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Linux/include/linux/kernfs.h

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  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_ACTIVATED        = 0x0010,
 42         KERNFS_NS               = 0x0020,
 43         KERNFS_HAS_SEQ_SHOW     = 0x0040,
 44         KERNFS_HAS_MMAP         = 0x0080,
 45         KERNFS_LOCKDEP          = 0x0100,
 46         KERNFS_SUICIDAL         = 0x0400,
 47         KERNFS_SUICIDED         = 0x0800,
 48         KERNFS_EMPTY_DIR        = 0x1000,
 49         KERNFS_HAS_RELEASE      = 0x2000,
 50 };
 51 
 52 /* @flags for kernfs_create_root() */
 53 enum kernfs_root_flag {
 54         /*
 55          * kernfs_nodes are created in the deactivated state and invisible.
 56          * They require explicit kernfs_activate() to become visible.  This
 57          * can be used to make related nodes become visible atomically
 58          * after all nodes are created successfully.
 59          */
 60         KERNFS_ROOT_CREATE_DEACTIVATED          = 0x0001,
 61 
 62         /*
 63          * For regular flies, if the opener has CAP_DAC_OVERRIDE, open(2)
 64          * succeeds regardless of the RW permissions.  sysfs had an extra
 65          * layer of enforcement where open(2) fails with -EACCES regardless
 66          * of CAP_DAC_OVERRIDE if the permission doesn't have the
 67          * respective read or write access at all (none of S_IRUGO or
 68          * S_IWUGO) or the respective operation isn't implemented.  The
 69          * following flag enables that behavior.
 70          */
 71         KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK       = 0x0002,
 72 
 73         /*
 74          * The filesystem supports exportfs operation, so userspace can use
 75          * fhandle to access nodes of the fs.
 76          */
 77         KERNFS_ROOT_SUPPORT_EXPORTOP            = 0x0004,
 78 };
 79 
 80 /* type-specific structures for kernfs_node union members */
 81 struct kernfs_elem_dir {
 82         unsigned long           subdirs;
 83         /* children rbtree starts here and goes through kn->rb */
 84         struct rb_root          children;
 85 
 86         /*
 87          * The kernfs hierarchy this directory belongs to.  This fits
 88          * better directly in kernfs_node but is here to save space.
 89          */
 90         struct kernfs_root      *root;
 91 };
 92 
 93 struct kernfs_elem_symlink {
 94         struct kernfs_node      *target_kn;
 95 };
 96 
 97 struct kernfs_elem_attr {
 98         const struct kernfs_ops *ops;
 99         struct kernfs_open_node *open;
100         loff_t                  size;
101         struct kernfs_node      *notify_next;   /* for kernfs_notify() */
102 };
103 
104 /* represent a kernfs node */
105 union kernfs_node_id {
106         struct {
107                 /*
108                  * blktrace will export this struct as a simplified 'struct
109                  * fid' (which is a big data struction), so userspace can use
110                  * it to find kernfs node. The layout must match the first two
111                  * fields of 'struct fid' exactly.
112                  */
113                 u32             ino;
114                 u32             generation;
115         };
116         u64                     id;
117 };
118 
119 /*
120  * kernfs_node - the building block of kernfs hierarchy.  Each and every
121  * kernfs node is represented by single kernfs_node.  Most fields are
122  * private to kernfs and shouldn't be accessed directly by kernfs users.
123  *
124  * As long as s_count reference is held, the kernfs_node itself is
125  * accessible.  Dereferencing elem or any other outer entity requires
126  * active reference.
127  */
128 struct kernfs_node {
129         atomic_t                count;
130         atomic_t                active;
131 #ifdef CONFIG_DEBUG_LOCK_ALLOC
132         struct lockdep_map      dep_map;
133 #endif
134         /*
135          * Use kernfs_get_parent() and kernfs_name/path() instead of
136          * accessing the following two fields directly.  If the node is
137          * never moved to a different parent, it is safe to access the
138          * parent directly.
