blk-mq: don't count completed flush data request as inflight in case of quiesce
[linux-block.git] / fs / pipe.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  linux/fs/pipe.c
4  *
5  *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
6  */
7
8 #include <linux/mm.h>
9 #include <linux/file.h>
10 #include <linux/poll.h>
11 #include <linux/slab.h>
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/fs.h>
15 #include <linux/log2.h>
16 #include <linux/mount.h>
17 #include <linux/pseudo_fs.h>
18 #include <linux/magic.h>
19 #include <linux/pipe_fs_i.h>
20 #include <linux/uio.h>
21 #include <linux/highmem.h>
22 #include <linux/pagemap.h>
23 #include <linux/audit.h>
24 #include <linux/syscalls.h>
25 #include <linux/fcntl.h>
26 #include <linux/memcontrol.h>
27 #include <linux/watch_queue.h>
28 #include <linux/sysctl.h>
29
30 #include <linux/uaccess.h>
31 #include <asm/ioctls.h>
32
33 #include "internal.h"
34
35 /*
36  * New pipe buffers will be restricted to this size while the user is exceeding
37  * their pipe buffer quota. The general pipe use case needs at least two
38  * buffers: one for data yet to be read, and one for new data. If this is less
39  * than two, then a write to a non-empty pipe may block even if the pipe is not
40  * full. This can occur with GNU make jobserver or similar uses of pipes as
41  * semaphores: multiple processes may be waiting to write tokens back to the
42  * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
43  *
44  * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
45  * own risk, namely: pipe writes to non-full pipes may block until the pipe is
46  * emptied.
47  */
48 #define PIPE_MIN_DEF_BUFFERS 2
49
50 /*
51  * The max size that a non-root user is allowed to grow the pipe. Can
52  * be set by root in /proc/sys/fs/pipe-max-size
53  */
54 static unsigned int pipe_max_size = 1048576;
55
56 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
57  * matches default values.
58  */
59 static unsigned long pipe_user_pages_hard;
60 static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
61
62 /*
63  * We use head and tail indices that aren't masked off, except at the point of
64  * dereference, but rather they're allowed to wrap naturally.  This means there
65  * isn't a dead spot in the buffer, but the ring has to be a power of two and
66  * <= 2^31.
67  * -- David Howells 2019-09-23.
68  *
69  * Reads with count = 0 should always return 0.
70  * -- Julian Bradfield 1999-06-07.
71  *
72  * FIFOs and Pipes now generate SIGIO for both readers and writers.
73  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
74  *
75  * pipe_read & write cleanup
76  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
77  */
78
79 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
80 {
81         if (pipe->files)
82                 mutex_lock_nested(&pipe->mutex, subclass);
83 }
84
85 void pipe_lock(struct pipe_inode_info *pipe)
86 {
87         /*
88          * pipe_lock() nests non-pipe inode locks (for writing to a file)
89          */
90         pipe_lock_nested(pipe, I_MUTEX_PARENT);
91 }
92 EXPORT_SYMBOL(pipe_lock);
93
94 void pipe_unlock(struct pipe_inode_info *pipe)
95 {
96         if (pipe->files)
97                 mutex_unlock(&pipe->mutex);
98 }
99 EXPORT_SYMBOL(pipe_unlock);
100
101 static inline void __pipe_lock(struct pipe_inode_info *pipe)
102 {
103         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
104 }
105
106 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
107 {
108         mutex_unlock(&pipe->mutex);
109 }
110
111 void pipe_double_lock(struct pipe_inode_info *pipe1,
112                       struct pipe_inode_info *pipe2)
113 {
114         BUG_ON(pipe1 == pipe2);
115
116         if (pipe1 < pipe2) {
117                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
118                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
119         } else {
120                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
121                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
122         }
123 }
124
125 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
126                                   struct pipe_buffer *buf)
127 {
128         struct page *page = buf->page;
129
130         /*
131          * If nobody else uses this page, and we don't already have a
132          * temporary page, let's keep track of it as a one-deep
133          * allocation cache. (Otherwise just release our reference to it)
134          */
135         if (page_count(page) == 1 && !pipe->tmp_page)
136                 pipe->tmp_page = page;
137         else
138                 put_page(page);
139 }
140
141 static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe,
142                 struct pipe_buffer *buf)
143 {
144         struct page *page = buf->page;
145
146         if (page_count(page) != 1)
147                 return false;
148         memcg_kmem_uncharge_page(page, 0);
149         __SetPageLocked(page);
150         return true;
151 }
152
153 /**
154  * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
155  * @pipe:       the pipe that the buffer belongs to
156  * @buf:        the buffer to attempt to steal
157  *
158  * Description:
159  *      This function attempts to steal the &struct page attached to
160  *      @buf. If successful, this function returns 0 and returns with
161  *      the page locked. The caller may then reuse the page for whatever
162  *      he wishes; the typical use is insertion into a different file
163  *      page cache.
164  */
165 bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
166                 struct pipe_buffer *buf)
167 {
168         struct page *page = buf->page;
169
170         /*
171          * A reference of one is golden, that means that the owner of this
172          * page is the only one holding a reference to it. lock the page
173          * and return OK.
174          */
175         if (page_count(page) == 1) {
176                 lock_page(page);
177                 return true;
178         }
179         return false;
180 }
181 EXPORT_SYMBOL(generic_pipe_buf_try_steal);
182
183 /**
184  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
185  * @pipe:       the pipe that the buffer belongs to
186  * @buf:        the buffer to get a reference to
187  *
188  * Description:
189  *      This function grabs an extra reference to @buf. It's used in
190  *      the tee() system call, when we duplicate the buffers in one
191  *      pipe into another.
192  */
193 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
194 {
195         return try_get_page(buf->page);
196 }
197 EXPORT_SYMBOL(generic_pipe_buf_get);
198
199 /**
200  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
201  * @pipe:       the pipe that the buffer belongs to
202  * @buf:        the buffer to put a reference to
203  *
204  * Description:
205  *      This function releases a reference to @buf.
