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