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_NS               = 0x0020,
  42         KERNFS_HAS_SEQ_SHOW     = 0x0040,
  43         KERNFS_HAS_MMAP         = 0x0080,
  44         KERNFS_LOCKDEP          = 0x0100,
  45         KERNFS_STATIC_NAME      = 0x0200,
  46         KERNFS_SUICIDAL         = 0x0400,
  47         KERNFS_SUICIDED         = 0x0800,
  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         const void              *ns;    /* namespace tag */
  95         unsigned int            hash;   /* ns + name hash */
  96         union {
  97                 struct kernfs_elem_dir          dir;
  98                 struct kernfs_elem_symlink      symlink;
  99                 struct kernfs_elem_attr         attr;
 100         };
 101
 102         void                    *priv;
 103
 104         unsigned short          flags;
 105         umode_t                 mode;
 106         unsigned int            ino;
 107         struct kernfs_iattrs    *iattr;
 108 };
 109
 110 /*
 111  * kernfs_dir_ops may be specified on kernfs_create_root() to support
 112  * directory manipulation syscalls.  These optional callbacks are invoked
 113  * on the matching syscalls and can perform any kernfs operations which
 114  * don't necessarily have to be the exact operation requested.  An active
 115  * reference is held for each kernfs_node parameter.
 116  */
 117 struct kernfs_dir_ops {
 118         int (*mkdir)(struct kernfs_node *parent, const char *name,
 119                      umode_t mode);
 120         int (*rmdir)(struct kernfs_node *kn);
 121         int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
 122                       const char *new_name);
 123 };
 124
 125 struct kernfs_root {
 126         /* published fields */
 127         struct kernfs_node      *kn;
 128
 129         /* private fields, do not use outside kernfs proper */
 130         struct ida              ino_ida;
 131         struct kernfs_dir_ops   *dir_ops;
 132         wait_queue_head_t       deactivate_waitq;
 133 };
 134
 135 struct kernfs_open_file {
 136         /* published fields */
 137         struct kernfs_node      *kn;
 138         struct file             *file;
 139
 140         /* private fields, do not use outside kernfs proper */
 141         struct mutex            mutex;
 142         int                     event;
 143         struct list_head        list;
 144
 145         bool                    mmapped;
 146         const struct vm_operations_struct *vm_ops;
 147 };
 148
 149 struct kernfs_ops {
 150         /*
 151          * Read is handled by either seq_file or raw_read().
 152          *
 153          * If seq_show() is present, seq_file path is active.  Other seq
 154          * operations are optional and if not implemented, the behavior is
 155          * equivalent to single_open().  @sf->private points to the
 156          * associated kernfs_open_file.
 157          *
 158          * read() is bounced through kernel buffer and a read larger than
 159          * PAGE_SIZE results in partial operation of PAGE_SIZE.
 160          */
 161         int (*seq_show)(struct seq_file *sf, void *v);
 162
 163         void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
 164         void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
 165         void (*seq_stop)(struct seq_file *sf, void *v);
 166
 167         ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
 168                         loff_t off);
 169
 170         /*
 171          * write() is bounced through kernel buffer and a write larger than
 172          * PAGE_SIZE results in partial operation of PAGE_SIZE.
 173          */
 174         ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
 175                          loff_t off);
 176
 177         int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
 178
 179 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 180         struct lock_class_key   lockdep_key;
 181 #endif
 182 };
 183
 184 #ifdef CONFIG_SYSFS
 185
 186 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 187 {
 188         return kn->flags & KERNFS_TYPE_MASK;
 189 }
 190
 191 /**
 192  * kernfs_enable_ns - enable namespace under a directory
 193  * @kn: directory of interest, should be empty
 194  *
 195  * This is to be called right after @kn is created to enable namespace
 196  * under it.  All children of @kn must have non-NULL namespace tags and
 197  * only the ones which match the super_block's tag will be visible.
 198  */
 199 static inline void kernfs_enable_ns(struct kernfs_node *kn)
 200 {
 201         WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
 202         WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
 203         kn->flags |= KERNFS_NS;
 204 }
 205
 206 /**
 207  * kernfs_ns_enabled - test whether namespace is enabled
 208  * @kn: the node to test
 209  *
 210  * Test whether namespace filtering is enabled for the children of @ns.
