4 * Copyright (C) 1991, 1992, 1999 Linus Torvalds
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>
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>
25 #include <asm/uaccess.h>
26 #include <asm/ioctls.h>
31 * The max size that a non-root user is allowed to grow the pipe. Can
32 * be set by root in /proc/sys/fs/pipe-max-size
34 unsigned int pipe_max_size = 1048576;
37 * Minimum pipe size, as required by POSIX
39 unsigned int pipe_min_size = PAGE_SIZE;
42 * We use a start+len construction, which provides full use of the
44 * -- Florian Coosmann (FGC)
46 * Reads with count = 0 should always return 0.
47 * -- Julian Bradfield 1999-06-07.
49 * FIFOs and Pipes now generate SIGIO for both readers and writers.
50 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
52 * pipe_read & write cleanup
53 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
56 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
59 mutex_lock_nested(&pipe->mutex, subclass);
62 void pipe_lock(struct pipe_inode_info *pipe)
65 * pipe_lock() nests non-pipe inode locks (for writing to a file)
67 pipe_lock_nested(pipe, I_MUTEX_PARENT);
69 EXPORT_SYMBOL(pipe_lock);
71 void pipe_unlock(struct pipe_inode_info *pipe)
74 mutex_unlock(&pipe->mutex);
76 EXPORT_SYMBOL(pipe_unlock);
78 static inline void __pipe_lock(struct pipe_inode_info *pipe)
80 mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
83 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
85 mutex_unlock(&pipe->mutex);
88 void pipe_double_lock(struct pipe_inode_info *pipe1,
89 struct pipe_inode_info *pipe2)
91 BUG_ON(pipe1 == pipe2);
94 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
95 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
97 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
98 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
102 /* Drop the inode semaphore and wait for a pipe event, atomically */
103 void pipe_wait(struct pipe_inode_info *pipe)
108 * Pipes are system-local resources, so sleeping on them
109 * is considered a noninteractive wait:
111 prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
114 finish_wait(&pipe->wait, &wait);
118 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
119 struct pipe_buffer *buf)
121 struct page *page = buf->page;
124 * If nobody else uses this page, and we don't already have a
125 * temporary page, let's keep track of it as a one-deep
126 * allocation cache. (Otherwise just release our reference to it)
128 if (page_count(page) == 1 && !pipe->tmp_page)
129 pipe->tmp_page = page;
131 page_cache_release(page);
135 * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
136 * @pipe: the pipe that the buffer belongs to
137 * @buf: the buffer to attempt to steal
140 * This function attempts to steal the &struct page attached to
141 * @buf. If successful, this function returns 0 and returns with
142 * the page locked. The caller may then reuse the page for whatever
143 * he wishes; the typical use is insertion into a different file
146 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
147 struct pipe_buffer *buf)
149 struct page *page = buf->page;
152 * A reference of one is golden, that means that the owner of this
153 * page is the only one holding a reference to it. lock the page
156 if (page_count(page) == 1) {
163 EXPORT_SYMBOL(generic_pipe_buf_steal);
166 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
167 * @pipe: the pipe that the buffer belongs to
168 * @buf: the buffer to get a reference to
171 * This function grabs an extra reference to @buf. It's used in
172 * in the tee() system call, when we duplicate the buffers in one
175 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
177 page_cache_get(buf->page);
179 EXPORT_SYMBOL(generic_pipe_buf_get);
182 * generic_pipe_buf_confirm - verify contents of the pipe buffer
183 * @info: the pipe that the buffer belongs to
184 * @buf: the buffer to confirm
187 * This function does nothing, because the generic pipe code uses
188 * pages that are always good when inserted into the pipe.
190 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
191 struct pipe_buffer *buf)
195 EXPORT_SYMBOL(generic_pipe_buf_confirm);
198 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
199 * @pipe: the pipe that the buffer belongs to
200 * @buf: the buffer to put a reference to
203 * This function releases a reference to @buf.
