fs/pipe.c

   1 /*
   2  *  linux/fs/pipe.c
   3  *
   4  *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
   5  */
   6
   7 #include <linux/mm.h>
   8 #include <linux/file.h>
   9 #include <linux/poll.h>
  10 #include <linux/slab.h>
  11 #include <linux/module.h>
  12 #include <linux/init.h>
  13 #include <linux/fs.h>
  14 #include <linux/log2.h>
  15 #include <linux/mount.h>
  16 #include <linux/magic.h>
  17 #include <linux/pipe_fs_i.h>
  18 #include <linux/uio.h>
  19 #include <linux/highmem.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/audit.h>
  22 #include <linux/syscalls.h>
  23 #include <linux/fcntl.h>
  24
  25 #include <asm/uaccess.h>
  26 #include <asm/ioctls.h>
  27
  28 #include "internal.h"
  29
  30 /*
  31  * The max size that a non-root user is allowed to grow the pipe. Can
  32  * be set by root in /proc/sys/fs/pipe-max-size
  33  */
  34 unsigned int pipe_max_size = 1048576;
  35
  36 /*
  37  * Minimum pipe size, as required by POSIX
  38  */
  39 unsigned int pipe_min_size = PAGE_SIZE;
  40
  41 /*
  42  * We use a start+len construction, which provides full use of the
  43  * allocated memory.
  44  * -- Florian Coosmann (FGC)
  45  *
  46  * Reads with count = 0 should always return 0.
  47  * -- Julian Bradfield 1999-06-07.
  48  *
  49  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  50  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  51  *
  52  * pipe_read & write cleanup
  53  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  54  */
  55
  56 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  57 {
  58         if (pipe->files)
  59                 mutex_lock_nested(&pipe->mutex, subclass);
  60 }
  61
  62 void pipe_lock(struct pipe_inode_info *pipe)
  63 {
  64         /*
  65          * pipe_lock() nests non-pipe inode locks (for writing to a file)
  66          */
  67         pipe_lock_nested(pipe, I_MUTEX_PARENT);
  68 }
  69 EXPORT_SYMBOL(pipe_lock);
  70
  71 void pipe_unlock(struct pipe_inode_info *pipe)
  72 {
  73         if (pipe->files)
  74                 mutex_unlock(&pipe->mutex);
  75 }
  76 EXPORT_SYMBOL(pipe_unlock);
  77
  78 static inline void __pipe_lock(struct pipe_inode_info *pipe)
  79 {
  80         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
  81 }
  82
  83 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
  84 {
  85         mutex_unlock(&pipe->mutex);
  86 }
  87
  88 void pipe_double_lock(struct pipe_inode_info *pipe1,
  89                       struct pipe_inode_info *pipe2)
  90 {
  91         BUG_ON(pipe1 == pipe2);
  92
  93         if (pipe1 < pipe2) {
  94                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
  95                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
  96         } else {
  97                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
  98                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
  99         }
 100 }
 101
 102 /* Drop the inode semaphore and wait for a pipe event, atomically */
 103 void pipe_wait(struct pipe_inode_info *pipe)
 104 {
 105         DEFINE_WAIT(wait);
 106
 107         /*
 108          * Pipes are system-local resources, so sleeping on them
 109          * is considered a noninteractive wait:
 110          */
 111         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
 112         pipe_unlock(pipe);
 113         schedule();
 114         finish_wait(&pipe->wait, &wait);
 115         pipe_lock(pipe);
 116 }
 117
 118 static int
 119 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
 120                         int atomic)
 121 {
 122         unsigned long copy;
 123
 124         while (len > 0) {
 125                 while (!iov->iov_len)
 126                         iov++;
 127                 copy = min_t(unsigned long, len, iov->iov_len);
 128
 129                 if (atomic) {
 130                         if (__copy_from_user_inatomic(to, iov->iov_base, copy))
 131                                 return -EFAULT;
 132                 } else {
 133                         if (copy_from_user(to, iov->iov_base, copy))
 134                                 return -EFAULT;
 135                 }
 136                 to += copy;
 137                 len -= copy;
 138                 iov->iov_base += copy;
 139                 iov->iov_len -= copy;
 140         }
 141         return 0;
 142 }
 143
 144 static int
 145 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
 146                       int atomic)
 147 {
 148         unsigned long copy;
 149
 150         while (len > 0) {
 151                 while (!iov->iov_len)
 152                         iov++;
 153                 copy = min_t(unsigned long, len, iov->iov_len);
 154
 155                 if (atomic) {
 156                         if (__copy_to_user_inatomic(iov->iov_base, from, copy))
 157                                 return -EFAULT;
 158                 } else {
 159                         if (copy_to_user(iov->iov_base, from, copy))
 160                                 return -EFAULT;
 161                 }
 162                 from += copy;
 163                 len -= copy;
 164                 iov->iov_base += copy;
 165                 iov->iov_len -= copy;
 166         }
 167         return 0;
 168 }
 169
 170 /*
 171  * Attempt to pre-fault in the user memory, so we can use atomic copies.
