kernel-doc: fix fs/pipe.c notation
[linux-2.6.git] / 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 #include <linux/pagemap.h>
19 #include <linux/audit.h>
20
21 #include <asm/uaccess.h>
22 #include <asm/ioctls.h>
23
24 /*
25  * We use a start+len construction, which provides full use of the 
26  * allocated memory.
27  * -- Florian Coosmann (FGC)
28  * 
29  * Reads with count = 0 should always return 0.
30  * -- Julian Bradfield 1999-06-07.
31  *
32  * FIFOs and Pipes now generate SIGIO for both readers and writers.
33  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
34  *
35  * pipe_read & write cleanup
36  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
37  */
38
39 /* Drop the inode semaphore and wait for a pipe event, atomically */
40 void pipe_wait(struct pipe_inode_info *pipe)
41 {
42         DEFINE_WAIT(wait);
43
44         /*
45          * Pipes are system-local resources, so sleeping on them
46          * is considered a noninteractive wait:
47          */
48         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
49         if (pipe->inode)
50                 mutex_unlock(&pipe->inode->i_mutex);
51         schedule();
52         finish_wait(&pipe->wait, &wait);
53         if (pipe->inode)
54                 mutex_lock(&pipe->inode->i_mutex);
55 }
56
57 static int
58 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
59                         int atomic)
60 {
61         unsigned long copy;
62
63         while (len > 0) {
64                 while (!iov->iov_len)
65                         iov++;
66                 copy = min_t(unsigned long, len, iov->iov_len);
67
68                 if (atomic) {
69                         if (__copy_from_user_inatomic(to, iov->iov_base, copy))
70                                 return -EFAULT;
71                 } else {
72                         if (copy_from_user(to, iov->iov_base, copy))
73                                 return -EFAULT;
74                 }
75                 to += copy;
76                 len -= copy;
77                 iov->iov_base += copy;
78                 iov->iov_len -= copy;
79         }
80         return 0;
81 }
82
83 static int
84 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
85                       int atomic)
86 {
87         unsigned long copy;
88
89         while (len > 0) {
90                 while (!iov->iov_len)
91                         iov++;
92                 copy = min_t(unsigned long, len, iov->iov_len);
93
94                 if (atomic) {
95                         if (__copy_to_user_inatomic(iov->iov_base, from, copy))
96                                 return -EFAULT;
97                 } else {
98                         if (copy_to_user(iov->iov_base, from, copy))
99                                 return -EFAULT;
100                 }
101                 from += copy;
102                 len -= copy;
103                 iov->iov_base += copy;
104                 iov->iov_len -= copy;
105         }
106         return 0;
107 }
108
109 /*
110  * Attempt to pre-fault in the user memory, so we can use atomic copies.
111  * Returns the number of bytes not faulted in.
112  */
113 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
114 {
115         while (!iov->iov_len)
116                 iov++;
117
118         while (len > 0) {
119                 unsigned long this_len;
120
121                 this_len = min_t(unsigned long, len, iov->iov_len);
122                 if (fault_in_pages_writeable(iov->iov_base, this_len))
123                         break;
124
125                 len -= this_len;
126                 iov++;
127         }
128
129         return len;
130 }
131
132 /*
133  * Pre-fault in the user memory, so we can use atomic copies.
134  */
135 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
136 {
137         while (!iov->iov_len)
138                 iov++;
139
140         while (len > 0) {
141                 unsigned long this_len;
142
143                 this_len = min_t(unsigned long, len, iov->iov_len);
144                 fault_in_pages_readable(iov->iov_base, this_len);
145                 len -= this_len;
146                 iov++;
147         }
148 }
149
150 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
151                                   struct pipe_buffer *buf)
152 {
153         struct page *page = buf->page;
154
155         /*
156          * If nobody else uses this page, and we don't already have a
157          * temporary page, let's keep track of it as a one-deep
158          * allocation cache. (Otherwise just release our reference to it)
159          */
160         if (page_count(page) == 1 && !pipe->tmp_page)
161                 pipe->tmp_page = page;
162         else
163                 page_cache_release(page);
164 }
165
166 /**
167  * generic_pipe_buf_map - virtually map a pipe buffer
168  * @pipe:       the pipe that the buffer belongs to
169  * @buf:        the buffer that should be mapped
170  * @atomic:     whether to use an atomic map
171  *
172  * Description:
173  *      This function returns a kernel virtual address mapping for the
174  *      pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
175  *      and the caller has to be careful not to fault before calling
176  *      the unmap function.
