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/wait.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_FLAG_MASK        ~KERNFS_TYPE_MASK
  39
  40 enum kernfs_node_flag {
  41         KERNFS_ACTIVATED        = 0x0010,
  42         KERNFS_NS               = 0x0020,
  43         KERNFS_HAS_SEQ_SHOW     = 0x0040,
  44         KERNFS_HAS_MMAP         = 0x0080,
  45         KERNFS_LOCKDEP          = 0x0100,
  46         KERNFS_STATIC_NAME      = 0x0200,
  47         KERNFS_SUICIDAL         = 0x0400,
  48         KERNFS_SUICIDED         = 0x0800,
  49 };
  50
  51 /* @flags for kernfs_create_root() */
  52 enum kernfs_root_flag {
  53         KERNFS_ROOT_CREATE_DEACTIVATED = 0x0001,
  54 };
  55
  56 /* type-specific structures for kernfs_node union members */
  57 struct kernfs_elem_dir {
  58         unsigned long           subdirs;
  59         /* children rbtree starts here and goes through kn->rb */
  60         struct rb_root          children;
  61
  62         /*
  63          * The kernfs hierarchy this directory belongs to.  This fits
  64          * better directly in kernfs_node but is here to save space.
  65          */
  66         struct kernfs_root      *root;
  67 };
  68
  69 struct kernfs_elem_symlink {
  70         struct kernfs_node      *target_kn;
  71 };
  72
  73 struct kernfs_elem_attr {
  74         const struct kernfs_ops *ops;
  75         struct kernfs_open_node *open;
  76         loff_t                  size;
  77 };
  78
  79 /*
  80  * kernfs_node - the building block of kernfs hierarchy.  Each and every
  81  * kernfs node is represented by single kernfs_node.  Most fields are
  82  * private to kernfs and shouldn't be accessed directly by kernfs users.
  83  *
  84  * As long as s_count reference is held, the kernfs_node itself is
  85  * accessible.  Dereferencing elem or any other outer entity requires
  86  * active reference.
  87  */
  88 struct kernfs_node {
  89         atomic_t                count;
  90         atomic_t                active;
  91 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  92         struct lockdep_map      dep_map;
  93 #endif
  94         /*
  95          * Use kernfs_get_parent() and kernfs_name/path() instead of
  96          * accessing the following two fields directly.  If the node is
  97          * never moved to a different parent, it is safe to access the
  98          * parent directly.
  99          */
 100         struct kernfs_node      *parent;
 101         const char              *name;
 102
 103         struct rb_node          rb;
 104
 105         const void              *ns;    /* namespace tag */
 106         unsigned int            hash;   /* ns + name hash */
 107         union {
 108                 struct kernfs_elem_dir          dir;
 109                 struct kernfs_elem_symlink      symlink;
 110                 struct kernfs_elem_attr         attr;
 111         };
 112
 113         void                    *priv;
 114
 115         unsigned short          flags;
 116         umode_t                 mode;
 117         unsigned int            ino;
 118         struct kernfs_iattrs    *iattr;
 119 };
 120
 121 /*
 122  * kernfs_syscall_ops may be specified on kernfs_create_root() to support
 123  * syscalls.  These optional callbacks are invoked on the matching syscalls
 124  * and can perform any kernfs operations which don't necessarily have to be
 125  * the exact operation requested.  An active reference is held for each
 126  * kernfs_node parameter.
 127  */
 128 struct kernfs_syscall_ops {
 129         int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
 130         int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
 131
 132         int (*mkdir)(struct kernfs_node *parent, const char *name,
 133                      umode_t mode);
 134         int (*rmdir)(struct kernfs_node *kn);
 135         int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
 136                       const char *new_name);
 137 };
 138
 139 struct kernfs_root {
 140         /* published fields */
 141         struct kernfs_node      *kn;
 142         unsigned int            flags;  /* KERNFS_ROOT_* flags */
 143
 144         /* private fields, do not use outside kernfs proper */
 145         struct ida              ino_ida;
 146         struct kernfs_syscall_ops *syscall_ops;
 147         wait_queue_head_t       deactivate_waitq;
 148 };
 149
 150 struct kernfs_open_file {
 151         /* published fields */
 152         struct kernfs_node      *kn;
 153         struct file             *file;
 154         void                    *priv;
 155
 156         /* private fields, do not use outside kernfs proper */
 157         struct mutex            mutex;
 158         int                     event;
 159         struct list_head        list;
 160
 161         size_t                  atomic_write_len;
 162         bool                    mmapped;
 163         const struct vm_operations_struct *vm_ops;
 164 };
 165
 166 struct kernfs_ops {
 167         /*
 168          * Read is handled by either seq_file or raw_read().
