consolidate pipe file creation
[linux-3.10.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/log2.h>
15 #include <linux/mount.h>
16 #include <linux/magic.h>
17 #include <linux/pipe_fs_i.h>
18 #include <linux/uio.h>
19 #include <linux/highmem.h>
20 #include <linux/pagemap.h>
21 #include <linux/audit.h>
22 #include <linux/syscalls.h>
23 #include <linux/fcntl.h>
24
25 #include <asm/uaccess.h>
26 #include <asm/ioctls.h>
27
28 /*
29  * The max size that a non-root user is allowed to grow the pipe. Can
30  * be set by root in /proc/sys/fs/pipe-max-size
31  */
32 unsigned int pipe_max_size = 1048576;
33
34 /*
35  * Minimum pipe size, as required by POSIX
36  */
37 unsigned int pipe_min_size = PAGE_SIZE;
38
39 /*
40  * We use a start+len construction, which provides full use of the 
41  * allocated memory.
42  * -- Florian Coosmann (FGC)
43  * 
44  * Reads with count = 0 should always return 0.
45  * -- Julian Bradfield 1999-06-07.
46  *
47  * FIFOs and Pipes now generate SIGIO for both readers and writers.
48  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
49  *
50  * pipe_read & write cleanup
51  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
52  */
53
54 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
55 {
56         if (pipe->inode)
57                 mutex_lock_nested(&pipe->inode->i_mutex, subclass);
58 }
59
60 void pipe_lock(struct pipe_inode_info *pipe)
61 {
62         /*
63          * pipe_lock() nests non-pipe inode locks (for writing to a file)
64          */
65         pipe_lock_nested(pipe, I_MUTEX_PARENT);
66 }
67 EXPORT_SYMBOL(pipe_lock);
68
69 void pipe_unlock(struct pipe_inode_info *pipe)
70 {
71         if (pipe->inode)
72                 mutex_unlock(&pipe->inode->i_mutex);
73 }
74 EXPORT_SYMBOL(pipe_unlock);
75
76 void pipe_double_lock(struct pipe_inode_info *pipe1,
77                       struct pipe_inode_info *pipe2)
78 {
79         BUG_ON(pipe1 == pipe2);
80
81         if (pipe1 < pipe2) {
82                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
83                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
84         } else {
85                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
86                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
87         }
88 }
89
90 /* Drop the inode semaphore and wait for a pipe event, atomically */
91 void pipe_wait(struct pipe_inode_info *pipe)
92 {
93         DEFINE_WAIT(wait);
94
95         /*
96          * Pipes are system-local resources, so sleeping on them
97          * is considered a noninteractive wait:
98          */
99         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
100         pipe_unlock(pipe);
101         schedule();
102         finish_wait(&pipe->wait, &wait);
103         pipe_lock(pipe);
104 }
105
106 static int
107 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
108                         int atomic)
109 {
110         unsigned long copy;
111
112         while (len > 0) {
113                 while (!iov->iov_len)
114                         iov++;
115                 copy = min_t(unsigned long, len, iov->iov_len);
116
117                 if (atomic) {
118                         if (__copy_from_user_inatomic(to, iov->iov_base, copy))
119                                 return -EFAULT;
120                 } else {
121                         if (copy_from_user(to, iov->iov_base, copy))
122                                 return -EFAULT;
123                 }
124                 to += copy;
125                 len -= copy;
126                 iov->iov_base += copy;
127                 iov->iov_len -= copy;
128         }
129         return 0;
130 }
131
132 static int
133 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
134                       int atomic)
135 {
136         unsigned long copy;
137
138         while (len > 0) {
139                 while (!iov->iov_len)
140                         iov++;
141                 copy = min_t(unsigned long, len, iov->iov_len);
142
143                 if (atomic) {
144                         if (__copy_to_user_inatomic(iov->iov_base, from, copy))
145                                 return -EFAULT;
146                 } else {
147                         if (copy_to_user(iov->iov_base, from, copy))
148                                 return -EFAULT;
149                 }
150                 from += copy;
151                 len -= copy;
152                 iov->iov_base += copy;
153                 iov->iov_len -= copy;
154         }
155         return 0;
156 }
157
158 /*
159  * Attempt to pre-fault in the user memory, so we can use atomic copies.
160  * Returns the number of bytes not faulted in.
161  */
162 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
163 {
164         while (!iov->iov_len)
165                 iov++;
166
167         while (len > 0) {
168                 unsigned long this_len;
169
170                 this_len = min_t(unsigned long, len, iov->iov_len);
171                 if (fault_in_pages_writeable(iov->iov_base, this_len))
172                         break;
173
174                 len -= this_len;
175                 iov++;
176         }
177
178         return len;
179 }
180
181 /*
182  * Pre-fault in the user memory, so we can use atomic copies.