 172  * Returns the number of bytes not faulted in.
 173  */
 174 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
 175 {
 176         while (!iov->iov_len)
 177                 iov++;
 178
 179         while (len > 0) {
 180                 unsigned long this_len;
 181
 182                 this_len = min_t(unsigned long, len, iov->iov_len);
 183                 if (fault_in_pages_writeable(iov->iov_base, this_len))
 184                         break;
 185
 186                 len -= this_len;
 187                 iov++;
 188         }
 189
 190         return len;
 191 }
 192
 193 /*
 194  * Pre-fault in the user memory, so we can use atomic copies.
 195  */
 196 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
 197 {
 198         while (!iov->iov_len)
 199                 iov++;
 200
 201         while (len > 0) {
 202                 unsigned long this_len;
 203
 204                 this_len = min_t(unsigned long, len, iov->iov_len);
 205                 fault_in_pages_readable(iov->iov_base, this_len);
 206                 len -= this_len;
 207                 iov++;
 208         }
 209 }
 210
 211 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 212                                   struct pipe_buffer *buf)
 213 {
 214         struct page *page = buf->page;
 215
 216         /*
 217          * If nobody else uses this page, and we don't already have a
 218          * temporary page, let's keep track of it as a one-deep
 219          * allocation cache. (Otherwise just release our reference to it)
 220          */
 221         if (page_count(page) == 1 && !pipe->tmp_page)
 222                 pipe->tmp_page = page;
 223         else
 224                 page_cache_release(page);
 225 }
 226
 227 /**
 228  * generic_pipe_buf_map - virtually map a pipe buffer
 229  * @pipe:       the pipe that the buffer belongs to
 230  * @buf:        the buffer that should be mapped
 231  * @atomic:     whether to use an atomic map
 232  *
 233  * Description:
 234  *      This function returns a kernel virtual address mapping for the
 235  *      pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
 236  *      and the caller has to be careful not to fault before calling
 237  *      the unmap function.
 238  *
 239  *      Note that this function calls kmap_atomic() if @atomic != 0.
 240  */
 241 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 242                            struct pipe_buffer *buf, int atomic)
 243 {
 244         if (atomic) {
 245                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 246                 return kmap_atomic(buf->page);
 247         }
 248
 249         return kmap(buf->page);
 250 }
 251 EXPORT_SYMBOL(generic_pipe_buf_map);
 252
 253 /**
 254  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
 255  * @pipe:       the pipe that the buffer belongs to
 256  * @buf:        the buffer that should be unmapped
 257  * @map_data:   the data that the mapping function returned
 258  *
 259  * Description:
 260  *      This function undoes the mapping that ->map() provided.
 261  */
 262 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 263                             struct pipe_buffer *buf, void *map_data)
 264 {
 265         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 266                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 267                 kunmap_atomic(map_data);
 268         } else
 269                 kunmap(buf->page);
 270 }
 271 EXPORT_SYMBOL(generic_pipe_buf_unmap);
 272
 273 /**
 274  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 275  * @pipe:       the pipe that the buffer belongs to
 276  * @buf:        the buffer to attempt to steal
 277  *
 278  * Description:
 279  *      This function attempts to steal the &struct page attached to
 280  *      @buf. If successful, this function returns 0 and returns with
 281  *      the page locked. The caller may then reuse the page for whatever
 282  *      he wishes; the typical use is insertion into a different file
 283  *      page cache.
 284  */
 285 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 286                            struct pipe_buffer *buf)
 287 {
 288         struct page *page = buf->page;
 289
 290         /*
 291          * A reference of one is golden, that means that the owner of this
 292          * page is the only one holding a reference to it. lock the page
 293          * and return OK.
 294          */
 295         if (page_count(page) == 1) {
 296                 lock_page(page);
 297                 return 0;
 298         }
 299
 300         return 1;
 301 }
 302 EXPORT_SYMBOL(generic_pipe_buf_steal);
 303
 304 /**
 305  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 306  * @pipe:       the pipe that the buffer belongs to
 307  * @buf:        the buffer to get a reference to
 308  *
 309  * Description:
 310  *      This function grabs an extra reference to @buf. It's used in
 311  *      in the tee() system call, when we duplicate the buffers in one
 312  *      pipe into another.
 313  */
 314 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 315 {
 316         page_cache_get(buf->page);
 317 }
 318 EXPORT_SYMBOL(generic_pipe_buf_get);
 319
 320 /**
 321  * generic_pipe_buf_confirm - verify contents of the pipe buffer
 322  * @info:       the pipe that the buffer belongs to
 323  * @buf:        the buffer to confirm
 324  *
 325  * Description:
 326  *      This function does nothing, because the generic pipe code uses
 327  *      pages that are always good when inserted into the pipe.