 169          *
 170          * If seq_show() is present, seq_file path is active.  Other seq
 171          * operations are optional and if not implemented, the behavior is
 172          * equivalent to single_open().  @sf->private points to the
 173          * associated kernfs_open_file.
 174          *
 175          * read() is bounced through kernel buffer and a read larger than
 176          * PAGE_SIZE results in partial operation of PAGE_SIZE.
 177          */
 178         int (*seq_show)(struct seq_file *sf, void *v);
 179
 180         void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
 181         void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
 182         void (*seq_stop)(struct seq_file *sf, void *v);
 183
 184         ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
 185                         loff_t off);
 186
 187         /*
 188          * write() is bounced through kernel buffer.  If atomic_write_len
 189          * is not set, a write larger than PAGE_SIZE results in partial
 190          * operations of PAGE_SIZE chunks.  If atomic_write_len is set,
 191          * writes upto the specified size are executed atomically but
 192          * larger ones are rejected with -E2BIG.
 193          */
 194         size_t atomic_write_len;
 195         ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
 196                          loff_t off);
 197
 198         int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
 199
 200 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 201         struct lock_class_key   lockdep_key;
 202 #endif
 203 };
 204
 205 #ifdef CONFIG_KERNFS
 206
 207 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 208 {
 209         return kn->flags & KERNFS_TYPE_MASK;
 210 }
 211
 212 /**
 213  * kernfs_enable_ns - enable namespace under a directory
 214  * @kn: directory of interest, should be empty
 215  *
 216  * This is to be called right after @kn is created to enable namespace
 217  * under it.  All children of @kn must have non-NULL namespace tags and
 218  * only the ones which match the super_block's tag will be visible.
 219  */
 220 static inline void kernfs_enable_ns(struct kernfs_node *kn)
 221 {
 222         WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
 223         WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
 224         kn->flags |= KERNFS_NS;
 225 }
 226
 227 /**
 228  * kernfs_ns_enabled - test whether namespace is enabled
 229  * @kn: the node to test
 230  *
 231  * Test whether namespace filtering is enabled for the children of @ns.
 232  */
 233 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 234 {
 235         return kn->flags & KERNFS_NS;
 236 }
 237
 238 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
 239 char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
 240                                 size_t buflen);
 241 void pr_cont_kernfs_name(struct kernfs_node *kn);
 242 void pr_cont_kernfs_path(struct kernfs_node *kn);
 243 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
 244 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
 245                                            const char *name, const void *ns);
 246 void kernfs_get(struct kernfs_node *kn);
 247 void kernfs_put(struct kernfs_node *kn);
 248
 249 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
 250 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
 251
 252 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
 253                                        unsigned int flags, void *priv);
 254 void kernfs_destroy_root(struct kernfs_root *root);
 255
 256 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 257                                          const char *name, umode_t mode,
 258                                          void *priv, const void *ns);
 259 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 260                                          const char *name,
 261                                          umode_t mode, loff_t size,
 262                                          const struct kernfs_ops *ops,
 263                                          void *priv, const void *ns,
 264                                          bool name_is_static,
 265                                          struct lock_class_key *key);
 266 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
 267                                        const char *name,
 268                                        struct kernfs_node *target);
 269 void kernfs_activate(struct kernfs_node *kn);
 270 void kernfs_remove(struct kernfs_node *kn);
 271 void kernfs_break_active_protection(struct kernfs_node *kn);
 272 void kernfs_unbreak_active_protection(struct kernfs_node *kn);
 273 bool kernfs_remove_self(struct kernfs_node *kn);
 274 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
 275                              const void *ns);
 276 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
 277                      const char *new_name, const void *new_ns);
 278 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
 279 void kernfs_notify(struct kernfs_node *kn);
 280
 281 const void *kernfs_super_ns(struct super_block *sb);
 282 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 283                                struct kernfs_root *root, bool *new_sb_created,
 284                                const void *ns);
 285 void kernfs_kill_sb(struct super_block *sb);
 286
 287 void kernfs_init(void);
 288
 289 #else   /* CONFIG_KERNFS */
 290
