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/uidgid.h>
19 #include <linux/wait.h>
25 struct vm_area_struct;
27 struct file_system_type;
29 struct kernfs_open_node;
32 enum kernfs_node_type {
38 #define KERNFS_TYPE_MASK 0x000f
39 #define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
41 enum kernfs_node_flag {
42 KERNFS_ACTIVATED = 0x0010,
44 KERNFS_HAS_SEQ_SHOW = 0x0040,
45 KERNFS_HAS_MMAP = 0x0080,
46 KERNFS_LOCKDEP = 0x0100,
47 KERNFS_SUICIDAL = 0x0400,
48 KERNFS_SUICIDED = 0x0800,
49 KERNFS_EMPTY_DIR = 0x1000,
50 KERNFS_HAS_RELEASE = 0x2000,
53 /* @flags for kernfs_create_root() */
54 enum kernfs_root_flag {
56 * kernfs_nodes are created in the deactivated state and invisible.
57 * They require explicit kernfs_activate() to become visible. This
58 * can be used to make related nodes become visible atomically
59 * after all nodes are created successfully.
61 KERNFS_ROOT_CREATE_DEACTIVATED = 0x0001,
64 * For regular flies, if the opener has CAP_DAC_OVERRIDE, open(2)
65 * succeeds regardless of the RW permissions. sysfs had an extra
66 * layer of enforcement where open(2) fails with -EACCES regardless
67 * of CAP_DAC_OVERRIDE if the permission doesn't have the
68 * respective read or write access at all (none of S_IRUGO or
69 * S_IWUGO) or the respective operation isn't implemented. The
70 * following flag enables that behavior.
72 KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK = 0x0002,
75 * The filesystem supports exportfs operation, so userspace can use
76 * fhandle to access nodes of the fs.
78 KERNFS_ROOT_SUPPORT_EXPORTOP = 0x0004,
81 /* type-specific structures for kernfs_node union members */
82 struct kernfs_elem_dir {
83 unsigned long subdirs;
84 /* children rbtree starts here and goes through kn->rb */
85 struct rb_root children;
88 * The kernfs hierarchy this directory belongs to. This fits
89 * better directly in kernfs_node but is here to save space.
91 struct kernfs_root *root;
94 struct kernfs_elem_symlink {
95 struct kernfs_node *target_kn;
98 struct kernfs_elem_attr {
99 const struct kernfs_ops *ops;
100 struct kernfs_open_node *open;
102 struct kernfs_node *notify_next; /* for kernfs_notify() */
105 /* represent a kernfs node */
106 union kernfs_node_id {
109 * blktrace will export this struct as a simplified 'struct
110 * fid' (which is a big data struction), so userspace can use
111 * it to find kernfs node. The layout must match the first two
112 * fields of 'struct fid' exactly.
121 * kernfs_node - the building block of kernfs hierarchy. Each and every
122 * kernfs node is represented by single kernfs_node. Most fields are
123 * private to kernfs and shouldn't be accessed directly by kernfs users.
125 * As long as s_count reference is held, the kernfs_node itself is
126 * accessible. Dereferencing elem or any other outer entity requires
132 #ifdef CONFIG_DEBUG_LOCK_ALLOC
133 struct lockdep_map dep_map;
136 * Use kernfs_get_parent() and kernfs_name/path() instead of
137 * accessing the following two fields directly. If the node is
138 * never moved to a different parent, it is safe to access the
141 struct kernfs_node *parent;
146 const void *ns; /* namespace tag */
147 unsigned int hash; /* ns + name hash */
149 struct kernfs_elem_dir dir;
150 struct kernfs_elem_symlink symlink;
151 struct kernfs_elem_attr attr;
156 union kernfs_node_id id;
157 unsigned short flags;
159 struct kernfs_iattrs *iattr;
163 * kernfs_syscall_ops may be specified on kernfs_create_root() to support
164 * syscalls. These optional callbacks are invoked on the matching syscalls
165 * and can perform any kernfs operations which don't necessarily have to be
166 * the exact operation requested. An active reference is held for each
167 * kernfs_node parameter.
169 struct kernfs_syscall_ops {
170 int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
171 int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
173 int (*mkdir)(struct kernfs_node *parent, const char *name,
175 int (*rmdir)(struct kernfs_node *kn);
176 int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
177 const char *new_name);
178 int (*show_path)(struct seq_file *sf, struct kernfs_node *kn,
179 struct kernfs_root *root);
183 /* published fields */
184 struct kernfs_node *kn;
185 unsigned int flags; /* KERNFS_ROOT_* flags */
187 /* private fields, do not use outside kernfs proper */
191 struct kernfs_syscall_ops *syscall_ops;
193 /* list of kernfs_super_info of this root, protected by kernfs_mutex */
194 struct list_head supers;
196 wait_queue_head_t deactivate_waitq;
199 struct kernfs_open_file {
200 /* published fields */
201 struct kernfs_node *kn;
203 struct seq_file *seq_file;
206 /* private fields, do not use outside kernfs proper */
208 struct mutex prealloc_mutex;
210 struct list_head list;
213 size_t atomic_write_len;
216 const struct vm_operations_struct *vm_ops;
221 * Optional open/release methods. Both are called with
222 * @of->seq_file populated.
