upload tizen1.0 sourceHEADmaster2.0alpha

1 files changed, 1294 insertions, 0 deletions

diff --git a/fs/pipe.c b/fs/pipe.c
new file mode 100644
index 00000000..a58d7ee7
--- /dev/null
+++ b/fs/pipe.c
@@ -0,0 +1,1294 @@
+/*
+ *  linux/fs/pipe.c
+ *
+ *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
+ */
+
+#include <linux/mm.h>
+#include <linux/file.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/log2.h>
+#include <linux/mount.h>
+#include <linux/pipe_fs_i.h>
+#include <linux/uio.h>
+#include <linux/highmem.h>
+#include <linux/pagemap.h>
+#include <linux/audit.h>
+#include <linux/syscalls.h>
+#include <linux/fcntl.h>
+
+#include <asm/uaccess.h>
+#include <asm/ioctls.h>
+
+/*
+ * The max size that a non-root user is allowed to grow the pipe. Can
+ * be set by root in /proc/sys/fs/pipe-max-size
+ */
+unsigned int pipe_max_size = 1048576;
+
+/*
+ * Minimum pipe size, as required by POSIX
+ */
+unsigned int pipe_min_size = PAGE_SIZE;
+
+/*
+ * We use a start+len construction, which provides full use of the 
+ * allocated memory.
+ * -- Florian Coosmann (FGC)
+ * 
+ * Reads with count = 0 should always return 0.
+ * -- Julian Bradfield 1999-06-07.
+ *
+ * FIFOs and Pipes now generate SIGIO for both readers and writers.
+ * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
+ *
+ * pipe_read & write cleanup
+ * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
+ */
+
+static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
+{
+	if (pipe->inode)
+		mutex_lock_nested(&pipe->inode->i_mutex, subclass);
+}
+
+void pipe_lock(struct pipe_inode_info *pipe)
+{
+	/*
+	 * pipe_lock() nests non-pipe inode locks (for writing to a file)
+	 */
+	pipe_lock_nested(pipe, I_MUTEX_PARENT);
+}
+EXPORT_SYMBOL(pipe_lock);
+
+void pipe_unlock(struct pipe_inode_info *pipe)
+{
+	if (pipe->inode)
+		mutex_unlock(&pipe->inode->i_mutex);
+}
+EXPORT_SYMBOL(pipe_unlock);
+
+void pipe_double_lock(struct pipe_inode_info *pipe1,
+		      struct pipe_inode_info *pipe2)
+{
+	BUG_ON(pipe1 == pipe2);
+
+	if (pipe1 < pipe2) {
+		pipe_lock_nested(pipe1, I_MUTEX_PARENT);
+		pipe_lock_nested(pipe2, I_MUTEX_CHILD);
+	} else {
+		pipe_lock_nested(pipe2, I_MUTEX_PARENT);
+		pipe_lock_nested(pipe1, I_MUTEX_CHILD);
+	}
+}
+
+/* Drop the inode semaphore and wait for a pipe event, atomically */
+void pipe_wait(struct pipe_inode_info *pipe)
+{
+	DEFINE_WAIT(wait);
+
+	/*
+	 * Pipes are system-local resources, so sleeping on them
+	 * is considered a noninteractive wait:
+	 */
+	prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
+	pipe_unlock(pipe);
+	schedule();
+	finish_wait(&pipe->wait, &wait);
+	pipe_lock(pipe);
+}
+
+static int
+pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
+			int atomic)
+{
+	unsigned long copy;
+
+	while (len > 0) {
+		while (!iov->iov_len)
+			iov++;
+		copy = min_t(unsigned long, len, iov->iov_len);
+
+		if (atomic) {
+			if (__copy_from_user_inatomic(to, iov->iov_base, copy))
+				return -EFAULT;
+		} else {
+			if (copy_from_user(to, iov->iov_base, copy))
+				return -EFAULT;
+		}
+		to += copy;
+		len -= copy;
+		iov->iov_base += copy;
+		iov->iov_len -= copy;
+	}
+	return 0;
+}
+
+static int
+pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
+		      int atomic)
+{
+	unsigned long copy;
+
+	while (len > 0) {
+		while (!iov->iov_len)
+			iov++;
+		copy = min_t(unsigned long, len, iov->iov_len);
+
+		if (atomic) {
+			if (__copy_to_user_inatomic(iov->iov_base, from, copy))
+				return -EFAULT;
+		} else {
+			if (copy_to_user(iov->iov_base, from, copy))
+				return -EFAULT;
+		}
+		from += copy;
+		len -= copy;
+		iov->iov_base += copy;
+		iov->iov_len -= copy;
+	}
+	return 0;
+}
+
+/*
+ * Attempt to pre-fault in the user memory, so we can use atomic copies.