205 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
206 struct pipe_buffer *buf)
208 page_cache_release(buf->page);
210 EXPORT_SYMBOL(generic_pipe_buf_release);
212 static const struct pipe_buf_operations anon_pipe_buf_ops = {
214 .confirm = generic_pipe_buf_confirm,
215 .release = anon_pipe_buf_release,
216 .steal = generic_pipe_buf_steal,
217 .get = generic_pipe_buf_get,
220 static const struct pipe_buf_operations packet_pipe_buf_ops = {
222 .confirm = generic_pipe_buf_confirm,
223 .release = anon_pipe_buf_release,
224 .steal = generic_pipe_buf_steal,
225 .get = generic_pipe_buf_get,
229 pipe_read(struct kiocb *iocb, struct iov_iter *to)
231 size_t total_len = iov_iter_count(to);
232 struct file *filp = iocb->ki_filp;
233 struct pipe_inode_info *pipe = filp->private_data;
237 /* Null read succeeds. */
238 if (unlikely(total_len == 0))
245 int bufs = pipe->nrbufs;
247 int curbuf = pipe->curbuf;
248 struct pipe_buffer *buf = pipe->bufs + curbuf;
249 const struct pipe_buf_operations *ops = buf->ops;
250 size_t chars = buf->len;
254 if (chars > total_len)
257 error = ops->confirm(pipe, buf);
264 written = copy_page_to_iter(buf->page, buf->offset, chars, to);
265 if (unlikely(written < chars)) {
271 buf->offset += chars;
274 /* Was it a packet buffer? Clean up and exit */
275 if (buf->flags & PIPE_BUF_FLAG_PACKET) {
282 ops->release(pipe, buf);
283 curbuf = (curbuf + 1) & (pipe->buffers - 1);
284 pipe->curbuf = curbuf;
285 pipe->nrbufs = --bufs;
290 break; /* common path: read succeeded */
292 if (bufs) /* More to do? */
296 if (!pipe->waiting_writers) {
297 /* syscall merging: Usually we must not sleep
298 * if O_NONBLOCK is set, or if we got some data.
299 * But if a writer sleeps in kernel space, then
300 * we can wait for that data without violating POSIX.
304 if (filp->f_flags & O_NONBLOCK) {
309 if (signal_pending(current)) {
315 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
316 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
322 /* Signal writers asynchronously that there is more room. */
324 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
325 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
332 static inline int is_packetized(struct file *file)
334 return (file->f_flags & O_DIRECT) != 0;
338 pipe_write(struct kiocb *iocb, struct iov_iter *from)
340 struct file *filp = iocb->ki_filp;
341 struct pipe_inode_info *pipe = filp->private_data;
344 size_t total_len = iov_iter_count(from);
347 /* Null write succeeds. */
348 if (unlikely(total_len == 0))
353 if (!pipe->readers) {
354 send_sig(SIGPIPE, current, 0);
359 /* We try to merge small writes */
360 chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
361 if (pipe->nrbufs && chars != 0) {
362 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
364 struct pipe_buffer *buf = pipe->bufs + lastbuf;
365 const struct pipe_buf_operations *ops = buf->ops;
366 int offset = buf->offset + buf->len;
368 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
369 int error = ops->confirm(pipe, buf);
373 ret = copy_page_from_iter(buf->page, offset, chars, from);
374 if (unlikely(ret < chars)) {
381 if (!iov_iter_count(from))
389 if (!pipe->readers) {
390 send_sig(SIGPIPE, current, 0);
396 if (bufs < pipe->buffers) {
397 int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
398 struct pipe_buffer *buf = pipe->bufs + newbuf;
399 struct page *page = pipe->tmp_page;
403 page = alloc_page(GFP_HIGHUSER);
404 if (unlikely(!page)) {
405 ret = ret ? : -ENOMEM;
408 pipe->tmp_page = page;
410 /* Always wake up, even if the copy fails. Otherwise
411 * we lock up (O_NONBLOCK-)readers that sleep due to
413 * FIXME! Is this really true?