224 int (*open)(struct kernfs_open_file *of);
225 void (*release)(struct kernfs_open_file *of);
228 * Read is handled by either seq_file or raw_read().
230 * If seq_show() is present, seq_file path is active. Other seq
231 * operations are optional and if not implemented, the behavior is
232 * equivalent to single_open(). @sf->private points to the
233 * associated kernfs_open_file.
235 * read() is bounced through kernel buffer and a read larger than
236 * PAGE_SIZE results in partial operation of PAGE_SIZE.
238 int (*seq_show)(struct seq_file *sf, void *v);
240 void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
241 void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
242 void (*seq_stop)(struct seq_file *sf, void *v);
244 ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
248 * write() is bounced through kernel buffer. If atomic_write_len
249 * is not set, a write larger than PAGE_SIZE results in partial
250 * operations of PAGE_SIZE chunks. If atomic_write_len is set,
251 * writes upto the specified size are executed atomically but
252 * larger ones are rejected with -E2BIG.
254 size_t atomic_write_len;
256 * "prealloc" causes a buffer to be allocated at open for
257 * all read/write requests. As ->seq_show uses seq_read()
258 * which does its own allocation, it is incompatible with
259 * ->prealloc. Provide ->read and ->write with ->prealloc.
262 ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
265 int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
267 #ifdef CONFIG_DEBUG_LOCK_ALLOC
268 struct lock_class_key lockdep_key;
274 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
276 return kn->flags & KERNFS_TYPE_MASK;
280 * kernfs_enable_ns - enable namespace under a directory
281 * @kn: directory of interest, should be empty
283 * This is to be called right after @kn is created to enable namespace
284 * under it. All children of @kn must have non-NULL namespace tags and
285 * only the ones which match the super_block's tag will be visible.
287 static inline void kernfs_enable_ns(struct kernfs_node *kn)
289 WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
290 WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
291 kn->flags |= KERNFS_NS;
295 * kernfs_ns_enabled - test whether namespace is enabled
296 * @kn: the node to test
298 * Test whether namespace filtering is enabled for the children of @ns.
300 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
302 return kn->flags & KERNFS_NS;
305 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
306 int kernfs_path_from_node(struct kernfs_node *root_kn, struct kernfs_node *kn,
307 char *buf, size_t buflen);
308 void pr_cont_kernfs_name(struct kernfs_node *kn);
309 void pr_cont_kernfs_path(struct kernfs_node *kn);
310 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
311 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
312 const char *name, const void *ns);
313 struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
314 const char *path, const void *ns);
315 void kernfs_get(struct kernfs_node *kn);
316 void kernfs_put(struct kernfs_node *kn);
318 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
319 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
320 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);
322 struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
323 struct super_block *sb);
324 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
325 unsigned int flags, void *priv);
326 void kernfs_destroy_root(struct kernfs_root *root);
328 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
329 const char *name, umode_t mode,
330 kuid_t uid, kgid_t gid,
331 void *priv, const void *ns);
332 struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
334 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
335 const char *name, umode_t mode,
336 kuid_t uid, kgid_t gid,
338 const struct kernfs_ops *ops,
339 void *priv, const void *ns,
340 struct lock_class_key *key);
341 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
343 struct kernfs_node *target);
344 void kernfs_activate(struct kernfs_node *kn);
345 void kernfs_remove(struct kernfs_node *kn);
346 void kernfs_break_active_protection(struct kernfs_node *kn);
347 void kernfs_unbreak_active_protection(struct kernfs_node *kn);
348 bool kernfs_remove_self(struct kernfs_node *kn);
349 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
351 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
352 const char *new_name, const void *new_ns);
353 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
354 void kernfs_notify(struct kernfs_node *kn);
356 const void *kernfs_super_ns(struct super_block *sb);
357 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
358 struct kernfs_root *root, unsigned long magic,
359 bool *new_sb_created, const void *ns);
360 void kernfs_kill_sb(struct super_block *sb);
361 struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns);
363 void kernfs_init(void);
365 struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
366 const union kernfs_node_id *id);
367 #else /* CONFIG_KERNFS */
369 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
370 { return 0; } /* whatever */
372 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
