[PATCH] relay: migrate from relayfs to a generic relay API

Original patch from Paul Mundt, sysfs parts removed by me since they
were broken.

Signed-off-by: Jens Axboe <axboe@suse.de>

12 files changed, 1212 insertions, 1290 deletions

diff --git a/fs/Kconfig b/fs/Kconfig
index e9749b0eecd..c8d0a209120 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -859,18 +859,6 @@ config RAMFS
 	  To compile this as a module, choose M here: the module will be called
 	  ramfs.
 
-config RELAYFS_FS
-	tristate "Relayfs file system support"
-	---help---
-	  Relayfs is a high-speed data relay filesystem designed to provide
-	  an efficient mechanism for tools and facilities to relay large
-	  amounts of data from kernel space to user space.
-
-	  To compile this code as a module, choose M here: the module will be
-	  called relayfs.
-
-	  If unsure, say N.
-
 config CONFIGFS_FS
 	tristate "Userspace-driven configuration filesystem (EXPERIMENTAL)"
 	depends on EXPERIMENTAL
diff --git a/fs/Makefile b/fs/Makefile
index 1db711319c8..080b3867be4 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -91,7 +91,6 @@ obj-$(CONFIG_AUTOFS4_FS)	+= autofs4/
 obj-$(CONFIG_ADFS_FS)		+= adfs/
 obj-$(CONFIG_FUSE_FS)		+= fuse/
 obj-$(CONFIG_UDF_FS)		+= udf/
-obj-$(CONFIG_RELAYFS_FS)	+= relayfs/
 obj-$(CONFIG_SUN_OPENPROMFS)	+= openpromfs/
 obj-$(CONFIG_JFS_FS)		+= jfs/
 obj-$(CONFIG_XFS_FS)		+= xfs/
diff --git a/fs/relayfs/Makefile b/fs/relayfs/Makefile
deleted file mode 100644
index e76e182cdb3..00000000000
--- a/fs/relayfs/Makefile
+++ /dev/null
@@ -1,4 +0,0 @@
-obj-$(CONFIG_RELAYFS_FS) += relayfs.o
-
-relayfs-y := relay.o inode.o buffers.o
-
diff --git a/fs/relayfs/buffers.c b/fs/relayfs/buffers.c
deleted file mode 100644
index 10187812771..00000000000
--- a/fs/relayfs/buffers.c
+++ /dev/null
@@ -1,190 +0,0 @@
-/*
- * RelayFS buffer management code.
- *
- * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
- * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
- *
- * This file is released under the GPL.
- */
-
-#include <linux/module.h>
-#include <linux/vmalloc.h>
-#include <linux/mm.h>
-#include <linux/relayfs_fs.h>
-#include "relay.h"
-#include "buffers.h"
-
-/*
- * close() vm_op implementation for relayfs file mapping.
- */
-static void relay_file_mmap_close(struct vm_area_struct *vma)
-{
-	struct rchan_buf *buf = vma->vm_private_data;
-	buf->chan->cb->buf_unmapped(buf, vma->vm_file);
-}
-
-/*
- * nopage() vm_op implementation for relayfs file mapping.
- */
-static struct page *relay_buf_nopage(struct vm_area_struct *vma,
-				     unsigned long address,
-				     int *type)
-{
-	struct page *page;
-	struct rchan_buf *buf = vma->vm_private_data;
-	unsigned long offset = address - vma->vm_start;
-
-	if (address > vma->vm_end)
-		return NOPAGE_SIGBUS; /* Disallow mremap */
-	if (!buf)
-		return NOPAGE_OOM;
-
-	page = vmalloc_to_page(buf->start + offset);
-	if (!page)
-		return NOPAGE_OOM;
-	get_page(page);
-
-	if (type)
-		*type = VM_FAULT_MINOR;
-
-	return page;
-}
-
-/*
- * vm_ops for relay file mappings.
- */
-static struct vm_operations_struct relay_file_mmap_ops = {
-	.nopage = relay_buf_nopage,
-	.close = relay_file_mmap_close,
-};
-
-/**
- *	relay_mmap_buf: - mmap channel buffer to process address space
- *	@buf: relay channel buffer
- *	@vma: vm_area_struct describing memory to be mapped
- *
- *	Returns 0 if ok, negative on error
- *
- *	Caller should already have grabbed mmap_sem.
- */
-int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
-{
-	unsigned long length = vma->vm_end - vma->vm_start;
-	struct file *filp = vma->vm_file;
-
-	if (!buf)
-		return -EBADF;
-
-	if (length != (unsigned long)buf->chan->alloc_size)
-		return -EINVAL;
-
-	vma->vm_ops = &relay_file_mmap_ops;
-	vma->vm_private_data = buf;
-	buf->chan->cb->buf_mapped(buf, filp);
-
-	return 0;
-}
-
-/**
- *	relay_alloc_buf - allocate a channel buffer
- *	@buf: the buffer struct
- *	@size: total size of the buffer
- *
- *	Returns a pointer to the resulting buffer, NULL if unsuccessful
- */
-static void *relay_alloc_buf(struct rchan_buf *buf, unsigned long size)
-{
-	void *mem;
-	unsigned int i, j, n_pages;
-
-	size = PAGE_ALIGN(size);
-	n_pages = size >> PAGE_SHIFT;
-
-	buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
-	if (!buf->page_array)
-		return NULL;
-
-	for (i = 0; i < n_pages; i++) {
-		buf->page_array[i] = alloc_page(GFP_KERNEL);
-		if (unlikely(!buf->page_array[i]))
-			goto depopulate;
-	}
-	mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
-	if (!mem)
-		goto depopulate;
-
-	memset(mem, 0, size);
-	buf->page_count = n_pages;
-	return mem;
-
-depopulate:
-	for (j = 0; j < i; j++)
-		__free_page(buf->page_array[j]);
-	kfree(buf->page_array);
-	return NULL;
-}
-
-/**
- *	relay_create_buf - allocate and initialize a channel buffer
- *	@alloc_size: size of the buffer to allocate
- *	@n_subbufs: number of sub-buffers in the channel
- *
- *	Returns channel buffer if successful, NULL otherwise
- */
-struct rchan_buf *relay_create_buf(struct rchan *chan)
-{
-	struct rchan_buf *buf = kcalloc(1, sizeof(struct rchan_buf), GFP_KERNEL);
-	if (!buf)
-		return NULL;
-
-	buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
-	if (!buf->padding)
-		goto free_buf;
-
-	buf->start = relay_alloc_buf(buf, chan->alloc_size);
-	if (!buf->start)
-		goto free_buf;
-
-	buf->chan = chan;
-	kref_get(&buf->chan->kref);
-	return buf;
-
-free_buf:
-	kfree(buf->padding);
-	kfree(buf);
-	return NULL;
-}
-
-/**
- *	relay_destroy_buf - destroy an rchan_buf struct and associated buffer
- *	@buf: the buffer struct
- */
-void relay_destroy_buf(struct rchan_buf *buf)
-{
-	struct rchan *chan = buf->chan;
-	unsigned int i;
-
-	if (likely(buf->start)) {
-		vunmap(buf->start);
-		for (i = 0; i < buf->page_count; i++)
-			__free_page(buf->page_array[i]);
-		kfree(buf->page_array);
-	}
-	kfree(buf->padding);
-	kfree(buf);
-	kref_put(&chan->kref, relay_destroy_channel);
-}
-
-/**
- *	relay_remove_buf - remove a channel buffer
- *
- *	Removes the file from the relayfs fileystem, which also frees the
- *	rchan_buf_struct and the channel buffer.  Should only be called from
- *	kref_put().
- */
-void relay_remove_buf(struct kref *kref)
-{
-	struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
-	buf->chan->cb->remove_buf_file(buf->dentry);
-	relay_destroy_buf(buf);
-}
diff --git a/fs/relayfs/buffers.h b/fs/relayfs/buffers.h
deleted file mode 100644
index 37a12493f64..00000000000
--- a/fs/relayfs/buffers.h
+++ /dev/null
@@ -1,12 +0,0 @@
-#ifndef _BUFFERS_H
-#define _BUFFERS_H
-
-/* This inspired by rtai/shmem */
-#define FIX_SIZE(x) (((x) - 1) & PAGE_MASK) + PAGE_SIZE
-
-extern int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma);
-extern struct rchan_buf *relay_create_buf(struct rchan *chan);
-extern void relay_destroy_buf(struct rchan_buf *buf);
-extern void relay_remove_buf(struct kref *kref);
-
-#endif/* _BUFFERS_H */
diff --git a/fs/relayfs/inode.c b/fs/relayfs/inode.c
deleted file mode 100644
index 383523011aa..00000000000
--- a/fs/relayfs/inode.c
+++ /dev/null
@@ -1,581 +0,0 @@
-/*
- * VFS-related code for RelayFS, a high-speed data relay filesystem.
- *
- * Copyright (C) 2003-2005 - Tom Zanussi <zanussi@us.ibm.com>, IBM Corp
- * Copyright (C) 2003-2005 - Karim Yaghmour <karim@opersys.com>
- *
- * Based on ramfs, Copyright (C) 2002 - Linus Torvalds
- *
- * This file is released under the GPL.
