much of security hassle,
1306  * no real gain from having the whole whorehouse mounted. So we don't need
1307  * any operations on the root directory. However, we need a non-trivial
1308  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1309  */
1310 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1311                          int flags, const char *dev_name, void *data)
1312 {
1313         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1314                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1315 }
1316
1317 static struct file_system_type pipe_fs_type = {
1318         .name           = "pipefs",
1319         .mount          = pipefs_mount,
1320         .kill_sb        = kill_anon_super,
1321 };
1322
1323 static int __init init_pipe_fs(void)
1324 {
1325         int err = register_filesystem(&pipe_fs_type);
1326
1327         if (!err) {
1328                 pipe_mnt = kern_mount(&pipe_fs_type);
1329                 if (IS_ERR(pipe_mnt)) {
1330                         err = PTR_ERR(pipe_mnt);
1331                         unregister_filesystem(&pipe_fs_type);
1332                 }
1333         }
1334         return err;
1335 }
1336
1337 fs_initcall(init_pipe_fs);