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         union {
  93                 struct kernfs_node      *removed_list;
  94         } u;
  95
  96         const void              *ns;    /* namespace tag */
  97         unsigned int            hash;   /* ns + name hash */
  98         union {
  99                 struct kernfs_elem_dir          dir;
 100                 struct kernfs_elem_symlink      symlink;
 101                 struct kernfs_elem_attr         attr;
 102         };
 103
 104         void                    *priv;
 105
 106         unsigned short          flags;
 107         umode_t                 mode;
 108         unsigned int            ino;
 109         struct kernfs_iattrs    *iattr;
 110 };
 111
 112 /*
 113  * kernfs_dir_ops may be specified on kernfs_create_root() to support
 114  * directory manipulation syscalls.  These optional callbacks are invoked
 115  * on the matching syscalls and can perform any kernfs operations which
 116  * don't necessarily have to be the exact operation requested.
 117  */
 118 struct kernfs_dir_ops {
 119         int (*mkdir)(struct kernfs_node *parent, const char *name,
 120                      umode_t mode);
 121         int (*rmdir)(struct kernfs_node *kn);
 122         int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
 123                       const char *new_name);
 124 };
 125
 126 struct kernfs_root {
 127         /* published fields */
 128         struct kernfs_node      *kn;
 129
 130         /* private fields, do not use outside kernfs proper */
 131         struct ida              ino_ida;
 132         struct kernfs_dir_ops   *dir_ops;
 133         wait_queue_head_t       deactivate_waitq;
 134 };
 135
 136 struct kernfs_open_file {
 137         /* published fields */
 138         struct kernfs_node      *kn;
 139         struct file             *file;
 140
 141         /* private fields, do not use outside kernfs proper */
 142         struct mutex            mutex;
 143         int                     event;
 144         struct list_head        list;
 145
 146         bool                    mmapped;
 147         const struct vm_operations_struct *vm_ops;
 148 };
 149
 150 struct kernfs_ops {
 151         /*
 152          * Read is handled by either seq_file or raw_read().
 153          *
 154          * If seq_show() is present, seq_file path is active.  Other seq
 155          * operations are optional and if not implemented, the behavior is
 156          * equivalent to single_open().  @sf->private points to the
 157          * associated kernfs_open_file.
 158          *
 159          * read() is bounced through kernel buffer and a read larger than
 160          * PAGE_SIZE results in partial operation of PAGE_SIZE.
 161          */
 162         int (*seq_show)(struct seq_file *sf, void *v);
 163
 164         void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
 165         void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
 166         void (*seq_stop)(struct seq_file *sf, void *v);
 167
 168         ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
 169                         loff_t off);
 170
 171         /*
 172          * write() is bounced through kernel buffer and a write larger than
 173          * PAGE_SIZE results in partial operation of PAGE_SIZE.
 174          */
 175         ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
 176                          loff_t off);
 177
 178         int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
 179
 180 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 181         struct lock_class_key   lockdep_key;
 182 #endif
 183 };
 184
 185 #ifdef CONFIG_SYSFS
 186
 187 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 188 {
 189         return kn->flags & KERNFS_TYPE_MASK;
 190 }
 191
 192 /**
 193  * kernfs_enable_ns - enable namespace under a directory
 194  * @kn: directory of interest, should be empty
 195  *
 196  * This is to be called right after @kn is created to enable namespace
 197  * under it.  All children of @kn must have non-NULL namespace tags and
 198  * only the ones which match the super_block's tag will be visible.
 199  */
 200 static inline void kernfs_enable_ns(struct kernfs_node *kn)
 201 {
 202         WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
 203         WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
 204         kn->flags |= KERNFS_NS;
 205 }
 206
 207 /**
 208  * kernfs_ns_enabled - test whether namespace is enabled
 209  * @kn: the node to test
 210  *
 211  * Test whether namespace filtering is enabled for the children of @ns.