206  */
207 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
208                               struct pipe_buffer *buf)
209 {
210         put_page(buf->page);
211 }
212 EXPORT_SYMBOL(generic_pipe_buf_release);
213
214 static const struct pipe_buf_operations anon_pipe_buf_ops = {
215         .release        = anon_pipe_buf_release,
216         .try_steal      = anon_pipe_buf_try_steal,
217         .get            = generic_pipe_buf_get,
218 };
219
220 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
221 static inline bool pipe_readable(const struct pipe_inode_info *pipe)
222 {
223         unsigned int head = READ_ONCE(pipe->head);
224         unsigned int tail = READ_ONCE(pipe->tail);
225         unsigned int writers = READ_ONCE(pipe->writers);
226
227         return !pipe_empty(head, tail) || !writers;
228 }
229
230 static inline unsigned int pipe_update_tail(struct pipe_inode_info *pipe,
231                                             struct pipe_buffer *buf,
232                                             unsigned int tail)
233 {
234         pipe_buf_release(pipe, buf);
235
236         /*
237          * If the pipe has a watch_queue, we need additional protection
238          * by the spinlock because notifications get posted with only
239          * this spinlock, no mutex
240          */
241         if (pipe_has_watch_queue(pipe)) {
242                 spin_lock_irq(&pipe->rd_wait.lock);
243 #ifdef CONFIG_WATCH_QUEUE
244                 if (buf->flags & PIPE_BUF_FLAG_LOSS)
245                         pipe->note_loss = true;
246 #endif
247                 pipe->tail = ++tail;
248                 spin_unlock_irq(&pipe->rd_wait.lock);
249                 return tail;
250         }
251
252         /*
253          * Without a watch_queue, we can simply increment the tail
254          * without the spinlock - the mutex is enough.
255          */
256         pipe->tail = ++tail;
257         return tail;
258 }
259
260 static ssize_t
261 pipe_read(struct kiocb *iocb, struct iov_iter *to)
262 {
263         size_t total_len = iov_iter_count(to);
264         struct file *filp = iocb->ki_filp;
265         struct pipe_inode_info *pipe = filp->private_data;
266         bool was_full, wake_next_reader = false;
267         ssize_t ret;
268
269         /* Null read succeeds. */
270         if (unlikely(total_len == 0))
271                 return 0;
272
273         ret = 0;
274         __pipe_lock(pipe);
275
276         /*
277          * We only wake up writers if the pipe was full when we started
278          * reading in order to avoid unnecessary wakeups.
279          *
280          * But when we do wake up writers, we do so using a sync wakeup
281          * (WF_SYNC), because we want them to get going and generate more
282          * data for us.
283          */
284         was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
285         for (;;) {
286                 /* Read ->head with a barrier vs post_one_notification() */
287                 unsigned int head = smp_load_acquire(&pipe->head);
288                 unsigned int tail = pipe->tail;
289                 unsigned int mask = pipe->ring_size - 1;
290
291 #ifdef CONFIG_WATCH_QUEUE
292                 if (pipe->note_loss) {
293                         struct watch_notification n;
294
295                         if (total_len < 8) {
296                                 if (ret == 0)
297                                         ret = -ENOBUFS;
298                                 break;
299                         }
300
301                         n.type = WATCH_TYPE_META;
302                         n.subtype = WATCH_META_LOSS_NOTIFICATION;
303                         n.info = watch_sizeof(n);
304                         if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
305                                 if (ret == 0)
306                                         ret = -EFAULT;
307                                 break;
308                         }
309                         ret += sizeof(n);
310                         total_len -= sizeof(n);
311                         pipe->note_loss = false;
312                 }
313 #endif
314
315                 if (!pipe_empty(head, tail)) {
316                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
317                         size_t chars = buf->len;
318                         size_t written;
319                         int error;
320
321                         if (chars > total_len) {
322                                 if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
323                                         if (ret == 0)
324                                                 ret = -ENOBUFS;
325                                         break;
326                                 }
327                                 chars = total_len;
328                         }
329
330                         error = pipe_buf_confirm(pipe, buf);
331                         if (error) {
332                                 if (!ret)
333                                         ret = error;
334                                 break;
335                         }
336
337                         written = copy_page_to_iter(buf->page, buf->offset, chars, to);
338                         if (unlikely(written < chars)) {
339                                 if (!ret)
340                                         ret = -EFAULT;
341                                 break;
342                         }
343                         ret += chars;
344                         buf->offset += chars;
345                         buf->len -= chars;
346
347                         /* Was it a packet buffer? Clean up and exit */
348                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
349                                 total_len = chars;
350                                 buf->len = 0;
351                         }
352
353                         if (!buf->len)
354                                 tail = pipe_update_tail(pipe, buf, tail);
355                         total_len -= chars;
356                         if (!total_len)
357                                 break;  /* common path: read succeeded */
358                         if (!pipe_empty(head, tail))    /* More to do? */
359                                 continue;
360                 }
361
362                 if (!pipe->writers)
363                         break;
364                 if (ret)
365                         break;
366                 if ((filp->f_flags & O_NONBLOCK) ||
367                     (iocb->ki_flags & IOCB_NOWAIT)) {
368                         ret = -EAGAIN;
369                         break;
370                 }
371                 __pipe_unlock(pipe);
372
373                 /*
374                  * We only get here if we didn't actually read anything.
375                  *
376                  * However, we could have seen (and removed) a zero-sized
377                  * pipe buffer, and might have made space in the buffers
378                  * that way.
379                  *
380                  * You can't make zero-sized pipe buffers by doing an empty
381                  * write (not even in packet mode), but they can happen if
382                  * the writer gets an EFAULT when trying to fill a buffer
383                  * that already got allocated and inserted in the buffer
384                  * array.