- */
-
-#include <linux/module.h>
-#include <linux/fs.h>
-#include <linux/mount.h>
-#include <linux/pagemap.h>
-#include <linux/init.h>
-#include <linux/string.h>
-#include <linux/backing-dev.h>
-#include <linux/namei.h>
-#include <linux/poll.h>
-#include <linux/relayfs_fs.h>
-#include "relay.h"
-#include "buffers.h"
-
-#define RELAYFS_MAGIC			0xF0B4A981
-
-static struct vfsmount *		relayfs_mount;
-static int				relayfs_mount_count;
-
-static struct backing_dev_info		relayfs_backing_dev_info = {
-	.ra_pages	= 0,	/* No readahead */
-	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
-};
-
-static struct inode *relayfs_get_inode(struct super_block *sb,
-				       int mode,
- 				       struct file_operations *fops,
-				       void *data)
-{
-	struct inode *inode;
-
-	inode = new_inode(sb);
-	if (!inode)
-		return NULL;
-
-	inode->i_mode = mode;
-	inode->i_uid = 0;
-	inode->i_gid = 0;
-	inode->i_blksize = PAGE_CACHE_SIZE;
-	inode->i_blocks = 0;
-	inode->i_mapping->backing_dev_info = &relayfs_backing_dev_info;
-	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
-	switch (mode & S_IFMT) {
-	case S_IFREG:
-		inode->i_fop = fops;
-		if (data)
-			inode->u.generic_ip = data;
-		break;
-	case S_IFDIR:
-		inode->i_op = &simple_dir_inode_operations;
-		inode->i_fop = &simple_dir_operations;
-
-		/* directory inodes start off with i_nlink == 2 (for "." entry) */
-		inode->i_nlink++;
-		break;
-	default:
-		break;
-	}
-
-	return inode;
-}
-
-/**
- *	relayfs_create_entry - create a relayfs directory or file
- *	@name: the name of the file to create
- *	@parent: parent directory
- *	@mode: mode
- *	@fops: file operations to use for the file
- *	@data: user-associated data for this file
- *
- *	Returns the new dentry, NULL on failure
- *
- *	Creates a file or directory with the specifed permissions.
- */
-static struct dentry *relayfs_create_entry(const char *name,
-					   struct dentry *parent,
-					   int mode,
-					   struct file_operations *fops,
-					   void *data)
-{
-	struct dentry *d;
-	struct inode *inode;
-	int error = 0;
-
-	BUG_ON(!name || !(S_ISREG(mode) || S_ISDIR(mode)));
-
-	error = simple_pin_fs("relayfs", &relayfs_mount, &relayfs_mount_count);
-	if (error) {
-		printk(KERN_ERR "Couldn't mount relayfs: errcode %d\n", error);
-		return NULL;
-	}
-
-	if (!parent && relayfs_mount && relayfs_mount->mnt_sb)
-		parent = relayfs_mount->mnt_sb->s_root;
-
-	if (!parent) {
-		simple_release_fs(&relayfs_mount, &relayfs_mount_count);
-		return NULL;
-	}
-
-	parent = dget(parent);
-	mutex_lock(&parent->d_inode->i_mutex);
-	d = lookup_one_len(name, parent, strlen(name));
-	if (IS_ERR(d)) {
-		d = NULL;
-		goto release_mount;
-	}
-
-	if (d->d_inode) {
-		d = NULL;
-		goto release_mount;
-	}
-
-	inode = relayfs_get_inode(parent->d_inode->i_sb, mode, fops, data);
-	if (!inode) {
-		d = NULL;
-		goto release_mount;
-	}
-
-	d_instantiate(d, inode);
-	dget(d);	/* Extra count - pin the dentry in core */
-
-	if (S_ISDIR(mode))
-		parent->d_inode->i_nlink++;
-
-	goto exit;
-
-release_mount:
-	simple_release_fs(&relayfs_mount, &relayfs_mount_count);
-
-exit:
-	mutex_unlock(&parent->d_inode->i_mutex);
-	dput(parent);
-	return d;
-}
-
-/**
- *	relayfs_create_file - create a file in the relay filesystem
- *	@name: the name of the file to create
- *	@parent: parent directory
- *	@mode: mode, if not specied the default perms are used
- *	@fops: file operations to use for the file
- *	@data: user-associated data for this file
- *
- *	Returns file dentry if successful, NULL otherwise.
- *
- *	The file will be created user r on behalf of current user.
- */
-struct dentry *relayfs_create_file(const char *name,
-				   struct dentry *parent,
-				   int mode,
-				   struct file_operations *fops,
-				   void *data)
-{
-	BUG_ON(!fops);
-
-	if (!mode)
-		mode = S_IRUSR;
-	mode = (mode & S_IALLUGO) | S_IFREG;
-
-	return relayfs_create_entry(name, parent, mode, fops, data);
-}
-
-/**
- *	relayfs_create_dir - create a directory in the relay filesystem
- *	@name: the name of the directory to create
- *	@parent: parent directory, NULL if parent should be fs root
- *
- *	Returns directory dentry if successful, NULL otherwise.
- *
- *	The directory will be created world rwx on behalf of current user.
- */
-struct dentry *relayfs_create_dir(const char *name, struct dentry *parent)
-{
-	int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
-	return relayfs_create_entry(name, parent, mode, NULL, NULL);
-}
-
-/**
- *	relayfs_remove - remove a file or directory in the relay filesystem
- *	@dentry: file or directory dentry
- *
- *	Returns 0 if successful, negative otherwise.
- */
-int relayfs_remove(struct dentry *dentry)
-{
-	struct dentry *parent;
-	int error = 0;
-
-	if (!dentry)
-		return -EINVAL;
-	parent = dentry->d_parent;
-	if (!parent)
-		return -EINVAL;
-
-	parent = dget(parent);
-	mutex_lock(&parent->d_inode->i_mutex);
-	if (dentry->d_inode) {
-		if (S_ISDIR(dentry->d_inode->i_mode))
-			error = simple_rmdir(parent->d_inode, dentry);
-		else
-			error = simple_unlink(parent->d_inode, dentry);
-		if (!error)
-			d_delete(dentry);
-	}
-	if (!error)
-		dput(dentry);
-	mutex_unlock(&parent->d_inode->i_mutex);
-	dput(parent);
-
-	if (!error)
-		simple_release_fs(&relayfs_mount, &relayfs_mount_count);
-
-	return error;
-}
-
-/**
- *	relayfs_remove_file - remove a file from relay filesystem
- *	@dentry: directory dentry
- *
- *	Returns 0 if successful, negative otherwise.
- */
-int relayfs_remove_file(struct dentry *dentry)
-{
-	return relayfs_remove(dentry);
-}
-
-/**
- *	relayfs_remove_dir - remove a directory in the relay filesystem
- *	@dentry: directory dentry
- *
- *	Returns 0 if successful, negative otherwise.
- */
-int relayfs_remove_dir(struct dentry *dentry)
-{
-	return relayfs_remove(dentry);
-}
-
-/**
- *	relay_file_open - open file op for relay files
- *	@inode: the inode
- *	@filp: the file
- *
- *	Increments the channel buffer refcount.
- */
-static int relay_file_open(struct inode *inode, struct file *filp)
-{
-	struct rchan_buf *buf = inode->u.generic_ip;
-	kref_get(&buf->kref);
-	filp->private_data = buf;
-
-	return 0;
-}
-
-/**
- *	relay_file_mmap - mmap file op for relay files
- *	@filp: the file
- *	@vma: the vma describing what to map
- *
- *	Calls upon relay_mmap_buf to map the file into user space.
- */
-static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
-{
-	struct rchan_buf *buf = filp->private_data;
-	return relay_mmap_buf(buf, vma);
-}
-
-/**
- *	relay_file_poll - poll file op for relay files
- *	@filp: the file
- *	@wait: poll table
- *
- *	Poll implemention.
- */
-static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
-{
-	unsigned int mask = 0;
-	struct rchan_buf *buf = filp->private_data;
-
-	if (buf->finalized)
-		return POLLERR;
-
-	if (filp->f_mode & FMODE_READ) {
-		poll_wait(filp, &buf->read_wait, wait);
-		if (!relay_buf_empty(buf))
-			mask |= POLLIN | POLLRDNORM;
-	}
-
-	return mask;
-}
-
-/**
- *	relay_file_release - release file op for relay files
- *	@inode: the inode
- *	@filp: the file
- *
- *	Decrements the channel refcount, as the filesystem is
- *	no longer using it.
- */
-static int relay_file_release(struct inode *inode, struct file *filp)
-{
-	struct rchan_buf *buf = filp->private_data;
-	kref_put(&buf->kref, relay_remove_buf);
-
-	return 0;
-}
-
-/**
- *	relay_file_read_consume - update the consumed count for the buffer
- */
-static void relay_file_read_consume(struct rchan_buf *buf,
-				    size_t read_pos,
-				    size_t bytes_consumed)
-{
-	size_t subbuf_size = buf->chan->subbuf_size;
-	size_t n_subbufs = buf->chan->n_subbufs;
-	size_t read_subbuf;
-
-	if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
-		relay_subbufs_consumed(buf->chan, buf->cpu, 1);
-		buf->bytes_consumed = 0;
-	}
-
-	buf->bytes_consumed += bytes_consumed;
-	read_subbuf = read_pos / buf->chan->subbuf_size;
-	if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
-		if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
-		    (buf->offset == subbuf_size))
-			return;
-		relay_subbufs_consumed(buf->chan, buf->cpu, 1);
-		buf->bytes_consumed = 0;
-	}
-}
-
-/**
- *	relay_file_read_avail - boolean, are there unconsumed bytes available?
