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/mount.h>
  15 #include <linux/pipe_fs_i.h>
  16 #include <linux/uio.h>
  17 #include <linux/highmem.h>
  18
  19 #include <asm/uaccess.h>
  20 #include <asm/ioctls.h>
  21
  22 /*
  23  * We use a start+len construction, which provides full use of the
  24  * allocated memory.
  25  * -- Florian Coosmann (FGC)
  26  *
  27  * Reads with count = 0 should always return 0.
  28  * -- Julian Bradfield 1999-06-07.
  29  *
  30  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  31  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  32  *
  33  * pipe_read & write cleanup
  34  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  35  */
  36
  37 /* Drop the inode semaphore and wait for a pipe event, atomically */
  38 void pipe_wait(struct inode * inode)
  39 {
  40         DEFINE_WAIT(wait);
  41
  42         prepare_to_wait(PIPE_WAIT(*inode), &wait, TASK_INTERRUPTIBLE);
  43         up(PIPE_SEM(*inode));
  44         schedule();
  45         finish_wait(PIPE_WAIT(*inode), &wait);
  46         down(PIPE_SEM(*inode));
  47 }
  48
  49 static inline int
  50 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len)
  51 {
  52         unsigned long copy;
  53
  54         while (len > 0) {
  55                 while (!iov->iov_len)
  56                         iov++;
  57                 copy = min_t(unsigned long, len, iov->iov_len);
  58
  59                 if (copy_from_user(to, iov->iov_base, copy))
  60                         return -EFAULT;
  61                 to += copy;
  62                 len -= copy;
  63                 iov->iov_base += copy;
  64                 iov->iov_len -= copy;
  65         }
  66         return 0;
  67 }
  68
  69 static inline int
  70 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len)
  71 {
  72         unsigned long copy;
  73
  74         while (len > 0) {
  75                 while (!iov->iov_len)
  76                         iov++;
  77                 copy = min_t(unsigned long, len, iov->iov_len);
  78
  79                 if (copy_to_user(iov->iov_base, from, copy))
  80                         return -EFAULT;
  81                 from += copy;
  82                 len -= copy;
  83                 iov->iov_base += copy;
  84                 iov->iov_len -= copy;
  85         }
  86         return 0;
  87 }
  88
  89 static void anon_pipe_buf_release(struct pipe_inode_info *info, struct pipe_buffer *buf)
  90 {
  91         struct page *page = buf->page;
  92
  93         if (info->tmp_page) {
  94                 __free_page(page);
  95                 return;
  96         }
  97         info->tmp_page = page;
  98 }
  99
 100 static void *anon_pipe_buf_map(struct file *file, struct pipe_inode_info *info, struct pipe_buffer *buf)
 101 {
 102         return kmap(buf->page);
 103 }
 104
 105 static void anon_pipe_buf_unmap(struct pipe_inode_info *info, struct pipe_buffer *buf)
 106 {
 107         kunmap(buf->page);
 108 }
 109
 110 static struct pipe_buf_operations anon_pipe_buf_ops = {
 111         .can_merge = 1,
 112         .map = anon_pipe_buf_map,
 113         .unmap = anon_pipe_buf_unmap,
 114         .release = anon_pipe_buf_release,
 115 };
 116
 117 static ssize_t
 118 pipe_readv(struct file *filp, const struct iovec *_iov,
 119            unsigned long nr_segs, loff_t *ppos)
 120 {
 121         struct inode *inode = filp->f_dentry->d_inode;
 122         struct pipe_inode_info *info;
 123         int do_wakeup;
 124         ssize_t ret;
 125         struct iovec *iov = (struct iovec *)_iov;
 126         size_t total_len;
 127
 128         total_len = iov_length(iov, nr_segs);
 129         /* Null read succeeds. */
 130         if (unlikely(total_len == 0))
 131                 return 0;
 132
 133         do_wakeup = 0;
 134         ret = 0;
 135         down(PIPE_SEM(*inode));
 136         info = inode->i_pipe;
 137         for (;;) {
 138                 int bufs = info->nrbufs;
 139                 if (bufs) {
 140                         int curbuf = info->curbuf;
 141                         struct pipe_buffer *buf = info->bufs + curbuf;