 291 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 292 { return 0; }   /* whatever */
 293
 294 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
 295
 296 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 297 { return false; }
 298
 299 static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
 300 { return -ENOSYS; }
 301
 302 static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
 303                                               size_t buflen)
 304 { return NULL; }
 305
 306 static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
 307 static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
 308
 309 static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
 310 { return NULL; }
 311
 312 static inline struct kernfs_node *
 313 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
 314                        const void *ns)
 315 { return NULL; }
 316
 317 static inline void kernfs_get(struct kernfs_node *kn) { }
 318 static inline void kernfs_put(struct kernfs_node *kn) { }
 319
 320 static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
 321 { return NULL; }
 322
 323 static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
 324 { return NULL; }
 325
 326 static inline struct kernfs_root *
 327 kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
 328                    void *priv)
 329 { return ERR_PTR(-ENOSYS); }
 330
 331 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
 332
 333 static inline struct kernfs_node *
 334 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
 335                      umode_t mode, void *priv, const void *ns)
 336 { return ERR_PTR(-ENOSYS); }
 337
 338 static inline struct kernfs_node *
 339 __kernfs_create_file(struct kernfs_node *parent, const char *name,
 340                      umode_t mode, loff_t size, const struct kernfs_ops *ops,
 341                      void *priv, const void *ns, bool name_is_static,
 342                      struct lock_class_key *key)
 343 { return ERR_PTR(-ENOSYS); }
 344
 345 static inline struct kernfs_node *
 346 kernfs_create_link(struct kernfs_node *parent, const char *name,
 347                    struct kernfs_node *target)
 348 { return ERR_PTR(-ENOSYS); }
 349
 350 static inline void kernfs_activate(struct kernfs_node *kn) { }
 351
 352 static inline void kernfs_remove(struct kernfs_node *kn) { }
 353
 354 static inline bool kernfs_remove_self(struct kernfs_node *kn)
 355 { return false; }
 356
 357 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
 358                                            const char *name, const void *ns)
 359 { return -ENOSYS; }
 360
 361 static inline int kernfs_rename_ns(struct kernfs_node *kn,
 362                                    struct kernfs_node *new_parent,
 363                                    const char *new_name, const void *new_ns)
 364 { return -ENOSYS; }
 365
 366 static inline int kernfs_setattr(struct kernfs_node *kn,
 367                                  const struct iattr *iattr)
 368 { return -ENOSYS; }
 369
 370 static inline void kernfs_notify(struct kernfs_node *kn) { }
 371
 372 static inline const void *kernfs_super_ns(struct super_block *sb)
 373 { return NULL; }
 374
 375 static inline struct dentry *
 376 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 377                 struct kernfs_root *root, bool *new_sb_created, const void *ns)
 378 { return ERR_PTR(-ENOSYS); }
 379
 380 static inline void kernfs_kill_sb(struct super_block *sb) { }
 381
 382 static inline void kernfs_init(void) { }
 383
 384 #endif  /* CONFIG_KERNFS */
 385
 386 static inline struct kernfs_node *
 387 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
 388 {
 389         return kernfs_find_and_get_ns(kn, name, NULL);
 390 }
 391
 392 static inline struct kernfs_node *
 393 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
 394                   void *priv)
 395 {
 396         return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
 397 }
 398
 399 static inline struct kernfs_node *
 400 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
 401                       umode_t mode, loff_t size, const struct kernfs_ops *ops,
 402                       void *priv, const void *ns)
 403 {
 404         struct lock_class_key *key = NULL;
 405
 406 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 407         key = (struct lock_class_key *)&ops->lockdep_key;
 408 #endif
 409         return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
 410                                     false, key);
 411 }
 412
 413 static inline struct kernfs_node *
 414 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
 415                    loff_t size, const struct kernfs_ops *ops, void *priv)
 416 {
 417         return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
 418 }
 419
 420 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
 421                                         const char *name)
 422 {
 423         return kernfs_remove_by_name_ns(parent, name, NULL);
 424 }
 425
 426 static inline int kernfs_rename(struct kernfs_node *kn,
 427                                 struct kernfs_node *new_parent,
 428                                 const char *new_name)
 429 {
 430         return kernfs_rename_ns(kn, new_parent, new_name, NULL);
 431 }
 432
 433 static inline struct dentry *
 434 kernfs_mount(struct file_system_type *fs_type, int flags,
 435              struct kernfs_root *root, bool *new_sb_created)
 436 {
 437         return kernfs_mount_ns(fs_type, flags, root, new_sb_created, NULL);
 438 }
 439
 440 #endif  /* __LINUX_KERNFS_H */