- */
-static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
-{
-	size_t bytes_produced, bytes_consumed, write_offset;
-	size_t subbuf_size = buf->chan->subbuf_size;
-	size_t n_subbufs = buf->chan->n_subbufs;
-	size_t produced = buf->subbufs_produced % n_subbufs;
-	size_t consumed = buf->subbufs_consumed % n_subbufs;
-
-	write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
-
-	if (consumed > produced) {
-		if ((produced > n_subbufs) &&
-		    (produced + n_subbufs - consumed <= n_subbufs))
-			produced += n_subbufs;
-	} else if (consumed == produced) {
-		if (buf->offset > subbuf_size) {
-			produced += n_subbufs;
-			if (buf->subbufs_produced == buf->subbufs_consumed)
-				consumed += n_subbufs;
-		}
-	}
-
-	if (buf->offset > subbuf_size)
-		bytes_produced = (produced - 1) * subbuf_size + write_offset;
-	else
-		bytes_produced = produced * subbuf_size + write_offset;
-	bytes_consumed = consumed * subbuf_size + buf->bytes_consumed;
-
-	if (bytes_produced == bytes_consumed)
-		return 0;
-
-	relay_file_read_consume(buf, read_pos, 0);
-
-	return 1;
-}
-
-/**
- *	relay_file_read_subbuf_avail - return bytes available in sub-buffer
- */
-static size_t relay_file_read_subbuf_avail(size_t read_pos,
-					   struct rchan_buf *buf)
-{
-	size_t padding, avail = 0;
-	size_t read_subbuf, read_offset, write_subbuf, write_offset;
-	size_t subbuf_size = buf->chan->subbuf_size;
-
-	write_subbuf = (buf->data - buf->start) / subbuf_size;
-	write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
-	read_subbuf = read_pos / subbuf_size;
-	read_offset = read_pos % subbuf_size;
-	padding = buf->padding[read_subbuf];
-
-	if (read_subbuf == write_subbuf) {
-		if (read_offset + padding < write_offset)
-			avail = write_offset - (read_offset + padding);
-	} else
-		avail = (subbuf_size - padding) - read_offset;
-
-	return avail;
-}
-
-/**
- *	relay_file_read_start_pos - find the first available byte to read
- *
- *	If the read_pos is in the middle of padding, return the
- *	position of the first actually available byte, otherwise
- *	return the original value.
- */
-static size_t relay_file_read_start_pos(size_t read_pos,
-					struct rchan_buf *buf)
-{
-	size_t read_subbuf, padding, padding_start, padding_end;
-	size_t subbuf_size = buf->chan->subbuf_size;
-	size_t n_subbufs = buf->chan->n_subbufs;
-
-	read_subbuf = read_pos / subbuf_size;
-	padding = buf->padding[read_subbuf];
-	padding_start = (read_subbuf + 1) * subbuf_size - padding;
-	padding_end = (read_subbuf + 1) * subbuf_size;
-	if (read_pos >= padding_start && read_pos < padding_end) {
-		read_subbuf = (read_subbuf + 1) % n_subbufs;
-		read_pos = read_subbuf * subbuf_size;
-	}
-
-	return read_pos;
-}
-
-/**
- *	relay_file_read_end_pos - return the new read position
- */
-static size_t relay_file_read_end_pos(struct rchan_buf *buf,
-				      size_t read_pos,
-				      size_t count)
-{
-	size_t read_subbuf, padding, end_pos;
-	size_t subbuf_size = buf->chan->subbuf_size;
-	size_t n_subbufs = buf->chan->n_subbufs;
-
-	read_subbuf = read_pos / subbuf_size;
-	padding = buf->padding[read_subbuf];
-	if (read_pos % subbuf_size + count + padding == subbuf_size)
-		end_pos = (read_subbuf + 1) * subbuf_size;
-	else
-		end_pos = read_pos + count;
-	if (end_pos >= subbuf_size * n_subbufs)
-		end_pos = 0;
-
-	return end_pos;
-}
-
-/**
- *	relay_file_read - read file op for relay files
- *	@filp: the file
- *	@buffer: the userspace buffer
- *	@count: number of bytes to read
- *	@ppos: position to read from
- *
- *	Reads count bytes or the number of bytes available in the
- *	current sub-buffer being read, whichever is smaller.
- */
-static ssize_t relay_file_read(struct file *filp,
-			       char __user *buffer,
-			       size_t count,
-			       loff_t *ppos)
-{
-	struct rchan_buf *buf = filp->private_data;
-	struct inode *inode = filp->f_dentry->d_inode;
-	size_t read_start, avail;
-	ssize_t ret = 0;
-	void *from;
-
-	mutex_lock(&inode->i_mutex);
-	if(!relay_file_read_avail(buf, *ppos))
-		goto out;
-
-	read_start = relay_file_read_start_pos(*ppos, buf);
-	avail = relay_file_read_subbuf_avail(read_start, buf);
-	if (!avail)
-		goto out;
-
-	from = buf->start + read_start;
-	ret = count = min(count, avail);
-	if (copy_to_user(buffer, from, count)) {
-		ret = -EFAULT;
-		goto out;
-	}
-	relay_file_read_consume(buf, read_start, count);
-	*ppos = relay_file_read_end_pos(buf, read_start, count);
-out:
-	mutex_unlock(&inode->i_mutex);
-	return ret;
-}
-
-struct file_operations relay_file_operations = {
-	.open		= relay_file_open,
-	.poll		= relay_file_poll,
-	.mmap		= relay_file_mmap,
-	.read		= relay_file_read,
-	.llseek		= no_llseek,
-	.release	= relay_file_release,
-};
-
-static struct super_operations relayfs_ops = {
-	.statfs		= simple_statfs,
-	.drop_inode	= generic_delete_inode,
-};
-
-static int relayfs_fill_super(struct super_block * sb, void * data, int silent)
-{
-	struct inode *inode;
-	struct dentry *root;
-	int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
-
-	sb->s_blocksize = PAGE_CACHE_SIZE;
-	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
-	sb->s_magic = RELAYFS_MAGIC;
-	sb->s_op = &relayfs_ops;
-	inode = relayfs_get_inode(sb, mode, NULL, NULL);
-
-	if (!inode)
-		return -ENOMEM;
-
-	root = d_alloc_root(inode);
-	if (!root) {
-		iput(inode);
-		return -ENOMEM;
-	}
-	sb->s_root = root;
-
-	return 0;
-}
-
-static struct super_block * relayfs_get_sb(struct file_system_type *fs_type,
-					   int flags, const char *dev_name,
-					   void *data)
-{
-	return get_sb_single(fs_type, flags, data, relayfs_fill_super);
-}
-
-static struct file_system_type relayfs_fs_type = {
-	.owner		= THIS_MODULE,
-	.name		= "relayfs",
-	.get_sb		= relayfs_get_sb,
-	.kill_sb	= kill_litter_super,
-};
-
-static int __init init_relayfs_fs(void)
-{
-	return register_filesystem(&relayfs_fs_type);
-}
-
-static void __exit exit_relayfs_fs(void)
-{
-
-
-
-
-
-	unregister_filesystem(&relayfs_fs_type);
-}
-
-module_init(init_relayfs_fs)
-module_exit(exit_relayfs_fs)
-
-EXPORT_SYMBOL_GPL(relay_file_operations);
-EXPORT_SYMBOL_GPL(relayfs_create_dir);
-EXPORT_SYMBOL_GPL(relayfs_remove_dir);
-EXPORT_SYMBOL_GPL(relayfs_create_file);
-EXPORT_SYMBOL_GPL(relayfs_remove_file);
-
-MODULE_AUTHOR("Tom Zanussi <zanussi@us.ibm.com> and Karim Yaghmour <karim@opersys.com>");
-MODULE_DESCRIPTION("Relay Filesystem");
-MODULE_LICENSE("GPL");
-
diff --git a/fs/relayfs/relay.c b/fs/relayfs/relay.c
deleted file mode 100644
index abf3ceaace4..00000000000
--- a/fs/relayfs/relay.c
+++ /dev/null
@@ -1,482 +0,0 @@
-/*
- * Public API and common code for RelayFS.
- *
- * See Documentation/filesystems/relayfs.txt for an overview of relayfs.
- *
- * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
- * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
- *
- * This file is released under the GPL.
- */
-
-#include <linux/errno.h>
-#include <linux/stddef.h>
-#include <linux/slab.h>
-#include <linux/module.h>
-#include <linux/string.h>
-#include <linux/relayfs_fs.h>
-#include "relay.h"
-#include "buffers.h"
-
-/**
- *	relay_buf_empty - boolean, is the channel buffer empty?
- *	@buf: channel buffer
- *
- *	Returns 1 if the buffer is empty, 0 otherwise.
- */
-int relay_buf_empty(struct rchan_buf *buf)
-{
-	return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
-}
-
-/**
- *	relay_buf_full - boolean, is the channel buffer full?
- *	@buf: channel buffer
- *
- *	Returns 1 if the buffer is full, 0 otherwise.
- */
-int relay_buf_full(struct rchan_buf *buf)
-{
-	size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
-	return (ready >= buf->chan->n_subbufs) ? 1 : 0;
-}
-
-/*
- * High-level relayfs kernel API and associated functions.
- */
-
-/*
- * rchan_callback implementations defining default channel behavior.  Used
- * in place of corresponding NULL values in client callback struct.
- */
-
-/*
- * subbuf_start() default callback.  Does nothing.
- */
-static int subbuf_start_default_callback (struct rchan_buf *buf,
-					  void *subbuf,
-					  void *prev_subbuf,
-					  size_t prev_padding)
-{
-	if (relay_buf_full(buf))
-		return 0;
-
-	return 1;
-}
-
-/*
- * buf_mapped() default callback.  Does nothing.
- */
-static void buf_mapped_default_callback(struct rchan_buf *buf,
-					struct file *filp)
-{
-}
-
-/*
- * buf_unmapped() default callback.  Does nothing.
- */
-static void buf_unmapped_default_callback(struct rchan_buf *buf,
-					  struct file *filp)
-{
-}
-
-/*
- * create_buf_file_create() default callback.  Creates file to represent buf.
- */
-static struct dentry *create_buf_file_default_callback(const char *filename,
-						       struct dentry *parent,
-						       int mode,
-						       struct rchan_buf *buf,
-						       int *is_global)
-{
-	return relayfs_create_file(filename, parent, mode,
-				   &relay_file_operations, buf);
-}
-
-/*
- * remove_buf_file() default callback.  Removes file representing relay buffer.
- */
-static int remove_buf_file_default_callback(struct dentry *dentry)
-{
-	return relayfs_remove(dentry);
-}
-
-/* relay channel default callbacks */
-static struct rchan_callbacks default_channel_callbacks = {
-	.subbuf_start = subbuf_start_default_callback,
-	.buf_mapped = buf_mapped_default_callback,
-	.buf_unmapped = buf_unmapped_default_callback,
-	.create_buf_file = create_buf_file_default_callback,
-	.remove_buf_file = remove_buf_file_default_callback,
-};
-
-/**
- *	wakeup_readers - wake up readers waiting on a channel
- *	@private: the channel buffer
- *
- *	This is the work function used to defer reader waking.  The
- *	reason waking is deferred is that calling directly from write
- *	causes problems if you're writing from say the scheduler.
