WSL2-Linux-Kernel/fs/relayfs/inode.c

582 строки
14 KiB
C

/*
* 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");