385                  *
386                  * So we still need to wake up any pending writers in the
387                  * _very_ unlikely case that the pipe was full, but we got
388                  * no data.
389                  */
390                 if (unlikely(was_full))
391                         wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
392                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
393
394                 /*
395                  * But because we didn't read anything, at this point we can
396                  * just return directly with -ERESTARTSYS if we're interrupted,
397                  * since we've done any required wakeups and there's no need
398                  * to mark anything accessed. And we've dropped the lock.
399                  */
400                 if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
401                         return -ERESTARTSYS;
402
403                 __pipe_lock(pipe);
404                 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
405                 wake_next_reader = true;
406         }
407         if (pipe_empty(pipe->head, pipe->tail))
408                 wake_next_reader = false;
409         __pipe_unlock(pipe);
410
411         if (was_full)
412                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
413         if (wake_next_reader)
414                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
415         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
416         if (ret > 0)
417                 file_accessed(filp);
418         return ret;
419 }
420
421 static inline int is_packetized(struct file *file)
422 {
423         return (file->f_flags & O_DIRECT) != 0;
424 }
425
426 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
427 static inline bool pipe_writable(const struct pipe_inode_info *pipe)
428 {
429         unsigned int head = READ_ONCE(pipe->head);
430         unsigned int tail = READ_ONCE(pipe->tail);
431         unsigned int max_usage = READ_ONCE(pipe->max_usage);
432
433         return !pipe_full(head, tail, max_usage) ||
434                 !READ_ONCE(pipe->readers);
435 }
436
437 static ssize_t
438 pipe_write(struct kiocb *iocb, struct iov_iter *from)
439 {
440         struct file *filp = iocb->ki_filp;
441         struct pipe_inode_info *pipe = filp->private_data;
442         unsigned int head;
443         ssize_t ret = 0;
444         size_t total_len = iov_iter_count(from);
445         ssize_t chars;
446         bool was_empty = false;
447         bool wake_next_writer = false;
448
449         /* Null write succeeds. */
450         if (unlikely(total_len == 0))
451                 return 0;
452
453         __pipe_lock(pipe);
454
455         if (!pipe->readers) {
456                 send_sig(SIGPIPE, current, 0);
457                 ret = -EPIPE;
458                 goto out;
459         }
460
461         if (pipe_has_watch_queue(pipe)) {
462                 ret = -EXDEV;
463                 goto out;
464         }
465
466         /*
467          * If it wasn't empty we try to merge new data into
468          * the last buffer.
469          *
470          * That naturally merges small writes, but it also
471          * page-aligns the rest of the writes for large writes
472          * spanning multiple pages.
473          */
474         head = pipe->head;
475         was_empty = pipe_empty(head, pipe->tail);
476         chars = total_len & (PAGE_SIZE-1);
477         if (chars && !was_empty) {
478                 unsigned int mask = pipe->ring_size - 1;
479                 struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
480                 int offset = buf->offset + buf->len;
481
482                 if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
483                     offset + chars <= PAGE_SIZE) {
484                         ret = pipe_buf_confirm(pipe, buf);
485                         if (ret)
486                                 goto out;
487
488                         ret = copy_page_from_iter(buf->page, offset, chars, from);
489                         if (unlikely(ret < chars)) {
490                                 ret = -EFAULT;
491                                 goto out;
492                         }
493
494                         buf->len += ret;
495                         if (!iov_iter_count(from))
496                                 goto out;
497                 }
498         }
499
500         for (;;) {
501                 if (!pipe->readers) {
502                         send_sig(SIGPIPE, current, 0);
503                         if (!ret)
504                                 ret = -EPIPE;
505                         break;
506                 }
507
508                 head = pipe->head;
509                 if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
510                         unsigned int mask = pipe->ring_size - 1;
511                         struct pipe_buffer *buf;
512                         struct page *page = pipe->tmp_page;
513                         int copied;
514
515                         if (!page) {
516                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
517                                 if (unlikely(!page)) {
518                                         ret = ret ? : -ENOMEM;
519                                         break;
520                                 }
521                                 pipe->tmp_page = page;
522                         }
523
524                         /* Allocate a slot in the ring in advance and attach an
525                          * empty buffer.  If we fault or otherwise fail to use
526                          * it, either the reader will consume it or it'll still
527                          * be there for the next write.
528                          */
529                         pipe->head = head + 1;
530
531                         /* Insert it into the buffer array */
532                         buf = &pipe->bufs[head & mask];
533                         buf->page = page;
534                         buf->ops = &anon_pipe_buf_ops;
535                         buf->offset = 0;
536                         buf->len = 0;
537                         if (is_packetized(filp))
538                                 buf->flags = PIPE_BUF_FLAG_PACKET;
539                         else
540                                 buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
541                         pipe->tmp_page = NULL;
542
543                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
544                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
545                                 if (!ret)
546                                         ret = -EFAULT;
547                                 break;
548                         }
549                         ret += copied;
550                         buf->len = copied;
551
552                         if (!iov_iter_count(from))
553                                 break;
554                 }
555
556                 if (!pipe_full(head, pipe->tail, pipe->max_usage))
557                         continue;
558
559                 /* Wait for buffer space to become available. */
560                 if ((filp->f_flags & O_NONBLOCK) ||
561                     (iocb->ki_flags & IOCB_NOWAIT)) {
562                         if (!ret)
563                                 ret = -EAGAIN;
564                         break;
565                 }
566                 if (signal_pending(current)) {
567                         if (!ret)
568                                 ret = -ERESTARTSYS;
569                         break;
570                 }
571
572                 /*
573                  * We're going to release the pipe lock and wait for more
574                  * space. We wake up any readers if necessary, and then
575                  * after waiting we need to re-check whether the pipe
576                  * become empty while we dropped the lock.