139          */
140         struct kernfs_node      *parent;
141         const char              *name;
142 
143         struct rb_node          rb;
144 
145         const void              *ns;    /* namespace tag */
146         unsigned int            hash;   /* ns + name hash */
147         union {
148                 struct kernfs_elem_dir          dir;
149                 struct kernfs_elem_symlink      symlink;
150                 struct kernfs_elem_attr         attr;
151         };
152 
153         void                    *priv;
154 
155         union kernfs_node_id    id;
156         unsigned short          flags;
157         umode_t                 mode;
158         struct kernfs_iattrs    *iattr;
159 };
160 
161 /*
162  * kernfs_syscall_ops may be specified on kernfs_create_root() to support
163  * syscalls.  These optional callbacks are invoked on the matching syscalls
164  * and can perform any kernfs operations which don't necessarily have to be
165  * the exact operation requested.  An active reference is held for each
166  * kernfs_node parameter.
167  */
168 struct kernfs_syscall_ops {
169         int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
170         int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
171 
172         int (*mkdir)(struct kernfs_node *parent, const char *name,
173                      umode_t mode);
174         int (*rmdir)(struct kernfs_node *kn);
175         int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
176                       const char *new_name);
177         int (*show_path)(struct seq_file *sf, struct kernfs_node *kn,
178                          struct kernfs_root *root);
179 };
180 
181 struct kernfs_root {
182         /* published fields */
183         struct kernfs_node      *kn;
184         unsigned int            flags;  /* KERNFS_ROOT_* flags */
185 
186         /* private fields, do not use outside kernfs proper */
187         struct idr              ino_idr;
188         u32                     next_generation;
189         struct kernfs_syscall_ops *syscall_ops;
190 
191         /* list of kernfs_super_info of this root, protected by kernfs_mutex */
192         struct list_head        supers;
193 
194         wait_queue_head_t       deactivate_waitq;
195 };
196 
197 struct kernfs_open_file {
198         /* published fields */
199         struct kernfs_node      *kn;
200         struct file             *file;
201         struct seq_file         *seq_file;
202         void                    *priv;
203 
204         /* private fields, do not use outside kernfs proper */
205         struct mutex            mutex;
206         struct mutex            prealloc_mutex;
207         int                     event;
208         struct list_head        list;
209         char                    *prealloc_buf;
210 
211         size_t                  atomic_write_len;
212         bool                    mmapped:1;
213         bool                    released:1;
214         const struct vm_operations_struct *vm_ops;
215 };
216 
217 struct kernfs_ops {
218         /*
219          * Optional open/release methods.  Both are called with
220          * @of->seq_file populated.
221          */
222         int (*open)(struct kernfs_open_file *of);
223         void (*release)(struct kernfs_open_file *of);
224 
225         /*
226          * Read is handled by either seq_file or raw_read().
227          *
228          * If seq_show() is present, seq_file path is active.  Other seq
229          * operations are optional and if not implemented, the behavior is
230          * equivalent to single_open().  @sf->private points to the
231          * associated kernfs_open_file.
232          *
233          * read() is bounced through kernel buffer and a read larger than
234          * PAGE_SIZE results in partial operation of PAGE_SIZE.
235          */
236         int (*seq_show)(struct seq_file *sf, void *v);
237 
238         void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
239         void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
240         void (*seq_stop)(struct seq_file *sf, void *v);
241 
242         ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
243                         loff_t off);
244 
245         /*
246          * write() is bounced through kernel buffer.  If atomic_write_len
247          * is not set, a write larger than PAGE_SIZE results in partial
248          * operations of PAGE_SIZE chunks.  If atomic_write_len is set,
249          * writes upto the specified size are executed atomically but
250          * larger ones are rejected with -E2BIG.
251          */
252         size_t atomic_write_len;
253         /*
254          * "prealloc" causes a buffer to be allocated at open for
255          * all read/write requests.  As ->seq_show uses seq_read()
256          * which does its own allocation, it is incompatible with
257          * ->prealloc.  Provide ->read and ->write with ->prealloc.
258          */
259         bool prealloc;
260         ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
261                          loff_t off);
262 
263         int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
264 
265 #ifdef CONFIG_DEBUG_LOCK_ALLOC
266         struct lock_class_key   lockdep_key;
267 #endif
268 };
269 
270 #ifdef CONFIG_KERNFS
271 
272 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
273 {
274         return kn->flags & KERNFS_TYPE_MASK;
275 }
276 
277 /**
278  * kernfs_enable_ns - enable namespace under a directory
279  * @kn: directory of interest, should be empty
280  *
281  * This is to be called right after @kn is created to enable namespace
282  * under it.  All children of @kn must have non-NULL namespace tags and
283  * only the ones which match the super_block's tag will be visible.