183  */
184 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
185 {
186         while (!iov->iov_len)
187                 iov++;
188
189         while (len > 0) {
190                 unsigned long this_len;
191
192                 this_len = min_t(unsigned long, len, iov->iov_len);
193                 fault_in_pages_readable(iov->iov_base, this_len);
194                 len -= this_len;
195                 iov++;
196         }
197 }
198
199 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
200                                   struct pipe_buffer *buf)
201 {
202         struct page *page = buf->page;
203
204         /*
205          * If nobody else uses this page, and we don't already have a
206          * temporary page, let's keep track of it as a one-deep
207          * allocation cache. (Otherwise just release our reference to it)
208          */
209         if (page_count(page) == 1 && !pipe->tmp_page)
210                 pipe->tmp_page = page;
211         else
212                 page_cache_release(page);
213 }
214
215 /**
216  * generic_pipe_buf_map - virtually map a pipe buffer
217  * @pipe:       the pipe that the buffer belongs to
218  * @buf:        the buffer that should be mapped
219  * @atomic:     whether to use an atomic map
220  *
221  * Description:
222  *      This function returns a kernel virtual address mapping for the
223  *      pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
224  *      and the caller has to be careful not to fault before calling
225  *      the unmap function.
226  *
227  *      Note that this function occupies KM_USER0 if @atomic != 0.
228  */
229 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
230                            struct pipe_buffer *buf, int atomic)
231 {
232         if (atomic) {
233                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
234                 return kmap_atomic(buf->page);
235         }
236
237         return kmap(buf->page);
238 }
239 EXPORT_SYMBOL(generic_pipe_buf_map);
240
241 /**
242  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
243  * @pipe:       the pipe that the buffer belongs to
244  * @buf:        the buffer that should be unmapped
245  * @map_data:   the data that the mapping function returned
246  *
247  * Description:
248  *      This function undoes the mapping that ->map() provided.
249  */
250 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
251                             struct pipe_buffer *buf, void *map_data)
252 {
253         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
254                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
255                 kunmap_atomic(map_data);
256         } else
257                 kunmap(buf->page);
258 }
259 EXPORT_SYMBOL(generic_pipe_buf_unmap);
260
261 /**
262  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
263  * @pipe:       the pipe that the buffer belongs to
264  * @buf:        the buffer to attempt to steal
265  *
266  * Description:
267  *      This function attempts to steal the &struct page attached to
268  *      @buf. If successful, this function returns 0 and returns with
269  *      the page locked. The caller may then reuse the page for whatever
270  *      he wishes; the typical use is insertion into a different file
271  *      page cache.
272  */
273 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
274                            struct pipe_buffer *buf)
275 {
276         struct page *page = buf->page;
277
278         /*
279          * A reference of one is golden, that means that the owner of this
280          * page is the only one holding a reference to it. lock the page
281          * and return OK.
282          */
283         if (page_count(page) == 1) {
284                 lock_page(page);
285                 return 0;
286         }
287
288         return 1;
289 }
290 EXPORT_SYMBOL(generic_pipe_buf_steal);
291
292 /**
293  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
294  * @pipe:       the pipe that the buffer belongs to
295  * @buf:        the buffer to get a reference to
296  *
297  * Description:
298  *      This function grabs an extra reference to @buf. It's used in
299  *      in the tee() system call, when we duplicate the buffers in one
300  *      pipe into another.
301  */
302 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
303 {
304         page_cache_get(buf->page);
305 }
306 EXPORT_SYMBOL(generic_pipe_buf_get);
307
308 /**
309  * generic_pipe_buf_confirm - verify contents of the pipe buffer
310  * @info:       the pipe that the buffer belongs to
311  * @buf:        the buffer to confirm
312  *
313  * Description:
314  *      This function does nothing, because the generic pipe code uses
315  *      pages that are always good when inserted into the pipe.
316  */
317 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
318                              struct pipe_buffer *buf)
319 {
320         return 0;
321 }
322 EXPORT_SYMBOL(generic_pipe_buf_confirm);
323
324 /**
325  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
326  * @pipe:       the pipe that the buffer belongs to
327  * @buf:        the buffer to put a reference to
328  *
329  * Description:
330  *      This function releases a reference to @buf.
