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Merge master.kernel.org:/pub/scm/linux/kernel/git/davem/sparc-2.6
[linux-2.6/kvm.git] / fs / pipe.c
blob68090e84f589305ebe80ee57e723c86494ca6143
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
20 #include <asm/uaccess.h>
21 #include <asm/ioctls.h>
22
23 /*
24 * We use a start+len construction, which provides full use of the
25 * allocated memory.
26 * -- Florian Coosmann (FGC)
27 *
28 * Reads with count = 0 should always return 0.
29 * -- Julian Bradfield 1999-06-07.
30 *
31 * FIFOs and Pipes now generate SIGIO for both readers and writers.
32 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
33 *
34 * pipe_read & write cleanup
35 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
36 */
37
38 /* Drop the inode semaphore and wait for a pipe event, atomically */
39 void pipe_wait(struct pipe_inode_info *pipe)
40 {
41 DEFINE_WAIT(wait);
42
43 /*
44 * Pipes are system-local resources, so sleeping on them
45 * is considered a noninteractive wait:
46 */
47 prepare_to_wait(&pipe->wait, &wait,
48 TASK_INTERRUPTIBLE | TASK_NONINTERACTIVE);
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 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
167 struct pipe_buffer *buf, int atomic)
168 {
169 if (atomic) {
170 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
171 return kmap_atomic(buf->page, KM_USER0);
172 }
173
174 return kmap(buf->page);
175 }
176
177 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
178 struct pipe_buffer *buf, void *map_data)
179 {
180 if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
181 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
182 kunmap_atomic(map_data, KM_USER0);
183 } else
184 kunmap(buf->page);
185 }
186
187 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
188 struct pipe_buffer *buf)
189 {
190 struct page *page = buf->page;
191
192 if (page_count(page) == 1) {
193 lock_page(page);
194 return 0;
195 }
196
197 return 1;
198 }
199
200 void generic_pipe_buf_get(struct pipe_inode_info *info, struct pipe_buffer *buf)
201 {
202 page_cache_get(buf->page);
203 }
204
205 int generic_pipe_buf_pin(struct pipe_inode_info *info, struct pipe_buffer *buf)
206 {
207 return 0;
208 }
209
210 static const struct pipe_buf_operations anon_pipe_buf_ops = {
211 .can_merge = 1,
212 .map = generic_pipe_buf_map,
213 .unmap = generic_pipe_buf_unmap,
214 .pin = generic_pipe_buf_pin,
215 .release = anon_pipe_buf_release,
216 .steal = generic_pipe_buf_steal,
217 .get = generic_pipe_buf_get,
218 };
219
220 static ssize_t
221 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
222 unsigned long nr_segs, loff_t pos)
223 {
224 struct file *filp = iocb->ki_filp;
225 struct inode *inode = filp->f_path.dentry->d_inode;
226 struct pipe_inode_info *pipe;
227 int do_wakeup;
228 ssize_t ret;
229 struct iovec *iov = (struct iovec *)_iov;
230 size_t total_len;
231
232 total_len = iov_length(iov, nr_segs);
233 /* Null read succeeds. */
234 if (unlikely(total_len == 0))
235 return 0;
236
237 do_wakeup = 0;
238 ret = 0;
239 mutex_lock(&inode->i_mutex);
240 pipe = inode->i_pipe;
241 for (;;) {
242 int bufs = pipe->nrbufs;
243 if (bufs) {
244 int curbuf = pipe->curbuf;
245 struct pipe_buffer *buf = pipe->bufs + curbuf;
246 const struct pipe_buf_operations *ops = buf->ops;
247 void *addr;
248 size_t chars = buf->len;
249 int error, atomic;
250
251 if (chars > total_len)
252 chars = total_len;
253
254 error = ops->pin(pipe, buf);
255 if (error) {
256 if (!ret)
257 error = ret;
258 break;
259 }
260
261 atomic = !iov_fault_in_pages_write(iov, chars);
262 redo:
263 addr = ops->map(pipe, buf, atomic);
264 error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
265 ops->unmap(pipe, buf, addr);
266 if (unlikely(error)) {
267 /*
268 * Just retry with the slow path if we failed.
