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#include <linux/mount.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/proc_ns.h>
#include <linux/magic.h>
#include <linux/ktime.h>
#include <linux/seq_file.h>
static struct vfsmount *nsfs_mnt;
static const struct file_operations ns_file_operations = {
.llseek = no_llseek,
};
static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
{
struct inode *inode = d_inode(dentry);
const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
ns_ops->name, inode->i_ino);
}
static void ns_prune_dentry(struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
if (inode) {
struct ns_common *ns = inode->i_private;
atomic_long_set(&ns->stashed, 0);
}
}
const struct dentry_operations ns_dentry_operations =
{
.d_prune = ns_prune_dentry,
.d_delete = always_delete_dentry,
.d_dname = ns_dname,
};
static void nsfs_evict(struct inode *inode)
{
struct ns_common *ns = inode->i_private;
clear_inode(inode);
ns->ops->put(ns);
}
void *ns_get_path(struct path *path, struct task_struct *task,
const struct proc_ns_operations *ns_ops)
{
struct vfsmount *mnt = mntget(nsfs_mnt);
struct qstr qname = { .name = "", };
struct dentry *dentry;
struct inode *inode;
struct ns_common *ns;
unsigned long d;
again:
ns = ns_ops->get(task);
if (!ns) {
mntput(mnt);
return ERR_PTR(-ENOENT);
}
rcu_read_lock();
d = atomic_long_read(&ns->stashed);
if (!d)
goto slow;
dentry = (struct dentry *)d;
if (!lockref_get_not_dead(&dentry->d_lockref))
goto slow;
rcu_read_unlock();
ns_ops->put(ns);
got_it:
path->mnt = mnt;
path->dentry = dentry;
return NULL;
slow:
rcu_read_unlock();
inode = new_inode_pseudo(mnt->mnt_sb);
if (!inode) {
ns_ops->put(ns);
mntput(mnt);
return ERR_PTR(-ENOMEM);
}
inode->i_ino = ns->inum;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_flags |= S_IMMUTABLE;
inode->i_mode = S_IFREG | S_IRUGO;
inode->i_fop = &ns_file_operations;
inode->i_private = ns;
dentry = d_alloc_pseudo(mnt->mnt_sb, &qname);
if (!dentry) {
iput(inode);
mntput(mnt);
return ERR_PTR(-ENOMEM);
}
d_instantiate(dentry, inode);
dentry->d_fsdata = (void *)ns_ops;
d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
if (d) {
d_delete(dentry); /* make sure ->d_prune() does nothing */
dput(dentry);
cpu_relax();
goto again;
}
goto got_it;
}
int ns_get_name(char *buf, size_t size, struct task_struct *task,
const struct proc_ns_operations *ns_ops)
{
struct ns_common *ns;
int res = -ENOENT;
ns = ns_ops->get(task);
if (ns) {
res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum);
ns_ops->put(ns);
}
return res;
}
struct file *proc_ns_fget(int fd)
{
struct file *file;
file = fget(fd);
if (!file)
return ERR_PTR(-EBADF);
if (file->f_op != &ns_file_operations)
goto out_invalid;
return file;
out_invalid:
fput(file);
return ERR_PTR(-EINVAL);
}
static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
return seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
}
static const struct super_operations nsfs_ops = {
.statfs = simple_statfs,
.evict_inode = nsfs_evict,
.show_path = nsfs_show_path,
};
static struct dentry *nsfs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
&ns_dentry_operations, NSFS_MAGIC);
}
static struct file_system_type nsfs = {
.name = "nsfs",
.mount = nsfs_mount,
.kill_sb = kill_anon_super,
};
void __init nsfs_init(void)
{
nsfs_mnt = kern_mount(&nsfs);
if (IS_ERR(nsfs_mnt))
panic("can't set nsfs up\n");
nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER;
}
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