331  */
332 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
333                               struct pipe_buffer *buf)
334 {
335         page_cache_release(buf->page);
336 }
337 EXPORT_SYMBOL(generic_pipe_buf_release);
338
339 static const struct pipe_buf_operations anon_pipe_buf_ops = {
340         .can_merge = 1,
341         .map = generic_pipe_buf_map,
342         .unmap = generic_pipe_buf_unmap,
343         .confirm = generic_pipe_buf_confirm,
344         .release = anon_pipe_buf_release,
345         .steal = generic_pipe_buf_steal,
346         .get = generic_pipe_buf_get,
347 };
348
349 static const struct pipe_buf_operations packet_pipe_buf_ops = {
350         .can_merge = 0,
351         .map = generic_pipe_buf_map,
352         .unmap = generic_pipe_buf_unmap,
353         .confirm = generic_pipe_buf_confirm,
354         .release = anon_pipe_buf_release,
355         .steal = generic_pipe_buf_steal,
356         .get = generic_pipe_buf_get,
357 };
358
359 static ssize_t
360 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
361            unsigned long nr_segs, loff_t pos)
362 {
363         struct file *filp = iocb->ki_filp;
364         struct inode *inode = filp->f_path.dentry->d_inode;
365         struct pipe_inode_info *pipe;
366         int do_wakeup;
367         ssize_t ret;
368         struct iovec *iov = (struct iovec *)_iov;
369         size_t total_len;
370
371         total_len = iov_length(iov, nr_segs);
372         /* Null read succeeds. */
373         if (unlikely(total_len == 0))
374                 return 0;
375
376         do_wakeup = 0;
377         ret = 0;
378         mutex_lock(&inode->i_mutex);
379         pipe = inode->i_pipe;
380         for (;;) {
381                 int bufs = pipe->nrbufs;
382                 if (bufs) {
383                         int curbuf = pipe->curbuf;
384                         struct pipe_buffer *buf = pipe->bufs + curbuf;
385                         const struct pipe_buf_operations *ops = buf->ops;
386                         void *addr;
387                         size_t chars = buf->len;
388                         int error, atomic;
389
390                         if (chars > total_len)
391                                 chars = total_len;
392
393                         error = ops->confirm(pipe, buf);
394                         if (error) {
395                                 if (!ret)
396                                         ret = error;
397                                 break;
398                         }
399
400                         atomic = !iov_fault_in_pages_write(iov, chars);
401 redo:
402                         addr = ops->map(pipe, buf, atomic);
403                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
404                         ops->unmap(pipe, buf, addr);
405                         if (unlikely(error)) {
406                                 /*
407                                  * Just retry with the slow path if we failed.
408                                  */
409                                 if (atomic) {
410                                         atomic = 0;
411                                         goto redo;
412                                 }
413                                 if (!ret)
414                                         ret = error;
415                                 break;
416                         }
417                         ret += chars;
418                         buf->offset += chars;
419                         buf->len -= chars;
420
421                         /* Was it a packet buffer? Clean up and exit */
422                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
423                                 total_len = chars;
424                                 buf->len = 0;
425                         }
426
427                         if (!buf->len) {
428                                 buf->ops = NULL;
429                                 ops->release(pipe, buf);
430                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
431                                 pipe->curbuf = curbuf;
432                                 pipe->nrbufs = --bufs;
433                                 do_wakeup = 1;
434                         }
435                         total_len -= chars;
436                         if (!total_len)
437                                 break;  /* common path: read succeeded */
438                 }
439                 if (bufs)       /* More to do? */
440                         continue;
441                 if (!pipe->writers)
442                         break;
443                 if (!pipe->waiting_writers) {
444                         /* syscall merging: Usually we must not sleep
445                          * if O_NONBLOCK is set, or if we got some data.
446                          * But if a writer sleeps in kernel space, then
447                          * we can wait for that data without violating POSIX.