 142                         struct pipe_buf_operations *ops = buf->ops;
 143                         void *addr;
 144                         size_t chars = buf->len;
 145                         int error;
 146
 147                         if (chars > total_len)
 148                                 chars = total_len;
 149
 150                         addr = ops->map(filp, info, buf);
 151                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars);
 152                         ops->unmap(info, buf);
 153                         if (unlikely(error)) {
 154                                 if (!ret) ret = -EFAULT;
 155                                 break;
 156                         }
 157                         ret += chars;
 158                         buf->offset += chars;
 159                         buf->len -= chars;
 160                         if (!buf->len) {
 161                                 buf->ops = NULL;
 162                                 ops->release(info, buf);
 163                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
 164                                 info->curbuf = curbuf;
 165                                 info->nrbufs = --bufs;
 166                                 do_wakeup = 1;
 167                         }
 168                         total_len -= chars;
 169                         if (!total_len)
 170                                 break;  /* common path: read succeeded */
 171                 }
 172                 if (bufs)       /* More to do? */
 173                         continue;
 174                 if (!PIPE_WRITERS(*inode))
 175                         break;
 176                 if (!PIPE_WAITING_WRITERS(*inode)) {
 177                         /* syscall merging: Usually we must not sleep
 178                          * if O_NONBLOCK is set, or if we got some data.
 179                          * But if a writer sleeps in kernel space, then
 180                          * we can wait for that data without violating POSIX.
 181                          */
 182                         if (ret)
 183                                 break;
 184                         if (filp->f_flags & O_NONBLOCK) {
 185                                 ret = -EAGAIN;
 186                                 break;
 187                         }
 188                 }
 189                 if (signal_pending(current)) {
 190                         if (!ret) ret = -ERESTARTSYS;
 191                         break;
 192                 }
 193                 if (do_wakeup) {
 194                         wake_up_interruptible_sync(PIPE_WAIT(*inode));
 195                         kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
 196                 }
 197                 pipe_wait(inode);
 198         }
 199         up(PIPE_SEM(*inode));
 200         /* Signal writers asynchronously that there is more room.  */
 201         if (do_wakeup) {
 202                 wake_up_interruptible(PIPE_WAIT(*inode));
 203                 kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
 204         }
 205         if (ret > 0)
 206                 file_accessed(filp);
 207         return ret;
 208 }
 209
 210 static ssize_t
 211 pipe_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 212 {
 213         struct iovec iov = { .iov_base = buf, .iov_len = count };
 214         return pipe_readv(filp, &iov, 1, ppos);
 215 }
 216
 217 static ssize_t
 218 pipe_writev(struct file *filp, const struct iovec *_iov,
 219             unsigned long nr_segs, loff_t *ppos)
 220 {
 221         struct inode *inode = filp->f_dentry->d_inode;
 222         struct pipe_inode_info *info;
 223         ssize_t ret;
 224         int do_wakeup;
 225         struct iovec *iov = (struct iovec *)_iov;
 226         size_t total_len;
 227         ssize_t chars;
 228
 229         total_len = iov_length(iov, nr_segs);
 230         /* Null write succeeds. */
 231         if (unlikely(total_len == 0))
 232                 return 0;
 233
 234         do_wakeup = 0;
 235         ret = 0;
 236         down(PIPE_SEM(*inode));
 237         info = inode->i_pipe;