374 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
377 static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
380 static inline int kernfs_path_from_node(struct kernfs_node *root_kn,
381 struct kernfs_node *kn,
382 char *buf, size_t buflen)
385 static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
386 static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
388 static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
391 static inline struct kernfs_node *
392 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
395 static inline struct kernfs_node *
396 kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path,
400 static inline void kernfs_get(struct kernfs_node *kn) { }
401 static inline void kernfs_put(struct kernfs_node *kn) { }
403 static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
406 static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
409 static inline struct inode *
410 kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
413 static inline struct kernfs_root *
414 kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
416 { return ERR_PTR(-ENOSYS); }
418 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
420 static inline struct kernfs_node *
421 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
422 umode_t mode, kuid_t uid, kgid_t gid,
423 void *priv, const void *ns)
424 { return ERR_PTR(-ENOSYS); }
426 static inline struct kernfs_node *
427 __kernfs_create_file(struct kernfs_node *parent, const char *name,
428 umode_t mode, kuid_t uid, kgid_t gid,
429 loff_t size, const struct kernfs_ops *ops,
430 void *priv, const void *ns, struct lock_class_key *key)
431 { return ERR_PTR(-ENOSYS); }
433 static inline struct kernfs_node *
434 kernfs_create_link(struct kernfs_node *parent, const char *name,
435 struct kernfs_node *target)
436 { return ERR_PTR(-ENOSYS); }
438 static inline void kernfs_activate(struct kernfs_node *kn) { }
440 static inline void kernfs_remove(struct kernfs_node *kn) { }
442 static inline bool kernfs_remove_self(struct kernfs_node *kn)
445 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
446 const char *name, const void *ns)
449 static inline int kernfs_rename_ns(struct kernfs_node *kn,
450 struct kernfs_node *new_parent,
451 const char *new_name, const void *new_ns)
454 static inline int kernfs_setattr(struct kernfs_node *kn,
455 const struct iattr *iattr)
458 static inline void kernfs_notify(struct kernfs_node *kn) { }
460 static inline const void *kernfs_super_ns(struct super_block *sb)
463 static inline struct dentry *
464 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
465 struct kernfs_root *root, unsigned long magic,
466 bool *new_sb_created, const void *ns)
467 { return ERR_PTR(-ENOSYS); }
469 static inline void kernfs_kill_sb(struct super_block *sb) { }
471 static inline void kernfs_init(void) { }
473 #endif /* CONFIG_KERNFS */
476 * kernfs_path - build full path of a given node
477 * @kn: kernfs_node of interest
478 * @buf: buffer to copy @kn's name into
479 * @buflen: size of @buf
481 * Builds and returns the full path of @kn in @buf of @buflen bytes. The
482 * path is built from the end of @buf so the returned pointer usually
483 * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
484 * and %NULL is returned.
486 static inline int kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
488 return kernfs_path_from_node(kn, NULL, buf, buflen);
491 static inline struct kernfs_node *
492 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
494 return kernfs_find_and_get_ns(kn, name, NULL);
497 static inline struct kernfs_node *
498 kernfs_walk_and_get(struct kernfs_node *kn, const char *path)
500 return kernfs_walk_and_get_ns(kn, path, NULL);
503 static inline struct kernfs_node *
504 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
507 return kernfs_create_dir_ns(parent, name, mode,
508 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
512 static inline struct kernfs_node *
513 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
514 umode_t mode, kuid_t uid, kgid_t gid,
515 loff_t size, const struct kernfs_ops *ops,
516 void *priv, const void *ns)
518 struct lock_class_key *key = NULL;
520 #ifdef CONFIG_DEBUG_LOCK_ALLOC
521 key = (struct lock_class_key *)&ops->lockdep_key;
523 return __kernfs_create_file(parent, name, mode, uid, gid,
524 size, ops, priv, ns, key);
527 static inline struct kernfs_node *
528 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
529 loff_t size, const struct kernfs_ops *ops, void *priv)
531 return kernfs_create_file_ns(parent, name, mode,
532 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
533 size, ops, priv, NULL);
536 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
539 return kernfs_remove_by_name_ns(parent, name, NULL);
542 static inline int kernfs_rename(struct kernfs_node *kn,
543 struct kernfs_node *new_parent,
544 const char *new_name)
546 return kernfs_rename_ns(kn, new_parent, new_name, NULL);
549 static inline struct dentry *
550 kernfs_mount(struct file_system_type *fs_type, int flags,
551 struct kernfs_root *root, unsigned long magic,
552 bool *new_sb_created)
554 return kernfs_mount_ns(fs_type, flags, root,
555 magic, new_sb_created, NULL);
558 #endif /* __LINUX_KERNFS_H */