448                          */
449                         if (ret)
450                                 break;
451                         if (filp->f_flags & O_NONBLOCK) {
452                                 ret = -EAGAIN;
453                                 break;
454                         }
455                 }
456                 if (signal_pending(current)) {
457                         if (!ret)
458                                 ret = -ERESTARTSYS;
459                         break;
460                 }
461                 if (do_wakeup) {
462                         wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
463                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
464                 }
465                 pipe_wait(pipe);
466         }
467         mutex_unlock(&inode->i_mutex);
468
469         /* Signal writers asynchronously that there is more room. */
470         if (do_wakeup) {
471                 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
472                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
473         }
474         if (ret > 0)
475                 file_accessed(filp);
476         return ret;
477 }
478
479 static inline int is_packetized(struct file *file)
480 {
481         return (file->f_flags & O_DIRECT) != 0;
482 }
483
484 static ssize_t
485 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
486             unsigned long nr_segs, loff_t ppos)
487 {
488         struct file *filp = iocb->ki_filp;
489         struct inode *inode = filp->f_path.dentry->d_inode;
490         struct pipe_inode_info *pipe;
491         ssize_t ret;
492         int do_wakeup;
493         struct iovec *iov = (struct iovec *)_iov;
494         size_t total_len;
495         ssize_t chars;
496
497         total_len = iov_length(iov, nr_segs);
498         /* Null write succeeds. */
499         if (unlikely(total_len == 0))
500                 return 0;
501
502         do_wakeup = 0;
503         ret = 0;
504         mutex_lock(&inode->i_mutex);
505         pipe = inode->i_pipe;
506
507         if (!pipe->readers) {
508                 send_sig(SIGPIPE, current, 0);
509                 ret = -EPIPE;
510                 goto out;
511         }
512
513         /* We try to merge small writes */
514         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
515         if (pipe->nrbufs && chars != 0) {
516                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
517                                                         (pipe->buffers - 1);
518                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
519                 const struct pipe_buf_operations *ops = buf->ops;
520                 int offset = buf->offset + buf->len;
521
522                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
523                         int error, atomic = 1;
524                         void *addr;
525
526                         error = ops->confirm(pipe, buf);
527                         if (error)
528                                 goto out;
529
530                         iov_fault_in_pages_read(iov, chars);
531 redo1:
532                         addr = ops->map(pipe, buf, atomic);
533                         error = pipe_iov_copy_from_user(offset + addr, iov,
534                                                         chars, atomic);
535                         ops->unmap(pipe, buf, addr);
536                         ret = error;
537                         do_wakeup = 1;
538                         if (error) {
539                                 if (atomic) {
540                                         atomic = 0;
541                                         goto redo1;
542                                 }
543                                 goto out;
544                         }
545                         buf->len += chars;
546                         total_len -= chars;
547                         ret = chars;
548                         if (!total_len)
549                                 goto out;
550                 }
551         }
552
553         for (;;) {
554                 int bufs;
555
556                 if (!pipe->readers) {
557                         send_sig(SIGPIPE, current, 0);
558                         if (!ret)
559                                 ret = -EPIPE;
560                         break;
561                 }
562                 bufs = pipe->nrbufs;
563                 if (bufs < pipe->buffers) {
564                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
565                         struct pipe_buffer *buf = pipe->bufs + newbuf;
566                         struct page *page = pipe->tmp_page;
567                         char *src;
568                         int error, atomic = 1;
569
570                         if (!page) {
571                                 page = alloc_page(GFP_HIGHUSER);
572                                 if (unlikely(!page)) {
573                                         ret = ret ? : -ENOMEM;
574                                         break;
575                                 }
576                                 pipe->tmp_page = page;
577                         }
578                         /* Always wake up, even if the copy fails. Otherwise
579                          * we lock up (O_NONBLOCK-)readers that sleep due to
580                          * syscall merging.
581                          * FIXME! Is this really true?
582                          */
583                         do_wakeup = 1;
584                         chars = PAGE_SIZE;
585                         if (chars > total_len)
586                                 chars = total_len;
587
588                         iov_fault_in_pages_read(iov, chars);
589 redo2:
590                         if (atomic)
591                                 src = kmap_atomic(page);
592                         else
593                                 src = kmap(page);
594
595                         error = pipe_iov_copy_from_user(src, iov, chars,
596                                                         atomic);