 238
 239         if (!PIPE_READERS(*inode)) {
 240                 send_sig(SIGPIPE, current, 0);
 241                 ret = -EPIPE;
 242                 goto out;
 243         }
 244
 245         /* We try to merge small writes */
 246         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 247         if (info->nrbufs && chars != 0) {
 248                 int lastbuf = (info->curbuf + info->nrbufs - 1) & (PIPE_BUFFERS-1);
 249                 struct pipe_buffer *buf = info->bufs + lastbuf;
 250                 struct pipe_buf_operations *ops = buf->ops;
 251                 int offset = buf->offset + buf->len;
 252                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 253                         void *addr = ops->map(filp, info, buf);
 254                         int error = pipe_iov_copy_from_user(offset + addr, iov, chars);
 255                         ops->unmap(info, buf);
 256                         ret = error;
 257                         do_wakeup = 1;
 258                         if (error)
 259                                 goto out;
 260                         buf->len += chars;
 261                         total_len -= chars;
 262                         ret = chars;
 263                         if (!total_len)
 264                                 goto out;
 265                 }
 266         }
 267
 268         for (;;) {
 269                 int bufs;
 270                 if (!PIPE_READERS(*inode)) {
 271                         send_sig(SIGPIPE, current, 0);
 272                         if (!ret) ret = -EPIPE;
 273                         break;
 274                 }
 275                 bufs = info->nrbufs;
 276                 if (bufs < PIPE_BUFFERS) {
 277                         int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS-1);
 278                         struct pipe_buffer *buf = info->bufs + newbuf;
 279                         struct page *page = info->tmp_page;
 280                         int error;
 281
 282                         if (!page) {
 283                                 page = alloc_page(GFP_HIGHUSER);
 284                                 if (unlikely(!page)) {
 285                                         ret = ret ? : -ENOMEM;
 286                                         break;
 287                                 }
 288                                 info->tmp_page = page;
 289                         }
 290                         /* Always wakeup, even if the copy fails. Otherwise
 291                          * we lock up (O_NONBLOCK-)readers that sleep due to
 292                          * syscall merging.
 293                          * FIXME! Is this really true?
 294                          */
 295                         do_wakeup = 1;
 296                         chars = PAGE_SIZE;
 297                         if (chars > total_len)
 298                                 chars = total_len;
 299
 300                         error = pipe_iov_copy_from_user(kmap(page), iov, chars);
 301                         kunmap(page);
 302                         if (unlikely(error)) {
 303                                 if (!ret) ret = -EFAULT;
 304                                 break;
 305                         }
 306                         ret += chars;
 307
 308                         /* Insert it into the buffer array */
 309                         buf->page = page;
 310                         buf->ops = &anon_pipe_buf_ops;
 311                         buf->offset = 0;
 312                         buf->len = chars;
 313                         info->nrbufs = ++bufs;
 314                         info->tmp_page = NULL;
 315
 316                         total_len -= chars;
 317                         if (!total_len)
 318                                 break;
 319                 }
 320                 if (bufs < PIPE_BUFFERS)
 321                         continue;
 322                 if (filp->f_flags & O_NONBLOCK) {
 323                         if (!ret) ret = -EAGAIN;
 324                         break;
 325                 }
 326                 if (signal_pending(current)) {