269 */
270 if (atomic) {
271 atomic = 0;
272 goto redo;
273 }
274 if (!ret)
275 ret = error;
276 break;
277 }
278 ret += chars;
279 buf->offset += chars;
280 buf->len -= chars;
281 if (!buf->len) {
282 buf->ops = NULL;
283 ops->release(pipe, buf);
284 curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
285 pipe->curbuf = curbuf;
286 pipe->nrbufs = --bufs;
287 do_wakeup = 1;
288 }
289 total_len -= chars;
290 if (!total_len)
291 break; /* common path: read succeeded */
292 }
293 if (bufs) /* More to do? */
294 continue;
295 if (!pipe->writers)
296 break;
297 if (!pipe->waiting_writers) {
298 /* syscall merging: Usually we must not sleep
299 * if O_NONBLOCK is set, or if we got some data.
300 * But if a writer sleeps in kernel space, then
301 * we can wait for that data without violating POSIX.
302 */
303 if (ret)
304 break;
305 if (filp->f_flags & O_NONBLOCK) {
306 ret = -EAGAIN;
307 break;
308 }
309 }
310 if (signal_pending(current)) {
311 if (!ret)
312 ret = -ERESTARTSYS;
313 break;
314 }
315 if (do_wakeup) {
316 wake_up_interruptible_sync(&pipe->wait);
317 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
318 }
319 pipe_wait(pipe);
320 }
321 mutex_unlock(&inode->i_mutex);
322
323 /* Signal writers asynchronously that there is more room. */
324 if (do_wakeup) {
325 wake_up_interruptible(&pipe->wait);
326 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
327 }
328 if (ret > 0)
329 file_accessed(filp);
330 return ret;
331 }
332
333 static ssize_t
334 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
335 unsigned long nr_segs, loff_t ppos)
336 {
337 struct file *filp = iocb->ki_filp;
338 struct inode *inode = filp->f_path.dentry->d_inode;
339 struct pipe_inode_info *pipe;
340 ssize_t ret;
341 int do_wakeup;
342 struct iovec *iov = (struct iovec *)_iov;
343 size_t total_len;
344 ssize_t chars;
345
346 total_len = iov_length(iov, nr_segs);
347 /* Null write succeeds. */
348 if (unlikely(total_len == 0))
349 return 0;
350
351 do_wakeup = 0;
352 ret = 0;
353 mutex_lock(&inode->i_mutex);
354 pipe = inode->i_pipe;
355
356 if (!pipe->readers) {
357 send_sig(SIGPIPE, current, 0);
358 ret = -EPIPE;
359 goto out;
360 }
361
362 /* We try to merge small writes */
363 chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
364 if (pipe->nrbufs && chars != 0) {
365 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
366 (PIPE_BUFFERS-1);
367 struct pipe_buffer *buf = pipe->bufs + lastbuf;
368 const struct pipe_buf_operations *ops = buf->ops;
369 int offset = buf->offset + buf->len;
370
371 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
372 int error, atomic = 1;
373 void *addr;
374
375 error = ops->pin(pipe, buf);
376 if (error)
377 goto out;
378
379 iov_fault_in_pages_read(iov, chars);
380 redo1:
381 addr = ops->map(pipe, buf, atomic);
382 error = pipe_iov_copy_from_user(offset + addr, iov,
383 chars, atomic);
384 ops->unmap(pipe, buf, addr);
385 ret = error;
386 do_wakeup = 1;
387 if (error) {
388 if (atomic) {
389 atomic = 0;
390 goto redo1;
391 }
392 goto out;
393 }
394 buf->len += chars;
395 total_len -= chars;
396 ret = chars;
397 if (!total_len)
398 goto out;
399 }
400 }
401
402 for (;;) {
403 int bufs;
404
405 if (!pipe->readers) {
406 send_sig(SIGPIPE, current, 0);
407 if (!ret)
408 ret = -EPIPE;
409 break;
410 }
411 bufs = pipe->nrbufs;
412 if (bufs < PIPE_BUFFERS) {
413 int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1);
414 struct pipe_buffer *buf = pipe->bufs + newbuf;
415 struct page *page = pipe->tmp_page;
416 char *src;
417 int error, atomic = 1;
418
419 if (!page) {
420 page = alloc_page(GFP_HIGHUSER);
421 if (unlikely(!page)) {
422 ret = ret ? : -ENOMEM;
423 break;
424 }
425 pipe->tmp_page = page;
426 }
427 /* Always wake up, even if the copy fails. Otherwise
428 * we lock up (O_NONBLOCK-)readers that sleep due to
429 * syscall merging.
430 * FIXME! Is this really true?