 328  */
 329 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 330                              struct pipe_buffer *buf)
 331 {
 332         return 0;
 333 }
 334 EXPORT_SYMBOL(generic_pipe_buf_confirm);
 335
 336 /**
 337  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 338  * @pipe:       the pipe that the buffer belongs to
 339  * @buf:        the buffer to put a reference to
 340  *
 341  * Description:
 342  *      This function releases a reference to @buf.
 343  */
 344 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 345                               struct pipe_buffer *buf)
 346 {
 347         page_cache_release(buf->page);
 348 }
 349 EXPORT_SYMBOL(generic_pipe_buf_release);
 350
 351 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 352         .can_merge = 1,
 353         .map = generic_pipe_buf_map,
 354         .unmap = generic_pipe_buf_unmap,
 355         .confirm = generic_pipe_buf_confirm,
 356         .release = anon_pipe_buf_release,
 357         .steal = generic_pipe_buf_steal,
 358         .get = generic_pipe_buf_get,
 359 };
 360
 361 static const struct pipe_buf_operations packet_pipe_buf_ops = {
 362         .can_merge = 0,
 363         .map = generic_pipe_buf_map,
 364         .unmap = generic_pipe_buf_unmap,
 365         .confirm = generic_pipe_buf_confirm,
 366         .release = anon_pipe_buf_release,
 367         .steal = generic_pipe_buf_steal,
 368         .get = generic_pipe_buf_get,
 369 };
 370
 371 static ssize_t
 372 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 373            unsigned long nr_segs, loff_t pos)
 374 {
 375         struct file *filp = iocb->ki_filp;
 376         struct pipe_inode_info *pipe = filp->private_data;
 377         int do_wakeup;
 378         ssize_t ret;
 379         struct iovec *iov = (struct iovec *)_iov;
 380         size_t total_len;
 381
 382         total_len = iov_length(iov, nr_segs);
 383         /* Null read succeeds. */
 384         if (unlikely(total_len == 0))
 385                 return 0;
 386
 387         do_wakeup = 0;
 388         ret = 0;
 389         __pipe_lock(pipe);
 390         for (;;) {
 391                 int bufs = pipe->nrbufs;
 392                 if (bufs) {
 393                         int curbuf = pipe->curbuf;
 394                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 395                         const struct pipe_buf_operations *ops = buf->ops;
 396                         void *addr;
 397                         size_t chars = buf->len;
 398                         int error, atomic;
 399
 400                         if (chars > total_len)
 401                                 chars = total_len;
 402
 403                         error = ops->confirm(pipe, buf);
 404                         if (error) {
 405                                 if (!ret)
 406                                         ret = error;
 407                                 break;
 408                         }
 409
 410                         atomic = !iov_fault_in_pages_write(iov, chars);
 411 redo:
 412                         addr = ops->map(pipe, buf, atomic);
 413                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
 414                         ops->unmap(pipe, buf, addr);
 415                         if (unlikely(error)) {
 416                                 /*
 417                                  * Just retry with the slow path if we failed.
 418                                  */
 419                                 if (atomic) {
 420                                         atomic = 0;
 421                                         goto redo;
 422                                 }
 423                                 if (!ret)
 424                                         ret = error;
 425                                 break;
 426                         }
 427                         ret += chars;
 428                         buf->offset += chars;
 429                         buf->len -= chars;
 430
 431                         /* Was it a packet buffer? Clean up and exit */
 432                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 433                                 total_len = chars;
 434                                 buf->len = 0;
 435                         }
 436
 437                         if (!buf->len) {
 438                                 buf->ops = NULL;
 439                                 ops->release(pipe, buf);
 440                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
 441                                 pipe->curbuf = curbuf;
 442                                 pipe->nrbufs = --bufs;
 443                                 do_wakeup = 1;
 444                         }
 445                         total_len -= chars;
 446                         if (!total_len)
 447                                 break;  /* common path: read succeeded */
 448                 }
 449                 if (bufs)       /* More to do? */
 450                         continue;
 451                 if (!pipe->writers)
 452                         break;
 453                 if (!pipe->waiting_writers) {
 454                         /* syscall merging: Usually we must not sleep
 455                          * if O_NONBLOCK is set, or if we got some data.
 456                          * But if a writer sleeps in kernel space, then
 457                          * we can wait for that data without violating POSIX.