- */
-static void wakeup_readers(void *private)
-{
-	struct rchan_buf *buf = private;
-	wake_up_interruptible(&buf->read_wait);
-}
-
-/**
- *	__relay_reset - reset a channel buffer
- *	@buf: the channel buffer
- *	@init: 1 if this is a first-time initialization
- *
- *	See relay_reset for description of effect.
- */
-static inline void __relay_reset(struct rchan_buf *buf, unsigned int init)
-{
-	size_t i;
-
-	if (init) {
-		init_waitqueue_head(&buf->read_wait);
-		kref_init(&buf->kref);
-		INIT_WORK(&buf->wake_readers, NULL, NULL);
-	} else {
-		cancel_delayed_work(&buf->wake_readers);
-		flush_scheduled_work();
-	}
-
-	buf->subbufs_produced = 0;
-	buf->subbufs_consumed = 0;
-	buf->bytes_consumed = 0;
-	buf->finalized = 0;
-	buf->data = buf->start;
-	buf->offset = 0;
-
-	for (i = 0; i < buf->chan->n_subbufs; i++)
-		buf->padding[i] = 0;
-
-	buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
-}
-
-/**
- *	relay_reset - reset the channel
- *	@chan: the channel
- *
- *	This has the effect of erasing all data from all channel buffers
- *	and restarting the channel in its initial state.  The buffers
- *	are not freed, so any mappings are still in effect.
- *
- *	NOTE: Care should be taken that the channel isn't actually
- *	being used by anything when this call is made.
- */
-void relay_reset(struct rchan *chan)
-{
-	unsigned int i;
-	struct rchan_buf *prev = NULL;
-
-	if (!chan)
-		return;
-
-	for (i = 0; i < NR_CPUS; i++) {
-		if (!chan->buf[i] || chan->buf[i] == prev)
-			break;
-		__relay_reset(chan->buf[i], 0);
-		prev = chan->buf[i];
-	}
-}
-
-/**
- *	relay_open_buf - create a new channel buffer in relayfs
- *
- *	Internal - used by relay_open().
- */
-static struct rchan_buf *relay_open_buf(struct rchan *chan,
-					const char *filename,
-					struct dentry *parent,
-					int *is_global)
-{
-	struct rchan_buf *buf;
-	struct dentry *dentry;
-
-	if (*is_global)
-		return chan->buf[0];
-
- 	buf = relay_create_buf(chan);
- 	if (!buf)
- 		return NULL;
-
-	/* Create file in fs */
- 	dentry = chan->cb->create_buf_file(filename, parent, S_IRUSR,
- 					   buf, is_global);
- 	if (!dentry) {
- 		relay_destroy_buf(buf);
-		return NULL;
- 	}
-
-	buf->dentry = dentry;
-	__relay_reset(buf, 1);
-
-	return buf;
-}
-
-/**
- *	relay_close_buf - close a channel buffer
- *	@buf: channel buffer
- *
- *	Marks the buffer finalized and restores the default callbacks.
- *	The channel buffer and channel buffer data structure are then freed
- *	automatically when the last reference is given up.
- */
-static inline void relay_close_buf(struct rchan_buf *buf)
-{
-	buf->finalized = 1;
-	buf->chan->cb = &default_channel_callbacks;
-	cancel_delayed_work(&buf->wake_readers);
-	flush_scheduled_work();
-	kref_put(&buf->kref, relay_remove_buf);
-}
-
-static inline void setup_callbacks(struct rchan *chan,
-				   struct rchan_callbacks *cb)
-{
-	if (!cb) {
-		chan->cb = &default_channel_callbacks;
-		return;
-	}
-
-	if (!cb->subbuf_start)
-		cb->subbuf_start = subbuf_start_default_callback;
-	if (!cb->buf_mapped)
-		cb->buf_mapped = buf_mapped_default_callback;
-	if (!cb->buf_unmapped)
-		cb->buf_unmapped = buf_unmapped_default_callback;
-	if (!cb->create_buf_file)
-		cb->create_buf_file = create_buf_file_default_callback;
-	if (!cb->remove_buf_file)
-		cb->remove_buf_file = remove_buf_file_default_callback;
-	chan->cb = cb;
-}
-
-/**
- *	relay_open - create a new relayfs channel
- *	@base_filename: base name of files to create
- *	@parent: dentry of parent directory, NULL for root directory
- *	@subbuf_size: size of sub-buffers
- *	@n_subbufs: number of sub-buffers
- *	@cb: client callback functions
- *
- *	Returns channel pointer if successful, NULL otherwise.
- *
- *	Creates a channel buffer for each cpu using the sizes and
- *	attributes specified.  The created channel buffer files
- *	will be named base_filename0...base_filenameN-1.  File
- *	permissions will be S_IRUSR.
- */
-struct rchan *relay_open(const char *base_filename,
-			 struct dentry *parent,
-			 size_t subbuf_size,
-			 size_t n_subbufs,
-			 struct rchan_callbacks *cb)
-{
-	unsigned int i;
-	struct rchan *chan;
-	char *tmpname;
-	int is_global = 0;
-
-	if (!base_filename)
-		return NULL;
-
-	if (!(subbuf_size && n_subbufs))
-		return NULL;
-
-	chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL);
-	if (!chan)
-		return NULL;
-
-	chan->version = RELAYFS_CHANNEL_VERSION;
-	chan->n_subbufs = n_subbufs;
-	chan->subbuf_size = subbuf_size;
-	chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
-	setup_callbacks(chan, cb);
-	kref_init(&chan->kref);
-
-	tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL);
-	if (!tmpname)
-		goto free_chan;
-
-	for_each_online_cpu(i) {
-		sprintf(tmpname, "%s%d", base_filename, i);
-		chan->buf[i] = relay_open_buf(chan, tmpname, parent,
-					      &is_global);
-		chan->buf[i]->cpu = i;
-		if (!chan->buf[i])
-			goto free_bufs;
-	}
-
-	kfree(tmpname);
-	return chan;
-
-free_bufs:
-	for (i = 0; i < NR_CPUS; i++) {
-		if (!chan->buf[i])
-			break;
-		relay_close_buf(chan->buf[i]);
-		if (is_global)
-			break;
-	}
-	kfree(tmpname);
-
-free_chan:
-	kref_put(&chan->kref, relay_destroy_channel);
-	return NULL;
-}
-
-/**
- *	relay_switch_subbuf - switch to a new sub-buffer
- *	@buf: channel buffer
- *	@length: size of current event
- *
- *	Returns either the length passed in or 0 if full.
-
- *	Performs sub-buffer-switch tasks such as invoking callbacks,
- *	updating padding counts, waking up readers, etc.
- */
-size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
-{
-	void *old, *new;
-	size_t old_subbuf, new_subbuf;
-
-	if (unlikely(length > buf->chan->subbuf_size))
-		goto toobig;
-
-	if (buf->offset != buf->chan->subbuf_size + 1) {
-		buf->prev_padding = buf->chan->subbuf_size - buf->offset;
-		old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
-		buf->padding[old_subbuf] = buf->prev_padding;
-		buf->subbufs_produced++;
-		if (waitqueue_active(&buf->read_wait)) {
-			PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
-			schedule_delayed_work(&buf->wake_readers, 1);
-		}
-	}
-
-	old = buf->data;
-	new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
-	new = buf->start + new_subbuf * buf->chan->subbuf_size;
-	buf->offset = 0;
-	if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
-		buf->offset = buf->chan->subbuf_size + 1;
-		return 0;
-	}
-	buf->data = new;
-	buf->padding[new_subbuf] = 0;
-
-	if (unlikely(length + buf->offset > buf->chan->subbuf_size))
-		goto toobig;
-
-	return length;
-
-toobig:
-	buf->chan->last_toobig = length;
-	return 0;
-}
-
-/**
- *	relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
- *	@chan: the channel
- *	@cpu: the cpu associated with the channel buffer to update
- *	@subbufs_consumed: number of sub-buffers to add to current buf's count
- *
- *	Adds to the channel buffer's consumed sub-buffer count.
- *	subbufs_consumed should be the number of sub-buffers newly consumed,
- *	not the total consumed.
- *
- *	NOTE: kernel clients don't need to call this function if the channel
- *	mode is 'overwrite'.
- */
-void relay_subbufs_consumed(struct rchan *chan,
-			    unsigned int cpu,
-			    size_t subbufs_consumed)
-{
-	struct rchan_buf *buf;
-
-	if (!chan)
-		return;
-
-	if (cpu >= NR_CPUS || !chan->buf[cpu])
-		return;
-
-	buf = chan->buf[cpu];
-	buf->subbufs_consumed += subbufs_consumed;
-	if (buf->subbufs_consumed > buf->subbufs_produced)
-		buf->subbufs_consumed = buf->subbufs_produced;
-}
-
-/**
- *	relay_destroy_channel - free the channel struct
- *
- *	Should only be called from kref_put().
- */
-void relay_destroy_channel(struct kref *kref)
-{
-	struct rchan *chan = container_of(kref, struct rchan, kref);
-	kfree(chan);
-}
-
-/**
- *	relay_close - close the channel
- *	@chan: the channel
- *
- *	Closes all channel buffers and frees the channel.
- */
-void relay_close(struct rchan *chan)
-{
-	unsigned int i;
-	struct rchan_buf *prev = NULL;
-
-	if (!chan)
-		return;
-
-	for (i = 0; i < NR_CPUS; i++) {
-		if (!chan->buf[i] || chan->buf[i] == prev)
-			break;
-		relay_close_buf(chan->buf[i]);
-		prev = chan->buf[i];
-	}
-
-	if (chan->last_toobig)
-		printk(KERN_WARNING "relayfs: one or more items not logged "
-		       "[item size (%Zd) > sub-buffer size (%Zd)]\n",
-		       chan->last_toobig, chan->subbuf_size);
-
-	kref_put(&chan->kref, relay_destroy_channel);
-}
-
-/**
- *	relay_flush - close the channel
- *	@chan: the channel
- *
- *	Flushes all channel buffers i.e. forces buffer switch.