577                  */
578                 __pipe_unlock(pipe);
579                 if (was_empty)
580                         wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
581                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
582                 wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
583                 __pipe_lock(pipe);
584                 was_empty = pipe_empty(pipe->head, pipe->tail);
585                 wake_next_writer = true;
586         }
587 out:
588         if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
589                 wake_next_writer = false;
590         __pipe_unlock(pipe);
591
592         /*
593          * If we do do a wakeup event, we do a 'sync' wakeup, because we
594          * want the reader to start processing things asap, rather than
595          * leave the data pending.
596          *
597          * This is particularly important for small writes, because of
598          * how (for example) the GNU make jobserver uses small writes to
599          * wake up pending jobs
600          *
601          * Epoll nonsensically wants a wakeup whether the pipe
602          * was already empty or not.
603          */
604         if (was_empty || pipe->poll_usage)
605                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
606         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
607         if (wake_next_writer)
608                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
609         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
610                 int err = file_update_time(filp);
611                 if (err)
612                         ret = err;
613                 sb_end_write(file_inode(filp)->i_sb);
614         }
615         return ret;
616 }
617
618 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
619 {
620         struct pipe_inode_info *pipe = filp->private_data;
621         unsigned int count, head, tail, mask;
622
623         switch (cmd) {
624         case FIONREAD:
625                 __pipe_lock(pipe);
626                 count = 0;
627                 head = pipe->head;
628                 tail = pipe->tail;
629                 mask = pipe->ring_size - 1;
630
631                 while (tail != head) {
632                         count += pipe->bufs[tail & mask].len;
633                         tail++;
634                 }
635                 __pipe_unlock(pipe);
636
637                 return put_user(count, (int __user *)arg);
638
639 #ifdef CONFIG_WATCH_QUEUE
640         case IOC_WATCH_QUEUE_SET_SIZE: {
641                 int ret;
642                 __pipe_lock(pipe);
643                 ret = watch_queue_set_size(pipe, arg);
644                 __pipe_unlock(pipe);
645                 return ret;
646         }
647
648         case IOC_WATCH_QUEUE_SET_FILTER:
649                 return watch_queue_set_filter(
650                         pipe, (struct watch_notification_filter __user *)arg);
651 #endif
652
653         default:
654                 return -ENOIOCTLCMD;
655         }
656 }
657
658 /* No kernel lock held - fine */
659 static __poll_t
660 pipe_poll(struct file *filp, poll_table *wait)
661 {
662         __poll_t mask;
663         struct pipe_inode_info *pipe = filp->private_data;
664         unsigned int head, tail;
665
666         /* Epoll has some historical nasty semantics, this enables them */
667         WRITE_ONCE(pipe->poll_usage, true);
668
669         /*
670          * Reading pipe state only -- no need for acquiring the semaphore.
671          *
672          * But because this is racy, the code has to add the
673          * entry to the poll table _first_ ..
674          */
675         if (filp->f_mode & FMODE_READ)
676                 poll_wait(filp, &pipe->rd_wait, wait);
677         if (filp->f_mode & FMODE_WRITE)
678                 poll_wait(filp, &pipe->wr_wait, wait);
679
680         /*
681          * .. and only then can you do the racy tests. That way,
682          * if something changes and you got it wrong, the poll
683          * table entry will wake you up and fix it.
684          */
685         head = READ_ONCE(pipe->head);
686         tail = READ_ONCE(pipe->tail);
687
688         mask = 0;
689         if (filp->f_mode & FMODE_READ) {
690                 if (!pipe_empty(head, tail))
691                         mask |= EPOLLIN | EPOLLRDNORM;
692                 if (!pipe->writers && filp->f_version != pipe->w_counter)
693                         mask |= EPOLLHUP;
694         }
695
696         if (filp->f_mode & FMODE_WRITE) {
697                 if (!pipe_full(head, tail, pipe->max_usage))
698                         mask |= EPOLLOUT | EPOLLWRNORM;
699                 /*
700                  * Most Unices do not set EPOLLERR for FIFOs but on Linux they
701                  * behave exactly like pipes for poll().
702                  */
703                 if (!pipe->readers)
704                         mask |= EPOLLERR;
705         }
706
707         return mask;
708 }
709
710 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
711 {
712         int kill = 0;
713
714         spin_lock(&inode->i_lock);
715         if (!--pipe->files) {
716                 inode->i_pipe = NULL;
717                 kill = 1;
718         }
719         spin_unlock(&inode->i_lock);
720
721         if (kill)
722                 free_pipe_info(pipe);
723 }
724
725 static int
726 pipe_release(struct inode *inode, struct file *file)
727 {
728         struct pipe_inode_info *pipe = file->private_data;
729
730         __pipe_lock(pipe);
731         if (file->f_mode & FMODE_READ)
732                 pipe->readers--;
733         if (file->f_mode & FMODE_WRITE)
734                 pipe->writers--;
735
736         /* Was that the last reader or writer, but not the other side? */
737         if (!pipe->readers != !pipe->writers) {
738                 wake_up_interruptible_all(&pipe->rd_wait);
739                 wake_up_interruptible_all(&pipe->wr_wait);
740                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
741                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
742         }
743         __pipe_unlock(pipe);
744
745         put_pipe_info(inode, pipe);
746         return 0;
747 }
748
749 static int
750 pipe_fasync(int fd, struct file *filp, int on)
751 {
752         struct pipe_inode_info *pipe = filp->private_data;
753         int retval = 0;
754
755         __pipe_lock(pipe);
756         if (filp->f_mode & FMODE_READ)
757                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
758         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
759                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
760                 if (retval < 0 && (filp->f_mode & FMODE_READ))
761                         /* this can happen only if on == T */
762                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
763         }
764         __pipe_unlock(pipe);
765         return retval;
766 }
767
768 unsigned long account_pipe_buffers(struct user_struct *user,
769                                    unsigned long old, unsigned long new)
770 {
771         return atomic_long_add_return(new - old, &user->pipe_bufs);
772 }
773
774 bool too_many_pipe_buffers_soft(unsigned long user_bufs)
775 {
776         unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
777
778         return soft_limit && user_bufs > soft_limit;
779 }
780
781 bool too_many_pipe_buffers_hard(unsigned long user_bufs)