177  *
178  *      Note that this function occupies KM_USER0 if @atomic != 0.
179  */
180 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
181                            struct pipe_buffer *buf, int atomic)
182 {
183         if (atomic) {
184                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
185                 return kmap_atomic(buf->page, KM_USER0);
186         }
187
188         return kmap(buf->page);
189 }
190
191 /**
192  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
193  * @pipe:       the pipe that the buffer belongs to
194  * @buf:        the buffer that should be unmapped
195  * @map_data:   the data that the mapping function returned
196  *
197  * Description:
198  *      This function undoes the mapping that ->map() provided.
199  */
200 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
201                             struct pipe_buffer *buf, void *map_data)
202 {
203         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
204                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
205                 kunmap_atomic(map_data, KM_USER0);
206         } else
207                 kunmap(buf->page);
208 }
209
210 /**
211  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
212  * @pipe:       the pipe that the buffer belongs to
213  * @buf:        the buffer to attempt to steal
214  *
215  * Description:
216  *      This function attempts to steal the &struct page attached to
217  *      @buf. If successful, this function returns 0 and returns with
218  *      the page locked. The caller may then reuse the page for whatever
219  *      he wishes; the typical use is insertion into a different file
220  *      page cache.
221  */
222 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
223                            struct pipe_buffer *buf)
224 {
225         struct page *page = buf->page;
226
227         /*
228          * A reference of one is golden, that means that the owner of this
229          * page is the only one holding a reference to it. lock the page
230          * and return OK.
231          */
232         if (page_count(page) == 1) {
233                 lock_page(page);
234                 return 0;
235         }
236
237         return 1;
238 }
239
240 /**
241  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
242  * @pipe:       the pipe that the buffer belongs to
243  * @buf:        the buffer to get a reference to
244  *
245  * Description:
246  *      This function grabs an extra reference to @buf. It's used in
247  *      in the tee() system call, when we duplicate the buffers in one
248  *      pipe into another.
249  */
250 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
251 {
252         page_cache_get(buf->page);
253 }
254
255 /**
256  * generic_pipe_buf_confirm - verify contents of the pipe buffer
257  * @info:       the pipe that the buffer belongs to
258  * @buf:        the buffer to confirm
259  *
260  * Description:
261  *      This function does nothing, because the generic pipe code uses
262  *      pages that are always good when inserted into the pipe.
263  */
264 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
265                              struct pipe_buffer *buf)
266 {
267         return 0;
268 }
269
270 static const struct pipe_buf_operations anon_pipe_buf_ops = {
271         .can_merge = 1,
272         .map = generic_pipe_buf_map,
273         .unmap = generic_pipe_buf_unmap,
274         .confirm = generic_pipe_buf_confirm,
275         .release = anon_pipe_buf_release,
276         .steal = generic_pipe_buf_steal,
277         .get = generic_pipe_buf_get,
278 };
279
280 static ssize_t
281 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
282            unsigned long nr_segs, loff_t pos)
283 {
284         struct file *filp = iocb->ki_filp;
285         struct inode *inode = filp->f_path.dentry->d_inode;
286         struct pipe_inode_info *pipe;
287         int do_wakeup;
288         ssize_t ret;
289         struct iovec *iov = (struct iovec *)_iov;
290         size_t total_len;
291
292         total_len = iov_length(iov, nr_segs);
293         /* Null read succeeds. */
294         if (unlikely(total_len == 0))
295                 return 0;
296
297         do_wakeup = 0;
298         ret = 0;
299         mutex_lock(&inode->i_mutex);
300         pipe = inode->i_pipe;
301         for (;;) {
302                 int bufs = pipe->nrbufs;
303                 if (bufs) {
304                         int curbuf = pipe->curbuf;
305                         struct pipe_buffer *buf = pipe->bufs + curbuf;
306                         const struct pipe_buf_operations *ops = buf->ops;
307                         void *addr;
308                         size_t chars = buf->len;
309                         int error, atomic;
310
311                         if (chars > total_len)
312                                 chars = total_len;
313
314                         error = ops->confirm(pipe, buf);
315                         if (error) {
316                                 if (!ret)
317                                         error = ret;
318                                 break;
319                         }
320
321                         atomic = !iov_fault_in_pages_write(iov, chars);
322 redo:
323                         addr = ops->map(pipe, buf, atomic);
324                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
325                         ops->unmap(pipe, buf, addr);
326                         if (unlikely(error)) {
327                                 /*
328                                  * Just retry with the slow path if we failed.
