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TOMOYO Linux Cross Reference
Linux/fs/nsfs.c

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  1 #include <linux/mount.h>
  2 #include <linux/file.h>
  3 #include <linux/fs.h>
  4 #include <linux/proc_ns.h>
  5 #include <linux/magic.h>
  6 #include <linux/ktime.h>
  7 
  8 static struct vfsmount *nsfs_mnt;
  9 
 10 static const struct file_operations ns_file_operations = {
 11         .llseek         = no_llseek,
 12 };
 13 
 14 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
 15 {
 16         struct inode *inode = d_inode(dentry);
 17         const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
 18 
 19         return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
 20                 ns_ops->name, inode->i_ino);
 21 }
 22 
 23 static void ns_prune_dentry(struct dentry *dentry)
 24 {
 25         struct inode *inode = d_inode(dentry);
 26         if (inode) {
 27                 struct ns_common *ns = inode->i_private;
 28                 atomic_long_set(&ns->stashed, 0);
 29         }
 30 }
 31 
 32 const struct dentry_operations ns_dentry_operations =
 33 {
 34         .d_prune        = ns_prune_dentry,
 35         .d_delete       = always_delete_dentry,
 36         .d_dname        = ns_dname,
 37 };
 38 
 39 static void nsfs_evict(struct inode *inode)
 40 {
 41         struct ns_common *ns = inode->i_private;
 42         clear_inode(inode);
 43         ns->ops->put(ns);
 44 }
 45 
 46 void *ns_get_path(struct path *path, struct task_struct *task,
 47                         const struct proc_ns_operations *ns_ops)
 48 {
 49         struct vfsmount *mnt = mntget(nsfs_mnt);
 50         struct qstr qname = { .name = "", };
 51         struct dentry *dentry;
 52         struct inode *inode;
 53         struct ns_common *ns;
 54         unsigned long d;
 55 
 56 again:
 57         ns = ns_ops->get(task);
 58         if (!ns) {
 59                 mntput(mnt);
 60                 return ERR_PTR(-ENOENT);
 61         }
 62         rcu_read_lock();
 63         d = atomic_long_read(&ns->stashed);
 64         if (!d)
 65                 goto slow;
 66         dentry = (struct dentry *)d;
 67         if (!lockref_get_not_dead(&dentry->d_lockref))
 68                 goto slow;
 69         rcu_read_unlock();
 70         ns_ops->put(ns);
 71 got_it:
 72         path->mnt = mnt;
 73         path->dentry = dentry;
 74         return NULL;
 75 slow:
 76         rcu_read_unlock();
 77         inode = new_inode_pseudo(mnt->mnt_sb);
 78         if (!inode) {
 79                 ns_ops->put(ns);
 80                 mntput(mnt);
 81                 return ERR_PTR(-ENOMEM);
 82         }
 83         inode->i_ino = ns->inum;
 84         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 85         inode->i_flags |= S_IMMUTABLE;
 86         inode->i_mode = S_IFREG | S_IRUGO;
 87         inode->i_fop = &ns_file_operations;
 88         inode->i_private = ns;
 89 
 90         dentry = d_alloc_pseudo(mnt->mnt_sb, &qname);
 91         if (!dentry) {
 92                 iput(inode);
 93                 mntput(mnt);
 94                 return ERR_PTR(-ENOMEM);
 95         }
 96         d_instantiate(dentry, inode);
 97         dentry->d_flags |= DCACHE_RCUACCESS;
 98         dentry->d_fsdata = (void *)ns_ops;
 99         d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
100         if (d) {
101                 d_delete(dentry);       /* make sure ->d_prune() does nothing */
102                 dput(dentry);
103                 cpu_relax();
104                 goto again;
105         }
106         goto got_it;
107 }
108 
109 int ns_get_name(char *buf, size_t size, struct task_struct *task,
110                         const struct proc_ns_operations *ns_ops)
111 {
112         struct ns_common *ns;
113         int res = -ENOENT;
114         ns = ns_ops->get(task);
115         if (ns) {
116                 res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum);
117                 ns_ops->put(ns);
118         }
119         return res;
120 }
121 
122 struct file *proc_ns_fget(int fd)
123 {
124         struct file *file;
125 
126         file = fget(fd);
127         if (!file)
128                 return ERR_PTR(-EBADF);
129 
130         if (file->f_op != &ns_file_operations)
131                 goto out_invalid;
132 
133         return file;
134 
135 out_invalid:
136         fput(file);
137         return ERR_PTR(-EINVAL);
138 }
139 
140 static const struct super_operations nsfs_ops = {
141         .statfs = simple_statfs,
142         .evict_inode = nsfs_evict,
143 };
144 static struct dentry *nsfs_mount(struct file_system_type *fs_type,
145                         int flags, const char *dev_name, void *data)
146 {
147         return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
148                         &ns_dentry_operations, NSFS_MAGIC);
149 }
150 static struct file_system_type nsfs = {
151         .name = "nsfs",
152         .mount = nsfs_mount,
153         .kill_sb = kill_anon_super,
154 };
155 
156 void __init nsfs_init(void)
157 {
158         nsfs_mnt = kern_mount(&nsfs);
159         if (IS_ERR(nsfs_mnt))
160                 panic("can't set nsfs up\n");
161         nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER;
162 }
163 

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