 327                         if (!ret) ret = -ERESTARTSYS;
 328                         break;
 329                 }
 330                 if (do_wakeup) {
 331                         wake_up_interruptible_sync(PIPE_WAIT(*inode));
 332                         kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
 333                         do_wakeup = 0;
 334                 }
 335                 PIPE_WAITING_WRITERS(*inode)++;
 336                 pipe_wait(inode);
 337                 PIPE_WAITING_WRITERS(*inode)--;
 338         }
 339 out:
 340         up(PIPE_SEM(*inode));
 341         if (do_wakeup) {
 342                 wake_up_interruptible(PIPE_WAIT(*inode));
 343                 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
 344         }
 345         if (ret > 0)
 346                 inode_update_time(inode, 1);    /* mtime and ctime */
 347         return ret;
 348 }
 349
 350 static ssize_t
 351 pipe_write(struct file *filp, const char __user *buf,
 352            size_t count, loff_t *ppos)
 353 {
 354         struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = count };
 355         return pipe_writev(filp, &iov, 1, ppos);
 356 }
 357
 358 static ssize_t
 359 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 360 {
 361         return -EBADF;
 362 }
 363
 364 static ssize_t
 365 bad_pipe_w(struct file *filp, const char __user *buf, size_t count, loff_t *ppos)
 366 {
 367         return -EBADF;
 368 }
 369
 370 static int
 371 pipe_ioctl(struct inode *pino, struct file *filp,
 372            unsigned int cmd, unsigned long arg)
 373 {
 374         struct inode *inode = filp->f_dentry->d_inode;
 375         struct pipe_inode_info *info;
 376         int count, buf, nrbufs;
 377
 378         switch (cmd) {
 379                 case FIONREAD:
 380                         down(PIPE_SEM(*inode));
 381                         info =  inode->i_pipe;
 382                         count = 0;
 383                         buf = info->curbuf;
 384                         nrbufs = info->nrbufs;
 385                         while (--nrbufs >= 0) {
 386                                 count += info->bufs[buf].len;
 387                                 buf = (buf+1) & (PIPE_BUFFERS-1);
 388                         }
 389                         up(PIPE_SEM(*inode));
 390                         return put_user(count, (int __user *)arg);
 391                 default:
 392                         return -EINVAL;
 393         }
 394 }
 395
 396 /* No kernel lock held - fine */
 397 static unsigned int
 398 pipe_poll(struct file *filp, poll_table *wait)
 399 {
 400         unsigned int mask;
 401         struct inode *inode = filp->f_dentry->d_inode;
 402         struct pipe_inode_info *info = inode->i_pipe;
 403         int nrbufs;
 404
 405         poll_wait(filp, PIPE_WAIT(*inode), wait);
 406
 407         /* Reading only -- no need for acquiring the semaphore.  */
 408         nrbufs = info->nrbufs;
 409         mask = 0;
 410         if (filp->f_mode & FMODE_READ) {
 411                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 412                 if (!PIPE_WRITERS(*inode) && filp->f_version != PIPE_WCOUNTER(*inode))
 413                         mask |= POLLHUP;
 414         }
 415
 416         if (filp->f_mode & FMODE_WRITE) {
 417                 mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
 418                 if (!PIPE_READERS(*inode))
 419                         mask |= POLLERR;
 420         }
 421
 422         return mask;
 423 }
 424
 425 /* FIXME: most Unices do not set POLLERR for fifos */
 426 #define fifo_poll pipe_poll
 427
 428 static int
 429 pipe_release(struct inode *inode, int decr, int decw)
 430 {
 431         down(PIPE_SEM(*inode));
 432         PIPE_READERS(*inode) -= decr;
 433         PIPE_WRITERS(*inode) -= decw;
 434         if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode)) {
 435                 free_pipe_info(inode);
 436         } else {
 437                 wake_up_interruptible(PIPE_WAIT(*inode));
 438                 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