329                                  */
330                                 if (atomic) {
331                                         atomic = 0;
332                                         goto redo;
333                                 }
334                                 if (!ret)
335                                         ret = error;
336                                 break;
337                         }
338                         ret += chars;
339                         buf->offset += chars;
340                         buf->len -= chars;
341                         if (!buf->len) {
342                                 buf->ops = NULL;
343                                 ops->release(pipe, buf);
344                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
345                                 pipe->curbuf = curbuf;
346                                 pipe->nrbufs = --bufs;
347                                 do_wakeup = 1;
348                         }
349                         total_len -= chars;
350                         if (!total_len)
351                                 break;  /* common path: read succeeded */
352                 }
353                 if (bufs)       /* More to do? */
354                         continue;
355                 if (!pipe->writers)
356                         break;
357                 if (!pipe->waiting_writers) {
358                         /* syscall merging: Usually we must not sleep
359                          * if O_NONBLOCK is set, or if we got some data.
360                          * But if a writer sleeps in kernel space, then
361                          * we can wait for that data without violating POSIX.
362                          */
363                         if (ret)
364                                 break;
365                         if (filp->f_flags & O_NONBLOCK) {
366                                 ret = -EAGAIN;
367                                 break;
368                         }
369                 }
370                 if (signal_pending(current)) {
371                         if (!ret)
372                                 ret = -ERESTARTSYS;
373                         break;
374                 }
375                 if (do_wakeup) {
376                         wake_up_interruptible_sync(&pipe->wait);
377                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
378                 }
379                 pipe_wait(pipe);
380         }
381         mutex_unlock(&inode->i_mutex);
382
383         /* Signal writers asynchronously that there is more room. */
384         if (do_wakeup) {
385                 wake_up_interruptible_sync(&pipe->wait);
386                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
387         }
388         if (ret > 0)
389                 file_accessed(filp);
390         return ret;
391 }
392
393 static ssize_t
394 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
395             unsigned long nr_segs, loff_t ppos)
396 {
397         struct file *filp = iocb->ki_filp;
398         struct inode *inode = filp->f_path.dentry->d_inode;
399         struct pipe_inode_info *pipe;
400         ssize_t ret;
401         int do_wakeup;
402         struct iovec *iov = (struct iovec *)_iov;
403         size_t total_len;
404         ssize_t chars;
405
406         total_len = iov_length(iov, nr_segs);
407         /* Null write succeeds. */
408         if (unlikely(total_len == 0))
409                 return 0;
410
411         do_wakeup = 0;
412         ret = 0;
413         mutex_lock(&inode->i_mutex);
414         pipe = inode->i_pipe;
415
416         if (!pipe->readers) {
417                 send_sig(SIGPIPE, current, 0);
418                 ret = -EPIPE;
419                 goto out;
420         }
421
422         /* We try to merge small writes */
423         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
424         if (pipe->nrbufs && chars != 0) {
425                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
426                                                         (PIPE_BUFFERS-1);
427                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
428                 const struct pipe_buf_operations *ops = buf->ops;
429                 int offset = buf->offset + buf->len;
430
431                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
432                         int error, atomic = 1;
433                         void *addr;
434
435                         error = ops->confirm(pipe, buf);
436                         if (error)
437                                 goto out;
438