+ * Returns the number of bytes not faulted in.
+ */
+static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
+{
+	while (!iov->iov_len)
+		iov++;
+
+	while (len > 0) {
+		unsigned long this_len;
+
+		this_len = min_t(unsigned long, len, iov->iov_len);
+		if (fault_in_pages_writeable(iov->iov_base, this_len))
+			break;
+
+		len -= this_len;
+		iov++;
+	}
+
+	return len;
+}
+
+/*
+ * Pre-fault in the user memory, so we can use atomic copies.
+ */
+static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
+{
+	while (!iov->iov_len)
+		iov++;
+
+	while (len > 0) {
+		unsigned long this_len;
+
+		this_len = min_t(unsigned long, len, iov->iov_len);
+		fault_in_pages_readable(iov->iov_base, this_len);
+		len -= this_len;
+		iov++;
+	}
+}
+
+static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
+				  struct pipe_buffer *buf)
+{
+	struct page *page = buf->page;
+
+	/*
+	 * If nobody else uses this page, and we don't already have a
+	 * temporary page, let's keep track of it as a one-deep
+	 * allocation cache. (Otherwise just release our reference to it)
+	 */
+	if (page_count(page) == 1 && !pipe->tmp_page)
+		pipe->tmp_page = page;
+	else
+		page_cache_release(page);
+}
+
+/**
+ * generic_pipe_buf_map - virtually map a pipe buffer
+ * @pipe:	the pipe that the buffer belongs to
+ * @buf:	the buffer that should be mapped
+ * @atomic:	whether to use an atomic map
+ *
+ * Description:
+ *	This function returns a kernel virtual address mapping for the
+ *	pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
+ *	and the caller has to be careful not to fault before calling
+ *	the unmap function.
+ *
+ *	Note that this function occupies KM_USER0 if @atomic != 0.
+ */
+void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
+			   struct pipe_buffer *buf, int atomic)
+{
+	if (atomic) {
+		buf->flags |= PIPE_BUF_FLAG_ATOMIC;
+		return kmap_atomic(buf->page, KM_USER0);
+	}
+
+	return kmap(buf->page);
+}
+EXPORT_SYMBOL(generic_pipe_buf_map);
+
+/**
+ * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
+ * @pipe:	the pipe that the buffer belongs to
+ * @buf:	the buffer that should be unmapped
+ * @map_data:	the data that the mapping function returned
+ *
+ * Description:
+ *	This function undoes the mapping that ->map() provided.
+ */
+void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
+			    struct pipe_buffer *buf, void *map_data)
+{
+	if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
+		buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
+		kunmap_atomic(map_data, KM_USER0);
+	} else
+		kunmap(buf->page);
+}
+EXPORT_SYMBOL(generic_pipe_buf_unmap);
+
+/**
+ * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
+ * @pipe:	the pipe that the buffer belongs to
+ * @buf:	the buffer to attempt to steal
+ *
+ * Description:
+ *	This function attempts to steal the &struct page attached to
+ *	@buf. If successful, this function returns 0 and returns with
+ *	the page locked. The caller may then reuse the page for whatever
+ *	he wishes; the typical use is insertion into a different file
+ *	page cache.
+ */
+int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
+			   struct pipe_buffer *buf)
+{
+	struct page *page = buf->page;
+
+	/*
+	 * A reference of one is golden, that means that the owner of this
+	 * page is the only one holding a reference to it. lock the page
+	 * and return OK.
+	 */
+	if (page_count(page) == 1) {
+		lock_page(page);
+		return 0;
+	}
+
+	return 1;
+}
+EXPORT_SYMBOL(generic_pipe_buf_steal);
+
+/**
+ * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
+ * @pipe:	the pipe that the buffer belongs to
+ * @buf:	the buffer to get a reference to
+ *
+ * Description:
+ *	This function grabs an extra reference to @buf. It's used in
+ *	in the tee() system call, when we duplicate the buffers in one
+ *	pipe into another.
+ */
+void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
+{
+	page_cache_get(buf->page);
+}
+EXPORT_SYMBOL(generic_pipe_buf_get);
+
+/**
+ * generic_pipe_buf_confirm - verify contents of the pipe buffer
+ * @info:	the pipe that the buffer belongs to
+ * @buf:	the buffer to confirm
+ *
+ * Description:
+ *	This function does nothing, because the generic pipe code uses
+ *	pages that are always good when inserted into the pipe.
