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 */
190 struct kernfs_syscall_ops
*syscall_ops
;
192 /* list of kernfs_super_info of this root, protected by kernfs_mutex */
193 struct list_head supers
;
195 wait_queue_head_t deactivate_waitq
;
198 struct kernfs_open_file
{
199 /* published fields */
200 struct kernfs_node
*kn
;
202 struct seq_file
*seq_file
;
205 /* private fields, do not use outside kernfs proper */
207 struct mutex prealloc_mutex
;
209 struct list_head list
;
212 size_t atomic_write_len
;
215 const struct vm_operations_struct
*vm_ops
;
220 * Optional open/release methods. Both are called with
221 * @of->seq_file populated.
223 int (*open
)(struct kernfs_open_file
*of
);
224 void (*release
)(struct kernfs_open_file
*of
);
227 * Read is handled by either seq_file or raw_read().
229 * If seq_show() is present, seq_file path is active. Other seq
230 * operations are optional and if not implemented, the behavior is
231 * equivalent to single_open(). @sf->private points to the
232 * associated kernfs_open_file.
234 * read() is bounced through kernel buffer and a read larger than
235 * PAGE_SIZE results in partial operation of PAGE_SIZE.
237 int (*seq_show
)(struct seq_file
*sf
, void *v
);
239 void *(*seq_start
)(struct seq_file
*sf
, loff_t
*ppos
);
240 void *(*seq_next
)(struct seq_file
*sf
, void *v
, loff_t
*ppos
);
241 void (*seq_stop
)(struct seq_file
*sf
, void *v
);
243 ssize_t (*read
)(struct kernfs_open_file
*of
, char *buf
, size_t bytes
,
247 * write() is bounced through kernel buffer. If atomic_write_len
248 * is not set, a write larger than PAGE_SIZE results in partial
249 * operations of PAGE_SIZE chunks. If atomic_write_len is set,
250 * writes upto the specified size are executed atomically but
251 * larger ones are rejected with -E2BIG.
253 size_t atomic_write_len
;
255 * "prealloc" causes a buffer to be allocated at open for
256 * all read/write requests. As ->seq_show uses seq_read()
257 * which does its own allocation, it is incompatible with
258 * ->prealloc. Provide ->read and ->write with ->prealloc.
261 ssize_t (*write
)(struct kernfs_open_file
*of
, char *buf
, size_t bytes
,
264 int (*mmap
)(struct kernfs_open_file
*of
, struct vm_area_struct
*vma
);
266 #ifdef CONFIG_DEBUG_LOCK_ALLOC
267 struct lock_class_key lockdep_key
;
273 static inline enum kernfs_node_type
kernfs_type(struct kernfs_node
*kn
)
275 return kn
->flags
& KERNFS_TYPE_MASK
;
279 * kernfs_enable_ns - enable namespace under a directory
280 * @kn: directory of interest, should be empty
282 * This is to be called right after @kn is created to enable namespace
283 * under it. All children of @kn must have non-NULL namespace tags and
284 * only the ones which match the super_block's tag will be visible.
286 static inline void kernfs_enable_ns(struct kernfs_node
*kn
)
288 WARN_ON_ONCE(kernfs_type(kn
) != KERNFS_DIR
);
289 WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn
->dir
.children
));
290 kn
->flags
|= KERNFS_NS
;
294 * kernfs_ns_enabled - test whether namespace is enabled
295 * @kn: the node to test
297 * Test whether namespace filtering is enabled for the children of @ns.