439                         iov_fault_in_pages_read(iov, chars);
440 redo1:
441                         addr = ops->map(pipe, buf, atomic);
442                         error = pipe_iov_copy_from_user(offset + addr, iov,
443                                                         chars, atomic);
444                         ops->unmap(pipe, buf, addr);
445                         ret = error;
446                         do_wakeup = 1;
447                         if (error) {
448                                 if (atomic) {
449                                         atomic = 0;
450                                         goto redo1;
451                                 }
452                                 goto out;
453                         }
454                         buf->len += chars;
455                         total_len -= chars;
456                         ret = chars;
457                         if (!total_len)
458                                 goto out;
459                 }
460         }
461
462         for (;;) {
463                 int bufs;
464
465                 if (!pipe->readers) {
466                         send_sig(SIGPIPE, current, 0);
467                         if (!ret)
468                                 ret = -EPIPE;
469                         break;
470                 }
471                 bufs = pipe->nrbufs;
472                 if (bufs < PIPE_BUFFERS) {
473                         int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1);
474                         struct pipe_buffer *buf = pipe->bufs + newbuf;
475                         struct page *page = pipe->tmp_page;
476                         char *src;
477                         int error, atomic = 1;
478
479                         if (!page) {
480                                 page = alloc_page(GFP_HIGHUSER);
481                                 if (unlikely(!page)) {
482                                         ret = ret ? : -ENOMEM;
483                                         break;
484                                 }
485                                 pipe->tmp_page = page;
486                         }
487                         /* Always wake up, even if the copy fails. Otherwise
488                          * we lock up (O_NONBLOCK-)readers that sleep due to
489                          * syscall merging.
490                          * FIXME! Is this really true?
491                          */
492                         do_wakeup = 1;
493                         chars = PAGE_SIZE;
494                         if (chars > total_len)
495                                 chars = total_len;
496
497                         iov_fault_in_pages_read(iov, chars);
498 redo2:
499                         if (atomic)
500                                 src = kmap_atomic(page, KM_USER0);
501                         else
502                                 src = kmap(page);
503
504                         error = pipe_iov_copy_from_user(src, iov, chars,
505                                                         atomic);
506                         if (atomic)
507                                 kunmap_atomic(src, KM_USER0);
508                         else
509                                 kunmap(page);
510
511                         if (unlikely(error)) {
512                                 if (atomic) {
513                                         atomic = 0;
514                                         goto redo2;
515                                 }
516                                 if (!ret)
517                                         ret = error;
518                                 break;
519                         }
520                         ret += chars;
521
522                         /* Insert it into the buffer array */
523                         buf->page = page;
524                         buf->ops = &anon_pipe_buf_ops;
525                         buf->offset = 0;
526                         buf->len = chars;
527                         pipe->nrbufs = ++bufs;
528                         pipe->tmp_page = NULL;
529
530                         total_len -= chars;
531                         if (!total_len)
532                                 break;
533                 }
534                 if (bufs < PIPE_BUFFERS)
535                         continue;
536                 if (filp->f_flags & O_NONBLOCK) {
537                         if (!ret)
538                                 ret = -EAGAIN;
539                         break;
540                 }
541                 if (signal_pending(current)) {
542                         if (!ret)