416 copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
417 if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
424 /* Insert it into the buffer array */
426 buf->ops = &anon_pipe_buf_ops;
430 if (is_packetized(filp)) {
431 buf->ops = &packet_pipe_buf_ops;
432 buf->flags = PIPE_BUF_FLAG_PACKET;
434 pipe->nrbufs = ++bufs;
435 pipe->tmp_page = NULL;
437 if (!iov_iter_count(from))
440 if (bufs < pipe->buffers)
442 if (filp->f_flags & O_NONBLOCK) {
447 if (signal_pending(current)) {
453 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
454 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
457 pipe->waiting_writers++;
459 pipe->waiting_writers--;
464 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
465 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
467 if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
468 int err = file_update_time(filp);
471 sb_end_write(file_inode(filp)->i_sb);
476 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
478 struct pipe_inode_info *pipe = filp->private_data;
479 int count, buf, nrbufs;
486 nrbufs = pipe->nrbufs;
487 while (--nrbufs >= 0) {
488 count += pipe->bufs[buf].len;
489 buf = (buf+1) & (pipe->buffers - 1);
493 return put_user(count, (int __user *)arg);
499 /* No kernel lock held - fine */
501 pipe_poll(struct file *filp, poll_table *wait)
504 struct pipe_inode_info *pipe = filp->private_data;
507 poll_wait(filp, &pipe->wait, wait);
509 /* Reading only -- no need for acquiring the semaphore. */
510 nrbufs = pipe->nrbufs;
512 if (filp->f_mode & FMODE_READ) {
513 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
514 if (!pipe->writers && filp->f_version != pipe->w_counter)
518 if (filp->f_mode & FMODE_WRITE) {
519 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
521 * Most Unices do not set POLLERR for FIFOs but on Linux they
522 * behave exactly like pipes for poll().
531 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
535 spin_lock(&inode->i_lock);
536 if (!--pipe->files) {
537 inode->i_pipe = NULL;
540 spin_unlock(&inode->i_lock);
543 free_pipe_info(pipe);
547 pipe_release(struct inode *inode, struct file *file)
549 struct pipe_inode_info *pipe = file->private_data;
552 if (file->f_mode & FMODE_READ)
554 if (file->f_mode & FMODE_WRITE)
557 if (pipe->readers || pipe->writers) {
558 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
559 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
560 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
564 put_pipe_info(inode, pipe);
569 pipe_fasync(int fd, struct file *filp, int on)
571 struct pipe_inode_info *pipe = filp->private_data;
575 if (filp->f_mode & FMODE_READ)
576 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
577 if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
578 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
579 if (retval < 0 && (filp->f_mode & FMODE_READ))
580 /* this can happen only if on == T */
581 fasync_helper(-1, filp, 0, &pipe->fasync_readers);
587 struct pipe_inode_info *alloc_pipe_info(void)
589 struct pipe_inode_info *pipe;
591 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
593 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
595 init_waitqueue_head(&pipe->wait);
596 pipe->r_counter = pipe->w_counter = 1;
597 pipe->buffers = PIPE_DEF_BUFFERS;
598 mutex_init(&pipe->mutex);
607 void free_pipe_info(struct pipe_inode_info *pipe)
611 for (i = 0; i < pipe->buffers; i++) {
612 struct pipe_buffer *buf = pipe->bufs + i;
614 buf->ops->release(pipe, buf);
617 __free_page(pipe->tmp_page);
622 static struct vfsmount *pipe_mnt __read_mostly;
625 * pipefs_dname() is called from d_path().