284  */
285 static inline void kernfs_enable_ns(struct kernfs_node *kn)
286 {
287         WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
288         WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
289         kn->flags |= KERNFS_NS;
290 }
291 
292 /**
293  * kernfs_ns_enabled - test whether namespace is enabled
294  * @kn: the node to test
295  *
296  * Test whether namespace filtering is enabled for the children of @ns.
297  */
298 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
299 {
300         return kn->flags & KERNFS_NS;
301 }
302 
303 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
304 int kernfs_path_from_node(struct kernfs_node *root_kn, struct kernfs_node *kn,
305                           char *buf, size_t buflen);
306 void pr_cont_kernfs_name(struct kernfs_node *kn);
307 void pr_cont_kernfs_path(struct kernfs_node *kn);
308 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
309 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
310                                            const char *name, const void *ns);
311 struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
312                                            const char *path, const void *ns);
313 void kernfs_get(struct kernfs_node *kn);
314 void kernfs_put(struct kernfs_node *kn);
315 
316 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
317 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
318 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);
319 
320 struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
321                                   struct super_block *sb);
322 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
323                                        unsigned int flags, void *priv);
324 void kernfs_destroy_root(struct kernfs_root *root);
325 
326 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
327                                          const char *name, umode_t mode,
328                                          void *priv, const void *ns);
329 struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
330                                             const char *name);
331 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
332                                          const char *name,
333                                          umode_t mode, loff_t size,
334                                          const struct kernfs_ops *ops,
335                                          void *priv, const void *ns,
336                                          struct lock_class_key *key);
337 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
338                                        const char *name,
339                                        struct kernfs_node *target);
340 void kernfs_activate(struct kernfs_node *kn);
341 void kernfs_remove(struct kernfs_node *kn);
342 void kernfs_break_active_protection(struct kernfs_node *kn);
343 void kernfs_unbreak_active_protection(struct kernfs_node *kn);
344 bool kernfs_remove_self(struct kernfs_node *kn);
345 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
346                              const void *ns);
347 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
348                      const char *new_name, const void *new_ns);
349 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
350 void kernfs_notify(struct kernfs_node *kn);
351 
352 const void *kernfs_super_ns(struct super_block *sb);
353 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
354                                struct kernfs_root *root, unsigned long magic,
355                                bool *new_sb_created, const void *ns);
356 void kernfs_kill_sb(struct super_block *sb);
357 struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns);
358 
359 void kernfs_init(void);
360 
361 struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
362         const union kernfs_node_id *id);
363 #else   /* CONFIG_KERNFS */
364 
365 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
366 { return 0; }   /* whatever */
367 
368 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
369 
370 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
371 { return false; }
372 
373 static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
374 { return -ENOSYS; }
375 
376 static inline int kernfs_path_from_node(struct kernfs_node *root_kn,
377                                         struct kernfs_node *kn,
378                                         char *buf, size_t buflen)
379 { return -ENOSYS; }
380 
381 static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
382 static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
383 
384 static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
385 { return NULL; }
386 
387 static inline struct kernfs_node *
388 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
389                        const void *ns)
390 { return NULL; }
391 static inline struct kernfs_node *
392 kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path,
393                        const void *ns)
394 { return NULL; }
395 
396 static inline void kernfs_get(struct kernfs_node *kn) { }
397 static inline void kernfs_put(struct kernfs_node *kn) { }
398 
399 static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
400 { return NULL; }
401 
402 static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