543                                 ret = -ERESTARTSYS;
544                         break;
545                 }
546                 if (do_wakeup) {
547                         wake_up_interruptible_sync(&pipe->wait);
548                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
549                         do_wakeup = 0;
550                 }
551                 pipe->waiting_writers++;
552                 pipe_wait(pipe);
553                 pipe->waiting_writers--;
554         }
555 out:
556         mutex_unlock(&inode->i_mutex);
557         if (do_wakeup) {
558                 wake_up_interruptible_sync(&pipe->wait);
559                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
560         }
561         if (ret > 0)
562                 file_update_time(filp);
563         return ret;
564 }
565
566 static ssize_t
567 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
568 {
569         return -EBADF;
570 }
571
572 static ssize_t
573 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
574            loff_t *ppos)
575 {
576         return -EBADF;
577 }
578
579 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
580 {
581         struct inode *inode = filp->f_path.dentry->d_inode;
582         struct pipe_inode_info *pipe;
583         int count, buf, nrbufs;
584
585         switch (cmd) {
586                 case FIONREAD:
587                         mutex_lock(&inode->i_mutex);
588                         pipe = inode->i_pipe;
589                         count = 0;
590                         buf = pipe->curbuf;
591                         nrbufs = pipe->nrbufs;
592                         while (--nrbufs >= 0) {
593                                 count += pipe->bufs[buf].len;
594                                 buf = (buf+1) & (PIPE_BUFFERS-1);
595                         }
596                         mutex_unlock(&inode->i_mutex);
597
598                         return put_user(count, (int __user *)arg);
599                 default:
600                         return -EINVAL;
601         }
602 }
603
604 /* No kernel lock held - fine */
605 static unsigned int
606 pipe_poll(struct file *filp, poll_table *wait)
607 {
608         unsigned int mask;
609         struct inode *inode = filp->f_path.dentry->d_inode;
610         struct pipe_inode_info *pipe = inode->i_pipe;
611         int nrbufs;
612
613         poll_wait(filp, &pipe->wait, wait);
614
615         /* Reading only -- no need for acquiring the semaphore.  */
616         nrbufs = pipe->nrbufs;
617         mask = 0;
618         if (filp->f_mode & FMODE_READ) {
619                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
620                 if (!pipe->writers && filp->f_version != pipe->w_counter)
621                         mask |= POLLHUP;
622         }
623
624         if (filp->f_mode & FMODE_WRITE) {
625                 mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
626                 /*
627                  * Most Unices do not set POLLERR for FIFOs but on Linux they
628                  * behave exactly like pipes for poll().
629                  */
630                 if (!pipe->readers)
631                         mask |= POLLERR;
632         }
633
634         return mask;
635 }
636
637 static int
638 pipe_release(struct inode *inode, int decr, int decw)
639 {
640         struct pipe_inode_info *pipe;
641
642         mutex_lock(&inode->i_mutex);
643         pipe = inode->i_pipe;
644         pipe->readers -= decr;
645         pipe->writers -= decw;
646
647         if (!pipe->readers && !pipe->writers) {
648                 free_pipe_info(inode);
649         } else {
650                 wake_up_interruptible_sync(&pipe->wait);
651                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
652                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
653         }
654         mutex_unlock(&inode->i_mutex);
655
656         return 0;
657 }
658
659 static int
660 pipe_read_fasync(int fd, struct file *filp, int on)
661 {
662         struct inode *inode = filp->f_path.dentry->d_inode;
663         int retval;
664
665         mutex_lock(&inode->i_mutex);
666         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
667         mutex_unlock(&inode->i_mutex);
668
669         if (retval < 0)
670                 return retval;
671
672         return 0;
673 }
674
675
676 static int
677 pipe_write_fasync(int fd, struct file *filp, int on)
678 {
679         struct inode *inode = filp->f_path.dentry->d_inode;
680         int retval;
681
682         mutex_lock(&inode->i_mutex);