+ */
+int generic_pipe_buf_confirm(struct pipe_inode_info *info,
+			     struct pipe_buffer *buf)
+{
+	return 0;
+}
+EXPORT_SYMBOL(generic_pipe_buf_confirm);
+
+/**
+ * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
+ * @pipe:	the pipe that the buffer belongs to
+ * @buf:	the buffer to put a reference to
+ *
+ * Description:
+ *	This function releases a reference to @buf.
+ */
+void generic_pipe_buf_release(struct pipe_inode_info *pipe,
+			      struct pipe_buffer *buf)
+{
+	page_cache_release(buf->page);
+}
+EXPORT_SYMBOL(generic_pipe_buf_release);
+
+static const struct pipe_buf_operations anon_pipe_buf_ops = {
+	.can_merge = 1,
+	.map = generic_pipe_buf_map,
+	.unmap = generic_pipe_buf_unmap,
+	.confirm = generic_pipe_buf_confirm,
+	.release = anon_pipe_buf_release,
+	.steal = generic_pipe_buf_steal,
+	.get = generic_pipe_buf_get,
+};
+
+static ssize_t
+pipe_read(struct kiocb *iocb, const struct iovec *_iov,
+	   unsigned long nr_segs, loff_t pos)
+{
+	struct file *filp = iocb->ki_filp;
+	struct inode *inode = filp->f_path.dentry->d_inode;
+	struct pipe_inode_info *pipe;
+	int do_wakeup;
+	ssize_t ret;
+	struct iovec *iov = (struct iovec *)_iov;
+	size_t total_len;
+
+	total_len = iov_length(iov, nr_segs);
+	/* Null read succeeds. */
+	if (unlikely(total_len == 0))
+		return 0;
+
+	do_wakeup = 0;
+	ret = 0;
+	mutex_lock(&inode->i_mutex);
+	pipe = inode->i_pipe;
+	for (;;) {
+		int bufs = pipe->nrbufs;
+		if (bufs) {
+			int curbuf = pipe->curbuf;
+			struct pipe_buffer *buf = pipe->bufs + curbuf;
+			const struct pipe_buf_operations *ops = buf->ops;
+			void *addr;
+			size_t chars = buf->len;
+			int error, atomic;
+
+			if (chars > total_len)
+				chars = total_len;
+
+			error = ops->confirm(pipe, buf);
+			if (error) {
+				if (!ret)
+					ret = error;
+				break;
+			}
+
+			atomic = !iov_fault_in_pages_write(iov, chars);
+redo:
+			addr = ops->map(pipe, buf, atomic);
+			error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
+			ops->unmap(pipe, buf, addr);
+			if (unlikely(error)) {
+				/*
+				 * Just retry with the slow path if we failed.
+				 */
+				if (atomic) {
+					atomic = 0;
+					goto redo;
+				}
+				if (!ret)
+					ret = error;
+				break;
+			}
+			ret += chars;
+			buf->offset += chars;
+			buf->len -= chars;
+			if (!buf->len) {
+				buf->ops = NULL;
+				ops->release(pipe, buf);
+				curbuf = (curbuf + 1) & (pipe->buffers - 1);
+				pipe->curbuf = curbuf;
+				pipe->nrbufs = --bufs;
+				do_wakeup = 1;
+			}
+			total_len -= chars;
+			if (!total_len)
+				break;	/* common path: read succeeded */
+		}
+		if (bufs)	/* More to do? */
+			continue;
+		if (!pipe->writers)
+			break;
+		if (!pipe->waiting_writers) {
+			/* syscall merging: Usually we must not sleep
+			 * if O_NONBLOCK is set, or if we got some data.
+			 * But if a writer sleeps in kernel space, then
+			 * we can wait for that data without violating POSIX.