299 static inline bool kernfs_ns_enabled(struct kernfs_node
*kn
)
301 return kn
->flags
& KERNFS_NS
;
304 int kernfs_name(struct kernfs_node
*kn
, char *buf
, size_t buflen
);
305 int kernfs_path_from_node(struct kernfs_node
*root_kn
, struct kernfs_node
*kn
,
306 char *buf
, size_t buflen
);
307 void pr_cont_kernfs_name(struct kernfs_node
*kn
);
308 void pr_cont_kernfs_path(struct kernfs_node
*kn
);
309 struct kernfs_node
*kernfs_get_parent(struct kernfs_node
*kn
);
310 struct kernfs_node
*kernfs_find_and_get_ns(struct kernfs_node
*parent
,
311 const char *name
, const void *ns
);
312 struct kernfs_node
*kernfs_walk_and_get_ns(struct kernfs_node
*parent
,
313 const char *path
, const void *ns
);
314 void kernfs_get(struct kernfs_node
*kn
);
315 void kernfs_put(struct kernfs_node
*kn
);
317 struct kernfs_node
*kernfs_node_from_dentry(struct dentry
*dentry
);
318 struct kernfs_root
*kernfs_root_from_sb(struct super_block
*sb
);
319 struct inode
*kernfs_get_inode(struct super_block
*sb
, struct kernfs_node
*kn
);
321 struct dentry
*kernfs_node_dentry(struct kernfs_node
*kn
,
322 struct super_block
*sb
);
323 struct kernfs_root
*kernfs_create_root(struct kernfs_syscall_ops
*scops
,
324 unsigned int flags
, void *priv
);
325 void kernfs_destroy_root(struct kernfs_root
*root
);
327 struct kernfs_node
*kernfs_create_dir_ns(struct kernfs_node
*parent
,
328 const char *name
, umode_t mode
,
329 kuid_t uid
, kgid_t gid
,
330 void *priv
, const void *ns
);
331 struct kernfs_node
*kernfs_create_empty_dir(struct kernfs_node
*parent
,
333 struct kernfs_node
*__kernfs_create_file(struct kernfs_node
*parent
,
334 const char *name
, umode_t mode
,
335 kuid_t uid
, kgid_t gid
,
337 const struct kernfs_ops
*ops
,
338 void *priv
, const void *ns
,
339 struct lock_class_key
*key
);
340 struct kernfs_node
*kernfs_create_link(struct kernfs_node
*parent
,
342 struct kernfs_node
*target
);
343 void kernfs_activate(struct kernfs_node
*kn
);
344 void kernfs_remove(struct kernfs_node
*kn
);
345 void kernfs_break_active_protection(struct kernfs_node
*kn
);
346 void kernfs_unbreak_active_protection(struct kernfs_node
*kn
);
347 bool kernfs_remove_self(struct kernfs_node
*kn
);
348 int kernfs_remove_by_name_ns(struct kernfs_node
*parent
, const char *name
,
350 int kernfs_rename_ns(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
351 const char *new_name
, const void *new_ns
);
352 int kernfs_setattr(struct kernfs_node
*kn
, const struct iattr
*iattr
);
353 void kernfs_notify(struct kernfs_node
*kn
);
355 const void *kernfs_super_ns(struct super_block
*sb
);
356 struct dentry
*kernfs_mount_ns(struct file_system_type
*fs_type
, int flags
,
357 struct kernfs_root
*root
, unsigned long magic
,
358 bool *new_sb_created
, const void *ns
);
359 void kernfs_kill_sb(struct super_block
*sb
);
360 struct super_block
*kernfs_pin_sb(struct kernfs_root
*root
, const void *ns
);
362 void kernfs_init(void);
364 struct kernfs_node
*kernfs_get_node_by_id(struct kernfs_root
*root
,
365 const union kernfs_node_id
*id
);
366 #else /* CONFIG_KERNFS */
368 static inline enum kernfs_node_type
kernfs_type(struct kernfs_node
*kn
)
369 { return 0; } /* whatever */
371 static inline void kernfs_enable_ns(struct kernfs_node
*kn
) { }
373 static inline bool kernfs_ns_enabled(struct kernfs_node
*kn
)
376 static inline int kernfs_name(struct kernfs_node
*kn
, char *buf
, size_t buflen
)
379 static inline int kernfs_path_from_node(struct kernfs_node
*root_kn
,
380 struct kernfs_node
*kn
,
381 char *buf
, size_t buflen
)
384 static inline void pr_cont_kernfs_name(struct kernfs_node
*kn
) { }
385 static inline void pr_cont_kernfs_path(struct kernfs_node
*kn
) { }
387 static inline struct kernfs_node
*kernfs_get_parent(struct kernfs_node
*kn
)
390 static inline struct kernfs_node
*
391 kernfs_find_and_get_ns(struct kernfs_node
*parent
, const char *name
,
394 static inline struct kernfs_node
*
395 kernfs_walk_and_get_ns(struct kernfs_node
*parent
, const char *path
,
399 static inline void kernfs_get(struct kernfs_node
*kn
) { }
400 static inline void kernfs_put(struct kernfs_node
*kn
) { }
402 static inline struct kernfs_node
*kernfs_node_from_dentry(struct dentry
*dentry
)
405 static inline struct kernfs_root
*kernfs_root_from_sb(struct super_block
*sb
)
408 static inline struct inode
*
409 kernfs_get_inode(struct super_block
*sb
, struct kernfs_node
*kn
)
412 static inline struct kernfs_root
*