627 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
629 return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
630 d_inode(dentry)->i_ino);
633 static const struct dentry_operations pipefs_dentry_operations = {
634 .d_dname = pipefs_dname,
637 static struct inode * get_pipe_inode(void)
639 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
640 struct pipe_inode_info *pipe;
645 inode->i_ino = get_next_ino();
647 pipe = alloc_pipe_info();
651 inode->i_pipe = pipe;
653 pipe->readers = pipe->writers = 1;
654 inode->i_fop = &pipefifo_fops;
657 * Mark the inode dirty from the very beginning,
658 * that way it will never be moved to the dirty
659 * list because "mark_inode_dirty()" will think
660 * that it already _is_ on the dirty list.
662 inode->i_state = I_DIRTY;
663 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
664 inode->i_uid = current_fsuid();
665 inode->i_gid = current_fsgid();
666 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
677 int create_pipe_files(struct file **res, int flags)
680 struct inode *inode = get_pipe_inode();
683 static struct qstr name = { .name = "" };
689 path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
692 path.mnt = mntget(pipe_mnt);
694 d_instantiate(path.dentry, inode);
696 f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
702 f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
703 f->private_data = inode->i_pipe;
705 res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
706 if (IS_ERR(res[0])) {
707 err = PTR_ERR(res[0]);
712 res[0]->private_data = inode->i_pipe;
713 res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
720 free_pipe_info(inode->i_pipe);
725 free_pipe_info(inode->i_pipe);
730 static int __do_pipe_flags(int *fd, struct file **files, int flags)
735 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
738 error = create_pipe_files(files, flags);
742 error = get_unused_fd_flags(flags);
747 error = get_unused_fd_flags(flags);
752 audit_fd_pair(fdr, fdw);
765 int do_pipe_flags(int *fd, int flags)
767 struct file *files[2];
768 int error = __do_pipe_flags(fd, files, flags);
770 fd_install(fd[0], files[0]);
771 fd_install(fd[1], files[1]);
777 * sys_pipe() is the normal C calling standard for creating
778 * a pipe. It's not the way Unix traditionally does this, though.
780 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
782 struct file *files[2];
786 error = __do_pipe_flags(fd, files, flags);
788 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
791 put_unused_fd(fd[0]);
792 put_unused_fd(fd[1]);
795 fd_install(fd[0], files[0]);
796 fd_install(fd[1], files[1]);
802 SYSCALL_DEFINE1(pipe, int __user *, fildes)
804 return sys_pipe2(fildes, 0);
807 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
811 while (cur == *cnt) {
813 if (signal_pending(current))
816 return cur == *cnt ? -ERESTARTSYS : 0;
819 static void wake_up_partner(struct pipe_inode_info *pipe)
821 wake_up_interruptible(&pipe->wait);
824 static int fifo_open(struct inode *inode, struct file *filp)
826 struct pipe_inode_info *pipe;
827 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
832 spin_lock(&inode->i_lock);
834 pipe = inode->i_pipe;
836 spin_unlock(&inode->i_lock);
838 spin_unlock(&inode->i_lock);
839 pipe = alloc_pipe_info();
843 spin_lock(&inode->i_lock);
844 if (unlikely(inode->i_pipe)) {
845 inode->i_pipe->files++;
846 spin_unlock(&inode->i_lock);
847 free_pipe_info(pipe);
848 pipe = inode->i_pipe;
850 inode->i_pipe = pipe;
851 spin_unlock(&inode->i_lock);
854 filp->private_data = pipe;
855 /* OK, we have a pipe and it's pinned down */
859 /* We can only do regular read/write on fifos */
860 filp->f_mode &= (FMODE_READ | FMODE_WRITE);
862 switch (filp->f_mode) {
866 * POSIX.1 says that O_NONBLOCK means return with the FIFO
867 * opened, even when there is no process writing the FIFO.
870 if (pipe->readers++ == 0)
871 wake_up_partner(pipe);
873 if (!is_pipe && !pipe->writers) {
874 if ((filp->f_flags & O_NONBLOCK)) {
875 /* suppress POLLHUP until we have
877 filp->f_version = pipe->w_counter;
879 if (wait_for_partner(pipe, &pipe->w_counter))
888 * POSIX.1 says that O_NONBLOCK means return -1 with
889 * errno=ENXIO when there is no process reading the FIFO.
