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