2 * kernfs.h - pseudo filesystem decoupled from vfs locking
4 * This file is released under the GPLv2.
7 #ifndef __LINUX_KERNFS_H
8 #define __LINUX_KERNFS_H
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>
24 struct vm_area_struct;
26 struct file_system_type;
28 struct kernfs_open_node;
31 enum kernfs_node_type {
37 #define KERNFS_TYPE_MASK 0x000f
38 #define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
40 enum kernfs_node_flag {
41 KERNFS_ACTIVATED = 0x0010,
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,
51 /* @flags for kernfs_create_root() */
52 enum kernfs_root_flag {
54 * kernfs_nodes are created in the deactivated state and invisible.
55 * They require explicit kernfs_activate() to become visible. This
56 * can be used to make related nodes become visible atomically
57 * after all nodes are created successfully.
59 KERNFS_ROOT_CREATE_DEACTIVATED = 0x0001,
62 * For regular flies, if the opener has CAP_DAC_OVERRIDE, open(2)
63 * succeeds regardless of the RW permissions. sysfs had an extra
64 * layer of enforcement where open(2) fails with -EACCES regardless
65 * of CAP_DAC_OVERRIDE if the permission doesn't have the
66 * respective read or write access at all (none of S_IRUGO or
67 * S_IWUGO) or the respective operation isn't implemented. The
68 * following flag enables that behavior.
70 KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK = 0x0002,
73 /* type-specific structures for kernfs_node union members */
74 struct kernfs_elem_dir {
75 unsigned long subdirs;
76 /* children rbtree starts here and goes through kn->rb */
77 struct rb_root children;
80 * The kernfs hierarchy this directory belongs to. This fits
81 * better directly in kernfs_node but is here to save space.
83 struct kernfs_root *root;
86 struct kernfs_elem_symlink {
87 struct kernfs_node *target_kn;
90 struct kernfs_elem_attr {
91 const struct kernfs_ops *ops;
92 struct kernfs_open_node *open;
97 * kernfs_node - the building block of kernfs hierarchy. Each and every
98 * kernfs node is represented by single kernfs_node. Most fields are
99 * private to kernfs and shouldn't be accessed directly by kernfs users.
101 * As long as s_count reference is held, the kernfs_node itself is
102 * accessible. Dereferencing elem or any other outer entity requires
108 #ifdef CONFIG_DEBUG_LOCK_ALLOC
109 struct lockdep_map dep_map;
112 * Use kernfs_get_parent() and kernfs_name/path() instead of
113 * accessing the following two fields directly. If the node is
114 * never moved to a different parent, it is safe to access the
117 struct kernfs_node *parent;
122 const void *ns; /* namespace tag */
123 unsigned int hash; /* ns + name hash */
125 struct kernfs_elem_dir dir;
126 struct kernfs_elem_symlink symlink;
127 struct kernfs_elem_attr attr;
132 unsigned short flags;
135 struct kernfs_iattrs *iattr;
139 * kernfs_syscall_ops may be specified on kernfs_create_root() to support
140 * syscalls. These optional callbacks are invoked on the matching syscalls
141 * and can perform any kernfs operations which don't necessarily have to be
142 * the exact operation requested. An active reference is held for each
143 * kernfs_node parameter.
145 struct kernfs_syscall_ops {
146 int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
147 int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
149 int (*mkdir)(struct kernfs_node *parent, const char *name,
151 int (*rmdir)(struct kernfs_node *kn);
152 int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
153 const char *new_name);
157 /* published fields */
158 struct kernfs_node *kn;
159 unsigned int flags; /* KERNFS_ROOT_* flags */
161 /* private fields, do not use outside kernfs proper */
163 struct kernfs_syscall_ops *syscall_ops;
164 wait_queue_head_t deactivate_waitq;
167 struct kernfs_open_file {
168 /* published fields */
169 struct kernfs_node *kn;
173 /* private fields, do not use outside kernfs proper */
176 struct list_head list;
178 size_t atomic_write_len;
180 const struct vm_operations_struct *vm_ops;
185 * Read is handled by either seq_file or raw_read().
187 * If seq_show() is present, seq_file path is active. Other seq
188 * operations are optional and if not implemented, the behavior is
189 * equivalent to single_open(). @sf->private points to the
190 * associated kernfs_open_file.
192 * read() is bounced through kernel buffer and a read larger than
193 * PAGE_SIZE results in partial operation of PAGE_SIZE.
195 int (*seq_show)(struct seq_file *sf, void *v);
197 void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
198 void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
199 void (*seq_stop)(struct seq_file *sf, void *v);
201 ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
205 * write() is bounced through kernel buffer. If atomic_write_len
206 * is not set, a write larger than PAGE_SIZE results in partial
207 * operations of PAGE_SIZE chunks. If atomic_write_len is set,
208 * writes upto the specified size are executed atomically but
209 * larger ones are rejected with -E2BIG.
211 size_t atomic_write_len;
212 ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
215 int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
217 #ifdef CONFIG_DEBUG_LOCK_ALLOC
218 struct lock_class_key lockdep_key;
224 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
226 return kn->flags & KERNFS_TYPE_MASK;
230 * kernfs_enable_ns - enable namespace under a directory
231 * @kn: directory of interest, should be empty
233 * This is to be called right after @kn is created to enable namespace
234 * under it. All children of @kn must have non-NULL namespace tags and
235 * only the ones which match the super_block's tag will be visible.