 439                 kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
 440         }
 441         up(PIPE_SEM(*inode));
 442
 443         return 0;
 444 }
 445
 446 static int
 447 pipe_read_fasync(int fd, struct file *filp, int on)
 448 {
 449         struct inode *inode = filp->f_dentry->d_inode;
 450         int retval;
 451
 452         down(PIPE_SEM(*inode));
 453         retval = fasync_helper(fd, filp, on, PIPE_FASYNC_READERS(*inode));
 454         up(PIPE_SEM(*inode));
 455
 456         if (retval < 0)
 457                 return retval;
 458
 459         return 0;
 460 }
 461
 462
 463 static int
 464 pipe_write_fasync(int fd, struct file *filp, int on)
 465 {
 466         struct inode *inode = filp->f_dentry->d_inode;
 467         int retval;
 468
 469         down(PIPE_SEM(*inode));
 470         retval = fasync_helper(fd, filp, on, PIPE_FASYNC_WRITERS(*inode));
 471         up(PIPE_SEM(*inode));
 472
 473         if (retval < 0)
 474                 return retval;
 475
 476         return 0;
 477 }
 478
 479
 480 static int
 481 pipe_rdwr_fasync(int fd, struct file *filp, int on)
 482 {
 483         struct inode *inode = filp->f_dentry->d_inode;
 484         int retval;
 485
 486         down(PIPE_SEM(*inode));
 487
 488         retval = fasync_helper(fd, filp, on, PIPE_FASYNC_READERS(*inode));
 489
 490         if (retval >= 0)
 491                 retval = fasync_helper(fd, filp, on, PIPE_FASYNC_WRITERS(*inode));
 492
 493         up(PIPE_SEM(*inode));
 494
 495         if (retval < 0)
 496                 return retval;
 497
 498         return 0;
 499 }
 500
 501
 502 static int
 503 pipe_read_release(struct inode *inode, struct file *filp)
 504 {
 505         pipe_read_fasync(-1, filp, 0);
 506         return pipe_release(inode, 1, 0);
 507 }
 508
 509 static int
 510 pipe_write_release(struct inode *inode, struct file *filp)
 511 {
 512         pipe_write_fasync(-1, filp, 0);
 513         return pipe_release(inode, 0, 1);
 514 }
 515
 516 static int
 517 pipe_rdwr_release(struct inode *inode, struct file *filp)
 518 {
 519         int decr, decw;
 520
 521         pipe_rdwr_fasync(-1, filp, 0);
 522         decr = (filp->f_mode & FMODE_READ) != 0;
 523         decw = (filp->f_mode & FMODE_WRITE) != 0;
 524         return pipe_release(inode, decr, decw);
 525 }
 526
 527 static int
 528 pipe_read_open(struct inode *inode, struct file *filp)
 529 {
 530         /* We could have perhaps used atomic_t, but this and friends
 531            below are the only places.  So it doesn't seem worthwhile.  */
 532         down(PIPE_SEM(*inode));
 533         PIPE_READERS(*inode)++;
 534         up(PIPE_SEM(*inode));
 535
 536         return 0;
 537 }
 538
 539 static int
 540 pipe_write_open(struct inode *inode, struct file *filp)
 541 {
 542         down(PIPE_SEM(*inode));
 543         PIPE_WRITERS(*inode)++;
 544         up(PIPE_SEM(*inode));
 545
 546         return 0;
 547 }
 548
 549 static int
 550 pipe_rdwr_open(struct inode *inode, struct file *filp)
 551 {
 552         down(PIPE_SEM(*inode));
 553         if (filp->f_mode & FMODE_READ)
 554                 PIPE_READERS(*inode)++;
 555         if (filp->f_mode & FMODE_WRITE)
 556                 PIPE_WRITERS(*inode)++;
 557         up(PIPE_SEM(*inode));
 558
 559         return 0;
 560 }
 561
 562 /*
 563  * The file_operations structs are not static because they
 564  * are also used in linux/fs/fifo.c to do operations on FIFOs.
 565  */
 566 struct file_operations read_fifo_fops = {
 567         .llseek         = no_llseek,
 568         .read           = pipe_read,
 569         .readv          = pipe_readv,
 570         .write          = bad_pipe_w,
 571         .poll           = fifo_poll,
 572         .ioctl          = pipe_ioctl,
 573         .open           = pipe_read_open,
 574         .release        = pipe_read_release,
 575         .fasync         = pipe_read_fasync,
 576 };
 577
 578 struct file_operations write_fifo_fops = {
 579         .llseek         = no_llseek,
 580         .read           = bad_pipe_r,
 581         .write          = pipe_write,
 582         .writev         = pipe_writev,