+			 */
+			if (ret)
+				break;
+			if (filp->f_flags & O_NONBLOCK) {
+				ret = -EAGAIN;
+				break;
+			}
+		}
+		if (signal_pending(current)) {
+			if (!ret)
+				ret = -ERESTARTSYS;
+			break;
+		}
+		if (do_wakeup) {
+			wake_up_interruptible_sync(&pipe->wait);
+ 			kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
+		}
+		pipe_wait(pipe);
+	}
+	mutex_unlock(&inode->i_mutex);
+
+	/* Signal writers asynchronously that there is more room. */
+	if (do_wakeup) {
+		wake_up_interruptible_sync(&pipe->wait);
+		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
+	}
+	if (ret > 0)
+		file_accessed(filp);
+	return ret;
+}
+
+static ssize_t
+pipe_write(struct kiocb *iocb, const struct iovec *_iov,
+	    unsigned long nr_segs, loff_t ppos)
+{
+	struct file *filp = iocb->ki_filp;
+	struct inode *inode = filp->f_path.dentry->d_inode;
+	struct pipe_inode_info *pipe;
+	ssize_t ret;
+	int do_wakeup;
+	struct iovec *iov = (struct iovec *)_iov;
+	size_t total_len;
+	ssize_t chars;
+
+	total_len = iov_length(iov, nr_segs);
+	/* Null write succeeds. */
+	if (unlikely(total_len == 0))
+		return 0;
+
+	do_wakeup = 0;
+	ret = 0;
+	mutex_lock(&inode->i_mutex);
+	pipe = inode->i_pipe;
+
+	if (!pipe->readers) {
+		send_sig(SIGPIPE, current, 0);
+		ret = -EPIPE;
+		goto out;
+	}
+
+	/* We try to merge small writes */
+	chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
+	if (pipe->nrbufs && chars != 0) {
+		int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
+							(pipe->buffers - 1);
+		struct pipe_buffer *buf = pipe->bufs + lastbuf;
+		const struct pipe_buf_operations *ops = buf->ops;
+		int offset = buf->offset + buf->len;
+
+		if (ops->can_merge && offset + chars <= PAGE_SIZE) {
+			int error, atomic = 1;
+			void *addr;
+
+			error = ops->confirm(pipe, buf);
+			if (error)
+				goto out;
+
+			iov_fault_in_pages_read(iov, chars);
+redo1:
+			addr = ops->map(pipe, buf, atomic);
+			error = pipe_iov_copy_from_user(offset + addr, iov,
+							chars, atomic);
+			ops->unmap(pipe, buf, addr);
+			ret = error;
+			do_wakeup = 1;
+			if (error) {
+				if (atomic) {
+					atomic = 0;
+					goto redo1;
+				}
+				goto out;
+			}
+			buf->len += chars;
+			total_len -= chars;
+			ret = chars;
+			if (!total_len)
+				goto out;
+		}
+	}
+
+	for (;;) {
+		int bufs;
+
+		if (!pipe->readers) {
+			send_sig(SIGPIPE, current, 0);
+			if (!ret)
+				ret = -EPIPE;
+			break;
+		}
+		bufs = pipe->nrbufs;
+		if (bufs < pipe->buffers) {
+			int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
+			struct pipe_buffer *buf = pipe->bufs + newbuf;
+			struct page *page = pipe->tmp_page;
+			char *src;
+			int error, atomic = 1;
+
+			if (!page) {
+				page = alloc_page(GFP_HIGHUSER);
+				if (unlikely(!page)) {
+					ret = ret ? : -ENOMEM;
+					break;
+				}
+				pipe->tmp_page = page;
+			}
+			/* Always wake up, even if the copy fails. Otherwise
+			 * we lock up (O_NONBLOCK-)readers that sleep due to
+			 * syscall merging.
+			 * FIXME! Is this really true?
+			 */
+			do_wakeup = 1;
+			chars = PAGE_SIZE;
+			if (chars > total_len)
+				chars = total_len;
+
+			iov_fault_in_pages_read(iov, chars);
+redo2:
+			if (atomic)
+				src = kmap_atomic(page, KM_USER0);
+			else
+				src = kmap(page);
+
+			error = pipe_iov_copy_from_user(src, iov, chars,
+							atomic);
+			if (atomic)
+				kunmap_atomic(src, KM_USER0);
+			else
+				kunmap(page);
+
+			if (unlikely(error)) {
+				if (atomic) {
+					atomic = 0;
+					goto redo2;
+				}
+				if (!ret)
+					ret = error;
+				break;
+			}
+			ret += chars;
+
+			/* Insert it into the buffer array */
+			buf->page = page;
+			buf->ops = &anon_pipe_buf_ops;
+			buf->offset = 0;
+			buf->len = chars;