431 */
432 do_wakeup = 1;
433 chars = PAGE_SIZE;
434 if (chars > total_len)
435 chars = total_len;
436
437 iov_fault_in_pages_read(iov, chars);
438 redo2:
439 if (atomic)
440 src = kmap_atomic(page, KM_USER0);
441 else
442 src = kmap(page);
443
444 error = pipe_iov_copy_from_user(src, iov, chars,
445 atomic);
446 if (atomic)
447 kunmap_atomic(src, KM_USER0);
448 else
449 kunmap(page);
450
451 if (unlikely(error)) {
452 if (atomic) {
453 atomic = 0;
454 goto redo2;
455 }
456 if (!ret)
457 ret = error;
458 break;
459 }
460 ret += chars;
461
462 /* Insert it into the buffer array */
463 buf->page = page;
464 buf->ops = &anon_pipe_buf_ops;
465 buf->offset = 0;
466 buf->len = chars;
467 pipe->nrbufs = ++bufs;
468 pipe->tmp_page = NULL;
469
470 total_len -= chars;
471 if (!total_len)
472 break;
473 }
474 if (bufs < PIPE_BUFFERS)
475 continue;
476 if (filp->f_flags & O_NONBLOCK) {
477 if (!ret)
478 ret = -EAGAIN;
479 break;
480 }
481 if (signal_pending(current)) {
482 if (!ret)
483 ret = -ERESTARTSYS;
484 break;
485 }
486 if (do_wakeup) {
487 wake_up_interruptible_sync(&pipe->wait);
488 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
489 do_wakeup = 0;
490 }
491 pipe->waiting_writers++;
492 pipe_wait(pipe);
493 pipe->waiting_writers--;
494 }
495 out:
496 mutex_unlock(&inode->i_mutex);
497 if (do_wakeup) {
498 wake_up_interruptible(&pipe->wait);
499 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
500 }
501 if (ret > 0)
502 file_update_time(filp);
503 return ret;
504 }
505
506 static ssize_t
507 bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
508 {
509 return -EBADF;
510 }
511
512 static ssize_t
513 bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
514 loff_t *ppos)
515 {
516 return -EBADF;
517 }
518
519 static int
520 pipe_ioctl(struct inode *pino, struct file *filp,
521 unsigned int cmd, unsigned long arg)
522 {
523 struct inode *inode = filp->f_path.dentry->d_inode;
524 struct pipe_inode_info *pipe;
525 int count, buf, nrbufs;
526
527 switch (cmd) {
528 case FIONREAD:
529 mutex_lock(&inode->i_mutex);
530 pipe = inode->i_pipe;
531 count = 0;
532 buf = pipe->curbuf;
533 nrbufs = pipe->nrbufs;
534 while (--nrbufs >= 0) {
535 count += pipe->bufs[buf].len;
536 buf = (buf+1) & (PIPE_BUFFERS-1);
537 }
538 mutex_unlock(&inode->i_mutex);
539
540 return put_user(count, (int __user *)arg);
541 default:
542 return -EINVAL;
543 }
544 }
545
546 /* No kernel lock held - fine */
547 static unsigned int
548 pipe_poll(struct file *filp, poll_table *wait)
549 {
550 unsigned int mask;
551 struct inode *inode = filp->f_path.dentry->d_inode;
552 struct pipe_inode_info *pipe = inode->i_pipe;
553 int nrbufs;
554
555 poll_wait(filp, &pipe->wait, wait);
556
557 /* Reading only -- no need for acquiring the semaphore. */
558 nrbufs = pipe->nrbufs;
559 mask = 0;
560 if (filp->f_mode & FMODE_READ) {
561 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
562 if (!pipe->writers && filp->f_version != pipe->w_counter)
563 mask |= POLLHUP;
564 }
565
566 if (filp->f_mode & FMODE_WRITE) {
567 mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
568 /*
569 * Most Unices do not set POLLERR for FIFOs but on Linux they
570 * behave exactly like pipes for poll().