- */
-void relay_flush(struct rchan *chan)
-{
-	unsigned int i;
-	struct rchan_buf *prev = NULL;
-
-	if (!chan)
-		return;
-
-	for (i = 0; i < NR_CPUS; i++) {
-		if (!chan->buf[i] || chan->buf[i] == prev)
-			break;
-		relay_switch_subbuf(chan->buf[i], 0);
-		prev = chan->buf[i];
-	}
-}
-
-EXPORT_SYMBOL_GPL(relay_open);
-EXPORT_SYMBOL_GPL(relay_close);
-EXPORT_SYMBOL_GPL(relay_flush);
-EXPORT_SYMBOL_GPL(relay_reset);
-EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
-EXPORT_SYMBOL_GPL(relay_switch_subbuf);
-EXPORT_SYMBOL_GPL(relay_buf_full);
diff --git a/fs/relayfs/relay.h b/fs/relayfs/relay.h
deleted file mode 100644
index 0993d3e5753..00000000000
--- a/fs/relayfs/relay.h
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef _RELAY_H
-#define _RELAY_H
-
-extern int relayfs_remove(struct dentry *dentry);
-extern int relay_buf_empty(struct rchan_buf *buf);
-extern void relay_destroy_channel(struct kref *kref);
-
-#endif /* _RELAY_H */
diff --git a/include/linux/relay.h b/include/linux/relay.h
new file mode 100644
index 00000000000..4bcc1531d6a
--- /dev/null
+++ b/include/linux/relay.h
@@ -0,0 +1,281 @@
+/*
+ * linux/include/linux/relay.h
+ *
+ * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
+ * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com)
+ *
+ * CONFIG_RELAY definitions and declarations
+ */
+
+#ifndef _LINUX_RELAY_H
+#define _LINUX_RELAY_H
+
+#include <linux/config.h>
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/list.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/kref.h>
+
+/* Needs a _much_ better name... */
+#define FIX_SIZE(x) ((((x) - 1) & PAGE_MASK) + PAGE_SIZE)
+
+/*
+ * Tracks changes to rchan/rchan_buf structs
+ */
+#define RELAYFS_CHANNEL_VERSION		6
+
+/*
+ * Per-cpu relay channel buffer
+ */
+struct rchan_buf
+{
+	void *start;			/* start of channel buffer */
+	void *data;			/* start of current sub-buffer */
+	size_t offset;			/* current offset into sub-buffer */
+	size_t subbufs_produced;	/* count of sub-buffers produced */
+	size_t subbufs_consumed;	/* count of sub-buffers consumed */
+	struct rchan *chan;		/* associated channel */
+	wait_queue_head_t read_wait;	/* reader wait queue */
+	struct work_struct wake_readers; /* reader wake-up work struct */
+	struct dentry *dentry;		/* channel file dentry */
+	struct kref kref;		/* channel buffer refcount */
+	struct page **page_array;	/* array of current buffer pages */
+	unsigned int page_count;	/* number of current buffer pages */
+	unsigned int finalized;		/* buffer has been finalized */
+	size_t *padding;		/* padding counts per sub-buffer */
+	size_t prev_padding;		/* temporary variable */
+	size_t bytes_consumed;		/* bytes consumed in cur read subbuf */
+	unsigned int cpu;		/* this buf's cpu */
+} ____cacheline_aligned;
+
+/*
+ * Relay channel data structure
+ */
+struct rchan
+{
+	u32 version;			/* the version of this struct */
+	size_t subbuf_size;		/* sub-buffer size */
+	size_t n_subbufs;		/* number of sub-buffers per buffer */
+	size_t alloc_size;		/* total buffer size allocated */
+	struct rchan_callbacks *cb;	/* client callbacks */
+	struct kref kref;		/* channel refcount */
+	void *private_data;		/* for user-defined data */
+	size_t last_toobig;		/* tried to log event > subbuf size */
+	struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
+};
+
+/*
+ * Relay channel client callbacks
+ */
+struct rchan_callbacks
+{
+	/*
+	 * subbuf_start - called on buffer-switch to a new sub-buffer
+	 * @buf: the channel buffer containing the new sub-buffer
+	 * @subbuf: the start of the new sub-buffer
+	 * @prev_subbuf: the start of the previous sub-buffer
+	 * @prev_padding: unused space at the end of previous sub-buffer
+	 *
+	 * The client should return 1 to continue logging, 0 to stop
+	 * logging.
+	 *
+	 * NOTE: subbuf_start will also be invoked when the buffer is
+	 *       created, so that the first sub-buffer can be initialized
+	 *       if necessary.  In this case, prev_subbuf will be NULL.
+	 *
+	 * NOTE: the client can reserve bytes at the beginning of the new
+	 *       sub-buffer by calling subbuf_start_reserve() in this callback.
+	 */
+	int (*subbuf_start) (struct rchan_buf *buf,
+			     void *subbuf,
+			     void *prev_subbuf,
+			     size_t prev_padding);
+
+	/*
+	 * buf_mapped - relay buffer mmap notification
+	 * @buf: the channel buffer
+	 * @filp: relay file pointer
+	 *
+	 * Called when a relay file is successfully mmapped
+	 */
+        void (*buf_mapped)(struct rchan_buf *buf,
+			   struct file *filp);
+
+	/*
+	 * buf_unmapped - relay buffer unmap notification
+	 * @buf: the channel buffer
+	 * @filp: relay file pointer
+	 *
+	 * Called when a relay file is successfully unmapped
+	 */
+        void (*buf_unmapped)(struct rchan_buf *buf,
+			     struct file *filp);
+	/*
+	 * create_buf_file - create file to represent a relay channel buffer
+	 * @filename: the name of the file to create
+	 * @parent: the parent of the file to create
+	 * @mode: the mode of the file to create
+	 * @buf: the channel buffer
+	 * @is_global: outparam - set non-zero if the buffer should be global
+	 *
+	 * Called during relay_open(), once for each per-cpu buffer,
+	 * to allow the client to create a file to be used to
+	 * represent the corresponding channel buffer.  If the file is
+	 * created outside of relay, the parent must also exist in
+	 * that filesystem.
+	 *
+	 * The callback should return the dentry of the file created
+	 * to represent the relay buffer.
+	 *
+	 * Setting the is_global outparam to a non-zero value will
+	 * cause relay_open() to create a single global buffer rather
+	 * than the default set of per-cpu buffers.
+	 *
+	 * See Documentation/filesystems/relayfs.txt for more info.
+	 */
+	struct dentry *(*create_buf_file)(const char *filename,
+					  struct dentry *parent,
+					  int mode,
+					  struct rchan_buf *buf,
+					  int *is_global);
+
+	/*
+	 * remove_buf_file - remove file representing a relay channel buffer
+	 * @dentry: the dentry of the file to remove
+	 *
+	 * Called during relay_close(), once for each per-cpu buffer,
+	 * to allow the client to remove a file used to represent a
+	 * channel buffer.
+	 *
+	 * The callback should return 0 if successful, negative if not.
+	 */
+	int (*remove_buf_file)(struct dentry *dentry);
+};
+
+/*
+ * CONFIG_RELAY kernel API, kernel/relay.c
+ */
+
+struct rchan *relay_open(const char *base_filename,
+			 struct dentry *parent,
+			 size_t subbuf_size,
+			 size_t n_subbufs,
+			 struct rchan_callbacks *cb);
+extern void relay_close(struct rchan *chan);
+extern void relay_flush(struct rchan *chan);
+extern void relay_subbufs_consumed(struct rchan *chan,
+				   unsigned int cpu,
+				   size_t consumed);
+extern void relay_reset(struct rchan *chan);
+extern int relay_buf_full(struct rchan_buf *buf);
+
+extern size_t relay_switch_subbuf(struct rchan_buf *buf,
+				  size_t length);
+
+/**
+ *	relay_write - write data into the channel
+ *	@chan: relay channel
+ *	@data: data to be written
+ *	@length: number of bytes to write
+ *
+ *	Writes data into the current cpu's channel buffer.
+ *
+ *	Protects the buffer by disabling interrupts.  Use this
+ *	if you might be logging from interrupt context.  Try
+ *	__relay_write() if you know you	won't be logging from
+ *	interrupt context.
+ */
+static inline void relay_write(struct rchan *chan,
+			       const void *data,
+			       size_t length)
+{
+	unsigned long flags;
+	struct rchan_buf *buf;
+
+	local_irq_save(flags);
+	buf = chan->buf[smp_processor_id()];
+	if (unlikely(buf->offset + length > chan->subbuf_size))
+		length = relay_switch_subbuf(buf, length);
+	memcpy(buf->data + buf->offset, data, length);
+	buf->offset += length;
+	local_irq_restore(flags);
+}
+
+/**
+ *	__relay_write - write data into the channel
+ *	@chan: relay channel
+ *	@data: data to be written
+ *	@length: number of bytes to write
+ *
+ *	Writes data into the current cpu's channel buffer.
+ *
+ *	Protects the buffer by disabling preemption.  Use
+ *	relay_write() if you might be logging from interrupt
+ *	context.
+ */
+static inline void __relay_write(struct rchan *chan,
+				 const void *data,
+				 size_t length)
+{
+	struct rchan_buf *buf;
+
+	buf = chan->buf[get_cpu()];
+	if (unlikely(buf->offset + length > buf->chan->subbuf_size))
+		length = relay_switch_subbuf(buf, length);
+	memcpy(buf->data + buf->offset, data, length);
+	buf->offset += length;
+	put_cpu();
+}
+
+/**
+ *	relay_reserve - reserve slot in channel buffer
+ *	@chan: relay channel
+ *	@length: number of bytes to reserve
+ *
+ *	Returns pointer to reserved slot, NULL if full.