597                         if (atomic)
598                                 kunmap_atomic(src);
599                         else
600                                 kunmap(page);
601
602                         if (unlikely(error)) {
603                                 if (atomic) {
604                                         atomic = 0;
605                                         goto redo2;
606                                 }
607                                 if (!ret)
608                                         ret = error;
609                                 break;
610                         }
611                         ret += chars;
612
613                         /* Insert it into the buffer array */
614                         buf->page = page;
615                         buf->ops = &anon_pipe_buf_ops;
616                         buf->offset = 0;
617                         buf->len = chars;
618                         buf->flags = 0;
619                         if (is_packetized(filp)) {
620                                 buf->ops = &packet_pipe_buf_ops;
621                                 buf->flags = PIPE_BUF_FLAG_PACKET;
622                         }
623                         pipe->nrbufs = ++bufs;
624                         pipe->tmp_page = NULL;
625
626                         total_len -= chars;
627                         if (!total_len)
628                                 break;
629                 }
630                 if (bufs < pipe->buffers)
631                         continue;
632                 if (filp->f_flags & O_NONBLOCK) {
633                         if (!ret)
634                                 ret = -EAGAIN;
635                         break;
636                 }
637                 if (signal_pending(current)) {
638                         if (!ret)
639                                 ret = -ERESTARTSYS;
640                         break;
641                 }
642                 if (do_wakeup) {
643                         wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
644                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
645                         do_wakeup = 0;
646                 }
647                 pipe->waiting_writers++;
648                 pipe_wait(pipe);
649                 pipe->waiting_writers--;
650         }
651 out:
652         mutex_unlock(&inode->i_mutex);
653         if (do_wakeup) {
654                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
655                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
656         }
657         if (ret > 0) {
658                 int err = file_update_time(filp);
659                 if (err)
660                         ret = err;
661         }
662         return ret;
663 }
664
665 static ssize_t
666 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
667 {
668         return -EBADF;
669 }
670
671 static ssize_t
672 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
673            loff_t *ppos)
674 {
675         return -EBADF;
676 }
677
678 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
679 {
680         struct inode *inode = filp->f_path.dentry->d_inode;
681         struct pipe_inode_info *pipe;
682         int count, buf, nrbufs;
683
684         switch (cmd) {
685                 case FIONREAD:
686                         mutex_lock(&inode->i_mutex);
687                         pipe = inode->i_pipe;
688                         count = 0;
689                         buf = pipe->curbuf;
690                         nrbufs = pipe->nrbufs;
691                         while (--nrbufs >= 0) {
692                                 count += pipe->bufs[buf].len;
693                                 buf = (buf+1) & (pipe->buffers - 1);
694                         }
695                         mutex_unlock(&inode->i_mutex);
696
697                         return put_user(count, (int __user *)arg);
698                 default:
699                         return -ENOIOCTLCMD;
700         }
701 }
702
703 /* No kernel lock held - fine */
704 static unsigned int
705 pipe_poll(struct file *filp, poll_table *wait)
706 {
707         unsigned int mask;
708         struct inode *inode = filp->f_path.dentry->d_inode;
709         struct pipe_inode_info *pipe = inode->i_pipe;
710         int nrbufs;
711
712         poll_wait(filp, &pipe->wait, wait);
713
714         /* Reading only -- no need for acquiring the semaphore.  */
715         nrbufs = pipe->nrbufs;
716         mask = 0;
717         if (filp->f_mode & FMODE_READ) {
718                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
719                 if (!pipe->writers && filp->f_version != pipe->w_counter)
720                         mask |= POLLHUP;
721         }
722
723         if (filp->f_mode & FMODE_WRITE) {
724                 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
725                 /*
726                  * Most Unices do not set POLLERR for FIFOs but on Linux they
727                  * behave exactly like pipes for poll().
728                  */
729                 if (!pipe->readers)
730                         mask |= POLLERR;
731         }
732
733         return mask;
734 }
735
736 static int
737 pipe_release(struct inode *inode, int decr, int decw)
738 {
739         struct pipe_inode_info *pipe;
740
741         mutex_lock(&inode->i_mutex);
742         pipe = inode->i_pipe;
743         pipe->readers -= decr;
744         pipe->writers -= decw;
745
746         if (!pipe->readers && !pipe->writers) {
747                 free_pipe_info(inode);
748         } else {
749                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
750                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
751                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
752         }
753         mutex_unlock(&inode->i_mutex);
754
755         return 0;
756 }
757
758 static int
759 pipe_read_fasync(int fd, struct file *filp, int on)
760 {
761         struct inode *inode = filp->f_path.dentry->d_inode;
762         int retval;
763