413 kernfs_create_root(struct kernfs_syscall_ops
*scops
, unsigned int flags
,
415 { return ERR_PTR(-ENOSYS
); }
417 static inline void kernfs_destroy_root(struct kernfs_root
*root
) { }
419 static inline struct kernfs_node
*
420 kernfs_create_dir_ns(struct kernfs_node
*parent
, const char *name
,
421 umode_t mode
, kuid_t uid
, kgid_t gid
,
422 void *priv
, const void *ns
)
423 { return ERR_PTR(-ENOSYS
); }
425 static inline struct kernfs_node
*
426 __kernfs_create_file(struct kernfs_node
*parent
, const char *name
,
427 umode_t mode
, kuid_t uid
, kgid_t gid
,
428 loff_t size
, const struct kernfs_ops
*ops
,
429 void *priv
, const void *ns
, struct lock_class_key
*key
)
430 { return ERR_PTR(-ENOSYS
); }
432 static inline struct kernfs_node
*
433 kernfs_create_link(struct kernfs_node
*parent
, const char *name
,
434 struct kernfs_node
*target
)
435 { return ERR_PTR(-ENOSYS
); }
437 static inline void kernfs_activate(struct kernfs_node
*kn
) { }
439 static inline void kernfs_remove(struct kernfs_node
*kn
) { }
441 static inline bool kernfs_remove_self(struct kernfs_node
*kn
)
444 static inline int kernfs_remove_by_name_ns(struct kernfs_node
*kn
,
445 const char *name
, const void *ns
)
448 static inline int kernfs_rename_ns(struct kernfs_node
*kn
,
449 struct kernfs_node
*new_parent
,
450 const char *new_name
, const void *new_ns
)
453 static inline int kernfs_setattr(struct kernfs_node
*kn
,
454 const struct iattr
*iattr
)
457 static inline void kernfs_notify(struct kernfs_node
*kn
) { }
459 static inline const void *kernfs_super_ns(struct super_block
*sb
)
462 static inline struct dentry
*
463 kernfs_mount_ns(struct file_system_type
*fs_type
, int flags
,
464 struct kernfs_root
*root
, unsigned long magic
,
465 bool *new_sb_created
, const void *ns
)
466 { return ERR_PTR(-ENOSYS
); }
468 static inline void kernfs_kill_sb(struct super_block
*sb
) { }
470 static inline void kernfs_init(void) { }
472 #endif /* CONFIG_KERNFS */
475 * kernfs_path - build full path of a given node
476 * @kn: kernfs_node of interest
477 * @buf: buffer to copy @kn's name into
478 * @buflen: size of @buf
480 * Builds and returns the full path of @kn in @buf of @buflen bytes. The
481 * path is built from the end of @buf so the returned pointer usually
482 * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
483 * and %NULL is returned.
485 static inline int kernfs_path(struct kernfs_node
*kn
, char *buf
, size_t buflen
)
487 return kernfs_path_from_node(kn
, NULL
, buf
, buflen
);
490 static inline struct kernfs_node
*
491 kernfs_find_and_get(struct kernfs_node
*kn
, const char *name
)
493 return kernfs_find_and_get_ns(kn
, name
, NULL
);
496 static inline struct kernfs_node
*
497 kernfs_walk_and_get(struct kernfs_node
*kn
, const char *path
)
499 return kernfs_walk_and_get_ns(kn
, path
, NULL
);
502 static inline struct kernfs_node
*
503 kernfs_create_dir(struct kernfs_node
*parent
, const char *name
, umode_t mode
,
506 return kernfs_create_dir_ns(parent
, name
, mode
,
507 GLOBAL_ROOT_UID
, GLOBAL_ROOT_GID
,
511 static inline struct kernfs_node
*
512 kernfs_create_file_ns(struct kernfs_node
*parent
, const char *name
,
513 umode_t mode
, kuid_t uid
, kgid_t gid
,
514 loff_t size
, const struct kernfs_ops
*ops
,
515 void *priv
, const void *ns
)
517 struct lock_class_key
*key
= NULL
;
519 #ifdef CONFIG_DEBUG_LOCK_ALLOC
520 key
= (struct lock_class_key
*)&ops
->lockdep_key
;
522 return __kernfs_create_file(parent
, name
, mode
, uid
, gid
,
523 size
, ops
, priv
, ns
, key
);
526 static inline struct kernfs_node
*
527 kernfs_create_file(struct kernfs_node
*parent
, const char *name
, umode_t mode
,
528 loff_t size
, const struct kernfs_ops
*ops
, void *priv
)
530 return kernfs_create_file_ns(parent
, name
, mode
,
531 GLOBAL_ROOT_UID
, GLOBAL_ROOT_GID
,
532 size
, ops
, priv
, NULL
);
535 static inline int kernfs_remove_by_name(struct kernfs_node
*parent
,
538 return kernfs_remove_by_name_ns(parent
, name
, NULL
);
541 static inline int kernfs_rename(struct kernfs_node
*kn
,
542 struct kernfs_node
*new_parent
,
543 const char *new_name
)
545 return kernfs_rename_ns(kn
, new_parent
, new_name
, NULL
);
548 static inline struct dentry
*
549 kernfs_mount(struct file_system_type
*fs_type
, int flags
,
550 struct kernfs_root
*root
, unsigned long magic
,
551 bool *new_sb_created
)
553 return kernfs_mount_ns(fs_type
, flags
, root
,
554 magic
, new_sb_created
, NULL
);
557 #endif /* __LINUX_KERNFS_H */