403 { return NULL; }
404 
405 static inline struct inode *
406 kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
407 { return NULL; }
408 
409 static inline struct kernfs_root *
410 kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
411                    void *priv)
412 { return ERR_PTR(-ENOSYS); }
413 
414 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
415 
416 static inline struct kernfs_node *
417 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
418                      umode_t mode, void *priv, const void *ns)
419 { return ERR_PTR(-ENOSYS); }
420 
421 static inline struct kernfs_node *
422 __kernfs_create_file(struct kernfs_node *parent, const char *name,
423                      umode_t mode, loff_t size, const struct kernfs_ops *ops,
424                      void *priv, const void *ns, struct lock_class_key *key)
425 { return ERR_PTR(-ENOSYS); }
426 
427 static inline struct kernfs_node *
428 kernfs_create_link(struct kernfs_node *parent, const char *name,
429                    struct kernfs_node *target)
430 { return ERR_PTR(-ENOSYS); }
431 
432 static inline void kernfs_activate(struct kernfs_node *kn) { }
433 
434 static inline void kernfs_remove(struct kernfs_node *kn) { }
435 
436 static inline bool kernfs_remove_self(struct kernfs_node *kn)
437 { return false; }
438 
439 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
440                                            const char *name, const void *ns)
441 { return -ENOSYS; }
442 
443 static inline int kernfs_rename_ns(struct kernfs_node *kn,
444                                    struct kernfs_node *new_parent,
445                                    const char *new_name, const void *new_ns)
446 { return -ENOSYS; }
447 
448 static inline int kernfs_setattr(struct kernfs_node *kn,
449                                  const struct iattr *iattr)
450 { return -ENOSYS; }
451 
452 static inline void kernfs_notify(struct kernfs_node *kn) { }
453 
454 static inline const void *kernfs_super_ns(struct super_block *sb)
455 { return NULL; }
456 
457 static inline struct dentry *
458 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
459                 struct kernfs_root *root, unsigned long magic,
460                 bool *new_sb_created, const void *ns)
461 { return ERR_PTR(-ENOSYS); }
462 
463 static inline void kernfs_kill_sb(struct super_block *sb) { }
464 
465 static inline void kernfs_init(void) { }
466 
467 #endif  /* CONFIG_KERNFS */
468 
469 /**
470  * kernfs_path - build full path of a given node
471  * @kn: kernfs_node of interest
472  * @buf: buffer to copy @kn's name into
473  * @buflen: size of @buf
474  *
475  * Builds and returns the full path of @kn in @buf of @buflen bytes.  The
476  * path is built from the end of @buf so the returned pointer usually
477  * doesn't match @buf.  If @buf isn't long enough, @buf is nul terminated
478  * and %NULL is returned.
479  */
480 static inline int kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
481 {
482         return kernfs_path_from_node(kn, NULL, buf, buflen);
483 }
484 
485 static inline struct kernfs_node *
486 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
487 {
488         return kernfs_find_and_get_ns(kn, name, NULL);
489 }
490 
491 static inline struct kernfs_node *
492 kernfs_walk_and_get(struct kernfs_node *kn, const char *path)
493 {
494         return kernfs_walk_and_get_ns(kn, path, NULL);
495 }
496 
497 static inline struct kernfs_node *
498 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
499                   void *priv)
500 {
501         return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
502 }
503 
504 static inline struct kernfs_node *
505 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
506                       umode_t mode, loff_t size, const struct kernfs_ops *ops,
507                       void *priv, const void *ns)
508 {
509         struct lock_class_key *key = NULL;
510 
511 #ifdef CONFIG_DEBUG_LOCK_ALLOC
512         key = (struct lock_class_key *)&ops->lockdep_key;
513 #endif
514         return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
515                                     key);
516 }
517 
518 static inline struct kernfs_node *
519 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
520                    loff_t size, const struct kernfs_ops *ops, void *priv)
521 {
522         return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
523 }
524 
525 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
526                                         const char *name)
527 {
528         return kernfs_remove_by_name_ns(parent, name, NULL);
529 }
530 
531 static inline int kernfs_rename(struct kernfs_node *kn,
532                                 struct kernfs_node *new_parent,
533                                 const char *new_name)
534 {
535         return kernfs_rename_ns(kn, new_parent, new_name, NULL);
536 }
537 
538 static inline struct dentry *
539 kernfs_mount(struct file_system_type *fs_type, int flags,
540                 struct kernfs_root *root, unsigned long magic,
541                 bool *new_sb_created)
542 {
543         return kernfs_mount_ns(fs_type, flags, root,
544                                 magic, new_sb_created, NULL);
545 }
546 
547 #endif  /* __LINUX_KERNFS_H */
548 

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