 458                          */
 459                         if (ret)
 460                                 break;
 461                         if (filp->f_flags & O_NONBLOCK) {
 462                                 ret = -EAGAIN;
 463                                 break;
 464                         }
 465                 }
 466                 if (signal_pending(current)) {
 467                         if (!ret)
 468                                 ret = -ERESTARTSYS;
 469                         break;
 470                 }
 471                 if (do_wakeup) {
 472                         wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 473                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 474                 }
 475                 pipe_wait(pipe);
 476         }
 477         __pipe_unlock(pipe);
 478
 479         /* Signal writers asynchronously that there is more room. */
 480         if (do_wakeup) {
 481                 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 482                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 483         }
 484         if (ret > 0)
 485                 file_accessed(filp);
 486         return ret;
 487 }
 488
 489 static inline int is_packetized(struct file *file)
 490 {
 491         return (file->f_flags & O_DIRECT) != 0;
 492 }
 493
 494 static ssize_t
 495 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 496             unsigned long nr_segs, loff_t ppos)
 497 {
 498         struct file *filp = iocb->ki_filp;
 499         struct pipe_inode_info *pipe = filp->private_data;
 500         ssize_t ret;
 501         int do_wakeup;
 502         struct iovec *iov = (struct iovec *)_iov;
 503         size_t total_len;
 504         ssize_t chars;
 505
 506         total_len = iov_length(iov, nr_segs);
 507         /* Null write succeeds. */
 508         if (unlikely(total_len == 0))
 509                 return 0;
 510
 511         do_wakeup = 0;
 512         ret = 0;
 513         __pipe_lock(pipe);
 514
 515         if (!pipe->readers) {
 516                 send_sig(SIGPIPE, current, 0);
 517                 ret = -EPIPE;
 518                 goto out;
 519         }
 520
 521         /* We try to merge small writes */
 522         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 523         if (pipe->nrbufs && chars != 0) {
 524                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 525                                                         (pipe->buffers - 1);
 526                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 527                 const struct pipe_buf_operations *ops = buf->ops;
 528                 int offset = buf->offset + buf->len;
 529
 530                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 531                         int error, atomic = 1;
 532                         void *addr;
 533
 534                         error = ops->confirm(pipe, buf);
 535                         if (error)
 536                                 goto out;
 537
 538                         iov_fault_in_pages_read(iov, chars);
 539 redo1:
 540                         addr = ops->map(pipe, buf, atomic);
 541                         error = pipe_iov_copy_from_user(offset + addr, iov,
 542                                                         chars, atomic);
 543                         ops->unmap(pipe, buf, addr);
 544                         ret = error;
 545                         do_wakeup = 1;
 546                         if (error) {
 547                                 if (atomic) {
 548                                         atomic = 0;
 549                                         goto redo1;
 550                                 }
 551                                 goto out;
 552                         }
 553                         buf->len += chars;
 554                         total_len -= chars;
 555                         ret = chars;
 556                         if (!total_len)
 557                                 goto out;
 558                 }
 559         }
 560
 561         for (;;) {
 562                 int bufs;
 563
 564                 if (!pipe->readers) {
 565                         send_sig(SIGPIPE, current, 0);
 566                         if (!ret)
 567                                 ret = -EPIPE;
 568                         break;
 569                 }
 570                 bufs = pipe->nrbufs;
 571                 if (bufs < pipe->buffers) {
 572                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 573                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 574                         struct page *page = pipe->tmp_page;
 575                         char *src;
 576                         int error, atomic = 1;
 577
 578                         if (!page) {
 579                                 page = alloc_page(GFP_HIGHUSER);
 580                                 if (unlikely(!page)) {
 581                                         ret = ret ? : -ENOMEM;
 582                                         break;
 583                                 }
 584                                 pipe->tmp_page = page;
 585                         }
 586                         /* Always wake up, even if the copy fails. Otherwise
 587                          * we lock up (O_NONBLOCK-)readers that sleep due to
 588                          * syscall merging.
 589                          * FIXME! Is this really true?
 590                          */
 591                         do_wakeup = 1;
 592                         chars = PAGE_SIZE;
 593                         if (chars > total_len)
 594                                 chars = total_len;
 595
 596                         iov_fault_in_pages_read(iov, chars);
 597 redo2:
 598                         if (atomic)
 599                                 src = kmap_atomic(page);
 600                         else
 601                                 src = kmap(page);
 602
 603                         error = pipe_iov_copy_from_user(src, iov, chars,
 604                                                         atomic);
 605                         if (atomic)
 606                                 kunmap_atomic(src);
 607                         else
 608                                 kunmap(page);
 609
 610                         if (unlikely(error)) {
 611                                 if (atomic) {
 612                                         atomic = 0;
 613                                         goto redo2;
 614                                 }
 615                                 if (!ret)
 616                                         ret = error;
 617                                 break;
 618                         }
 619                         ret += chars;
 620
 621                         /* Insert it into the buffer array */
 622                         buf->page = page;
 623                         buf->ops = &anon_pipe_buf_ops;
 624                         buf->offset = 0;