683         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
684         mutex_unlock(&inode->i_mutex);
685
686         if (retval < 0)
687                 return retval;
688
689         return 0;
690 }
691
692
693 static int
694 pipe_rdwr_fasync(int fd, struct file *filp, int on)
695 {
696         struct inode *inode = filp->f_path.dentry->d_inode;
697         struct pipe_inode_info *pipe = inode->i_pipe;
698         int retval;
699
700         mutex_lock(&inode->i_mutex);
701
702         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
703
704         if (retval >= 0)
705                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
706
707         mutex_unlock(&inode->i_mutex);
708
709         if (retval < 0)
710                 return retval;
711
712         return 0;
713 }
714
715
716 static int
717 pipe_read_release(struct inode *inode, struct file *filp)
718 {
719         pipe_read_fasync(-1, filp, 0);
720         return pipe_release(inode, 1, 0);
721 }
722
723 static int
724 pipe_write_release(struct inode *inode, struct file *filp)
725 {
726         pipe_write_fasync(-1, filp, 0);
727         return pipe_release(inode, 0, 1);
728 }
729
730 static int
731 pipe_rdwr_release(struct inode *inode, struct file *filp)
732 {
733         int decr, decw;
734
735         pipe_rdwr_fasync(-1, filp, 0);
736         decr = (filp->f_mode & FMODE_READ) != 0;
737         decw = (filp->f_mode & FMODE_WRITE) != 0;
738         return pipe_release(inode, decr, decw);
739 }
740
741 static int
742 pipe_read_open(struct inode *inode, struct file *filp)
743 {
744         /* We could have perhaps used atomic_t, but this and friends
745            below are the only places.  So it doesn't seem worthwhile.  */
746         mutex_lock(&inode->i_mutex);
747         inode->i_pipe->readers++;
748         mutex_unlock(&inode->i_mutex);
749
750         return 0;
751 }
752
753 static int
754 pipe_write_open(struct inode *inode, struct file *filp)
755 {
756         mutex_lock(&inode->i_mutex);
757         inode->i_pipe->writers++;
758         mutex_unlock(&inode->i_mutex);
759
760         return 0;
761 }
762
763 static int
764 pipe_rdwr_open(struct inode *inode, struct file *filp)
765 {
766         mutex_lock(&inode->i_mutex);
767         if (filp->f_mode & FMODE_READ)
768                 inode->i_pipe->readers++;
769         if (filp->f_mode & FMODE_WRITE)
770                 inode->i_pipe->writers++;
771         mutex_unlock(&inode->i_mutex);
772
773         return 0;
774 }
775
776 /*
777  * The file_operations structs are not static because they
778  * are also used in linux/fs/fifo.c to do operations on FIFOs.
779  */
780 const struct file_operations read_fifo_fops = {
781         .llseek         = no_llseek,
782         .read           = do_sync_read,
783         .aio_read       = pipe_read,
784         .write          = bad_pipe_w,
785         .poll           = pipe_poll,
786         .unlocked_ioctl = pipe_ioctl,
787         .open           = pipe_read_open,
788         .release        = pipe_read_release,
789         .fasync         = pipe_read_fasync,
790 };
791
792 const struct file_operations write_fifo_fops = {
793         .llseek         = no_llseek,
794         .read           = bad_pipe_r,
795         .write          = do_sync_write,
796         .aio_write      = pipe_write,
797         .poll           = pipe_poll,
798         .unlocked_ioctl = pipe_ioctl,
799         .open           = pipe_write_open,
800         .release        = pipe_write_release,
801         .fasync         = pipe_write_fasync,
802 };
803
804 const struct file_operations rdwr_fifo_fops = {
805         .llseek         = no_llseek,
806         .read           = do_sync_read,
807         .aio_read       = pipe_read,
808         .write          = do_sync_write,
809         .aio_write      = pipe_write,
810         .poll           = pipe_poll,
811         .unlocked_ioctl = pipe_ioctl,
812         .open           = pipe_rdwr_open,
813         .release        = pipe_rdwr_release,
814         .fasync         = pipe_rdwr_fasync,
815 };
816
817 static const struct file_operations read_pipe_fops = {
818         .llseek         = no_llseek,
819         .read           = do_sync_read,
820         .aio_read       = pipe_read,
821         .write          = bad_pipe_w,
822         .poll           = pipe_poll,
823         .unlocked_ioctl = pipe_ioctl,
824         .open           = pipe_read_open,
825         .release        = pipe_read_release,
826         .fasync         = pipe_read_fasync,
827 };
828
829 static const struct file_operations write_pipe_fops = {
830         .llseek         = no_llseek,