571 */
572 if (!pipe->readers)
573 mask |= POLLERR;
574 }
575
576 return mask;
577 }
578
579 static int
580 pipe_release(struct inode *inode, int decr, int decw)
581 {
582 struct pipe_inode_info *pipe;
583
584 mutex_lock(&inode->i_mutex);
585 pipe = inode->i_pipe;
586 pipe->readers -= decr;
587 pipe->writers -= decw;
588
589 if (!pipe->readers && !pipe->writers) {
590 free_pipe_info(inode);
591 } else {
592 wake_up_interruptible(&pipe->wait);
593 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
594 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
595 }
596 mutex_unlock(&inode->i_mutex);
597
598 return 0;
599 }
600
601 static int
602 pipe_read_fasync(int fd, struct file *filp, int on)
603 {
604 struct inode *inode = filp->f_path.dentry->d_inode;
605 int retval;
606
607 mutex_lock(&inode->i_mutex);
608 retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
609 mutex_unlock(&inode->i_mutex);
610
611 if (retval < 0)
612 return retval;
613
614 return 0;
615 }
616
617
618 static int
619 pipe_write_fasync(int fd, struct file *filp, int on)
620 {
621 struct inode *inode = filp->f_path.dentry->d_inode;
622 int retval;
623
624 mutex_lock(&inode->i_mutex);
625 retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
626 mutex_unlock(&inode->i_mutex);
627
628 if (retval < 0)
629 return retval;
630
631 return 0;
632 }
633
634
635 static int
636 pipe_rdwr_fasync(int fd, struct file *filp, int on)
637 {
638 struct inode *inode = filp->f_path.dentry->d_inode;
639 struct pipe_inode_info *pipe = inode->i_pipe;
640 int retval;
641
642 mutex_lock(&inode->i_mutex);
643
644 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
645
646 if (retval >= 0)
647 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
648
649 mutex_unlock(&inode->i_mutex);
650
651 if (retval < 0)
652 return retval;
653
654 return 0;
655 }
656
657
658 static int
659 pipe_read_release(struct inode *inode, struct file *filp)
660 {
661 pipe_read_fasync(-1, filp, 0);
662 return pipe_release(inode, 1, 0);
663 }
664
665 static int
666 pipe_write_release(struct inode *inode, struct file *filp)
667 {
668 pipe_write_fasync(-1, filp, 0);
669 return pipe_release(inode, 0, 1);
670 }
671
672 static int
673 pipe_rdwr_release(struct inode *inode, struct file *filp)
674 {
675 int decr, decw;
676
677 pipe_rdwr_fasync(-1, filp, 0);
678 decr = (filp->f_mode & FMODE_READ) != 0;
679 decw = (filp->f_mode & FMODE_WRITE) != 0;
680 return pipe_release(inode, decr, decw);
681 }
682
683 static int
684 pipe_read_open(struct inode *inode, struct file *filp)
685 {
686 /* We could have perhaps used atomic_t, but this and friends
687 below are the only places. So it doesn't seem worthwhile. */
688 mutex_lock(&inode->i_mutex);
689 inode->i_pipe->readers++;
690 mutex_unlock(&inode->i_mutex);
691
692 return 0;
693 }
694
695 static int
696 pipe_write_open(struct inode *inode, struct file *filp)
697 {
698 mutex_lock(&inode->i_mutex);
699 inode->i_pipe->writers++;
700 mutex_unlock(&inode->i_mutex);
701
702 return 0;
703 }
704
705 static int
706 pipe_rdwr_open(struct inode *inode, struct file *filp)
707 {
708 mutex_lock(&inode->i_mutex);
709 if (filp->f_mode & FMODE_READ)
710 inode->i_pipe->readers++;
711 if (filp->f_mode & FMODE_WRITE)
712 inode->i_pipe->writers++;
713 mutex_unlock(&inode->i_mutex);
714
715 return 0;
716 }
717
718 /*
719 * The file_operations structs are not static because they
720 * are also used in linux/fs/fifo.c to do operations on FIFOs.
