include/linux/kernfs.h

   1 /*
   2  * kernfs.h - pseudo filesystem decoupled from vfs locking
   3  *
   4  * This file is released under the GPLv2.
   5  */
   6
   7 #ifndef __LINUX_KERNFS_H
   8 #define __LINUX_KERNFS_H
   9
  10 #include <linux/kernel.h>
  11 #include <linux/err.h>
  12 #include <linux/list.h>
  13 #include <linux/mutex.h>
  14 #include <linux/idr.h>
  15 #include <linux/lockdep.h>
  16 #include <linux/rbtree.h>
  17 #include <linux/atomic.h>
  18 #include <linux/completion.h>
  19
  20 struct file;
  21 struct dentry;
  22 struct iattr;
  23 struct seq_file;
  24 struct vm_area_struct;
  25 struct super_block;
  26 struct file_system_type;
  27
  28 struct kernfs_open_node;
  29 struct kernfs_iattrs;
  30
  31 enum kernfs_node_type {
  32         KERNFS_DIR              = 0x0001,
  33         KERNFS_FILE             = 0x0002,
  34         KERNFS_LINK             = 0x0004,
  35 };
  36
  37 #define KERNFS_TYPE_MASK        0x000f
  38 #define KERNFS_ACTIVE_REF       KERNFS_FILE
  39 #define KERNFS_FLAG_MASK        ~KERNFS_TYPE_MASK
  40
  41 enum kernfs_node_flag {
  42         KERNFS_REMOVED          = 0x0010,
  43         KERNFS_NS               = 0x0020,
  44         KERNFS_HAS_SEQ_SHOW     = 0x0040,
  45         KERNFS_HAS_MMAP         = 0x0080,
  46         KERNFS_LOCKDEP          = 0x0100,
  47         KERNFS_STATIC_NAME      = 0x0200,
  48 };
  49
  50 /* type-specific structures for kernfs_node union members */
  51 struct kernfs_elem_dir {
  52         unsigned long           subdirs;
  53         /* children rbtree starts here and goes through kn->rb */
  54         struct rb_root          children;
  55
  56         /*
  57          * The kernfs hierarchy this directory belongs to.  This fits
  58          * better directly in kernfs_node but is here to save space.
  59          */
  60         struct kernfs_root      *root;
  61 };
  62
  63 struct kernfs_elem_symlink {
  64         struct kernfs_node      *target_kn;
  65 };
  66
  67 struct kernfs_elem_attr {
  68         const struct kernfs_ops *ops;
  69         struct kernfs_open_node *open;
  70         loff_t                  size;
  71 };
  72
  73 /*
  74  * kernfs_node - the building block of kernfs hierarchy.  Each and every
  75  * kernfs node is represented by single kernfs_node.  Most fields are
  76  * private to kernfs and shouldn't be accessed directly by kernfs users.
  77  *
  78  * As long as s_count reference is held, the kernfs_node itself is
  79  * accessible.  Dereferencing elem or any other outer entity requires
  80  * active reference.
  81  */
  82 struct kernfs_node {
  83         atomic_t                count;
  84         atomic_t                active;
  85 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  86         struct lockdep_map      dep_map;
  87 #endif
  88         /* the following two fields are published */
  89         struct kernfs_node      *parent;
  90         const char              *name;
  91
  92         struct rb_node          rb;
  93
  94         union {
  95                 struct completion       *completion;
  96                 struct kernfs_node      *removed_list;
  97         } u;
  98
  99         const void              *ns;    /* namespace tag */
 100         unsigned int            hash;   /* ns + name hash */
 101         union {
 102                 struct kernfs_elem_dir          dir;
 103                 struct kernfs_elem_symlink      symlink;
 104                 struct kernfs_elem_attr         attr;
 105         };
 106
 107         void                    *priv;
 108
 109         unsigned short          flags;
 110         umode_t                 mode;
 111         unsigned int            ino;
 112         struct kernfs_iattrs    *iattr;
 113 };
 114
 115 /*
 116  * kernfs_dir_ops may be specified on kernfs_create_root() to support
 117  * directory manipulation syscalls.  These optional callbacks are invoked
 118  * on the matching syscalls and can perform any kernfs operations which
 119  * don't necessarily have to be the exact operation requested.