 625                         buf->len = chars;
 626                         buf->flags = 0;
 627                         if (is_packetized(filp)) {
 628                                 buf->ops = &packet_pipe_buf_ops;
 629                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 630                         }
 631                         pipe->nrbufs = ++bufs;
 632                         pipe->tmp_page = NULL;
 633
 634                         total_len -= chars;
 635                         if (!total_len)
 636                                 break;
 637                 }
 638                 if (bufs < pipe->buffers)
 639                         continue;
 640                 if (filp->f_flags & O_NONBLOCK) {
 641                         if (!ret)
 642                                 ret = -EAGAIN;
 643                         break;
 644                 }
 645                 if (signal_pending(current)) {
 646                         if (!ret)
 647                                 ret = -ERESTARTSYS;
 648                         break;
 649                 }
 650                 if (do_wakeup) {
 651                         wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 652                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 653                         do_wakeup = 0;
 654                 }
 655                 pipe->waiting_writers++;
 656                 pipe_wait(pipe);
 657                 pipe->waiting_writers--;
 658         }
 659 out:
 660         __pipe_unlock(pipe);
 661         if (do_wakeup) {
 662                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 663                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 664         }
 665         if (ret > 0) {
 666                 int err = file_update_time(filp);
 667                 if (err)
 668                         ret = err;
 669         }
 670         return ret;
 671 }
 672
 673 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 674 {
 675         struct pipe_inode_info *pipe = filp->private_data;
 676         int count, buf, nrbufs;
 677
 678         switch (cmd) {
 679                 case FIONREAD:
 680                         __pipe_lock(pipe);
 681                         count = 0;
 682                         buf = pipe->curbuf;
 683                         nrbufs = pipe->nrbufs;
 684                         while (--nrbufs >= 0) {
 685                                 count += pipe->bufs[buf].len;
 686                                 buf = (buf+1) & (pipe->buffers - 1);
 687                         }
 688                         __pipe_unlock(pipe);
 689
 690                         return put_user(count, (int __user *)arg);
 691                 default:
 692                         return -ENOIOCTLCMD;
 693         }
 694 }
 695
 696 /* No kernel lock held - fine */
 697 static unsigned int
 698 pipe_poll(struct file *filp, poll_table *wait)
 699 {
 700         unsigned int mask;
 701         struct pipe_inode_info *pipe = filp->private_data;
 702         int nrbufs;
 703
 704         poll_wait(filp, &pipe->wait, wait);
 705
 706         /* Reading only -- no need for acquiring the semaphore.  */
 707         nrbufs = pipe->nrbufs;
 708         mask = 0;
 709         if (filp->f_mode & FMODE_READ) {
 710                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 711                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 712                         mask |= POLLHUP;
 713         }
 714
 715         if (filp->f_mode & FMODE_WRITE) {
 716                 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 717                 /*
 718                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 719                  * behave exactly like pipes for poll().
 720                  */
 721                 if (!pipe->readers)
 722                         mask |= POLLERR;
 723         }
 724
 725         return mask;
 726 }
 727
 728 static int
 729 pipe_release(struct inode *inode, struct file *file)
 730 {
 731         struct pipe_inode_info *pipe = inode->i_pipe;
 732         int kill = 0;
 733
 734         __pipe_lock(pipe);
 735         if (file->f_mode & FMODE_READ)
 736                 pipe->readers--;
 737         if (file->f_mode & FMODE_WRITE)
 738                 pipe->writers--;
 739
 740         if (pipe->readers || pipe->writers) {
 741                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
 742                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 743                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 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         __pipe_unlock(pipe);
 752
 753         if (kill)
 754                 __free_pipe_info(pipe);
 755
 756         return 0;
 757 }
 758
 759 static int
 760 pipe_fasync(int fd, struct file *filp, int on)
 761 {
 762         struct pipe_inode_info *pipe = filp->private_data;
 763         int retval = 0;
 764
 765         __pipe_lock(pipe);
 766         if (filp->f_mode & FMODE_READ)
 767                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 768         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 769                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 770                 if (retval < 0 && (filp->f_mode & FMODE_READ))
 771                         /* this can happen only if on == T */
 772                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 773         }
 774         __pipe_unlock(pipe);
 775         return retval;
 776 }
 777
 778 struct pipe_inode_info *alloc_pipe_info(void)
 779 {
 780         struct pipe_inode_info *pipe;
 781
 782         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 783         if (pipe) {
 784                 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
 785                 if (pipe->bufs) {
 786                         init_waitqueue_head(&pipe->wait);
 787                         pipe->r_counter = pipe->w_counter = 1;
 788                         pipe->buffers = PIPE_DEF_BUFFERS;
 789                         mutex_init(&pipe->mutex);
 790                         return pipe;
 791                 }
 792                 kfree(pipe);
 793         }
 794
 795         return NULL;
 796 }
 797
 798 void __free_pipe_info(struct pipe_inode_info *pipe)
 799 {
 800         int i;
 801
 802         for (i = 0; i < pipe->buffers; i++) {
 803                 struct pipe_buffer *buf = pipe->bufs + i;
 804                 if (buf->ops)
 805                         buf->ops->release(pipe, buf);
 806         }
 807         if (pipe->tmp_page)
 808                 __free_page(pipe->tmp_page);
 809         kfree(pipe->bufs);
 810         kfree(pipe);
 811 }
 812
 813 void free_pipe_info(struct inode *inode)
 814 {
 815         __free_pipe_info(inode->i_pipe);
 816         inode->i_pipe = NULL;
 817 }
 818
 819 static struct vfsmount *pipe_mnt __read_mostly;
 820
 821 /*
 822  * pipefs_dname() is called from d_path().
