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Commit b86ff981 authored by Jens Axboe's avatar Jens Axboe
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[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: default avatarJens Axboe <axboe@suse.de>
parent b0e6e962
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Showing with 1212 additions and 808 deletions
fs/Kconfig
View file @ b86ff981
......@@ -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
......
fs/Makefile
View file @ b86ff981
......@@ -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/
......
fs/relayfs/Makefile deleted 100644 → 0
View file @ b0e6e962
obj-$(CONFIG_RELAYFS_FS) += relayfs.o
relayfs-y := relay.o inode.o buffers.o
fs/relayfs/buffers.c deleted 100644 → 0
View file @ b0e6e962
/*
* 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);
}
fs/relayfs/buffers.h deleted 100644 → 0
View file @ b0e6e962
#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 */
fs/relayfs/inode.c deleted 100644 → 0
View file @ b0e6e962
/*
* 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");
fs/relayfs/relay.h deleted 100644 → 0
View file @ b0e6e962
#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 */
include/linux/relay.h 0 → 100644
View file @ b86ff981
/*
* 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 */
init/Kconfig
View file @ b86ff981
......@@ -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
......
kernel/Makefile
View file @ b86ff981
......@@ -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
......
fs/relayfs/relay.c → kernel/relay.c
View file @ b86ff981
/*
* Public API and common code for RelayFS.
* 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/relayfs_fs.h>
#include "relay.h"
#include "buffers.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?
......@@ -28,6 +215,7 @@ 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?
......@@ -40,9 +228,10 @@ 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 relayfs kernel API and associated functions.
* High-level relay kernel API and associated functions.
*/
/*
......@@ -81,7 +270,7 @@ static void buf_unmapped_default_callback(struct rchan_buf *buf,
}
/*
* create_buf_file_create() default callback. Creates file to represent buf.
* create_buf_file_create() default callback. Does nothing.
*/
static struct dentry *create_buf_file_default_callback(const char *filename,
struct dentry *parent,
......@@ -89,16 +278,15 @@ static struct dentry *create_buf_file_default_callback(const char *filename,
struct rchan_buf *buf,
int *is_global)
{
return relayfs_create_file(filename, parent, mode,
&relay_file_operations, buf);
return NULL;
}
/*
* remove_buf_file() default callback. Removes file representing relay buffer.
* remove_buf_file() default callback. Does nothing.
*/
static int remove_buf_file_default_callback(struct dentry *dentry)
{
return relayfs_remove(dentry);
return -EINVAL;
}
/* relay channel default callbacks */
......@@ -183,9 +371,10 @@ void relay_reset(struct rchan *chan)
prev = chan->buf[i];
}
}
EXPORT_SYMBOL_GPL(relay_reset);
/**
* relay_open_buf - create a new channel buffer in relayfs
* relay_open_buf - create a new relay channel buffer
*
* Internal - used by relay_open().
*/
......@@ -200,17 +389,17 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan,
if (*is_global)
return chan->buf[0];
buf = relay_create_buf(chan);
if (!buf)
return NULL;
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);
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);
......@@ -229,7 +418,6 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan,
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);
......@@ -257,7 +445,7 @@ static inline void setup_callbacks(struct rchan *chan,
}
/**
* relay_open - create a new relayfs channel
* 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
......@@ -307,9 +495,10 @@ struct rchan *relay_open(const char *base_filename,
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;
chan->buf[i]->cpu = i;
}
kfree(tmpname);
......@@ -329,6 +518,7 @@ struct rchan *relay_open(const char *base_filename,
kref_put(&chan->kref, relay_destroy_channel);
return NULL;
}
EXPORT_SYMBOL_GPL(relay_open);
/**
* relay_switch_subbuf - switch to a new sub-buffer
......@@ -336,7 +526,7 @@ struct rchan *relay_open(const char *base_filename,
* @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.
*/
......@@ -379,6 +569,7 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
buf->chan->last_toobig = length;
return 0;
}
EXPORT_SYMBOL_GPL(relay_switch_subbuf);
/**
* relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
......@@ -410,17 +601,7 @@ void relay_subbufs_consumed(struct rchan *chan,
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);
}
EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
/**
* relay_close - close the channel
......@@ -444,12 +625,13 @@ void relay_close(struct rchan *chan)
}
if (chan->last_toobig)
printk(KERN_WARNING "relayfs: one or more items not logged "
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
......@@ -472,11 +654,266 @@ void relay_flush(struct rchan *chan)
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);
/**
* 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);
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