782 {
783         unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
784
785         return hard_limit && user_bufs > hard_limit;
786 }
787
788 bool pipe_is_unprivileged_user(void)
789 {
790         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
791 }
792
793 struct pipe_inode_info *alloc_pipe_info(void)
794 {
795         struct pipe_inode_info *pipe;
796         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
797         struct user_struct *user = get_current_user();
798         unsigned long user_bufs;
799         unsigned int max_size = READ_ONCE(pipe_max_size);
800
801         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
802         if (pipe == NULL)
803                 goto out_free_uid;
804
805         if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
806                 pipe_bufs = max_size >> PAGE_SHIFT;
807
808         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
809
810         if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
811                 user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
812                 pipe_bufs = PIPE_MIN_DEF_BUFFERS;
813         }
814
815         if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
816                 goto out_revert_acct;
817
818         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
819                              GFP_KERNEL_ACCOUNT);
820
821         if (pipe->bufs) {
822                 init_waitqueue_head(&pipe->rd_wait);
823                 init_waitqueue_head(&pipe->wr_wait);
824                 pipe->r_counter = pipe->w_counter = 1;
825                 pipe->max_usage = pipe_bufs;
826                 pipe->ring_size = pipe_bufs;
827                 pipe->nr_accounted = pipe_bufs;
828                 pipe->user = user;
829                 mutex_init(&pipe->mutex);
830                 return pipe;
831         }
832
833 out_revert_acct:
834         (void) account_pipe_buffers(user, pipe_bufs, 0);
835         kfree(pipe);
836 out_free_uid:
837         free_uid(user);
838         return NULL;
839 }
840
841 void free_pipe_info(struct pipe_inode_info *pipe)
842 {
843         unsigned int i;
844
845 #ifdef CONFIG_WATCH_QUEUE
846         if (pipe->watch_queue)
847                 watch_queue_clear(pipe->watch_queue);
848 #endif
849
850         (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
851         free_uid(pipe->user);
852         for (i = 0; i < pipe->ring_size; i++) {
853                 struct pipe_buffer *buf = pipe->bufs + i;
854                 if (buf->ops)
855                         pipe_buf_release(pipe, buf);
856         }
857 #ifdef CONFIG_WATCH_QUEUE
858         if (pipe->watch_queue)
859                 put_watch_queue(pipe->watch_queue);
860 #endif
861         if (pipe->tmp_page)
862                 __free_page(pipe->tmp_page);
863         kfree(pipe->bufs);
864         kfree(pipe);
865 }
866
867 static struct vfsmount *pipe_mnt __ro_after_init;
868
869 /*
870  * pipefs_dname() is called from d_path().
871  */
872 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
873 {
874         return dynamic_dname(buffer, buflen, "pipe:[%lu]",
875                                 d_inode(dentry)->i_ino);
876 }
877
878 static const struct dentry_operations pipefs_dentry_operations = {
879         .d_dname        = pipefs_dname,
880 };
881
882 static struct inode * get_pipe_inode(void)
883 {
884         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
885         struct pipe_inode_info *pipe;
886
887         if (!inode)
888                 goto fail_inode;
889
890         inode->i_ino = get_next_ino();
891
892         pipe = alloc_pipe_info();
893         if (!pipe)
894                 goto fail_iput;
895
896         inode->i_pipe = pipe;
897         pipe->files = 2;
898         pipe->readers = pipe->writers = 1;
899         inode->i_fop = &pipefifo_fops;
900
901         /*
902          * Mark the inode dirty from the very beginning,
903          * that way it will never be moved to the dirty
904          * list because "mark_inode_dirty()" will think
905          * that it already _is_ on the dirty list.
906          */
907         inode->i_state = I_DIRTY;
908         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
909         inode->i_uid = current_fsuid();
910         inode->i_gid = current_fsgid();
911         simple_inode_init_ts(inode);
912
913         return inode;
914
915 fail_iput:
916         iput(inode);
917
918 fail_inode:
919         return NULL;
920 }
921
922 int create_pipe_files(struct file **res, int flags)
923 {
924         struct inode *inode = get_pipe_inode();
925         struct file *f;
926         int error;
927
928         if (!inode)
929                 return -ENFILE;
930
931         if (flags & O_NOTIFICATION_PIPE) {
932                 error = watch_queue_init(inode->i_pipe);
933                 if (error) {
934                         free_pipe_info(inode->i_pipe);
935                         iput(inode);
936                         return error;
937                 }
938         }
939
940         f = alloc_file_pseudo(inode, pipe_mnt, "",
941                                 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
942                                 &pipefifo_fops);
943         if (IS_ERR(f)) {
944                 free_pipe_info(inode->i_pipe);
945                 iput(inode);
946                 return PTR_ERR(f);
947         }
948
949         f->private_data = inode->i_pipe;
950
951         res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
952                                   &pipefifo_fops);
953         if (IS_ERR(res[0])) {
954                 put_pipe_info(inode, inode->i_pipe);
955                 fput(f);
956                 return PTR_ERR(res[0]);
957         }
958         res[0]->private_data = inode->i_pipe;
959         res[1] = f;
960         stream_open(inode, res[0]);
961         stream_open(inode, res[1]);
962         return 0;
963 }
964
965 static int __do_pipe_flags(int *fd, struct file **files, int flags)
966 {
967         int error;
968         int fdw, fdr;
969
970         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
971                 return -EINVAL;
972
973         error = create_pipe_files(files, flags);
974         if (error)
975                 return error;
976
977         error = get_unused_fd_flags(flags);
978         if (error < 0)
979                 goto err_read_pipe;
980         fdr = error;
981
982         error = get_unused_fd_flags(flags);
983         if (error < 0)
984                 goto err_fdr;
985         fdw = error;
986
987         audit_fd_pair(fdr, fdw);
988         fd[0] = fdr;
989         fd[1] = fdw;
990         /* pipe groks IOCB_NOWAIT */
991         files[0]->f_mode |= FMODE_NOWAIT;
992         files[1]->f_mode |= FMODE_NOWAIT;
993         return 0;
994
995  err_fdr:
996         put_unused_fd(fdr);
997  err_read_pipe:
998         fput(files[0]);
999         fput(files[1]);
1000         return error;
1001 }
1002
1003 int do_pipe_flags(int *fd, int flags)
1004 {
1005         struct file *files[2];
1006         int error = __do_pipe_flags(fd, files, flags);
1007         if (!error) {
1008                 fd_install(fd[0], files[0]);
1009                 fd_install(fd[1], files[1]);
1010         }
1011         return error;
1012 }
1013
1014 /*
1015  * sys_pipe() is the normal C calling standard for creating
1016  * a pipe. It's not the way Unix traditionally does this, though.