892 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
896 if (!pipe->writers++)
897 wake_up_partner(pipe);
899 if (!is_pipe && !pipe->readers) {
900 if (wait_for_partner(pipe, &pipe->r_counter))
905 case FMODE_READ | FMODE_WRITE:
908 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
909 * This implementation will NEVER block on a O_RDWR open, since
910 * the process can at least talk to itself.
917 if (pipe->readers == 1 || pipe->writers == 1)
918 wake_up_partner(pipe);
931 if (!--pipe->readers)
932 wake_up_interruptible(&pipe->wait);
937 if (!--pipe->writers)
938 wake_up_interruptible(&pipe->wait);
945 put_pipe_info(inode, pipe);
949 const struct file_operations pipefifo_fops = {
952 .read_iter = pipe_read,
953 .write_iter = pipe_write,
955 .unlocked_ioctl = pipe_ioctl,
956 .release = pipe_release,
957 .fasync = pipe_fasync,
961 * Allocate a new array of pipe buffers and copy the info over. Returns the
962 * pipe size if successful, or return -ERROR on error.
964 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
966 struct pipe_buffer *bufs;
969 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
970 * expect a lot of shrink+grow operations, just free and allocate
971 * again like we would do for growing. If the pipe currently
972 * contains more buffers than arg, then return busy.
974 if (nr_pages < pipe->nrbufs)
977 bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
982 * The pipe array wraps around, so just start the new one at zero
983 * and adjust the indexes.
989 tail = pipe->curbuf + pipe->nrbufs;
990 if (tail < pipe->buffers)
993 tail &= (pipe->buffers - 1);
995 head = pipe->nrbufs - tail;
997 memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
999 memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1005 pipe->buffers = nr_pages;
1006 return nr_pages * PAGE_SIZE;
1010 * Currently we rely on the pipe array holding a power-of-2 number
1013 static inline unsigned int round_pipe_size(unsigned int size)
1015 unsigned long nr_pages;
1017 nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1018 return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1022 * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1023 * will return an error.
1025 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1026 size_t *lenp, loff_t *ppos)
1030 ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1031 if (ret < 0 || !write)
1034 pipe_max_size = round_pipe_size(pipe_max_size);
1039 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1040 * location, so checking ->i_pipe is not enough to verify that this is a
1043 struct pipe_inode_info *get_pipe_info(struct file *file)
1045 return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1048 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1050 struct pipe_inode_info *pipe;
1053 pipe = get_pipe_info(file);
1060 case F_SETPIPE_SZ: {
1061 unsigned int size, nr_pages;
1063 size = round_pipe_size(arg);
1064 nr_pages = size >> PAGE_SHIFT;
1070 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1074 ret = pipe_set_size(pipe, nr_pages);
1078 ret = pipe->buffers * PAGE_SIZE;
1086 __pipe_unlock(pipe);
1090 static const struct super_operations pipefs_ops = {
1091 .destroy_inode = free_inode_nonrcu,
1092 .statfs = simple_statfs,
1096 * pipefs should _never_ be mounted by userland - too much of security hassle,
1097 * no real gain from having the whole whorehouse mounted. So we don't need
1098 * any operations on the root directory. However, we need a non-trivial
1099 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1101 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1102 int flags, const char *dev_name, void *data)
1104 return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1105 &pipefs_dentry_operations, PIPEFS_MAGIC);
1108 static struct file_system_type pipe_fs_type = {
1110 .mount = pipefs_mount,
1111 .kill_sb = kill_anon_super,
1114 static int __init init_pipe_fs(void)
1116 int err = register_filesystem(&pipe_fs_type);
1119 pipe_mnt = kern_mount(&pipe_fs_type);
1120 if (IS_ERR(pipe_mnt)) {
1121 err = PTR_ERR(pipe_mnt);
1122 unregister_filesystem(&pipe_fs_type);
1128 fs_initcall(init_pipe_fs);