721 */
722 const struct file_operations read_fifo_fops = {
723 .llseek = no_llseek,
724 .read = do_sync_read,
725 .aio_read = pipe_read,
726 .write = bad_pipe_w,
727 .poll = pipe_poll,
728 .ioctl = pipe_ioctl,
729 .open = pipe_read_open,
730 .release = pipe_read_release,
731 .fasync = pipe_read_fasync,
732 };
733
734 const struct file_operations write_fifo_fops = {
735 .llseek = no_llseek,
736 .read = bad_pipe_r,
737 .write = do_sync_write,
738 .aio_write = pipe_write,
739 .poll = pipe_poll,
740 .ioctl = pipe_ioctl,
741 .open = pipe_write_open,
742 .release = pipe_write_release,
743 .fasync = pipe_write_fasync,
744 };
745
746 const struct file_operations rdwr_fifo_fops = {
747 .llseek = no_llseek,
748 .read = do_sync_read,
749 .aio_read = pipe_read,
750 .write = do_sync_write,
751 .aio_write = pipe_write,
752 .poll = pipe_poll,
753 .ioctl = pipe_ioctl,
754 .open = pipe_rdwr_open,
755 .release = pipe_rdwr_release,
756 .fasync = pipe_rdwr_fasync,
757 };
758
759 static const struct file_operations read_pipe_fops = {
760 .llseek = no_llseek,
761 .read = do_sync_read,
762 .aio_read = pipe_read,
763 .write = bad_pipe_w,
764 .poll = pipe_poll,
765 .ioctl = pipe_ioctl,
766 .open = pipe_read_open,
767 .release = pipe_read_release,
768 .fasync = pipe_read_fasync,
769 };
770
771 static const struct file_operations write_pipe_fops = {
772 .llseek = no_llseek,
773 .read = bad_pipe_r,
774 .write = do_sync_write,
775 .aio_write = pipe_write,
776 .poll = pipe_poll,
777 .ioctl = pipe_ioctl,
778 .open = pipe_write_open,
779 .release = pipe_write_release,
780 .fasync = pipe_write_fasync,
781 };
782
783 static const struct file_operations rdwr_pipe_fops = {
784 .llseek = no_llseek,
785 .read = do_sync_read,
786 .aio_read = pipe_read,
787 .write = do_sync_write,
788 .aio_write = pipe_write,
789 .poll = pipe_poll,
790 .ioctl = pipe_ioctl,
791 .open = pipe_rdwr_open,
792 .release = pipe_rdwr_release,
793 .fasync = pipe_rdwr_fasync,
794 };
795
796 struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
797 {
798 struct pipe_inode_info *pipe;
799
800 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
801 if (pipe) {
802 init_waitqueue_head(&pipe->wait);
803 pipe->r_counter = pipe->w_counter = 1;
804 pipe->inode = inode;
805 }
806
807 return pipe;
808 }
809
810 void __free_pipe_info(struct pipe_inode_info *pipe)
811 {
812 int i;
813
814 for (i = 0; i < PIPE_BUFFERS; i++) {
815 struct pipe_buffer *buf = pipe->bufs + i;
816 if (buf->ops)
817 buf->ops->release(pipe, buf);
818 }
819 if (pipe->tmp_page)
820 __free_page(pipe->tmp_page);
821 kfree(pipe);
822 }
823
824 void free_pipe_info(struct inode *inode)
825 {
826 __free_pipe_info(inode->i_pipe);
827 inode->i_pipe = NULL;
828 }
829
830 static struct vfsmount *pipe_mnt __read_mostly;
831 static int pipefs_delete_dentry(struct dentry *dentry)
832 {
833 /*
834 * At creation time, we pretended this dentry was hashed
835 * (by clearing DCACHE_UNHASHED bit in d_flags)
836 * At delete time, we restore the truth : not hashed.
837 * (so that dput() can proceed correctly)
838 */
839 dentry->d_flags |= DCACHE_UNHASHED;
840 return 0;
841 }
842
843 static struct dentry_operations pipefs_dentry_operations = {
844 .d_delete = pipefs_delete_dentry,
845 };
846
847 static struct inode * get_pipe_inode(void)
848 {
849 struct inode *inode = new_inode(pipe_mnt->mnt_sb);
850 struct pipe_inode_info *pipe;
851
852 if (!inode)
853 goto fail_inode;
854
855 pipe = alloc_pipe_info(inode);
856 if (!pipe)
857 goto fail_iput;
858 inode->i_pipe = pipe;
859
860 pipe->readers = pipe->writers = 1;
861 inode->i_fop = &rdwr_pipe_fops;
862
863 /*
864 * Mark the inode dirty from the very beginning,
865 * that way it will never be moved to the dirty
866 * list because "mark_inode_dirty()" will think
867 * that it already _is_ on the dirty list.
868 */
869 inode->i_state = I_DIRTY;
870 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
871 inode->i_uid = current->fsuid;
872 inode->i_gid = current->fsgid;
873 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
874
875 return inode;
876
877 fail_iput:
878 iput(inode);
879
880 fail_inode:
881 return NULL;
882 }
883
884 struct file *create_write_pipe(void)
885 {
886 int err;
887 struct inode *inode;
888 struct file *f;
889 struct dentry *dentry;
890 char name[32];
891 struct qstr this;
892
893 f = get_empty_filp();
894 if (!f)
895 return ERR_PTR(-ENFILE);
896 err = -ENFILE;
897 inode = get_pipe_inode();
898 if (!inode)
899 goto err_file;
900
901 this.len = sprintf(name, "[%lu]", inode->i_ino);
902 this.name = name;
903 this.hash = 0;
904 err = -ENOMEM;
905 dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this);
906 if (!dentry)
907 goto err_inode;
908
909 dentry->d_op = &pipefs_dentry_operations;
910 /*
911 * We dont want to publish this dentry into global dentry hash table.