 823  */
 824 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 825 {
 826         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 827                                 dentry->d_inode->i_ino);
 828 }
 829
 830 static const struct dentry_operations pipefs_dentry_operations = {
 831         .d_dname        = pipefs_dname,
 832 };
 833
 834 static struct inode * get_pipe_inode(void)
 835 {
 836         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 837         struct pipe_inode_info *pipe;
 838
 839         if (!inode)
 840                 goto fail_inode;
 841
 842         inode->i_ino = get_next_ino();
 843
 844         pipe = alloc_pipe_info();
 845         if (!pipe)
 846                 goto fail_iput;
 847
 848         inode->i_pipe = pipe;
 849         pipe->files = 2;
 850         pipe->readers = pipe->writers = 1;
 851         inode->i_fop = &pipefifo_fops;
 852
 853         /*
 854          * Mark the inode dirty from the very beginning,
 855          * that way it will never be moved to the dirty
 856          * list because "mark_inode_dirty()" will think
 857          * that it already _is_ on the dirty list.
 858          */
 859         inode->i_state = I_DIRTY;
 860         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 861         inode->i_uid = current_fsuid();
 862         inode->i_gid = current_fsgid();
 863         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 864
 865         return inode;
 866
 867 fail_iput:
 868         iput(inode);
 869
 870 fail_inode:
 871         return NULL;
 872 }
 873
 874 int create_pipe_files(struct file **res, int flags)
 875 {
 876         int err;
 877         struct inode *inode = get_pipe_inode();
 878         struct file *f;
 879         struct path path;
 880         static struct qstr name = { .name = "" };
 881
 882         if (!inode)
 883                 return -ENFILE;
 884
 885         err = -ENOMEM;
 886         path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
 887         if (!path.dentry)
 888                 goto err_inode;
 889         path.mnt = mntget(pipe_mnt);
 890
 891         d_instantiate(path.dentry, inode);
 892
 893         err = -ENFILE;
 894         f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
 895         if (IS_ERR(f))
 896                 goto err_dentry;
 897
 898         f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
 899         f->private_data = inode->i_pipe;
 900
 901         res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
 902         if (IS_ERR(res[0]))
 903                 goto err_file;
 904
 905         path_get(&path);
 906         res[0]->private_data = inode->i_pipe;
 907         res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
 908         res[1] = f;
 909         return 0;
 910
 911 err_file:
 912         put_filp(f);
 913 err_dentry:
 914         free_pipe_info(inode);
 915         path_put(&path);
 916         return err;
 917
 918 err_inode:
 919         free_pipe_info(inode);
 920         iput(inode);
 921         return err;
 922 }
 923
 924 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 925 {
 926         int error;
 927         int fdw, fdr;
 928
 929         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
 930                 return -EINVAL;
 931
 932         error = create_pipe_files(files, flags);
 933         if (error)
 934                 return error;
 935
 936         error = get_unused_fd_flags(flags);
 937         if (error < 0)
 938                 goto err_read_pipe;
 939         fdr = error;
 940
 941         error = get_unused_fd_flags(flags);
 942         if (error < 0)
 943                 goto err_fdr;
 944         fdw = error;
 945
 946         audit_fd_pair(fdr, fdw);
 947         fd[0] = fdr;
 948         fd[1] = fdw;
 949         return 0;
 950
 951  err_fdr:
 952         put_unused_fd(fdr);
 953  err_read_pipe:
 954         fput(files[0]);
 955         fput(files[1]);
 956         return error;
 957 }
 958
 959 int do_pipe_flags(int *fd, int flags)
 960 {
 961         struct file *files[2];
 962         int error = __do_pipe_flags(fd, files, flags);
 963         if (!error) {
 964                 fd_install(fd[0], files[0]);
 965                 fd_install(fd[1], files[1]);
 966         }
 967         return error;
 968 }
 969
 970 /*
 971  * sys_pipe() is the normal C calling standard for creating
 972  * a pipe. It's not the way Unix traditionally does this, though.