+ *
+ *	Reserves a slot in the current cpu's channel buffer.
+ *	Does not protect the buffer at all - caller must provide
+ *	appropriate synchronization.
+ */
+static inline void *relay_reserve(struct rchan *chan, size_t length)
+{
+	void *reserved;
+	struct rchan_buf *buf = chan->buf[smp_processor_id()];
+
+	if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
+		length = relay_switch_subbuf(buf, length);
+		if (!length)
+			return NULL;
+	}
+	reserved = buf->data + buf->offset;
+	buf->offset += length;
+
+	return reserved;
+}
+
+/**
+ *	subbuf_start_reserve - reserve bytes at the start of a sub-buffer
+ *	@buf: relay channel buffer
+ *	@length: number of bytes to reserve
+ *
+ *	Helper function used to reserve bytes at the beginning of
+ *	a sub-buffer in the subbuf_start() callback.
+ */
+static inline void subbuf_start_reserve(struct rchan_buf *buf,
+					size_t length)
+{
+	BUG_ON(length >= buf->chan->subbuf_size - 1);
+	buf->offset = length;
+}
+
+/*
+ * exported relay file operations, kernel/relay.c
+ */
+extern struct file_operations relay_file_operations;
+
+#endif /* _LINUX_RELAY_H */
+
diff --git a/init/Kconfig b/init/Kconfig
index 38416a199de..1d19fd25204 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -214,6 +214,17 @@ config CPUSETS
 
 	  Say N if unsure.
 
+config RELAY
+	bool "Kernel->user space relay support (formerly relayfs)"
+	help
+	  This option enables support for relay interface support in
+	  certain file systems (such as debugfs).
+	  It is designed to provide an efficient mechanism for tools and
+	  facilities to relay large amounts of data from kernel space to
+	  user space.
+
+	  If unsure, say N.
+
 source "usr/Kconfig"
 
 config UID16
diff --git a/kernel/Makefile b/kernel/Makefile
index 4ae0fbde815..aebd7a78984 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
 obj-$(CONFIG_SECCOMP) += seccomp.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
+obj-$(CONFIG_RELAY) += relay.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff --git a/kernel/relay.c b/kernel/relay.c
new file mode 100644
index 00000000000..9358e8eb847
--- /dev/null
+++ b/kernel/relay.c
@@ -0,0 +1,919 @@
+/*
+ * Public API and common code for kernel->userspace relay file support.
+ *
+ * See Documentation/filesystems/relayfs.txt for an overview of relayfs.
+ *
+ * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
+ * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
+ *
+ * Moved to kernel/relay.c by Paul Mundt, 2006.
+ *
+ * This file is released under the GPL.
+ */
+#include <linux/errno.h>
+#include <linux/stddef.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/relay.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+
+/*
+ * close() vm_op implementation for relay file mapping.
+ */
+static void relay_file_mmap_close(struct vm_area_struct *vma)
+{
+	struct rchan_buf *buf = vma->vm_private_data;
+	buf->chan->cb->buf_unmapped(buf, vma->vm_file);
+}
+
+/*
+ * nopage() vm_op implementation for relay file mapping.
+ */
+static struct page *relay_buf_nopage(struct vm_area_struct *vma,
+				     unsigned long address,
+				     int *type)
+{
+	struct page *page;
+	struct rchan_buf *buf = vma->vm_private_data;
+	unsigned long offset = address - vma->vm_start;
+
+	if (address > vma->vm_end)
+		return NOPAGE_SIGBUS; /* Disallow mremap */
+	if (!buf)
+		return NOPAGE_OOM;
+
+	page = vmalloc_to_page(buf->start + offset);
+	if (!page)
+		return NOPAGE_OOM;
+	get_page(page);
+
+	if (type)
+		*type = VM_FAULT_MINOR;
+
+	return page;
+}
+
+/*
+ * vm_ops for relay file mappings.
+ */
+static struct vm_operations_struct relay_file_mmap_ops = {
+	.nopage = relay_buf_nopage,
+	.close = relay_file_mmap_close,
+};
+
+/**
+ *	relay_mmap_buf: - mmap channel buffer to process address space
+ *	@buf: relay channel buffer
+ *	@vma: vm_area_struct describing memory to be mapped
+ *
+ *	Returns 0 if ok, negative on error
+ *
+ *	Caller should already have grabbed mmap_sem.
+ */
+int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
+{
+	unsigned long length = vma->vm_end - vma->vm_start;
+	struct file *filp = vma->vm_file;
+
+	if (!buf)
+		return -EBADF;
+
+	if (length != (unsigned long)buf->chan->alloc_size)
+		return -EINVAL;
+
+	vma->vm_ops = &relay_file_mmap_ops;
+	vma->vm_private_data = buf;
+	buf->chan->cb->buf_mapped(buf, filp);
+
+	return 0;
+}
+
+/**
+ *	relay_alloc_buf - allocate a channel buffer
+ *	@buf: the buffer struct
+ *	@size: total size of the buffer
+ *
+ *	Returns a pointer to the resulting buffer, NULL if unsuccessful
+ */
+static void *relay_alloc_buf(struct rchan_buf *buf, unsigned long size)
+{
+	void *mem;
+	unsigned int i, j, n_pages;
+
+	size = PAGE_ALIGN(size);
+	n_pages = size >> PAGE_SHIFT;
+
+	buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
+	if (!buf->page_array)
+		return NULL;
+
+	for (i = 0; i < n_pages; i++) {
+		buf->page_array[i] = alloc_page(GFP_KERNEL);
+		if (unlikely(!buf->page_array[i]))
+			goto depopulate;
+	}
+	mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
+	if (!mem)
+		goto depopulate;
+
+	memset(mem, 0, size);
+	buf->page_count = n_pages;
+	return mem;
+
+depopulate:
+	for (j = 0; j < i; j++)
+		__free_page(buf->page_array[j]);
+	kfree(buf->page_array);
+	return NULL;
+}
+
+/**
+ *	relay_create_buf - allocate and initialize a channel buffer
+ *	@alloc_size: size of the buffer to allocate
+ *	@n_subbufs: number of sub-buffers in the channel
+ *
+ *	Returns channel buffer if successful, NULL otherwise
+ */
+struct rchan_buf *relay_create_buf(struct rchan *chan)
+{
+	struct rchan_buf *buf = kcalloc(1, sizeof(struct rchan_buf), GFP_KERNEL);
+	if (!buf)
+		return NULL;
+
+	buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
+	if (!buf->padding)
+		goto free_buf;
+
+	buf->start = relay_alloc_buf(buf, chan->alloc_size);
+	if (!buf->start)
+		goto free_buf;
+
+	buf->chan = chan;
+	kref_get(&buf->chan->kref);
+	return buf;
+
+free_buf:
+	kfree(buf->padding);
+	kfree(buf);
+	return NULL;
+}
+
+/**
+ *	relay_destroy_channel - free the channel struct
+ *
+ *	Should only be called from kref_put().
+ */
+void relay_destroy_channel(struct kref *kref)
+{
+	struct rchan *chan = container_of(kref, struct rchan, kref);
+	kfree(chan);
+}
+
+/**
+ *	relay_destroy_buf - destroy an rchan_buf struct and associated buffer
+ *	@buf: the buffer struct
+ */
+void relay_destroy_buf(struct rchan_buf *buf)
+{
+	struct rchan *chan = buf->chan;
+	unsigned int i;
+
+	if (likely(buf->start)) {
+		vunmap(buf->start);
+		for (i = 0; i < buf->page_count; i++)
+			__free_page(buf->page_array[i]);
+		kfree(buf->page_array);
+	}
+	kfree(buf->padding);
+	kfree(buf);
+	kref_put(&chan->kref, relay_destroy_channel);
+}
+
+/**
+ *	relay_remove_buf - remove a channel buffer
+ *
+ *	Removes the file from the fileystem, which also frees the
+ *	rchan_buf_struct and the channel buffer.  Should only be called from
+ *	kref_put().
+ */
+void relay_remove_buf(struct kref *kref)
+{
+	struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
+	buf->chan->cb->remove_buf_file(buf->dentry);
+	relay_destroy_buf(buf);
+}
+
+/**
+ *	relay_buf_empty - boolean, is the channel buffer empty?
+ *	@buf: channel buffer
+ *
+ *	Returns 1 if the buffer is empty, 0 otherwise.
+ */
+int relay_buf_empty(struct rchan_buf *buf)
+{
+	return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
+}
+EXPORT_SYMBOL_GPL(relay_buf_empty);
+
+/**
+ *	relay_buf_full - boolean, is the channel buffer full?
+ *	@buf: channel buffer
+ *
+ *	Returns 1 if the buffer is full, 0 otherwise.
+ */
+int relay_buf_full(struct rchan_buf *buf)
+{
+	size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
+	return (ready >= buf->chan->n_subbufs) ? 1 : 0;
+}
+EXPORT_SYMBOL_GPL(relay_buf_full);
+
+/*
+ * High-level relay kernel API and associated functions.
+ */
+
+/*
+ * rchan_callback implementations defining default channel behavior.  Used
+ * in place of corresponding NULL values in client callback struct.
+ */
+
+/*
+ * subbuf_start() default callback.  Does nothing.
+ */
+static int subbuf_start_default_callback (struct rchan_buf *buf,
+					  void *subbuf,
+					  void *prev_subbuf,
+					  size_t prev_padding)
+{
+	if (relay_buf_full(buf))
+		return 0;
+
+	return 1;
+}
+
+/*
+ * buf_mapped() default callback.  Does nothing.
+ */
+static void buf_mapped_default_callback(struct rchan_buf *buf,
+					struct file *filp)
+{
+}
+
+/*
+ * buf_unmapped() default callback.  Does nothing.
+ */
+static void buf_unmapped_default_callback(struct rchan_buf *buf,
+					  struct file *filp)
+{
+}
+
+/*
+ * create_buf_file_create() default callback.  Does nothing.