1017  */
1018 static int do_pipe2(int __user *fildes, int flags)
1019 {
1020         struct file *files[2];
1021         int fd[2];
1022         int error;
1023
1024         error = __do_pipe_flags(fd, files, flags);
1025         if (!error) {
1026                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
1027                         fput(files[0]);
1028                         fput(files[1]);
1029                         put_unused_fd(fd[0]);
1030                         put_unused_fd(fd[1]);
1031                         error = -EFAULT;
1032                 } else {
1033                         fd_install(fd[0], files[0]);
1034                         fd_install(fd[1], files[1]);
1035                 }
1036         }
1037         return error;
1038 }
1039
1040 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1041 {
1042         return do_pipe2(fildes, flags);
1043 }
1044
1045 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1046 {
1047         return do_pipe2(fildes, 0);
1048 }
1049
1050 /*
1051  * This is the stupid "wait for pipe to be readable or writable"
1052  * model.
1053  *
1054  * See pipe_read/write() for the proper kind of exclusive wait,
1055  * but that requires that we wake up any other readers/writers
1056  * if we then do not end up reading everything (ie the whole
1057  * "wake_next_reader/writer" logic in pipe_read/write()).
1058  */
1059 void pipe_wait_readable(struct pipe_inode_info *pipe)
1060 {
1061         pipe_unlock(pipe);
1062         wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1063         pipe_lock(pipe);
1064 }
1065
1066 void pipe_wait_writable(struct pipe_inode_info *pipe)
1067 {
1068         pipe_unlock(pipe);
1069         wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1070         pipe_lock(pipe);
1071 }
1072
1073 /*
1074  * This depends on both the wait (here) and the wakeup (wake_up_partner)
1075  * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1076  * race with the count check and waitqueue prep.
1077  *
1078  * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1079  * then check the condition you're waiting for, and only then sleep. But
1080  * because of the pipe lock, we can check the condition before being on
1081  * the wait queue.
1082  *
1083  * We use the 'rd_wait' waitqueue for pipe partner waiting.
1084  */
1085 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1086 {
1087         DEFINE_WAIT(rdwait);
1088         int cur = *cnt;
1089
1090         while (cur == *cnt) {
1091                 prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1092                 pipe_unlock(pipe);
1093                 schedule();
1094                 finish_wait(&pipe->rd_wait, &rdwait);
1095                 pipe_lock(pipe);
1096                 if (signal_pending(current))
1097                         break;
1098         }
1099         return cur == *cnt ? -ERESTARTSYS : 0;
1100 }
1101
1102 static void wake_up_partner(struct pipe_inode_info *pipe)
1103 {
1104         wake_up_interruptible_all(&pipe->rd_wait);
1105 }
1106
1107 static int fifo_open(struct inode *inode, struct file *filp)
1108 {
1109         struct pipe_inode_info *pipe;
1110         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1111         int ret;
1112
1113         filp->f_version = 0;
1114
1115         spin_lock(&inode->i_lock);
1116         if (inode->i_pipe) {
1117                 pipe = inode->i_pipe;
1118                 pipe->files++;
1119                 spin_unlock(&inode->i_lock);
1120         } else {
1121                 spin_unlock(&inode->i_lock);
1122                 pipe = alloc_pipe_info();
1123                 if (!pipe)
1124                         return -ENOMEM;
1125                 pipe->files = 1;
1126                 spin_lock(&inode->i_lock);
1127                 if (unlikely(inode->i_pipe)) {
1128                         inode->i_pipe->files++;
1129                         spin_unlock(&inode->i_lock);
1130                         free_pipe_info(pipe);
1131                         pipe = inode->i_pipe;
1132                 } else {
1133                         inode->i_pipe = pipe;
1134                         spin_unlock(&inode->i_lock);
1135                 }
1136         }
1137         filp->private_data = pipe;
1138         /* OK, we have a pipe and it's pinned down */
1139
1140         __pipe_lock(pipe);
1141
1142         /* We can only do regular read/write on fifos */
1143         stream_open(inode, filp);
1144
1145         switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1146         case FMODE_READ:
1147         /*
1148          *  O_RDONLY
1149          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1150          *  opened, even when there is no process writing the FIFO.
1151          */
1152                 pipe->r_counter++;
1153                 if (pipe->readers++ == 0)
1154                         wake_up_partner(pipe);
1155
1156                 if (!is_pipe && !pipe->writers) {
1157                         if ((filp->f_flags & O_NONBLOCK)) {
1158                                 /* suppress EPOLLHUP until we have
1159                                  * seen a writer */
1160                                 filp->f_version = pipe->w_counter;
1161                         } else {
1162                                 if (wait_for_partner(pipe, &pipe->w_counter))
1163                                         goto err_rd;
1164                         }
1165                 }
1166                 break;
1167
1168         case FMODE_WRITE:
1169         /*
1170          *  O_WRONLY
1171          *  POSIX.1 says that O_NONBLOCK means return -1 with
1172          *  errno=ENXIO when there is no process reading the FIFO.