912 * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
913 * This permits a working /proc/$pid/fd/XXX on pipes
914 */
915 dentry->d_flags &= ~DCACHE_UNHASHED;
916 d_instantiate(dentry, inode);
917 f->f_path.mnt = mntget(pipe_mnt);
918 f->f_path.dentry = dentry;
919 f->f_mapping = inode->i_mapping;
920
921 f->f_flags = O_WRONLY;
922 f->f_op = &write_pipe_fops;
923 f->f_mode = FMODE_WRITE;
924 f->f_version = 0;
925
926 return f;
927
928 err_inode:
929 free_pipe_info(inode);
930 iput(inode);
931 err_file:
932 put_filp(f);
933 return ERR_PTR(err);
934 }
935
936 void free_write_pipe(struct file *f)
937 {
938 free_pipe_info(f->f_dentry->d_inode);
939 dput(f->f_path.dentry);
940 mntput(f->f_path.mnt);
941 put_filp(f);
942 }
943
944 struct file *create_read_pipe(struct file *wrf)
945 {
946 struct file *f = get_empty_filp();
947 if (!f)
948 return ERR_PTR(-ENFILE);
949
950 /* Grab pipe from the writer */
951 f->f_path.mnt = mntget(wrf->f_path.mnt);
952 f->f_path.dentry = dget(wrf->f_path.dentry);
953 f->f_mapping = wrf->f_path.dentry->d_inode->i_mapping;
954
955 f->f_pos = 0;
956 f->f_flags = O_RDONLY;
957 f->f_op = &read_pipe_fops;
958 f->f_mode = FMODE_READ;
959 f->f_version = 0;
960
961 return f;
962 }
963
964 int do_pipe(int *fd)
965 {
966 struct file *fw, *fr;
967 int error;
968 int fdw, fdr;
969
970 fw = create_write_pipe();
971 if (IS_ERR(fw))
972 return PTR_ERR(fw);
973 fr = create_read_pipe(fw);
974 error = PTR_ERR(fr);
975 if (IS_ERR(fr))
976 goto err_write_pipe;
977
978 error = get_unused_fd();
979 if (error < 0)
980 goto err_read_pipe;
981 fdr = error;
982
983 error = get_unused_fd();
984 if (error < 0)
985 goto err_fdr;
986 fdw = error;
987
988 fd_install(fdr, fr);
989 fd_install(fdw, fw);
990 fd[0] = fdr;
991 fd[1] = fdw;
992
993 return 0;
994
995 err_fdr:
996 put_unused_fd(fdr);
997 err_read_pipe:
998 dput(fr->f_dentry);
999 mntput(fr->f_vfsmnt);
1000 put_filp(fr);
1001 err_write_pipe:
1002 free_write_pipe(fw);
1003 return error;
1004 }
1005
1006 /*
1007 * pipefs should _never_ be mounted by userland - too much of security hassle,
1008 * no real gain from having the whole whorehouse mounted. So we don't need
1009 * any operations on the root directory. However, we need a non-trivial
1010 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1011 */
1012 static int pipefs_get_sb(struct file_system_type *fs_type,
1013 int flags, const char *dev_name, void *data,
1014 struct vfsmount *mnt)
1015 {
1016 return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
1017 }
1018
1019 static struct file_system_type pipe_fs_type = {
1020 .name = "pipefs",
1021 .get_sb = pipefs_get_sb,
1022 .kill_sb = kill_anon_super,
1023 };
1024
1025 static int __init init_pipe_fs(void)
1026 {
1027 int err = register_filesystem(&pipe_fs_type);
1028
1029 if (!err) {
1030 pipe_mnt = kern_mount(&pipe_fs_type);
1031 if (IS_ERR(pipe_mnt)) {
1032 err = PTR_ERR(pipe_mnt);
1033 unregister_filesystem(&pipe_fs_type);
1034 }
1035 }
1036 return err;
1037 }
1038
1039 static void __exit exit_pipe_fs(void)
1040 {
1041 unregister_filesystem(&pipe_fs_type);
1042 mntput(pipe_mnt);
1043 }
1044
1045 fs_initcall(init_pipe_fs);
1046 module_exit(exit_pipe_fs);
kernel-based virtual machine