 973  */
 974 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
 975 {
 976         struct file *files[2];
 977         int fd[2];
 978         int error;
 979
 980         error = __do_pipe_flags(fd, files, flags);
 981         if (!error) {
 982                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
 983                         fput(files[0]);
 984                         fput(files[1]);
 985                         put_unused_fd(fd[0]);
 986                         put_unused_fd(fd[1]);
 987                         error = -EFAULT;
 988                 } else {
 989                         fd_install(fd[0], files[0]);
 990                         fd_install(fd[1], files[1]);
 991                 }
 992         }
 993         return error;
 994 }
 995
 996 SYSCALL_DEFINE1(pipe, int __user *, fildes)
 997 {
 998         return sys_pipe2(fildes, 0);
 999 }
1000
1001 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1002 {
1003         int cur = *cnt;
1004
1005         while (cur == *cnt) {
1006                 pipe_wait(pipe);
1007                 if (signal_pending(current))
1008                         break;
1009         }
1010         return cur == *cnt ? -ERESTARTSYS : 0;
1011 }
1012
1013 static void wake_up_partner(struct pipe_inode_info *pipe)
1014 {
1015         wake_up_interruptible(&pipe->wait);
1016 }
1017
1018 static int fifo_open(struct inode *inode, struct file *filp)
1019 {
1020         struct pipe_inode_info *pipe;
1021         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1022         int kill = 0;
1023         int ret;
1024
1025         filp->f_version = 0;
1026
1027         spin_lock(&inode->i_lock);
1028         if (inode->i_pipe) {
1029                 pipe = inode->i_pipe;
1030                 pipe->files++;
1031                 spin_unlock(&inode->i_lock);
1032         } else {
1033                 spin_unlock(&inode->i_lock);
1034                 pipe = alloc_pipe_info();
1035                 if (!pipe)
1036                         return -ENOMEM;
1037                 pipe->files = 1;
1038                 spin_lock(&inode->i_lock);
1039                 if (unlikely(inode->i_pipe)) {
1040                         inode->i_pipe->files++;
1041                         spin_unlock(&inode->i_lock);
1042                         __free_pipe_info(pipe);
1043                         pipe = inode->i_pipe;
1044                 } else {
1045                         inode->i_pipe = pipe;
1046                         spin_unlock(&inode->i_lock);
1047                 }
1048         }
1049         filp->private_data = pipe;
1050         /* OK, we have a pipe and it's pinned down */
1051
1052         __pipe_lock(pipe);
1053
1054         /* We can only do regular read/write on fifos */
1055         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
1056
1057         switch (filp->f_mode) {
1058         case FMODE_READ:
1059         /*
1060          *  O_RDONLY
1061          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1062          *  opened, even when there is no process writing the FIFO.
1063          */
1064                 pipe->r_counter++;
1065                 if (pipe->readers++ == 0)
1066                         wake_up_partner(pipe);
1067
1068                 if (!is_pipe && !pipe->writers) {
1069                         if ((filp->f_flags & O_NONBLOCK)) {
1070                                 /* suppress POLLHUP until we have
1071                                  * seen a writer */
1072                                 filp->f_version = pipe->w_counter;
1073                         } else {
1074                                 if (wait_for_partner(pipe, &pipe->w_counter))
1075                                         goto err_rd;
1076                         }
1077                 }
1078                 break;
1079
1080         case FMODE_WRITE:
1081         /*
1082          *  O_WRONLY
1083          *  POSIX.1 says that O_NONBLOCK means return -1 with
1084          *  errno=ENXIO when there is no process reading the FIFO.
1085          */
1086                 ret = -ENXIO;
1087                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1088                         goto err;
1089
1090                 pipe->w_counter++;
1091                 if (!pipe->writers++)
1092                         wake_up_partner(pipe);
1093
1094                 if (!is_pipe && !pipe->readers) {
1095                         if (wait_for_partner(pipe, &pipe->r_counter))
1096                                 goto err_wr;
1097                 }
1098                 break;
1099
1100         case FMODE_READ | FMODE_WRITE:
1101         /*
1102          *  O_RDWR
1103          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1104          *  This implementation will NEVER block on a O_RDWR open, since
1105          *  the process can at least talk to itself.
1106          */
1107
1108                 pipe->readers++;
1109                 pipe->writers++;
1110                 pipe->r_counter++;
1111                 pipe->w_counter++;
1112                 if (pipe->readers == 1 || pipe->writers == 1)
1113                         wake_up_partner(pipe);
1114                 break;
1115
1116         default:
1117                 ret = -EINVAL;
1118                 goto err;
1119         }
1120
1121         /* Ok! */
1122         __pipe_unlock(pipe);
1123         return 0;
1124
1125 err_rd:
1126         if (!--pipe->readers)
1127                 wake_up_interruptible(&pipe->wait);
1128         ret = -ERESTARTSYS;
1129         goto err;
1130
1131 err_wr:
1132         if (!--pipe->writers)
1133                 wake_up_interruptible(&pipe->wait);
1134         ret = -ERESTARTSYS;
1135         goto err;
1136
1137 err:
1138         spin_lock(&inode->i_lock);
1139         if (!--pipe->files) {
1140                 inode->i_pipe = NULL;
1141                 kill = 1;
1142         }
1143         spin_unlock(&inode->i_lock);
1144         __pipe_unlock(pipe);
1145         if (kill)
1146                 __free_pipe_info(pipe);
1147         return ret;
1148 }
1149
1150 const struct file_operations pipefifo_fops = {
1151         .open           = fifo_open,
1152         .llseek         = no_llseek,
1153         .read           = do_sync_read,
1154         .aio_read       = pipe_read,
1155         .write          = do_sync_write,
1156         .aio_write      = pipe_write,
1157         .poll           = pipe_poll,
1158         .unlocked_ioctl = pipe_ioctl,
1159         .release        = pipe_release,
1160         .fasync         = pipe_fasync,
1161 };
1162
1163 /*
1164  * Allocate a new array of pipe buffers and copy the info over. Returns the
1165  * pipe size if successful, or return -ERROR on error.