764         mutex_lock(&inode->i_mutex);
765         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
766         mutex_unlock(&inode->i_mutex);
767
768         return retval;
769 }
770
771
772 static int
773 pipe_write_fasync(int fd, struct file *filp, int on)
774 {
775         struct inode *inode = filp->f_path.dentry->d_inode;
776         int retval;
777
778         mutex_lock(&inode->i_mutex);
779         retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
780         mutex_unlock(&inode->i_mutex);
781
782         return retval;
783 }
784
785
786 static int
787 pipe_rdwr_fasync(int fd, struct file *filp, int on)
788 {
789         struct inode *inode = filp->f_path.dentry->d_inode;
790         struct pipe_inode_info *pipe = inode->i_pipe;
791         int retval;
792
793         mutex_lock(&inode->i_mutex);
794         retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
795         if (retval >= 0) {
796                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
797                 if (retval < 0) /* this can happen only if on == T */
798                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
799         }
800         mutex_unlock(&inode->i_mutex);
801         return retval;
802 }
803
804
805 static int
806 pipe_read_release(struct inode *inode, struct file *filp)
807 {
808         return pipe_release(inode, 1, 0);
809 }
810
811 static int
812 pipe_write_release(struct inode *inode, struct file *filp)
813 {
814         return pipe_release(inode, 0, 1);
815 }
816
817 static int
818 pipe_rdwr_release(struct inode *inode, struct file *filp)
819 {
820         int decr, decw;
821
822         decr = (filp->f_mode & FMODE_READ) != 0;
823         decw = (filp->f_mode & FMODE_WRITE) != 0;
824         return pipe_release(inode, decr, decw);
825 }
826
827 static int
828 pipe_read_open(struct inode *inode, struct file *filp)
829 {
830         int ret = -ENOENT;
831
832         mutex_lock(&inode->i_mutex);
833
834         if (inode->i_pipe) {
835                 ret = 0;
836                 inode->i_pipe->readers++;
837         }
838
839         mutex_unlock(&inode->i_mutex);
840
841         return ret;
842 }
843
844 static int
845 pipe_write_open(struct inode *inode, struct file *filp)
846 {
847         int ret = -ENOENT;
848
849         mutex_lock(&inode->i_mutex);
850
851         if (inode->i_pipe) {
852                 ret = 0;
853                 inode->i_pipe->writers++;
854         }
855
856         mutex_unlock(&inode->i_mutex);
857
858         return ret;
859 }
860
861 static int
862 pipe_rdwr_open(struct inode *inode, struct file *filp)
863 {
864         int ret = -ENOENT;
865
866         mutex_lock(&inode->i_mutex);
867
868         if (inode->i_pipe) {
869                 ret = 0;
870                 if (filp->f_mode & FMODE_READ)
871                         inode->i_pipe->readers++;
872                 if (filp->f_mode & FMODE_WRITE)
873                         inode->i_pipe->writers++;
874         }
875
876         mutex_unlock(&inode->i_mutex);
877
878         return ret;
879 }
880
881 /*
882  * The file_operations structs are not static because they
883  * are also used in linux/fs/fifo.c to do operations on FIFOs.
884  *
885  * Pipes reuse fifos' file_operations structs.
886  */
887 const struct file_operations read_pipefifo_fops = {
888         .llseek         = no_llseek,
889         .read           = do_sync_read,
890         .aio_read       = pipe_read,
891         .write          = bad_pipe_w,
892         .poll           = pipe_poll,
893         .unlocked_ioctl = pipe_ioctl,
894         .open           = pipe_read_open,
895         .release        = pipe_read_release,
896         .fasync         = pipe_read_fasync,
897 };
898
899 const struct file_operations write_pipefifo_fops = {
900         .llseek         = no_llseek,
901         .read           = bad_pipe_r,
902         .write          = do_sync_write,
903         .aio_write      = pipe_write,
904         .poll           = pipe_poll,
905         .unlocked_ioctl = pipe_ioctl,
906         .open           = pipe_write_open,
907         .release        = pipe_write_release,
908         .fasync         = pipe_write_fasync,
909 };
910
911 const struct file_operations rdwr_pipefifo_fops = {
912         .llseek         = no_llseek,
913         .read           = do_sync_read,
914         .aio_read       = pipe_read,
915         .write          = do_sync_write,
916         .aio_write      = pipe_write,
917         .poll           = pipe_poll,
918         .unlocked_ioctl = pipe_ioctl,
919         .open           = pipe_rdwr_open,
920         .release        = pipe_rdwr_release,
921         .fasync         = pipe_rdwr_fasync,
922 };
923
924 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
925 {
926         struct pipe_inode_info *pipe;
927
928         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
929         if (pipe) {
930                 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
931                 if (pipe->bufs) {
932                         init_waitqueue_head(&pipe->wait);
933                         pipe->r_counter = pipe->w_counter = 1;
934                         pipe->inode = inode;
935                         pipe->buffers = PIPE_DEF_BUFFERS;
936                         return pipe;
937                 }
938                 kfree(pipe);
939         }
940
941         return NULL;
942 }
943
944 void __free_pipe_info(struct pipe_inode_info *pipe)
945 {
946         int i;
947
948         for (i = 0; i < pipe->buffers; i++) {
949                 struct pipe_buffer *buf = pipe->bufs + i;
950                 if (buf->ops)
951                         buf->ops->release(pipe, buf);
952         }
953         if (pipe->tmp_page)
954                 __free_page(pipe->tmp_page);
955         kfree(pipe->bufs);
956         kfree(pipe);
957 }
958
959 void free_pipe_info(struct inode *inode)
960 {
961         __free_pipe_info(inode->i_pipe);
962         inode->i_pipe = NULL;
963 }
964
965 static struct vfsmount *pipe_mnt __read_mostly;
966
967 /*
968  * pipefs_dname() is called from d_path().