 583         .poll           = fifo_poll,
 584         .ioctl          = pipe_ioctl,
 585         .open           = pipe_write_open,
 586         .release        = pipe_write_release,
 587         .fasync         = pipe_write_fasync,
 588 };
 589
 590 struct file_operations rdwr_fifo_fops = {
 591         .llseek         = no_llseek,
 592         .read           = pipe_read,
 593         .readv          = pipe_readv,
 594         .write          = pipe_write,
 595         .writev         = pipe_writev,
 596         .poll           = fifo_poll,
 597         .ioctl          = pipe_ioctl,
 598         .open           = pipe_rdwr_open,
 599         .release        = pipe_rdwr_release,
 600         .fasync         = pipe_rdwr_fasync,
 601 };
 602
 603 struct file_operations read_pipe_fops = {
 604         .llseek         = no_llseek,
 605         .read           = pipe_read,
 606         .readv          = pipe_readv,
 607         .write          = bad_pipe_w,
 608         .poll           = pipe_poll,
 609         .ioctl          = pipe_ioctl,
 610         .open           = pipe_read_open,
 611         .release        = pipe_read_release,
 612         .fasync         = pipe_read_fasync,
 613 };
 614
 615 struct file_operations write_pipe_fops = {
 616         .llseek         = no_llseek,
 617         .read           = bad_pipe_r,
 618         .write          = pipe_write,
 619         .writev         = pipe_writev,
 620         .poll           = pipe_poll,
 621         .ioctl          = pipe_ioctl,
 622         .open           = pipe_write_open,
 623         .release        = pipe_write_release,
 624         .fasync         = pipe_write_fasync,
 625 };
 626
 627 struct file_operations rdwr_pipe_fops = {
 628         .llseek         = no_llseek,
 629         .read           = pipe_read,
 630         .readv          = pipe_readv,
 631         .write          = pipe_write,
 632         .writev         = pipe_writev,
 633         .poll           = pipe_poll,
 634         .ioctl          = pipe_ioctl,
 635         .open           = pipe_rdwr_open,
 636         .release        = pipe_rdwr_release,
 637         .fasync         = pipe_rdwr_fasync,
 638 };
 639
 640 void free_pipe_info(struct inode *inode)
 641 {
 642         int i;
 643         struct pipe_inode_info *info = inode->i_pipe;
 644
 645         inode->i_pipe = NULL;
 646         for (i = 0; i < PIPE_BUFFERS; i++) {
 647                 struct pipe_buffer *buf = info->bufs + i;
 648                 if (buf->ops)
 649                         buf->ops->release(info, buf);
 650         }
 651         if (info->tmp_page)
 652                 __free_page(info->tmp_page);
 653         kfree(info);
 654 }
 655
 656 struct inode* pipe_new(struct inode* inode)
 657 {
 658         struct pipe_inode_info *info;
 659
 660         info = kmalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 661         if (!info)
 662                 goto fail_page;
 663         memset(info, 0, sizeof(*info));
 664         inode->i_pipe = info;
 665
 666         init_waitqueue_head(PIPE_WAIT(*inode));
 667         PIPE_RCOUNTER(*inode) = PIPE_WCOUNTER(*inode) = 1;
 668
 669         return inode;
 670 fail_page:
 671         return NULL;
 672 }
 673
 674 static struct vfsmount *pipe_mnt;
 675 static int pipefs_delete_dentry(struct dentry *dentry)
 676 {
 677         return 1;
 678 }
 679 static struct dentry_operations pipefs_dentry_operations = {
 680         .d_delete       = pipefs_delete_dentry,
 681 };
 682
 683 static struct inode * get_pipe_inode(void)
 684 {
 685         struct inode *inode = new_inode(pipe_mnt->mnt_sb);
 686
 687         if (!inode)
 688                 goto fail_inode;
 689
 690         if(!pipe_new(inode))
 691                 goto fail_iput;
 692         PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 1;
 693         inode->i_fop = &rdwr_pipe_fops;
 694
 695         /*
 696          * Mark the inode dirty from the very beginning,
 697          * that way it will never be moved to the dirty
 698          * list because "mark_inode_dirty()" will think
 699          * that it already _is_ on the dirty list.