1166  */
1167 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1168 {
1169         struct pipe_buffer *bufs;
1170
1171         /*
1172          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1173          * expect a lot of shrink+grow operations, just free and allocate
1174          * again like we would do for growing. If the pipe currently
1175          * contains more buffers than arg, then return busy.
1176          */
1177         if (nr_pages < pipe->nrbufs)
1178                 return -EBUSY;
1179
1180         bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
1181         if (unlikely(!bufs))
1182                 return -ENOMEM;
1183
1184         /*
1185          * The pipe array wraps around, so just start the new one at zero
1186          * and adjust the indexes.
1187          */
1188         if (pipe->nrbufs) {
1189                 unsigned int tail;
1190                 unsigned int head;
1191
1192                 tail = pipe->curbuf + pipe->nrbufs;
1193                 if (tail < pipe->buffers)
1194                         tail = 0;
1195                 else
1196                         tail &= (pipe->buffers - 1);
1197
1198                 head = pipe->nrbufs - tail;
1199                 if (head)
1200                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1201                 if (tail)
1202                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1203         }
1204
1205         pipe->curbuf = 0;
1206         kfree(pipe->bufs);
1207         pipe->bufs = bufs;
1208         pipe->buffers = nr_pages;
1209         return nr_pages * PAGE_SIZE;
1210 }
1211
1212 /*
1213  * Currently we rely on the pipe array holding a power-of-2 number
1214  * of pages.
1215  */
1216 static inline unsigned int round_pipe_size(unsigned int size)
1217 {
1218         unsigned long nr_pages;
1219
1220         nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1221         return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1222 }
1223
1224 /*
1225  * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1226  * will return an error.
1227  */
1228 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1229                  size_t *lenp, loff_t *ppos)
1230 {
1231         int ret;
1232
1233         ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1234         if (ret < 0 || !write)
1235                 return ret;
1236
1237         pipe_max_size = round_pipe_size(pipe_max_size);
1238         return ret;
1239 }
1240
1241 /*
1242  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1243  * location, so checking ->i_pipe is not enough to verify that this is a
1244  * pipe.
1245  */
1246 struct pipe_inode_info *get_pipe_info(struct file *file)
1247 {
1248         return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1249 }
1250
1251 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1252 {
1253         struct pipe_inode_info *pipe;
1254         long ret;
1255
1256         pipe = get_pipe_info(file);
1257         if (!pipe)
1258                 return -EBADF;
1259
1260         __pipe_lock(pipe);
1261
1262         switch (cmd) {
1263         case F_SETPIPE_SZ: {
1264                 unsigned int size, nr_pages;
1265
1266                 size = round_pipe_size(arg);
1267                 nr_pages = size >> PAGE_SHIFT;
1268
1269                 ret = -EINVAL;
1270                 if (!nr_pages)
1271                         goto out;
1272
1273                 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1274                         ret = -EPERM;
1275                         goto out;
1276                 }
1277                 ret = pipe_set_size(pipe, nr_pages);
1278                 break;
1279                 }
1280         case F_GETPIPE_SZ:
1281                 ret = pipe->buffers * PAGE_SIZE;
1282                 break;
1283         default:
1284                 ret = -EINVAL;
1285                 break;
1286         }
1287
1288 out:
1289         __pipe_unlock(pipe);
1290         return ret;
1291 }
1292
1293 static const struct super_operations pipefs_ops = {
1294         .destroy_inode = free_inode_nonrcu,
1295         .statfs = simple_statfs,
1296 };
1297
1298 /*
1299  * pipefs should _never_ be mounted by userland - too much of security hassle,
1300  * no real gain from having the whole whorehouse mounted. So we don't need
1301  * any operations on the root directory. However, we need a non-trivial
1302  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1303  */
1304 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1305                          int flags, const char *dev_name, void *data)
1306 {
1307         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1308                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1309 }
1310
1311 static struct file_system_type pipe_fs_type = {
1312         .name           = "pipefs",
1313         .mount          = pipefs_mount,
1314         .kill_sb        = kill_anon_super,
1315 };
1316
1317 static int __init init_pipe_fs(void)
1318 {
1319         int err = register_filesystem(&pipe_fs_type);
1320
1321         if (!err) {
1322                 pipe_mnt = kern_mount(&pipe_fs_type);
1323                 if (IS_ERR(pipe_mnt)) {
1324                         err = PTR_ERR(pipe_mnt);
1325                         unregister_filesystem(&pipe_fs_type);
1326                 }
1327         }
1328         return err;
1329 }
1330
1331 fs_initcall(init_pipe_fs);