+			pipe->nrbufs = ++bufs;
+			pipe->tmp_page = NULL;
+
+			total_len -= chars;
+			if (!total_len)
+				break;
+		}
+		if (bufs < pipe->buffers)
+			continue;
+		if (filp->f_flags & O_NONBLOCK) {
+			if (!ret)
+				ret = -EAGAIN;
+			break;
+		}
+		if (signal_pending(current)) {
+			if (!ret)
+				ret = -ERESTARTSYS;
+			break;
+		}
+		if (do_wakeup) {
+			wake_up_interruptible_sync(&pipe->wait);
+			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+			do_wakeup = 0;
+		}
+		pipe->waiting_writers++;
+		pipe_wait(pipe);
+		pipe->waiting_writers--;
+	}
+out:
+	mutex_unlock(&inode->i_mutex);
+	if (do_wakeup) {
+		wake_up_interruptible_sync(&pipe->wait);
+		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+	}
+	if (ret > 0)
+		file_update_time(filp);
+	return ret;
+}
+
+static ssize_t
+bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
+{
+	return -EBADF;
+}
+
+static ssize_t
+bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
+	   loff_t *ppos)
+{
+	return -EBADF;
+}
+
+static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	struct inode *inode = filp->f_path.dentry->d_inode;
+	struct pipe_inode_info *pipe;
+	int count, buf, nrbufs;
+
+	switch (cmd) {
+		case FIONREAD:
+			mutex_lock(&inode->i_mutex);
+			pipe = inode->i_pipe;
+			count = 0;
+			buf = pipe->curbuf;
+			nrbufs = pipe->nrbufs;
+			while (--nrbufs >= 0) {
+				count += pipe->bufs[buf].len;
+				buf = (buf+1) & (pipe->buffers - 1);
+			}
+			mutex_unlock(&inode->i_mutex);
+
+			return put_user(count, (int __user *)arg);
+		default:
+			return -EINVAL;
+	}
+}
+
+/* No kernel lock held - fine */
+static unsigned int
+pipe_poll(struct file *filp, poll_table *wait)
+{
+	unsigned int mask;
+	struct inode *inode = filp->f_path.dentry->d_inode;
+	struct pipe_inode_info *pipe = inode->i_pipe;
+	int nrbufs;
+
+	poll_wait(filp, &pipe->wait, wait);
+
+	/* Reading only -- no need for acquiring the semaphore.  */
+	nrbufs = pipe->nrbufs;
+	mask = 0;
+	if (filp->f_mode & FMODE_READ) {
+		mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
+		if (!pipe->writers && filp->f_version != pipe->w_counter)
+			mask |= POLLHUP;
+	}
+
+	if (filp->f_mode & FMODE_WRITE) {
+		mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
+		/*
+		 * Most Unices do not set POLLERR for FIFOs but on Linux they
+		 * behave exactly like pipes for poll().
+		 */
+		if (!pipe->readers)
+			mask |= POLLERR;
+	}
+
+	return mask;
+}
+
+static int
+pipe_release(struct inode *inode, int decr, int decw)
+{
+	struct pipe_inode_info *pipe;
+
+	mutex_lock(&inode->i_mutex);
+	pipe = inode->i_pipe;
+	pipe->readers -= decr;
+	pipe->writers -= decw;
+
+	if (!pipe->readers && !pipe->writers) {
+		free_pipe_info(inode);
+	} else {
+		wake_up_interruptible_sync(&pipe->wait);
+		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
+	}
+	mutex_unlock(&inode->i_mutex);
+
+	return 0;
+}
+
+static int
+pipe_read_fasync(int fd, struct file *filp, int on)
+{
+	struct inode *inode = filp->f_path.dentry->d_inode;
+	int retval;
+
+	mutex_lock(&inode->i_mutex);
+	retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
+	mutex_unlock(&inode->i_mutex);
+
+	return retval;
+}
+
+
+static int
+pipe_write_fasync(int fd, struct file *filp, int on)
+{
+	struct inode *inode = filp->f_path.dentry->d_inode;
+	int retval;
+
+	mutex_lock(&inode->i_mutex);
+	retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
+	mutex_unlock(&inode->i_mutex);
+
+	return retval;
+}
+
+
+static int
+pipe_rdwr_fasync(int fd, struct file *filp, int on)
+{
+	struct inode *inode = filp->f_path.dentry->d_inode;
+	struct pipe_inode_info *pipe = inode->i_pipe;
+	int retval;
+
+	mutex_lock(&inode->i_mutex);