+ */
+static struct dentry *create_buf_file_default_callback(const char *filename,
+						       struct dentry *parent,
+						       int mode,
+						       struct rchan_buf *buf,
+						       int *is_global)
+{
+	return NULL;
+}
+
+/*
+ * remove_buf_file() default callback.  Does nothing.
+ */
+static int remove_buf_file_default_callback(struct dentry *dentry)
+{
+	return -EINVAL;
+}
+
+/* relay channel default callbacks */
+static struct rchan_callbacks default_channel_callbacks = {
+	.subbuf_start = subbuf_start_default_callback,
+	.buf_mapped = buf_mapped_default_callback,
+	.buf_unmapped = buf_unmapped_default_callback,
+	.create_buf_file = create_buf_file_default_callback,
+	.remove_buf_file = remove_buf_file_default_callback,
+};
+
+/**
+ *	wakeup_readers - wake up readers waiting on a channel
+ *	@private: the channel buffer
+ *
+ *	This is the work function used to defer reader waking.  The
+ *	reason waking is deferred is that calling directly from write
+ *	causes problems if you're writing from say the scheduler.
+ */
+static void wakeup_readers(void *private)
+{
+	struct rchan_buf *buf = private;
+	wake_up_interruptible(&buf->read_wait);
+}
+
+/**
+ *	__relay_reset - reset a channel buffer
+ *	@buf: the channel buffer
+ *	@init: 1 if this is a first-time initialization
+ *
+ *	See relay_reset for description of effect.
+ */
+static inline void __relay_reset(struct rchan_buf *buf, unsigned int init)
+{
+	size_t i;
+
+	if (init) {
+		init_waitqueue_head(&buf->read_wait);
+		kref_init(&buf->kref);
+		INIT_WORK(&buf->wake_readers, NULL, NULL);
+	} else {
+		cancel_delayed_work(&buf->wake_readers);
+		flush_scheduled_work();
+	}
+
+	buf->subbufs_produced = 0;
+	buf->subbufs_consumed = 0;
+	buf->bytes_consumed = 0;
+	buf->finalized = 0;
+	buf->data = buf->start;
+	buf->offset = 0;
+
+	for (i = 0; i < buf->chan->n_subbufs; i++)
+		buf->padding[i] = 0;
+
+	buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
+}
+
+/**
+ *	relay_reset - reset the channel
+ *	@chan: the channel
+ *
+ *	This has the effect of erasing all data from all channel buffers
+ *	and restarting the channel in its initial state.  The buffers
+ *	are not freed, so any mappings are still in effect.
+ *
+ *	NOTE: Care should be taken that the channel isn't actually
+ *	being used by anything when this call is made.
+ */
+void relay_reset(struct rchan *chan)
+{
+	unsigned int i;
+	struct rchan_buf *prev = NULL;
+
+	if (!chan)
+		return;
+
+	for (i = 0; i < NR_CPUS; i++) {
+		if (!chan->buf[i] || chan->buf[i] == prev)
+			break;
+		__relay_reset(chan->buf[i], 0);
+		prev = chan->buf[i];
+	}
+}
+EXPORT_SYMBOL_GPL(relay_reset);
+
+/**
+ *	relay_open_buf - create a new relay channel buffer
+ *
+ *	Internal - used by relay_open().
+ */
+static struct rchan_buf *relay_open_buf(struct rchan *chan,
+					const char *filename,
+					struct dentry *parent,
+					int *is_global)
+{
+	struct rchan_buf *buf;
+	struct dentry *dentry;
+
+	if (*is_global)
+		return chan->buf[0];
+
+	buf = relay_create_buf(chan);
+	if (!buf)
+		return NULL;
+
+	/* Create file in fs */
+	dentry = chan->cb->create_buf_file(filename, parent, S_IRUSR,
+					   buf, is_global);
+	if (!dentry) {
+		relay_destroy_buf(buf);
+		return NULL;
+	}
+
+	buf->dentry = dentry;
+	__relay_reset(buf, 1);
+
+	return buf;
+}
+
+/**
+ *	relay_close_buf - close a channel buffer
+ *	@buf: channel buffer
+ *
+ *	Marks the buffer finalized and restores the default callbacks.
+ *	The channel buffer and channel buffer data structure are then freed
+ *	automatically when the last reference is given up.
+ */
+static inline void relay_close_buf(struct rchan_buf *buf)
+{
+	buf->finalized = 1;
+	cancel_delayed_work(&buf->wake_readers);
+	flush_scheduled_work();
+	kref_put(&buf->kref, relay_remove_buf);
+}
+
+static inline void setup_callbacks(struct rchan *chan,
+				   struct rchan_callbacks *cb)
+{
+	if (!cb) {
+		chan->cb = &default_channel_callbacks;
+		return;
+	}
+
+	if (!cb->subbuf_start)
+		cb->subbuf_start = subbuf_start_default_callback;
+	if (!cb->buf_mapped)
+		cb->buf_mapped = buf_mapped_default_callback;
+	if (!cb->buf_unmapped)
+		cb->buf_unmapped = buf_unmapped_default_callback;
+	if (!cb->create_buf_file)
+		cb->create_buf_file = create_buf_file_default_callback;
+	if (!cb->remove_buf_file)
+		cb->remove_buf_file = remove_buf_file_default_callback;
+	chan->cb = cb;
+}
+
+/**
+ *	relay_open - create a new relay channel
+ *	@base_filename: base name of files to create
+ *	@parent: dentry of parent directory, NULL for root directory
+ *	@subbuf_size: size of sub-buffers
+ *	@n_subbufs: number of sub-buffers
+ *	@cb: client callback functions
+ *
+ *	Returns channel pointer if successful, NULL otherwise.
+ *
+ *	Creates a channel buffer for each cpu using the sizes and
+ *	attributes specified.  The created channel buffer files
+ *	will be named base_filename0...base_filenameN-1.  File
+ *	permissions will be S_IRUSR.
+ */
+struct rchan *relay_open(const char *base_filename,
+			 struct dentry *parent,
+			 size_t subbuf_size,
+			 size_t n_subbufs,
+			 struct rchan_callbacks *cb)
+{
+	unsigned int i;
+	struct rchan *chan;
+	char *tmpname;
+	int is_global = 0;
+
+	if (!base_filename)
+		return NULL;
+
+	if (!(subbuf_size && n_subbufs))
+		return NULL;
+
+	chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL);
+	if (!chan)
+		return NULL;
+
+	chan->version = RELAYFS_CHANNEL_VERSION;
+	chan->n_subbufs = n_subbufs;
+	chan->subbuf_size = subbuf_size;
+	chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
+	setup_callbacks(chan, cb);
+	kref_init(&chan->kref);
+
+	tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL);
+	if (!tmpname)
+		goto free_chan;
+
+	for_each_online_cpu(i) {
+		sprintf(tmpname, "%s%d", base_filename, i);
+		chan->buf[i] = relay_open_buf(chan, tmpname, parent,
+					      &is_global);
+		if (!chan->buf[i])
+			goto free_bufs;
+
+		chan->buf[i]->cpu = i;
+	}
+
+	kfree(tmpname);
+	return chan;
+
+free_bufs:
+	for (i = 0; i < NR_CPUS; i++) {
+		if (!chan->buf[i])
+			break;
+		relay_close_buf(chan->buf[i]);
+		if (is_global)
+			break;
+	}
+	kfree(tmpname);
+
+free_chan:
+	kref_put(&chan->kref, relay_destroy_channel);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(relay_open);
+
+/**
+ *	relay_switch_subbuf - switch to a new sub-buffer
+ *	@buf: channel buffer
+ *	@length: size of current event
+ *
+ *	Returns either the length passed in or 0 if full.
+ *
+ *	Performs sub-buffer-switch tasks such as invoking callbacks,
+ *	updating padding counts, waking up readers, etc.
+ */
+size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
+{
+	void *old, *new;
+	size_t old_subbuf, new_subbuf;
+
+	if (unlikely(length > buf->chan->subbuf_size))
+		goto toobig;
+
+	if (buf->offset != buf->chan->subbuf_size + 1) {
+		buf->prev_padding = buf->chan->subbuf_size - buf->offset;
+		old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
+		buf->padding[old_subbuf] = buf->prev_padding;
+		buf->subbufs_produced++;
+		if (waitqueue_active(&buf->read_wait)) {
+			PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
+			schedule_delayed_work(&buf->wake_readers, 1);
+		}
+	}
+
+	old = buf->data;
+	new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
+	new = buf->start + new_subbuf * buf->chan->subbuf_size;
+	buf->offset = 0;
+	if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
+		buf->offset = buf->chan->subbuf_size + 1;
+		return 0;
+	}
+	buf->data = new;
+	buf->padding[new_subbuf] = 0;
+
+	if (unlikely(length + buf->offset > buf->chan->subbuf_size))
+		goto toobig;
+
+	return length;
+
+toobig:
+	buf->chan->last_toobig = length;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(relay_switch_subbuf);
+
+/**
+ *	relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
+ *	@chan: the channel
+ *	@cpu: the cpu associated with the channel buffer to update
+ *	@subbufs_consumed: number of sub-buffers to add to current buf's count
+ *
+ *	Adds to the channel buffer's consumed sub-buffer count.
+ *	subbufs_consumed should be the number of sub-buffers newly consumed,
+ *	not the total consumed.
+ *
+ *	NOTE: kernel clients don't need to call this function if the channel
+ *	mode is 'overwrite'.
+ */
+void relay_subbufs_consumed(struct rchan *chan,
+			    unsigned int cpu,
+			    size_t subbufs_consumed)
+{
+	struct rchan_buf *buf;
+
+	if (!chan)
+		return;
+
+	if (cpu >= NR_CPUS || !chan->buf[cpu])
+		return;
+
+	buf = chan->buf[cpu];
+	buf->subbufs_consumed += subbufs_consumed;
+	if (buf->subbufs_consumed > buf->subbufs_produced)
+		buf->subbufs_consumed = buf->subbufs_produced;
+}
+EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
+
+/**
+ *	relay_close - close the channel
+ *	@chan: the channel
+ *
+ *	Closes all channel buffers and frees the channel.
