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1.pipe fs init
static int __init init_pipe_fs(void)
{
int err = register_filesystem(&pipe_fs_type);


if (!err) {
pipe_mnt = kern_mount(&pipe_fs_type);
if (IS_ERR(pipe_mnt)) {
err = PTR_ERR(pipe_mnt);
unregister_filesystem(&pipe_fs_type);
}
}
return err;
}

2.struct super_operations pipefs_ops
static const struct super_operations pipefs_ops = {
.destroy_inode = free_inode_nonrcu,
.statfs = simple_statfs,
};

3.struct dentry_operations pipefs_dentry_operations
static const struct dentry_operations pipefs_dentry_operations = {
.d_dname = pipefs_dname,
};

4.struct file_operations pipefifo_fops 
const struct file_operations pipefifo_fops = {
.open = fifo_open,
.llseek = no_llseek,
.read = do_sync_read,
.aio_read = pipe_read,
.write = do_sync_write,
.aio_write = pipe_write,
.poll = pipe_poll,
.unlocked_ioctl = pipe_ioctl,
.release = pipe_release,
.fasync = pipe_fasync,
};

5.create_pipe_files
int create_pipe_files(struct file **res, int flags)
{
int err;
struct inode *inode = get_pipe_inode();
struct file *f;
struct path path;
static struct qstr name = { .name = "" };


if (!inode)
return -ENFILE;


err = -ENOMEM;
path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
if (!path.dentry)
goto err_inode;
path.mnt = mntget(pipe_mnt);


d_instantiate(path.dentry, inode);


err = -ENFILE;
f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
if (IS_ERR(f))
goto err_dentry;


f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
f->private_data = inode->i_pipe;


res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
if (IS_ERR(res[0]))
goto err_file;


path_get(&path);
res[0]->private_data = inode->i_pipe;
res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
res[1] = f;
return 0;


err_file:
put_filp(f);
err_dentry:
free_pipe_info(inode->i_pipe);
path_put(&path);
return err;


err_inode:
free_pipe_info(inode->i_pipe);
iput(inode);
return err;
}