+	retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
+	if (retval >= 0) {
+		retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
+		if (retval < 0) /* this can happen only if on == T */
+			fasync_helper(-1, filp, 0, &pipe->fasync_readers);
+	}
+	mutex_unlock(&inode->i_mutex);
+	return retval;
+}
+
+
+static int
+pipe_read_release(struct inode *inode, struct file *filp)
+{
+	return pipe_release(inode, 1, 0);
+}
+
+static int
+pipe_write_release(struct inode *inode, struct file *filp)
+{
+	return pipe_release(inode, 0, 1);
+}
+
+static int
+pipe_rdwr_release(struct inode *inode, struct file *filp)
+{
+	int decr, decw;
+
+	decr = (filp->f_mode & FMODE_READ) != 0;
+	decw = (filp->f_mode & FMODE_WRITE) != 0;
+	return pipe_release(inode, decr, decw);
+}
+
+static int
+pipe_read_open(struct inode *inode, struct file *filp)
+{
+	int ret = -ENOENT;
+
+	mutex_lock(&inode->i_mutex);
+
+	if (inode->i_pipe) {
+		ret = 0;
+		inode->i_pipe->readers++;
+	}
+
+	mutex_unlock(&inode->i_mutex);
+
+	return ret;
+}
+
+static int
+pipe_write_open(struct inode *inode, struct file *filp)
+{
+	int ret = -ENOENT;
+
+	mutex_lock(&inode->i_mutex);
+
+	if (inode->i_pipe) {
+		ret = 0;
+		inode->i_pipe->writers++;
+	}
+
+	mutex_unlock(&inode->i_mutex);
+
+	return ret;
+}
+
+static int
+pipe_rdwr_open(struct inode *inode, struct file *filp)
+{
+	int ret = -ENOENT;
+
+	mutex_lock(&inode->i_mutex);
+
+	if (inode->i_pipe) {
+		ret = 0;
+		if (filp->f_mode & FMODE_READ)
+			inode->i_pipe->readers++;
+		if (filp->f_mode & FMODE_WRITE)
+			inode->i_pipe->writers++;
+	}
+
+	mutex_unlock(&inode->i_mutex);
+
+	return ret;
+}
+
+/*
+ * The file_operations structs are not static because they
+ * are also used in linux/fs/fifo.c to do operations on FIFOs.
+ *
+ * Pipes reuse fifos' file_operations structs.
+ */
+const struct file_operations read_pipefifo_fops = {
+	.llseek		= no_llseek,
+	.read		= do_sync_read,
+	.aio_read	= pipe_read,
+	.write		= bad_pipe_w,
+	.poll		= pipe_poll,
+	.unlocked_ioctl	= pipe_ioctl,
+	.open		= pipe_read_open,
+	.release	= pipe_read_release,
+	.fasync		= pipe_read_fasync,
+};
+
+const struct file_operations write_pipefifo_fops = {
+	.llseek		= no_llseek,
+	.read		= bad_pipe_r,
+	.write		= do_sync_write,
+	.aio_write	= pipe_write,
+	.poll		= pipe_poll,
+	.unlocked_ioctl	= pipe_ioctl,
+	.open		= pipe_write_open,
+	.release	= pipe_write_release,
+	.fasync		= pipe_write_fasync,
+};
+
+const struct file_operations rdwr_pipefifo_fops = {
+	.llseek		= no_llseek,
+	.read		= do_sync_read,
+	.aio_read	= pipe_read,
+	.write		= do_sync_write,
+	.aio_write	= pipe_write,
+	.poll		= pipe_poll,
+	.unlocked_ioctl	= pipe_ioctl,
+	.open		= pipe_rdwr_open,
+	.release	= pipe_rdwr_release,
+	.fasync		= pipe_rdwr_fasync,
+};
+
+struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
+{
+	struct pipe_inode_info *pipe;
+
+	pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
+	if (pipe) {
+		pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
+		if (pipe->bufs) {
+			init_waitqueue_head(&pipe->wait);
+			pipe->r_counter = pipe->w_counter = 1;
+			pipe->inode = inode;
+			pipe->buffers = PIPE_DEF_BUFFERS;
+			return pipe;
+		}
+		kfree(pipe);
+	}
+
+	return NULL;
+}
+
+void __free_pipe_info(struct pipe_inode_info *pipe)
+{
+	int i;
+
+	for (i = 0; i < pipe->buffers; i++) {
+		struct pipe_buffer *buf = pipe->bufs + i;
+		if (buf->ops)
+			buf->ops->release(pipe, buf);
+	}
+	if (pipe->tmp_page)
+		__free_page(pipe->tmp_page);
+	kfree(pipe->bufs);
+	kfree(pipe);
+}
+
+void free_pipe_info(struct inode *inode)
+{
+	__free_pipe_info(inode->i_pipe);
+	inode->i_pipe = NULL;
+}
+
+static struct vfsmount *pipe_mnt __read_mostly;
+
+/*
+ * pipefs_dname() is called from d_path().