237 static inline void kernfs_enable_ns(struct kernfs_node *kn)
239 WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
240 WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
241 kn->flags |= KERNFS_NS;
245 * kernfs_ns_enabled - test whether namespace is enabled
246 * @kn: the node to test
248 * Test whether namespace filtering is enabled for the children of @ns.
250 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
252 return kn->flags & KERNFS_NS;
255 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
256 char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
258 void pr_cont_kernfs_name(struct kernfs_node *kn);
259 void pr_cont_kernfs_path(struct kernfs_node *kn);
260 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
261 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
262 const char *name, const void *ns);
263 void kernfs_get(struct kernfs_node *kn);
264 void kernfs_put(struct kernfs_node *kn);
266 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
267 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
269 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
270 unsigned int flags, void *priv);
271 void kernfs_destroy_root(struct kernfs_root *root);
273 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
274 const char *name, umode_t mode,
275 void *priv, const void *ns);
276 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
278 umode_t mode, loff_t size,
279 const struct kernfs_ops *ops,
280 void *priv, const void *ns,
282 struct lock_class_key *key);
283 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
285 struct kernfs_node *target);
286 void kernfs_activate(struct kernfs_node *kn);
287 void kernfs_remove(struct kernfs_node *kn);
288 void kernfs_break_active_protection(struct kernfs_node *kn);
289 void kernfs_unbreak_active_protection(struct kernfs_node *kn);
290 bool kernfs_remove_self(struct kernfs_node *kn);
291 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
293 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
294 const char *new_name, const void *new_ns);
295 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
296 void kernfs_notify(struct kernfs_node *kn);
298 const void *kernfs_super_ns(struct super_block *sb);
299 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
300 struct kernfs_root *root, bool *new_sb_created,
302 void kernfs_kill_sb(struct super_block *sb);
304 void kernfs_init(void);
306 #else /* CONFIG_KERNFS */
308 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
309 { return 0; } /* whatever */
311 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
313 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
316 static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
319 static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
323 static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
324 static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
326 static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
329 static inline struct kernfs_node *
330 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
334 static inline void kernfs_get(struct kernfs_node *kn) { }
335 static inline void kernfs_put(struct kernfs_node *kn) { }
337 static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
340 static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
343 static inline struct kernfs_root *
344 kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
346 { return ERR_PTR(-ENOSYS); }
348 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
350 static inline struct kernfs_node *
351 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
352 umode_t mode, void *priv, const void *ns)
353 { return ERR_PTR(-ENOSYS); }
355 static inline struct kernfs_node *
356 __kernfs_create_file(struct kernfs_node *parent, const char *name,
357 umode_t mode, loff_t size, const struct kernfs_ops *ops,
358 void *priv, const void *ns, bool name_is_static,
359 struct lock_class_key *key)
360 { return ERR_PTR(-ENOSYS); }
362 static inline struct kernfs_node *
363 kernfs_create_link(struct kernfs_node *parent, const char *name,
364 struct kernfs_node *target)
365 { return ERR_PTR(-ENOSYS); }
367 static inline void kernfs_activate(struct kernfs_node *kn) { }
369 static inline void kernfs_remove(struct kernfs_node *kn) { }
371 static inline bool kernfs_remove_self(struct kernfs_node *kn)
374 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
375 const char *name, const void *ns)
378 static inline int kernfs_rename_ns(struct kernfs_node *kn,
379 struct kernfs_node *new_parent,
380 const char *new_name, const void *new_ns)
383 static inline int kernfs_setattr(struct kernfs_node *kn,
384 const struct iattr *iattr)
387 static inline void kernfs_notify(struct kernfs_node *kn) { }
389 static inline const void *kernfs_super_ns(struct super_block *sb)
392 static inline struct dentry *
393 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
394 struct kernfs_root *root, bool *new_sb_created, const void *ns)
395 { return ERR_PTR(-ENOSYS); }
397 static inline void kernfs_kill_sb(struct super_block *sb) { }
399 static inline void kernfs_init(void) { }
401 #endif /* CONFIG_KERNFS */
403 static inline struct kernfs_node *
404 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
406 return kernfs_find_and_get_ns(kn, name, NULL);
409 static inline struct kernfs_node *
410 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
413 return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
416 static inline struct kernfs_node *
417 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
418 umode_t mode, loff_t size, const struct kernfs_ops *ops,
419 void *priv, const void *ns)
421 struct lock_class_key *key = NULL;
423 #ifdef CONFIG_DEBUG_LOCK_ALLOC
424 key = (struct lock_class_key *)&ops->lockdep_key;
426 return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
430 static inline struct kernfs_node *
431 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
432 loff_t size, const struct kernfs_ops *ops, void *priv)
434 return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
437 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
440 return kernfs_remove_by_name_ns(parent, name, NULL);
443 static inline int kernfs_rename(struct kernfs_node *kn,
444 struct kernfs_node *new_parent,
445 const char *new_name)
447 return kernfs_rename_ns(kn, new_parent, new_name, NULL);
450 static inline struct dentry *
451 kernfs_mount(struct file_system_type *fs_type, int flags,
452 struct kernfs_root *root, bool *new_sb_created)
454 return kernfs_mount_ns(fs_type, flags, root, new_sb_created, NULL);
457 #endif /* __LINUX_KERNFS_H */