1173          */
1174                 ret = -ENXIO;
1175                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1176                         goto err;
1177
1178                 pipe->w_counter++;
1179                 if (!pipe->writers++)
1180                         wake_up_partner(pipe);
1181
1182                 if (!is_pipe && !pipe->readers) {
1183                         if (wait_for_partner(pipe, &pipe->r_counter))
1184                                 goto err_wr;
1185                 }
1186                 break;
1187
1188         case FMODE_READ | FMODE_WRITE:
1189         /*
1190          *  O_RDWR
1191          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1192          *  This implementation will NEVER block on a O_RDWR open, since
1193          *  the process can at least talk to itself.
1194          */
1195
1196                 pipe->readers++;
1197                 pipe->writers++;
1198                 pipe->r_counter++;
1199                 pipe->w_counter++;
1200                 if (pipe->readers == 1 || pipe->writers == 1)
1201                         wake_up_partner(pipe);
1202                 break;
1203
1204         default:
1205                 ret = -EINVAL;
1206                 goto err;
1207         }
1208
1209         /* Ok! */
1210         __pipe_unlock(pipe);
1211         return 0;
1212
1213 err_rd:
1214         if (!--pipe->readers)
1215                 wake_up_interruptible(&pipe->wr_wait);
1216         ret = -ERESTARTSYS;
1217         goto err;
1218
1219 err_wr:
1220         if (!--pipe->writers)
1221                 wake_up_interruptible_all(&pipe->rd_wait);
1222         ret = -ERESTARTSYS;
1223         goto err;
1224
1225 err:
1226         __pipe_unlock(pipe);
1227
1228         put_pipe_info(inode, pipe);
1229         return ret;
1230 }
1231
1232 const struct file_operations pipefifo_fops = {
1233         .open           = fifo_open,
1234         .llseek         = no_llseek,
1235         .read_iter      = pipe_read,
1236         .write_iter     = pipe_write,
1237         .poll           = pipe_poll,
1238         .unlocked_ioctl = pipe_ioctl,
1239         .release        = pipe_release,
1240         .fasync         = pipe_fasync,
1241         .splice_write   = iter_file_splice_write,
1242 };
1243
1244 /*
1245  * Currently we rely on the pipe array holding a power-of-2 number
1246  * of pages. Returns 0 on error.
1247  */
1248 unsigned int round_pipe_size(unsigned int size)
1249 {
1250         if (size > (1U << 31))
1251                 return 0;
1252
1253         /* Minimum pipe size, as required by POSIX */
1254         if (size < PAGE_SIZE)
1255                 return PAGE_SIZE;
1256
1257         return roundup_pow_of_two(size);
1258 }
1259
1260 /*
1261  * Resize the pipe ring to a number of slots.
1262  *
1263  * Note the pipe can be reduced in capacity, but only if the current
1264  * occupancy doesn't exceed nr_slots; if it does, EBUSY will be
1265  * returned instead.
1266  */
1267 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1268 {
1269         struct pipe_buffer *bufs;
1270         unsigned int head, tail, mask, n;
1271
1272         bufs = kcalloc(nr_slots, sizeof(*bufs),
1273                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1274         if (unlikely(!bufs))
1275                 return -ENOMEM;
1276
1277         spin_lock_irq(&pipe->rd_wait.lock);
1278         mask = pipe->ring_size - 1;
1279         head = pipe->head;
1280         tail = pipe->tail;
1281
1282         n = pipe_occupancy(head, tail);
1283         if (nr_slots < n) {
1284                 spin_unlock_irq(&pipe->rd_wait.lock);
1285                 kfree(bufs);
1286                 return -EBUSY;
1287         }
1288
1289         /*
1290          * The pipe array wraps around, so just start the new one at zero
1291          * and adjust the indices.
1292          */
1293         if (n > 0) {
1294                 unsigned int h = head & mask;
1295                 unsigned int t = tail & mask;
1296                 if (h > t) {
1297                         memcpy(bufs, pipe->bufs + t,
1298                                n * sizeof(struct pipe_buffer));
1299                 } else {
1300                         unsigned int tsize = pipe->ring_size - t;
1301                         if (h > 0)
1302                                 memcpy(bufs + tsize, pipe->bufs,
1303                                        h * sizeof(struct pipe_buffer));
1304                         memcpy(bufs, pipe->bufs + t,
1305                                tsize * sizeof(struct pipe_buffer));
1306                 }
1307         }
1308
1309         head = n;
1310         tail = 0;
1311
1312         kfree(pipe->bufs);
1313         pipe->bufs = bufs;
1314         pipe->ring_size = nr_slots;
1315         if (pipe->max_usage > nr_slots)
1316                 pipe->max_usage = nr_slots;
1317         pipe->tail = tail;
1318         pipe->head = head;
1319
1320         spin_unlock_irq(&pipe->rd_wait.lock);
1321
1322         /* This might have made more room for writers */
1323         wake_up_interruptible(&pipe->wr_wait);
1324         return 0;
1325 }
1326
1327 /*
1328  * Allocate a new array of pipe buffers and copy the info over. Returns the
1329  * pipe size if successful, or return -ERROR on error.
1330  */
1331 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned int arg)
1332 {
1333         unsigned long user_bufs;
1334         unsigned int nr_slots, size;
1335         long ret = 0;
1336
1337         if (pipe_has_watch_queue(pipe))
1338                 return -EBUSY;
1339
1340         size = round_pipe_size(arg);
1341         nr_slots = size >> PAGE_SHIFT;
1342
1343         if (!nr_slots)
1344                 return -EINVAL;
1345
1346         /*
1347          * If trying to increase the pipe capacity, check that an
1348          * unprivileged user is not trying to exceed various limits
1349          * (soft limit check here, hard limit check just below).