969  */
970 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
971 {
972         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
973                                 dentry->d_inode->i_ino);
974 }
975
976 static const struct dentry_operations pipefs_dentry_operations = {
977         .d_dname        = pipefs_dname,
978 };
979
980 static struct inode * get_pipe_inode(void)
981 {
982         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
983         struct pipe_inode_info *pipe;
984
985         if (!inode)
986                 goto fail_inode;
987
988         inode->i_ino = get_next_ino();
989
990         pipe = alloc_pipe_info(inode);
991         if (!pipe)
992                 goto fail_iput;
993         inode->i_pipe = pipe;
994
995         pipe->readers = pipe->writers = 1;
996         inode->i_fop = &rdwr_pipefifo_fops;
997
998         /*
999          * Mark the inode dirty from the very beginning,
1000          * that way it will never be moved to the dirty
1001          * list because "mark_inode_dirty()" will think
1002          * that it already _is_ on the dirty list.
1003          */
1004         inode->i_state = I_DIRTY;
1005         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
1006         inode->i_uid = current_fsuid();
1007         inode->i_gid = current_fsgid();
1008         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1009
1010         return inode;
1011
1012 fail_iput:
1013         iput(inode);
1014
1015 fail_inode:
1016         return NULL;
1017 }
1018
1019 int create_pipe_files(struct file **res, int flags)
1020 {
1021         int err;
1022         struct inode *inode = get_pipe_inode();
1023         struct file *f;
1024         struct path path;
1025         static struct qstr name = { .name = "" };
1026
1027         if (!inode)
1028                 return -ENFILE;
1029
1030         err = -ENOMEM;
1031         path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
1032         if (!path.dentry)
1033                 goto err_inode;
1034         path.mnt = mntget(pipe_mnt);
1035
1036         d_instantiate(path.dentry, inode);
1037
1038         err = -ENFILE;
1039         f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
1040         if (!f)
1041                 goto err_dentry;
1042
1043         f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
1044
1045         res[0] = alloc_file(&path, FMODE_READ, &read_pipefifo_fops);
1046         if (!res[0])
1047                 goto err_file;
1048
1049         path_get(&path);
1050         res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
1051         res[1] = f;
1052         return 0;
1053
1054 err_file:
1055         put_filp(f);
1056 err_dentry:
1057         free_pipe_info(inode);
1058         path_put(&path);
1059         return err;
1060
1061 err_inode:
1062         free_pipe_info(inode);
1063         iput(inode);
1064         return err;
1065 }
1066
1067 int do_pipe_flags(int *fd, int flags)
1068 {
1069         struct file *files[2];
1070         int error;
1071         int fdw, fdr;
1072
1073         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
1074                 return -EINVAL;
1075
1076         error = create_pipe_files(files, flags);
1077         if (error)
1078                 return error;
1079
1080         error = get_unused_fd_flags(flags);
1081         if (error < 0)
1082                 goto err_read_pipe;
1083         fdr = error;
1084
1085         error = get_unused_fd_flags(flags);
1086         if (error < 0)
1087                 goto err_fdr;
1088         fdw = error;
1089
1090         audit_fd_pair(fdr, fdw);
1091         fd_install(fdr, files[0]);
1092         fd_install(fdw, files[1]);
1093         fd[0] = fdr;
1094         fd[1] = fdw;
1095
1096         return 0;
1097
1098  err_fdr:
1099         put_unused_fd(fdr);
1100  err_read_pipe:
1101         fput(files[0]);
1102         fput(files[1]);
1103         return error;
1104 }
1105
1106 /*
1107  * sys_pipe() is the normal C calling standard for creating
1108  * a pipe. It's not the way Unix traditionally does this, though.
1109  */
1110 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1111 {
1112         int fd[2];
1113         int error;
1114
1115         error = do_pipe_flags(fd, flags);
1116         if (!error) {
1117                 if (copy_to_user(fildes, fd, sizeof(fd))) {
1118                         sys_close(fd[0]);
1119                         sys_close(fd[1]);
1120                         error = -EFAULT;
1121                 }
1122         }
1123         return error;
1124 }
1125
1126 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1127 {
1128         return sys_pipe2(fildes, 0);
1129 }
1130
1131 /*
1132  * Allocate a new array of pipe buffers and copy the info over. Returns the
1133  * pipe size if successful, or return -ERROR on error.
1134  */
1135 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1136 {
1137         struct pipe_buffer *bufs;
1138
1139         /*
1140          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1141          * expect a lot of shrink+grow operations, just free and allocate
1142          * again like we would do for growing. If the pipe currently
1143          * contains more buffers than arg, then return busy.