 211  */
 212 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 213 {
 214         return kn->flags & KERNFS_NS;
 215 }
 216
 217 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
 218                                            const char *name, const void *ns);
 219 void kernfs_get(struct kernfs_node *kn);
 220 void kernfs_put(struct kernfs_node *kn);
 221
 222 struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops,
 223                                        void *priv);
 224 void kernfs_destroy_root(struct kernfs_root *root);
 225
 226 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 227                                          const char *name, umode_t mode,
 228                                          void *priv, const void *ns);
 229 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 230                                          const char *name,
 231                                          umode_t mode, loff_t size,
 232                                          const struct kernfs_ops *ops,
 233                                          void *priv, const void *ns,
 234                                          bool name_is_static,
 235                                          struct lock_class_key *key);
 236 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
 237                                        const char *name,
 238                                        struct kernfs_node *target);
 239 void kernfs_remove(struct kernfs_node *kn);
 240 void kernfs_break_active_protection(struct kernfs_node *kn);
 241 void kernfs_unbreak_active_protection(struct kernfs_node *kn);
 242 bool kernfs_remove_self(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, const void *ns);
 253 void kernfs_kill_sb(struct super_block *sb);
 254
 255 void kernfs_init(void);
 256
 257 #else   /* CONFIG_SYSFS */
 258
 259 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 260 { return 0; }   /* whatever */
 261
 262 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
 263
 264 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 265 { return false; }
 266
 267 static inline struct kernfs_node *
 268 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
 269                        const void *ns)
 270 { return NULL; }
 271
 272 static inline void kernfs_get(struct kernfs_node *kn) { }
 273 static inline void kernfs_put(struct kernfs_node *kn) { }
 274
 275 static inline struct kernfs_root *
 276 kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
 277 { return ERR_PTR(-ENOSYS); }
 278
 279 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
 280
 281 static inline struct kernfs_node *
 282 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
 283                      umode_t mode, void *priv, const void *ns)
 284 { return ERR_PTR(-ENOSYS); }
 285
 286 static inline struct kernfs_node *
 287 __kernfs_create_file(struct kernfs_node *parent, const char *name,
 288                      umode_t mode, loff_t size, const struct kernfs_ops *ops,
 289                      void *priv, const void *ns, bool name_is_static,
 290                      struct lock_class_key *key)
 291 { return ERR_PTR(-ENOSYS); }
 292
 293 static inline struct kernfs_node *
 294 kernfs_create_link(struct kernfs_node *parent, const char *name,
 295                    struct kernfs_node *target)
 296 { return ERR_PTR(-ENOSYS); }
 297
 298 static inline void kernfs_remove(struct kernfs_node *kn) { }
 299
 300 static inline bool kernfs_remove_self(struct kernfs_node *kn)
 301 { return false; }
 302
 303 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
 304                                            const char *name, const void *ns)
 305 { return -ENOSYS; }
 306
 307 static inline int kernfs_rename_ns(struct kernfs_node *kn,
 308                                    struct kernfs_node *new_parent,
 309                                    const char *new_name, const void *new_ns)
 310 { return -ENOSYS; }
 311
 312 static inline int kernfs_setattr(struct kernfs_node *kn,
 313                                  const struct iattr *iattr)
 314 { return -ENOSYS; }
 315
 316 static inline void kernfs_notify(struct kernfs_node *kn) { }
 317
 318 static inline const void *kernfs_super_ns(struct super_block *sb)
 319 { return NULL; }
 320
 321 static inline struct dentry *
 322 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 323                 struct kernfs_root *root, const void *ns)
 324 { return ERR_PTR(-ENOSYS); }
 325
 326 static inline void kernfs_kill_sb(struct super_block *sb) { }
 327
 328 static inline void kernfs_init(void) { }
 329
 330 #endif  /* CONFIG_SYSFS */
 331
 332 static inline struct kernfs_node *
 333 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
 334 {
 335         return kernfs_find_and_get_ns(kn, name, NULL);
 336 }
 337
 338 static inline struct kernfs_node *
 339 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
 340                   void *priv)
 341 {
 342         return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
 343 }
 344
 345 static inline struct kernfs_node *
 346 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
 347                       umode_t mode, loff_t size, const struct kernfs_ops *ops,
 348                       void *priv, const void *ns)
 349 {
 350         struct lock_class_key *key = NULL;
 351
 352 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 353         key = (struct lock_class_key *)&ops->lockdep_key;
 354 #endif
 355         return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
 356                                     false, key);
 357 }
 358
 359 static inline struct kernfs_node *
 360 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
 361                    loff_t size, const struct kernfs_ops *ops, void *priv)
 362 {
 363         return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
 364 }
 365
 366 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
 367                                         const char *name)
 368 {
 369         return kernfs_remove_by_name_ns(parent, name, NULL);
 370 }
 371
 372 static inline struct dentry *
 373 kernfs_mount(struct file_system_type *fs_type, int flags,
 374              struct kernfs_root *root)
 375 {
 376         return kernfs_mount_ns(fs_type, flags, root, NULL);
 377 }
 378
 379 #endif  /* __LINUX_KERNFS_H */