 700          */
 701         inode->i_state = I_DIRTY;
 702         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 703         inode->i_uid = current->fsuid;
 704         inode->i_gid = current->fsgid;
 705         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 706         inode->i_blksize = PAGE_SIZE;
 707         return inode;
 708
 709 fail_iput:
 710         iput(inode);
 711 fail_inode:
 712         return NULL;
 713 }
 714
 715 int do_pipe(int *fd)
 716 {
 717         struct qstr this;
 718         char name[32];
 719         struct dentry *dentry;
 720         struct inode * inode;
 721         struct file *f1, *f2;
 722         int error;
 723         int i,j;
 724
 725         error = -ENFILE;
 726         f1 = get_empty_filp();
 727         if (!f1)
 728                 goto no_files;
 729
 730         f2 = get_empty_filp();
 731         if (!f2)
 732                 goto close_f1;
 733
 734         inode = get_pipe_inode();
 735         if (!inode)
 736                 goto close_f12;
 737
 738         error = get_unused_fd();
 739         if (error < 0)
 740                 goto close_f12_inode;
 741         i = error;
 742
 743         error = get_unused_fd();
 744         if (error < 0)
 745                 goto close_f12_inode_i;
 746         j = error;
 747
 748         error = -ENOMEM;
 749         sprintf(name, "[%lu]", inode->i_ino);
 750         this.name = name;
 751         this.len = strlen(name);
 752         this.hash = inode->i_ino; /* will go */
 753         dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this);
 754         if (!dentry)
 755                 goto close_f12_inode_i_j;
 756         dentry->d_op = &pipefs_dentry_operations;
 757         d_add(dentry, inode);
 758         f1->f_vfsmnt = f2->f_vfsmnt = mntget(mntget(pipe_mnt));
 759         f1->f_dentry = f2->f_dentry = dget(dentry);
 760         f1->f_mapping = f2->f_mapping = inode->i_mapping;
 761
 762         /* read file */
 763         f1->f_pos = f2->f_pos = 0;
 764         f1->f_flags = O_RDONLY;
 765         f1->f_op = &read_pipe_fops;
 766         f1->f_mode = FMODE_READ;
 767         f1->f_version = 0;
 768
 769         /* write file */
 770         f2->f_flags = O_WRONLY;
 771         f2->f_op = &write_pipe_fops;
 772         f2->f_mode = FMODE_WRITE;
 773         f2->f_version = 0;
 774
 775         fd_install(i, f1);
 776         fd_install(j, f2);
 777         fd[0] = i;
 778         fd[1] = j;
 779         return 0;
 780
 781 close_f12_inode_i_j:
 782         put_unused_fd(j);
 783 close_f12_inode_i:
 784         put_unused_fd(i);
 785 close_f12_inode:
 786         free_pipe_info(inode);
 787         iput(inode);
 788 close_f12:
 789         put_filp(f2);
 790 close_f1:
 791         put_filp(f1);
 792 no_files:
 793         return error;
 794 }
 795
 796 /*
 797  * pipefs should _never_ be mounted by userland - too much of security hassle,
 798  * no real gain from having the whole whorehouse mounted. So we don't need
 799  * any operations on the root directory. However, we need a non-trivial
 800  * d_name - pipe: will go nicely and kill the special-casing in procfs.
 801  */
 802
 803 static struct super_block *pipefs_get_sb(struct file_system_type *fs_type,
 804         int flags, const char *dev_name, void *data)
 805 {
 806         return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC);
 807 }
 808
 809 static struct file_system_type pipe_fs_type = {
 810         .name           = "pipefs",
 811         .get_sb         = pipefs_get_sb,
 812         .kill_sb        = kill_anon_super,
 813 };
 814
 815 static int __init init_pipe_fs(void)
 816 {
 817         int err = register_filesystem(&pipe_fs_type);
 818         if (!err) {
 819                 pipe_mnt = kern_mount(&pipe_fs_type);
 820                 if (IS_ERR(pipe_mnt)) {
 821                         err = PTR_ERR(pipe_mnt);
 822                         unregister_filesystem(&pipe_fs_type);
 823                 }
 824         }
 825         return err;
 826 }
 827
 828 static void __exit exit_pipe_fs(void)
 829 {
 830         unregister_filesystem(&pipe_fs_type);
 831         mntput(pipe_mnt);
 832 }
 833
 834 fs_initcall(init_pipe_fs);
 835 module_exit(exit_pipe_fs);