+ */
+static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+	return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
+				dentry->d_inode->i_ino);
+}
+
+static const struct dentry_operations pipefs_dentry_operations = {
+	.d_dname	= pipefs_dname,
+};
+
+static struct inode * get_pipe_inode(void)
+{
+	struct inode *inode = new_inode(pipe_mnt->mnt_sb);
+	struct pipe_inode_info *pipe;
+
+	if (!inode)
+		goto fail_inode;
+
+	pipe = alloc_pipe_info(inode);
+	if (!pipe)
+		goto fail_iput;
+	inode->i_pipe = pipe;
+
+	pipe->readers = pipe->writers = 1;
+	inode->i_fop = &rdwr_pipefifo_fops;
+
+	/*
+	 * Mark the inode dirty from the very beginning,
+	 * that way it will never be moved to the dirty
+	 * list because "mark_inode_dirty()" will think
+	 * that it already _is_ on the dirty list.
+	 */
+	inode->i_state = I_DIRTY;
+	inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
+	inode->i_uid = current_fsuid();
+	inode->i_gid = current_fsgid();
+	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+
+	return inode;
+
+fail_iput:
+	iput(inode);
+
+fail_inode:
+	return NULL;
+}
+
+struct file *create_write_pipe(int flags)
+{
+	int err;
+	struct inode *inode;
+	struct file *f;
+	struct path path;
+	struct qstr name = { .name = "" };
+
+	err = -ENFILE;
+	inode = get_pipe_inode();
+	if (!inode)
+		goto err;
+
+	err = -ENOMEM;
+	path.dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
+	if (!path.dentry)
+		goto err_inode;
+	path.mnt = mntget(pipe_mnt);
+
+	path.dentry->d_op = &pipefs_dentry_operations;
+	d_instantiate(path.dentry, inode);
+
+	err = -ENFILE;
+	f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
+	if (!f)
+		goto err_dentry;
+	f->f_mapping = inode->i_mapping;
+
+	f->f_flags = O_WRONLY | (flags & O_NONBLOCK);
+	f->f_version = 0;
+
+	return f;
+
+ err_dentry:
+	free_pipe_info(inode);
+	path_put(&path);
+	return ERR_PTR(err);
+
+ err_inode:
+	free_pipe_info(inode);
+	iput(inode);
+ err:
+	return ERR_PTR(err);
+}
+
+void free_write_pipe(struct file *f)
+{
+	free_pipe_info(f->f_dentry->d_inode);
+	path_put(&f->f_path);
+	put_filp(f);
+}
+
+struct file *create_read_pipe(struct file *wrf, int flags)
+{
+	/* Grab pipe from the writer */
+	struct file *f = alloc_file(&wrf->f_path, FMODE_READ,
+				    &read_pipefifo_fops);
+	if (!f)
+		return ERR_PTR(-ENFILE);
+
+	path_get(&wrf->f_path);
+	f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
+
+	return f;
+}
+
+int do_pipe_flags(int *fd, int flags)
+{
+	struct file *fw, *fr;
+	int error;
+	int fdw, fdr;
+
+	if (flags & ~(O_CLOEXEC | O_NONBLOCK))
+		return -EINVAL;
+
+	fw = create_write_pipe(flags);
+	if (IS_ERR(fw))
+		return PTR_ERR(fw);
+	fr = create_read_pipe(fw, flags);
+	error = PTR_ERR(fr);
+	if (IS_ERR(fr))
+		goto err_write_pipe;
+
+	error = get_unused_fd_flags(flags);
+	if (error < 0)
+		goto err_read_pipe;
+	fdr = error;
+
+	error = get_unused_fd_flags(flags);
+	if (error < 0)
+		goto err_fdr;
+	fdw = error;
+
+	audit_fd_pair(fdr, fdw);
+	fd_install(fdr, fr);
+	fd_install(fdw, fw);
+	fd[0] = fdr;
+	fd[1] = fdw;
+
+	return 0;
+
+ err_fdr:
+	put_unused_fd(fdr);
+ err_read_pipe:
+	path_put(&fr->f_path);
+	put_filp(fr);
+ err_write_pipe:
+	free_write_pipe(fw);
+	return error;
+}
+
+/*
+ * sys_pipe() is the normal C calling standard for creating
+ * a pipe. It's not the way Unix traditionally does this, though.
+ */
+SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
+{
+	int fd[2];
+	int error;
+
+	error = do_pipe_flags(fd, flags);
+	if (!error) {
+		if (copy_to_user(fildes, fd, sizeof(fd))) {
+			sys_close(fd[0]);
+			sys_close(fd[1]);
+			error = -EFAULT;
+		}
+	}
+	return error;
+}
+
+SYSCALL_DEFINE1(pipe, int __user *, fildes)
+{
+	return sys_pipe2(fildes, 0);
+}
+
+/*
+ * Allocate a new array of pipe buffers and copy the info over. Returns the
+ * pipe size if successful, or return -ERROR on error.