831         .read           = bad_pipe_r,
832         .write          = do_sync_write,
833         .aio_write      = pipe_write,
834         .poll           = pipe_poll,
835         .unlocked_ioctl = pipe_ioctl,
836         .open           = pipe_write_open,
837         .release        = pipe_write_release,
838         .fasync         = pipe_write_fasync,
839 };
840
841 static const struct file_operations rdwr_pipe_fops = {
842         .llseek         = no_llseek,
843         .read           = do_sync_read,
844         .aio_read       = pipe_read,
845         .write          = do_sync_write,
846         .aio_write      = pipe_write,
847         .poll           = pipe_poll,
848         .unlocked_ioctl = pipe_ioctl,
849         .open           = pipe_rdwr_open,
850         .release        = pipe_rdwr_release,
851         .fasync         = pipe_rdwr_fasync,
852 };
853
854 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
855 {
856         struct pipe_inode_info *pipe;
857
858         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
859         if (pipe) {
860                 init_waitqueue_head(&pipe->wait);
861                 pipe->r_counter = pipe->w_counter = 1;
862                 pipe->inode = inode;
863         }
864
865         return pipe;
866 }
867
868 void __free_pipe_info(struct pipe_inode_info *pipe)
869 {
870         int i;
871
872         for (i = 0; i < PIPE_BUFFERS; i++) {
873                 struct pipe_buffer *buf = pipe->bufs + i;
874                 if (buf->ops)
875                         buf->ops->release(pipe, buf);
876         }
877         if (pipe->tmp_page)
878                 __free_page(pipe->tmp_page);
879         kfree(pipe);
880 }
881
882 void free_pipe_info(struct inode *inode)
883 {
884         __free_pipe_info(inode->i_pipe);
885         inode->i_pipe = NULL;
886 }
887
888 static struct vfsmount *pipe_mnt __read_mostly;
889 static int pipefs_delete_dentry(struct dentry *dentry)
890 {
891         /*
892          * At creation time, we pretended this dentry was hashed
893          * (by clearing DCACHE_UNHASHED bit in d_flags)
894          * At delete time, we restore the truth : not hashed.
895          * (so that dput() can proceed correctly)
896          */
897         dentry->d_flags |= DCACHE_UNHASHED;
898         return 0;
899 }
900
901 /*
902  * pipefs_dname() is called from d_path().
903  */
904 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
905 {
906         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
907                                 dentry->d_inode->i_ino);
908 }
909
910 static struct dentry_operations pipefs_dentry_operations = {
911         .d_delete       = pipefs_delete_dentry,
912         .d_dname        = pipefs_dname,
913 };
914
915 static struct inode * get_pipe_inode(void)
916 {
917         struct inode *inode = new_inode(pipe_mnt->mnt_sb);
918         struct pipe_inode_info *pipe;
919
920         if (!inode)
921                 goto fail_inode;
922
923         pipe = alloc_pipe_info(inode);
924         if (!pipe)
925                 goto fail_iput;
926         inode->i_pipe = pipe;
927
928         pipe->readers = pipe->writers = 1;
929         inode->i_fop = &rdwr_pipe_fops;
930
931         /*
932          * Mark the inode dirty from the very beginning,
933          * that way it will never be moved to the dirty
934          * list because "mark_inode_dirty()" will think
935          * that it already _is_ on the dirty list.
936          */
937         inode->i_state = I_DIRTY;
938         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
939         inode->i_uid = current->fsuid;
940         inode->i_gid = current->fsgid;
941         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
942
943         return inode;
944
945 fail_iput:
946         iput(inode);
947
948 fail_inode:
949         return NULL;
950 }
951
952 struct file *create_write_pipe(void)
953 {
954         int err;
955         struct inode *inode;
956         struct file *f;
957         struct dentry *dentry;
958         struct qstr name = { .name = "" };
959
960         f = get_empty_filp();
961         if (!f)
962                 return ERR_PTR(-ENFILE);
963         err = -ENFILE;
964         inode = get_pipe_inode();
965         if (!inode)
966                 goto err_file;
967
968         err = -ENOMEM;
969         dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
970         if (!dentry)
971                 goto err_inode;
972
973         dentry->d_op = &pipefs_dentry_operations;
974         /*
975          * We dont want to publish this dentry into global dentry hash table.