+ */
+void relay_close(struct rchan *chan)
+{
+	unsigned int i;
+	struct rchan_buf *prev = NULL;
+
+	if (!chan)
+		return;
+
+	for (i = 0; i < NR_CPUS; i++) {
+		if (!chan->buf[i] || chan->buf[i] == prev)
+			break;
+		relay_close_buf(chan->buf[i]);
+		prev = chan->buf[i];
+	}
+
+	if (chan->last_toobig)
+		printk(KERN_WARNING "relay: one or more items not logged "
+		       "[item size (%Zd) > sub-buffer size (%Zd)]\n",
+		       chan->last_toobig, chan->subbuf_size);
+
+	kref_put(&chan->kref, relay_destroy_channel);
+}
+EXPORT_SYMBOL_GPL(relay_close);
+
+/**
+ *	relay_flush - close the channel
+ *	@chan: the channel
+ *
+ *	Flushes all channel buffers i.e. forces buffer switch.
+ */
+void relay_flush(struct rchan *chan)
+{
+	unsigned int i;
+	struct rchan_buf *prev = NULL;
+
+	if (!chan)
+		return;
+
+	for (i = 0; i < NR_CPUS; i++) {
+		if (!chan->buf[i] || chan->buf[i] == prev)
+			break;
+		relay_switch_subbuf(chan->buf[i], 0);
+		prev = chan->buf[i];
+	}
+}
+EXPORT_SYMBOL_GPL(relay_flush);
+
+/**
+ *	relay_file_open - open file op for relay files
+ *	@inode: the inode
+ *	@filp: the file
+ *
+ *	Increments the channel buffer refcount.
+ */
+static int relay_file_open(struct inode *inode, struct file *filp)
+{
+	struct rchan_buf *buf = inode->u.generic_ip;
+	kref_get(&buf->kref);
+	filp->private_data = buf;
+
+	return 0;
+}
+
+/**
+ *	relay_file_mmap - mmap file op for relay files
+ *	@filp: the file
+ *	@vma: the vma describing what to map
+ *
+ *	Calls upon relay_mmap_buf to map the file into user space.
+ */
+static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct rchan_buf *buf = filp->private_data;
+	return relay_mmap_buf(buf, vma);
+}
+
+/**
+ *	relay_file_poll - poll file op for relay files
+ *	@filp: the file
+ *	@wait: poll table
+ *
+ *	Poll implemention.
+ */
+static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
+{
+	unsigned int mask = 0;
+	struct rchan_buf *buf = filp->private_data;
+
+	if (buf->finalized)
+		return POLLERR;
+
+	if (filp->f_mode & FMODE_READ) {
+		poll_wait(filp, &buf->read_wait, wait);
+		if (!relay_buf_empty(buf))
+			mask |= POLLIN | POLLRDNORM;
+	}
+
+	return mask;
+}
+
+/**
+ *	relay_file_release - release file op for relay files
+ *	@inode: the inode
+ *	@filp: the file
+ *
+ *	Decrements the channel refcount, as the filesystem is
+ *	no longer using it.
+ */
+static int relay_file_release(struct inode *inode, struct file *filp)
+{
+	struct rchan_buf *buf = filp->private_data;
+	kref_put(&buf->kref, relay_remove_buf);
+
+	return 0;
+}
+
+/**
+ *	relay_file_read_consume - update the consumed count for the buffer
+ */
+static void relay_file_read_consume(struct rchan_buf *buf,
+				    size_t read_pos,
+				    size_t bytes_consumed)
+{
+	size_t subbuf_size = buf->chan->subbuf_size;
+	size_t n_subbufs = buf->chan->n_subbufs;
+	size_t read_subbuf;
+
+	if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
+		relay_subbufs_consumed(buf->chan, buf->cpu, 1);
+		buf->bytes_consumed = 0;
+	}
+
+	buf->bytes_consumed += bytes_consumed;
+	read_subbuf = read_pos / buf->chan->subbuf_size;
+	if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
+		if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
+		    (buf->offset == subbuf_size))
+			return;
+		relay_subbufs_consumed(buf->chan, buf->cpu, 1);
+		buf->bytes_consumed = 0;
+	}
+}
+
+/**
+ *	relay_file_read_avail - boolean, are there unconsumed bytes available?
+ */
+static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
+{
+	size_t bytes_produced, bytes_consumed, write_offset;
+	size_t subbuf_size = buf->chan->subbuf_size;
+	size_t n_subbufs = buf->chan->n_subbufs;
+	size_t produced = buf->subbufs_produced % n_subbufs;
+	size_t consumed = buf->subbufs_consumed % n_subbufs;
+
+	write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
+
+	if (consumed > produced) {
+		if ((produced > n_subbufs) &&
+		    (produced + n_subbufs - consumed <= n_subbufs))
+			produced += n_subbufs;
+	} else if (consumed == produced) {
+		if (buf->offset > subbuf_size) {
+			produced += n_subbufs;
+			if (buf->subbufs_produced == buf->subbufs_consumed)
+				consumed += n_subbufs;
+		}
+	}
+
+	if (buf->offset > subbuf_size)
+		bytes_produced = (produced - 1) * subbuf_size + write_offset;
+	else
+		bytes_produced = produced * subbuf_size + write_offset;
+	bytes_consumed = consumed * subbuf_size + buf->bytes_consumed;
+
+	if (bytes_produced == bytes_consumed)
+		return 0;
+
+	relay_file_read_consume(buf, read_pos, 0);
+
+	return 1;
+}
+
+/**
+ *	relay_file_read_subbuf_avail - return bytes available in sub-buffer
+ */
+static size_t relay_file_read_subbuf_avail(size_t read_pos,
+					   struct rchan_buf *buf)
+{
+	size_t padding, avail = 0;
+	size_t read_subbuf, read_offset, write_subbuf, write_offset;
+	size_t subbuf_size = buf->chan->subbuf_size;
+
+	write_subbuf = (buf->data - buf->start) / subbuf_size;
+	write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
+	read_subbuf = read_pos / subbuf_size;
+	read_offset = read_pos % subbuf_size;
+	padding = buf->padding[read_subbuf];
+
+	if (read_subbuf == write_subbuf) {
+		if (read_offset + padding < write_offset)
+			avail = write_offset - (read_offset + padding);
+	} else
+		avail = (subbuf_size - padding) - read_offset;
+
+	return avail;
+}
+
+/**
+ *	relay_file_read_start_pos - find the first available byte to read
+ *
+ *	If the read_pos is in the middle of padding, return the
+ *	position of the first actually available byte, otherwise
+ *	return the original value.
+ */
+static size_t relay_file_read_start_pos(size_t read_pos,
+					struct rchan_buf *buf)
+{
+	size_t read_subbuf, padding, padding_start, padding_end;
+	size_t subbuf_size = buf->chan->subbuf_size;
+	size_t n_subbufs = buf->chan->n_subbufs;
+
+	read_subbuf = read_pos / subbuf_size;
+	padding = buf->padding[read_subbuf];
+	padding_start = (read_subbuf + 1) * subbuf_size - padding;
+	padding_end = (read_subbuf + 1) * subbuf_size;
+	if (read_pos >= padding_start && read_pos < padding_end) {
+		read_subbuf = (read_subbuf + 1) % n_subbufs;
+		read_pos = read_subbuf * subbuf_size;
+	}
+
+	return read_pos;
+}
+
+/**
+ *	relay_file_read_end_pos - return the new read position
+ */
+static size_t relay_file_read_end_pos(struct rchan_buf *buf,
+				      size_t read_pos,
+				      size_t count)
+{
+	size_t read_subbuf, padding, end_pos;
+	size_t subbuf_size = buf->chan->subbuf_size;
+	size_t n_subbufs = buf->chan->n_subbufs;
+
+	read_subbuf = read_pos / subbuf_size;
+	padding = buf->padding[read_subbuf];
+	if (read_pos % subbuf_size + count + padding == subbuf_size)
+		end_pos = (read_subbuf + 1) * subbuf_size;
+	else
+		end_pos = read_pos + count;
+	if (end_pos >= subbuf_size * n_subbufs)
+		end_pos = 0;
+
+	return end_pos;
+}
+
+/**
+ *	relay_file_read - read file op for relay files
+ *	@filp: the file
+ *	@buffer: the userspace buffer
+ *	@count: number of bytes to read
+ *	@ppos: position to read from
+ *
+ *	Reads count bytes or the number of bytes available in the
+ *	current sub-buffer being read, whichever is smaller.
+ */
+static ssize_t relay_file_read(struct file *filp,
+			       char __user *buffer,
+			       size_t count,
+			       loff_t *ppos)
+{
+	struct rchan_buf *buf = filp->private_data;
+	struct inode *inode = filp->f_dentry->d_inode;
+	size_t read_start, avail;
+	ssize_t ret = 0;
+	void *from;
+
+	mutex_lock(&inode->i_mutex);
+	if(!relay_file_read_avail(buf, *ppos))
+		goto out;
+
+	read_start = relay_file_read_start_pos(*ppos, buf);
+	avail = relay_file_read_subbuf_avail(read_start, buf);
+	if (!avail)
+		goto out;
+
+	from = buf->start + read_start;
+	ret = count = min(count, avail);
+	if (copy_to_user(buffer, from, count)) {
+		ret = -EFAULT;
+		goto out;
+	}
+	relay_file_read_consume(buf, read_start, count);
+	*ppos = relay_file_read_end_pos(buf, read_start, count);
+out:
+	mutex_unlock(&inode->i_mutex);
+	return ret;
+}
+
+struct file_operations relay_file_operations = {
+	.open		= relay_file_open,
+	.poll		= relay_file_poll,
+	.mmap		= relay_file_mmap,
+	.read		= relay_file_read,
+	.llseek		= no_llseek,
+	.release	= relay_file_release,
+};
+EXPORT_SYMBOL_GPL(relay_file_operations);