+ */
+static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
+{
+	struct pipe_buffer *bufs;
+
+	/*
+	 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
+	 * expect a lot of shrink+grow operations, just free and allocate
+	 * again like we would do for growing. If the pipe currently
+	 * contains more buffers than arg, then return busy.
+	 */
+	if (nr_pages < pipe->nrbufs)
+		return -EBUSY;
+
+	bufs = kcalloc(nr_pages, sizeof(struct pipe_buffer), GFP_KERNEL);
+	if (unlikely(!bufs))
+		return -ENOMEM;
+
+	/*
+	 * The pipe array wraps around, so just start the new one at zero
+	 * and adjust the indexes.
+	 */
+	if (pipe->nrbufs) {
+		unsigned int tail;
+		unsigned int head;
+
+		tail = pipe->curbuf + pipe->nrbufs;
+		if (tail < pipe->buffers)
+			tail = 0;
+		else
+			tail &= (pipe->buffers - 1);
+
+		head = pipe->nrbufs - tail;
+		if (head)
+			memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
+		if (tail)
+			memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
+	}
+
+	pipe->curbuf = 0;
+	kfree(pipe->bufs);
+	pipe->bufs = bufs;
+	pipe->buffers = nr_pages;
+	return nr_pages * PAGE_SIZE;
+}
+
+/*
+ * Currently we rely on the pipe array holding a power-of-2 number
+ * of pages.
+ */
+static inline unsigned int round_pipe_size(unsigned int size)
+{
+	unsigned long nr_pages;
+
+	nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
+}
+
+/*
+ * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
+ * will return an error.
+ */
+int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
+		 size_t *lenp, loff_t *ppos)
+{
+	int ret;
+
+	ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
+	if (ret < 0 || !write)
+		return ret;
+
+	pipe_max_size = round_pipe_size(pipe_max_size);
+	return ret;
+}
+
+/*
+ * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
+ * location, so checking ->i_pipe is not enough to verify that this is a
+ * pipe.
+ */
+struct pipe_inode_info *get_pipe_info(struct file *file)
+{
+	struct inode *i = file->f_path.dentry->d_inode;
+
+	return S_ISFIFO(i->i_mode) ? i->i_pipe : NULL;
+}
+
+long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct pipe_inode_info *pipe;
+	long ret;
+
+	pipe = get_pipe_info(file);
+	if (!pipe)
+		return -EBADF;
+
+	mutex_lock(&pipe->inode->i_mutex);
+
+	switch (cmd) {
+	case F_SETPIPE_SZ: {
+		unsigned int size, nr_pages;
+
+		size = round_pipe_size(arg);
+		nr_pages = size >> PAGE_SHIFT;
+
+		ret = -EINVAL;
+		if (!nr_pages)
+			goto out;
+
+		if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
+			ret = -EPERM;
+			goto out;
+		}
+		ret = pipe_set_size(pipe, nr_pages);
+		break;
+		}
+	case F_GETPIPE_SZ:
+		ret = pipe->buffers * PAGE_SIZE;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+out:
+	mutex_unlock(&pipe->inode->i_mutex);
+	return ret;
+}
+
+/*
+ * pipefs should _never_ be mounted by userland - too much of security hassle,
+ * no real gain from having the whole whorehouse mounted. So we don't need
+ * any operations on the root directory. However, we need a non-trivial
+ * d_name - pipe: will go nicely and kill the special-casing in procfs.
+ */
+static int pipefs_get_sb(struct file_system_type *fs_type,
+			 int flags, const char *dev_name, void *data,
+			 struct vfsmount *mnt)
+{
+	return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
+}
+
+static struct file_system_type pipe_fs_type = {
+	.name		= "pipefs",
+	.get_sb		= pipefs_get_sb,
+	.kill_sb	= kill_anon_super,
+};
+
+static int __init init_pipe_fs(void)
+{
+	int err = register_filesystem(&pipe_fs_type);
+
+	if (!err) {
+		pipe_mnt = kern_mount(&pipe_fs_type);
+		if (IS_ERR(pipe_mnt)) {
+			err = PTR_ERR(pipe_mnt);
+			unregister_filesystem(&pipe_fs_type);
+		}
+	}
+	return err;
+}
+
+static void __exit exit_pipe_fs(void)
+{
+	unregister_filesystem(&pipe_fs_type);
+	mntput(pipe_mnt);
+}
+
+fs_initcall(init_pipe_fs);
+module_exit(exit_pipe_fs);