 120  */
 121 struct kernfs_dir_ops {
 122         int (*mkdir)(struct kernfs_node *parent, const char *name,
 123                      umode_t mode);
 124         int (*rmdir)(struct kernfs_node *kn);
 125         int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
 126                       const char *new_name);
 127 };
 128
 129 struct kernfs_root {
 130         /* published fields */
 131         struct kernfs_node      *kn;
 132
 133         /* private fields, do not use outside kernfs proper */
 134         struct ida              ino_ida;
 135         struct kernfs_dir_ops   *dir_ops;
 136 };
 137
 138 struct kernfs_open_file {
 139         /* published fields */
 140         struct kernfs_node      *kn;
 141         struct file             *file;
 142
 143         /* private fields, do not use outside kernfs proper */
 144         struct mutex            mutex;
 145         int                     event;
 146         struct list_head        list;
 147
 148         bool                    mmapped;
 149         const struct vm_operations_struct *vm_ops;
 150 };
 151
 152 struct kernfs_ops {
 153         /*
 154          * Read is handled by either seq_file or raw_read().
 155          *
 156          * If seq_show() is present, seq_file path is active.  Other seq
 157          * operations are optional and if not implemented, the behavior is
 158          * equivalent to single_open().  @sf->private points to the
 159          * associated kernfs_open_file.
 160          *
 161          * read() is bounced through kernel buffer and a read larger than
 162          * PAGE_SIZE results in partial operation of PAGE_SIZE.
 163          */
 164         int (*seq_show)(struct seq_file *sf, void *v);
 165
 166         void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
 167         void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
 168         void (*seq_stop)(struct seq_file *sf, void *v);
 169
 170         ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
 171                         loff_t off);
 172
 173         /*
 174          * write() is bounced through kernel buffer and a write larger than
 175          * PAGE_SIZE results in partial operation of PAGE_SIZE.
 176          */
 177         ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
 178                          loff_t off);
 179
 180         int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
 181
 182 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 183         struct lock_class_key   lockdep_key;
 184 #endif
 185 };
 186
 187 #ifdef CONFIG_SYSFS
 188
 189 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 190 {
 191         return kn->flags & KERNFS_TYPE_MASK;
 192 }
 193
 194 /**
 195  * kernfs_enable_ns - enable namespace under a directory
 196  * @kn: directory of interest, should be empty
 197  *
 198  * This is to be called right after @kn is created to enable namespace
 199  * under it.  All children of @kn must have non-NULL namespace tags and
 200  * only the ones which match the super_block's tag will be visible.
 201  */
 202 static inline void kernfs_enable_ns(struct kernfs_node *kn)
 203 {
 204         WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
 205         WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
 206         kn->flags |= KERNFS_NS;
 207 }
 208
 209 /**
 210  * kernfs_ns_enabled - test whether namespace is enabled
 211  * @kn: the node to test
 212  *
 213  * Test whether namespace filtering is enabled for the children of @ns.