 212  */
 213 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 214 {
 215         return kn->flags & KERNFS_NS;
 216 }
 217
 218 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
 219                                            const char *name, const void *ns);
 220 void kernfs_get(struct kernfs_node *kn);
 221 void kernfs_put(struct kernfs_node *kn);
 222
 223 struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops,
 224                                        void *priv);
 225 void kernfs_destroy_root(struct kernfs_root *root);
 226
 227 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 228                                          const char *name, umode_t mode,
 229                                          void *priv, const void *ns);
 230 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 231                                          const char *name,
 232                                          umode_t mode, loff_t size,
 233                                          const struct kernfs_ops *ops,
 234                                          void *priv, const void *ns,
 235                                          bool name_is_static,
 236                                          struct lock_class_key *key);
 237 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
 238                                        const char *name,
 239                                        struct kernfs_node *target);
 240 void kernfs_remove(struct kernfs_node *kn);
 241 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
 242                              const void *ns);
 243 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
 244                      const char *new_name, const void *new_ns);
 245 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
 246 void kernfs_notify(struct kernfs_node *kn);
 247
 248 const void *kernfs_super_ns(struct super_block *sb);
 249 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 250                                struct kernfs_root *root, const void *ns);
 251 void kernfs_kill_sb(struct super_block *sb);
 252
 253 void kernfs_init(void);
 254
 255 #else   /* CONFIG_SYSFS */
 256
 257 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 258 { return 0; }   /* whatever */
 259
 260 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
 261
 262 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 263 { return false; }
 264
 265 static inline struct kernfs_node *
 266 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
 267                        const void *ns)
 268 { return NULL; }
 269
 270 static inline void kernfs_get(struct kernfs_node *kn) { }
 271 static inline void kernfs_put(struct kernfs_node *kn) { }
 272
 273 static inline struct kernfs_root *
 274 kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
 275 { return ERR_PTR(-ENOSYS); }
 276
 277 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
 278
 279 static inline struct kernfs_node *
 280 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
 281                      umode_t mode, void *priv, const void *ns)
 282 { return ERR_PTR(-ENOSYS); }
 283
 284 static inline struct kernfs_node *
 285 __kernfs_create_file(struct kernfs_node *parent, const char *name,
 286                      umode_t mode, loff_t size, const struct kernfs_ops *ops,
 287                      void *priv, const void *ns, bool name_is_static,
 288                      struct lock_class_key *key)
 289 { return ERR_PTR(-ENOSYS); }
 290
 291 static inline struct kernfs_node *
 292 kernfs_create_link(struct kernfs_node *parent, const char *name,
 293                    struct kernfs_node *target)
 294 { return ERR_PTR(-ENOSYS); }
 295
 296 static inline void kernfs_remove(struct kernfs_node *kn) { }
 297
 298 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
 299                                            const char *name, const void *ns)
 300 { return -ENOSYS; }
 301
 302 static inline int kernfs_rename_ns(struct kernfs_node *kn,
 303                                    struct kernfs_node *new_parent,
 304                                    const char *new_name, const void *new_ns)
 305 { return -ENOSYS; }
 306
 307 static inline int kernfs_setattr(struct kernfs_node *kn,
 308                                  const struct iattr *iattr)
 309 { return -ENOSYS; }
 310
 311 static inline void kernfs_notify(struct kernfs_node *kn) { }
 312
 313 static inline const void *kernfs_super_ns(struct super_block *sb)
 314 { return NULL; }
 315
 316 static inline struct dentry *
 317 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 318                 struct kernfs_root *root, const void *ns)
 319 { return ERR_PTR(-ENOSYS); }
 320
 321 static inline void kernfs_kill_sb(struct super_block *sb) { }
 322
 323 static inline void kernfs_init(void) { }
 324
 325 #endif  /* CONFIG_SYSFS */
 326
 327 static inline struct kernfs_node *
 328 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
 329 {
 330         return kernfs_find_and_get_ns(kn, name, NULL);
 331 }
 332
 333 static inline struct kernfs_node *
 334 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
 335                   void *priv)
 336 {
 337         return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
 338 }
 339
 340 static inline struct kernfs_node *
 341 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
 342                       umode_t mode, loff_t size, const struct kernfs_ops *ops,
 343                       void *priv, const void *ns)
 344 {
 345         struct lock_class_key *key = NULL;
 346
 347 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 348         key = (struct lock_class_key *)&ops->lockdep_key;
 349 #endif
 350         return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
 351                                     false, key);
 352 }
 353
 354 static inline struct kernfs_node *
 355 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
 356                    loff_t size, const struct kernfs_ops *ops, void *priv)
 357 {
 358         return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
 359 }
 360
 361 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
 362                                         const char *name)
 363 {
 364         return kernfs_remove_by_name_ns(parent, name, NULL);
 365 }
 366
 367 static inline struct dentry *
 368 kernfs_mount(struct file_system_type *fs_type, int flags,
 369              struct kernfs_root *root)
 370 {
 371         return kernfs_mount_ns(fs_type, flags, root, NULL);
 372 }
 373
 374 #endif  /* __LINUX_KERNFS_H */