1350          * Decreasing the pipe capacity is always permitted, even
1351          * if the user is currently over a limit.
1352          */
1353         if (nr_slots > pipe->max_usage &&
1354                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1355                 return -EPERM;
1356
1357         user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1358
1359         if (nr_slots > pipe->max_usage &&
1360                         (too_many_pipe_buffers_hard(user_bufs) ||
1361                          too_many_pipe_buffers_soft(user_bufs)) &&
1362                         pipe_is_unprivileged_user()) {
1363                 ret = -EPERM;
1364                 goto out_revert_acct;
1365         }
1366
1367         ret = pipe_resize_ring(pipe, nr_slots);
1368         if (ret < 0)
1369                 goto out_revert_acct;
1370
1371         pipe->max_usage = nr_slots;
1372         pipe->nr_accounted = nr_slots;
1373         return pipe->max_usage * PAGE_SIZE;
1374
1375 out_revert_acct:
1376         (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1377         return ret;
1378 }
1379
1380 /*
1381  * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1382  * not enough to verify that this is a pipe.
1383  */
1384 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1385 {
1386         struct pipe_inode_info *pipe = file->private_data;
1387
1388         if (file->f_op != &pipefifo_fops || !pipe)
1389                 return NULL;
1390         if (for_splice && pipe_has_watch_queue(pipe))
1391                 return NULL;
1392         return pipe;
1393 }
1394
1395 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
1396 {
1397         struct pipe_inode_info *pipe;
1398         long ret;
1399
1400         pipe = get_pipe_info(file, false);
1401         if (!pipe)
1402                 return -EBADF;
1403
1404         __pipe_lock(pipe);
1405
1406         switch (cmd) {
1407         case F_SETPIPE_SZ:
1408                 ret = pipe_set_size(pipe, arg);
1409                 break;
1410         case F_GETPIPE_SZ:
1411                 ret = pipe->max_usage * PAGE_SIZE;
1412                 break;
1413         default:
1414                 ret = -EINVAL;
1415                 break;
1416         }
1417
1418         __pipe_unlock(pipe);
1419         return ret;
1420 }
1421
1422 static const struct super_operations pipefs_ops = {
1423         .destroy_inode = free_inode_nonrcu,
1424         .statfs = simple_statfs,
1425 };
1426
1427 /*
1428  * pipefs should _never_ be mounted by userland - too much of security hassle,
1429  * no real gain from having the whole whorehouse mounted. So we don't need
1430  * any operations on the root directory. However, we need a non-trivial
1431  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1432  */
1433
1434 static int pipefs_init_fs_context(struct fs_context *fc)
1435 {
1436         struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1437         if (!ctx)
1438                 return -ENOMEM;
1439         ctx->ops = &pipefs_ops;
1440         ctx->dops = &pipefs_dentry_operations;
1441         return 0;
1442 }
1443
1444 static struct file_system_type pipe_fs_type = {
1445         .name           = "pipefs",
1446         .init_fs_context = pipefs_init_fs_context,
1447         .kill_sb        = kill_anon_super,
1448 };
1449
1450 #ifdef CONFIG_SYSCTL
1451 static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
1452                                         unsigned int *valp,
1453                                         int write, void *data)
1454 {
1455         if (write) {
1456                 unsigned int val;
1457
1458                 val = round_pipe_size(*lvalp);
1459                 if (val == 0)
1460                         return -EINVAL;
1461
1462                 *valp = val;
1463         } else {
1464                 unsigned int val = *valp;
1465                 *lvalp = (unsigned long) val;
1466         }
1467
1468         return 0;
1469 }
1470
1471 static int proc_dopipe_max_size(struct ctl_table *table, int write,
1472                                 void *buffer, size_t *lenp, loff_t *ppos)
1473 {
1474         return do_proc_douintvec(table, write, buffer, lenp, ppos,
1475                                  do_proc_dopipe_max_size_conv, NULL);
1476 }
1477
1478 static struct ctl_table fs_pipe_sysctls[] = {
1479         {
1480                 .procname       = "pipe-max-size",
1481                 .data           = &pipe_max_size,
1482                 .maxlen         = sizeof(pipe_max_size),
1483                 .mode           = 0644,
1484                 .proc_handler   = proc_dopipe_max_size,
1485         },
1486         {
1487                 .procname       = "pipe-user-pages-hard",
1488                 .data           = &pipe_user_pages_hard,
1489                 .maxlen         = sizeof(pipe_user_pages_hard),
1490                 .mode           = 0644,
1491                 .proc_handler   = proc_doulongvec_minmax,
1492         },
1493         {
1494                 .procname       = "pipe-user-pages-soft",
1495                 .data           = &pipe_user_pages_soft,
1496                 .maxlen         = sizeof(pipe_user_pages_soft),
1497                 .mode           = 0644,
1498                 .proc_handler   = proc_doulongvec_minmax,
1499         },
1500         { }
1501 };
1502 #endif
1503
1504 static int __init init_pipe_fs(void)
1505 {
1506         int err = register_filesystem(&pipe_fs_type);
1507
1508         if (!err) {
1509                 pipe_mnt = kern_mount(&pipe_fs_type);
1510                 if (IS_ERR(pipe_mnt)) {
1511                         err = PTR_ERR(pipe_mnt);
1512                         unregister_filesystem(&pipe_fs_type);
1513                 }
1514         }
1515 #ifdef CONFIG_SYSCTL
1516         register_sysctl_init("fs", fs_pipe_sysctls);
1517 #endif
1518         return err;
1519 }
1520
1521 fs_initcall(init_pipe_fs);