 214  */
 215 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 216 {
 217         return kn->flags & KERNFS_NS;
 218 }
 219
 220 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
 221                                            const char *name, const void *ns);
 222 void kernfs_get(struct kernfs_node *kn);
 223 void kernfs_put(struct kernfs_node *kn);
 224
 225 struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops,
 226                                        void *priv);
 227 void kernfs_destroy_root(struct kernfs_root *root);
 228
 229 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 230                                          const char *name, umode_t mode,
 231                                          void *priv, const void *ns);
 232 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 233                                          const char *name,
 234                                          umode_t mode, loff_t size,
 235                                          const struct kernfs_ops *ops,
 236                                          void *priv, const void *ns,
 237                                          bool name_is_static,
 238                                          struct lock_class_key *key);
 239 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
 240                                        const char *name,
 241                                        struct kernfs_node *target);
 242 void kernfs_remove(struct kernfs_node *kn);
 243 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
 244                              const void *ns);
 245 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
 246                      const char *new_name, const void *new_ns);
 247 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
 248 void kernfs_notify(struct kernfs_node *kn);
 249
 250 const void *kernfs_super_ns(struct super_block *sb);
 251 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 252                                struct kernfs_root *root, bool *new_sb_created,
 253                                const void *ns);
 254 void kernfs_kill_sb(struct super_block *sb);
 255
 256 void kernfs_init(void);
 257
 258 #else   /* CONFIG_SYSFS */
 259
 260 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 261 { return 0; }   /* whatever */
 262
 263 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
 264
 265 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 266 { return false; }
 267
 268 static inline struct kernfs_node *
 269 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
 270                        const void *ns)
 271 { return NULL; }
 272
 273 static inline void kernfs_get(struct kernfs_node *kn) { }
 274 static inline void kernfs_put(struct kernfs_node *kn) { }
 275
 276 static inline struct kernfs_root *
 277 kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
 278 { return ERR_PTR(-ENOSYS); }
 279
 280 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
 281
 282 static inline struct kernfs_node *
 283 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
 284                      umode_t mode, void *priv, const void *ns)
 285 { return ERR_PTR(-ENOSYS); }
 286
 287 static inline struct kernfs_node *
 288 __kernfs_create_file(struct kernfs_node *parent, const char *name,
 289                      umode_t mode, loff_t size, const struct kernfs_ops *ops,
 290                      void *priv, const void *ns, bool name_is_static,
 291                      struct lock_class_key *key)
 292 { return ERR_PTR(-ENOSYS); }
 293
 294 static inline struct kernfs_node *
 295 kernfs_create_link(struct kernfs_node *parent, const char *name,
 296                    struct kernfs_node *target)
 297 { return ERR_PTR(-ENOSYS); }
 298
 299 static inline void kernfs_remove(struct kernfs_node *kn) { }
 300
 301 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
 302                                            const char *name, const void *ns)
 303 { return -ENOSYS; }
 304
 305 static inline int kernfs_rename_ns(struct kernfs_node *kn,
 306                                    struct kernfs_node *new_parent,
 307                                    const char *new_name, const void *new_ns)
 308 { return -ENOSYS; }
 309
 310 static inline int kernfs_setattr(struct kernfs_node *kn,
 311                                  const struct iattr *iattr)
 312 { return -ENOSYS; }
 313
 314 static inline void kernfs_notify(struct kernfs_node *kn) { }
 315
 316 static inline const void *kernfs_super_ns(struct super_block *sb)
 317 { return NULL; }
 318
 319 static inline struct dentry *
 320 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 321                 struct kernfs_root *root, bool *new_sb_created, const void *ns)
 322 { return ERR_PTR(-ENOSYS); }
 323
 324 static inline void kernfs_kill_sb(struct super_block *sb) { }
 325
 326 static inline void kernfs_init(void) { }
 327
 328 #endif  /* CONFIG_SYSFS */
 329
 330 static inline struct kernfs_node *
 331 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
 332 {
 333         return kernfs_find_and_get_ns(kn, name, NULL);
 334 }
 335
 336 static inline struct kernfs_node *
 337 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
 338                   void *priv)
 339 {
 340         return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
 341 }
 342
 343 static inline struct kernfs_node *
 344 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
 345                       umode_t mode, loff_t size, const struct kernfs_ops *ops,
 346                       void *priv, const void *ns)
 347 {
 348         struct lock_class_key *key = NULL;
 349
 350 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 351         key = (struct lock_class_key *)&ops->lockdep_key;
 352 #endif
 353         return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
 354                                     false, key);
 355 }
 356
 357 static inline struct kernfs_node *
 358 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
 359                    loff_t size, const struct kernfs_ops *ops, void *priv)
 360 {
 361         return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
 362 }
 363
 364 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
 365                                         const char *name)
 366 {
 367         return kernfs_remove_by_name_ns(parent, name, NULL);
 368 }
 369
 370 static inline struct dentry *
 371 kernfs_mount(struct file_system_type *fs_type, int flags,
 372              struct kernfs_root *root, bool *new_sb_created)
 373 {
 374         return kernfs_mount_ns(fs_type, flags, root, new_sb_created, NULL);
 375 }
 376
 377 #endif  /* __LINUX_KERNFS_H */