976          * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
977          * This permits a working /proc/$pid/fd/XXX on pipes
978          */
979         dentry->d_flags &= ~DCACHE_UNHASHED;
980         d_instantiate(dentry, inode);
981         f->f_path.mnt = mntget(pipe_mnt);
982         f->f_path.dentry = dentry;
983         f->f_mapping = inode->i_mapping;
984
985         f->f_flags = O_WRONLY;
986         f->f_op = &write_pipe_fops;
987         f->f_mode = FMODE_WRITE;
988         f->f_version = 0;
989
990         return f;
991
992  err_inode:
993         free_pipe_info(inode);
994         iput(inode);
995  err_file:
996         put_filp(f);
997         return ERR_PTR(err);
998 }
999
1000 void free_write_pipe(struct file *f)
1001 {
1002         free_pipe_info(f->f_dentry->d_inode);
1003         dput(f->f_path.dentry);
1004         mntput(f->f_path.mnt);
1005         put_filp(f);
1006 }
1007
1008 struct file *create_read_pipe(struct file *wrf)
1009 {
1010         struct file *f = get_empty_filp();
1011         if (!f)
1012                 return ERR_PTR(-ENFILE);
1013
1014         /* Grab pipe from the writer */
1015         f->f_path.mnt = mntget(wrf->f_path.mnt);
1016         f->f_path.dentry = dget(wrf->f_path.dentry);
1017         f->f_mapping = wrf->f_path.dentry->d_inode->i_mapping;
1018
1019         f->f_pos = 0;
1020         f->f_flags = O_RDONLY;
1021         f->f_op = &read_pipe_fops;
1022         f->f_mode = FMODE_READ;
1023         f->f_version = 0;
1024
1025         return f;
1026 }
1027
1028 int do_pipe(int *fd)
1029 {
1030         struct file *fw, *fr;
1031         int error;
1032         int fdw, fdr;
1033
1034         fw = create_write_pipe();
1035         if (IS_ERR(fw))
1036                 return PTR_ERR(fw);
1037         fr = create_read_pipe(fw);
1038         error = PTR_ERR(fr);
1039         if (IS_ERR(fr))
1040                 goto err_write_pipe;
1041
1042         error = get_unused_fd();
1043         if (error < 0)
1044                 goto err_read_pipe;
1045         fdr = error;
1046
1047         error = get_unused_fd();
1048         if (error < 0)
1049                 goto err_fdr;
1050         fdw = error;
1051
1052         error = audit_fd_pair(fdr, fdw);
1053         if (error < 0)
1054                 goto err_fdw;
1055
1056         fd_install(fdr, fr);
1057         fd_install(fdw, fw);
1058         fd[0] = fdr;
1059         fd[1] = fdw;
1060
1061         return 0;
1062
1063  err_fdw:
1064         put_unused_fd(fdw);
1065  err_fdr:
1066         put_unused_fd(fdr);
1067  err_read_pipe:
1068         dput(fr->f_dentry);
1069         mntput(fr->f_vfsmnt);
1070         put_filp(fr);
1071  err_write_pipe:
1072         free_write_pipe(fw);
1073         return error;
1074 }
1075
1076 /*
1077  * pipefs should _never_ be mounted by userland - too much of security hassle,
1078  * no real gain from having the whole whorehouse mounted. So we don't need
1079  * any operations on the root directory. However, we need a non-trivial
1080  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1081  */
1082 static int pipefs_get_sb(struct file_system_type *fs_type,
1083                          int flags, const char *dev_name, void *data,
1084                          struct vfsmount *mnt)
1085 {
1086         return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
1087 }
1088
1089 static struct file_system_type pipe_fs_type = {
1090         .name           = "pipefs",
1091         .get_sb         = pipefs_get_sb,
1092         .kill_sb        = kill_anon_super,
1093 };
1094
1095 static int __init init_pipe_fs(void)
1096 {
1097         int err = register_filesystem(&pipe_fs_type);
1098
1099         if (!err) {
1100                 pipe_mnt = kern_mount(&pipe_fs_type);
1101                 if (IS_ERR(pipe_mnt)) {
1102                         err = PTR_ERR(pipe_mnt);
1103                         unregister_filesystem(&pipe_fs_type);
1104                 }
1105         }
1106         return err;
1107 }
1108
1109 static void __exit exit_pipe_fs(void)
1110 {
1111         unregister_filesystem(&pipe_fs_type);
1112         mntput(pipe_mnt);
1113 }
1114
1115 fs_initcall(init_pipe_fs);
1116 module_exit(exit_pipe_fs);