1144          */
1145         if (nr_pages < pipe->nrbufs)
1146                 return -EBUSY;
1147
1148         bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
1149         if (unlikely(!bufs))
1150                 return -ENOMEM;
1151
1152         /*
1153          * The pipe array wraps around, so just start the new one at zero
1154          * and adjust the indexes.
1155          */
1156         if (pipe->nrbufs) {
1157                 unsigned int tail;
1158                 unsigned int head;
1159
1160                 tail = pipe->curbuf + pipe->nrbufs;
1161                 if (tail < pipe->buffers)
1162                         tail = 0;
1163                 else
1164                         tail &= (pipe->buffers - 1);
1165
1166                 head = pipe->nrbufs - tail;
1167                 if (head)
1168                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1169                 if (tail)
1170                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1171         }
1172
1173         pipe->curbuf = 0;
1174         kfree(pipe->bufs);
1175         pipe->bufs = bufs;
1176         pipe->buffers = nr_pages;
1177         return nr_pages * PAGE_SIZE;
1178 }
1179
1180 /*
1181  * Currently we rely on the pipe array holding a power-of-2 number
1182  * of pages.
1183  */
1184 static inline unsigned int round_pipe_size(unsigned int size)
1185 {
1186         unsigned long nr_pages;
1187
1188         nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1189         return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1190 }
1191
1192 /*
1193  * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1194  * will return an error.
1195  */
1196 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1197                  size_t *lenp, loff_t *ppos)
1198 {
1199         int ret;
1200
1201         ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1202         if (ret < 0 || !write)
1203                 return ret;
1204
1205         pipe_max_size = round_pipe_size(pipe_max_size);
1206         return ret;
1207 }
1208
1209 /*
1210  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1211  * location, so checking ->i_pipe is not enough to verify that this is a
1212  * pipe.
1213  */
1214 struct pipe_inode_info *get_pipe_info(struct file *file)
1215 {
1216         struct inode *i = file->f_path.dentry->d_inode;
1217
1218         return S_ISFIFO(i->i_mode) ? i->i_pipe : NULL;
1219 }
1220
1221 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1222 {
1223         struct pipe_inode_info *pipe;
1224         long ret;
1225
1226         pipe = get_pipe_info(file);
1227         if (!pipe)
1228                 return -EBADF;
1229
1230         mutex_lock(&pipe->inode->i_mutex);
1231
1232         switch (cmd) {
1233         case F_SETPIPE_SZ: {
1234                 unsigned int size, nr_pages;
1235
1236                 size = round_pipe_size(arg);
1237                 nr_pages = size >> PAGE_SHIFT;
1238
1239                 ret = -EINVAL;
1240                 if (!nr_pages)
1241                         goto out;
1242
1243                 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1244                         ret = -EPERM;
1245                         goto out;
1246                 }
1247                 ret = pipe_set_size(pipe, nr_pages);
1248                 break;
1249                 }
1250         case F_GETPIPE_SZ:
1251                 ret = pipe->buffers * PAGE_SIZE;
1252                 break;
1253         default:
1254                 ret = -EINVAL;
1255                 break;
1256         }
1257
1258 out:
1259         mutex_unlock(&pipe->inode->i_mutex);
1260         return ret;
1261 }
1262
1263 static const struct super_operations pipefs_ops = {
1264         .destroy_inode = free_inode_nonrcu,
1265         .statfs = simple_statfs,
1266 };
1267
1268 /*
1269  * pipefs should _never_ be mounted by userland - too much of security hassle,
1270  * no real gain from having the whole whorehouse mounted. So we don't need
1271  * any operations on the root directory. However, we need a non-trivial
1272  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1273  */
1274 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1275                          int flags, const char *dev_name, void *data)
1276 {
1277         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1278                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1279 }
1280
1281 static struct file_system_type pipe_fs_type = {
1282         .name           = "pipefs",
1283         .mount          = pipefs_mount,
1284         .kill_sb        = kill_anon_super,
1285 };
1286
1287 static int __init init_pipe_fs(void)
1288 {
1289         int err = register_filesystem(&pipe_fs_type);
1290
1291         if (!err) {
1292                 pipe_mnt = kern_mount(&pipe_fs_type);
1293                 if (IS_ERR(pipe_mnt)) {
1294                         err = PTR_ERR(pipe_mnt);
1295                         unregister_filesystem(&pipe_fs_type);
1296                 }
1297         }
1298         return err;
1299 }
1300
1301 fs_initcall(init_pipe_fs);