2 * fs/kernfs/dir.c - kernfs directory implementation
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
8 * This file is released under the GPLv2.
11 #include <linux/sched.h>
13 #include <linux/namei.h>
14 #include <linux/idr.h>
15 #include <linux/slab.h>
16 #include <linux/security.h>
17 #include <linux/hash.h>
19 #include "kernfs-internal.h"
21 DEFINE_MUTEX(kernfs_mutex
);
22 static DEFINE_SPINLOCK(kernfs_rename_lock
); /* kn->parent and ->name */
23 static char kernfs_pr_cont_buf
[PATH_MAX
]; /* protected by rename_lock */
25 #define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
27 static bool kernfs_active(struct kernfs_node
*kn
)
29 lockdep_assert_held(&kernfs_mutex
);
30 return atomic_read(&kn
->active
) >= 0;
33 static bool kernfs_lockdep(struct kernfs_node
*kn
)
35 #ifdef CONFIG_DEBUG_LOCK_ALLOC
36 return kn
->flags
& KERNFS_LOCKDEP
;
42 static int kernfs_name_locked(struct kernfs_node
*kn
, char *buf
, size_t buflen
)
44 return strlcpy(buf
, kn
->parent
? kn
->name
: "/", buflen
);
47 static char * __must_check
kernfs_path_locked(struct kernfs_node
*kn
, char *buf
,
50 char *p
= buf
+ buflen
;
56 len
= strlen(kn
->name
);
57 if (p
- buf
< len
+ 1) {
63 memcpy(p
, kn
->name
, len
);
66 } while (kn
&& kn
->parent
);
72 * kernfs_name - obtain the name of a given node
73 * @kn: kernfs_node of interest
74 * @buf: buffer to copy @kn's name into
75 * @buflen: size of @buf
77 * Copies the name of @kn into @buf of @buflen bytes. The behavior is
78 * similar to strlcpy(). It returns the length of @kn's name and if @buf
79 * isn't long enough, it's filled upto @buflen-1 and nul terminated.
81 * This function can be called from any context.
83 int kernfs_name(struct kernfs_node
*kn
, char *buf
, size_t buflen
)
88 spin_lock_irqsave(&kernfs_rename_lock
, flags
);
89 ret
= kernfs_name_locked(kn
, buf
, buflen
);
90 spin_unlock_irqrestore(&kernfs_rename_lock
, flags
);
95 * kernfs_path - build full path of a given node
96 * @kn: kernfs_node of interest
97 * @buf: buffer to copy @kn's name into
98 * @buflen: size of @buf
100 * Builds and returns the full path of @kn in @buf of @buflen bytes. The
101 * path is built from the end of @buf so the returned pointer usually
102 * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
103 * and %NULL is returned.
105 char *kernfs_path(struct kernfs_node
*kn
, char *buf
, size_t buflen
)
110 spin_lock_irqsave(&kernfs_rename_lock
, flags
);
111 p
= kernfs_path_locked(kn
, buf
, buflen
);
112 spin_unlock_irqrestore(&kernfs_rename_lock
, flags
);
115 EXPORT_SYMBOL_GPL(kernfs_path
);
118 * pr_cont_kernfs_name - pr_cont name of a kernfs_node
119 * @kn: kernfs_node of interest
121 * This function can be called from any context.
123 void pr_cont_kernfs_name(struct kernfs_node
*kn
)
127 spin_lock_irqsave(&kernfs_rename_lock
, flags
);
129 kernfs_name_locked(kn
, kernfs_pr_cont_buf
, sizeof(kernfs_pr_cont_buf
));
130 pr_cont("%s", kernfs_pr_cont_buf
);
132 spin_unlock_irqrestore(&kernfs_rename_lock
, flags
);
136 * pr_cont_kernfs_path - pr_cont path of a kernfs_node
137 * @kn: kernfs_node of interest
139 * This function can be called from any context.
141 void pr_cont_kernfs_path(struct kernfs_node
*kn
)
146 spin_lock_irqsave(&kernfs_rename_lock
, flags
);
148 p
= kernfs_path_locked(kn
, kernfs_pr_cont_buf
,
149 sizeof(kernfs_pr_cont_buf
));
153 pr_cont("<name too long>");
155 spin_unlock_irqrestore(&kernfs_rename_lock
, flags
);
159 * kernfs_get_parent - determine the parent node and pin it
160 * @kn: kernfs_node of interest
162 * Determines @kn's parent, pins and returns it. This function can be
163 * called from any context.
165 struct kernfs_node
*kernfs_get_parent(struct kernfs_node
*kn
)
167 struct kernfs_node
*parent
;
170 spin_lock_irqsave(&kernfs_rename_lock
, flags
);
173 spin_unlock_irqrestore(&kernfs_rename_lock
, flags
);
180 * @name: Null terminated string to hash
181 * @ns: Namespace tag to hash
183 * Returns 31 bit hash of ns + name (so it fits in an off_t )
185 static unsigned int kernfs_name_hash(const char *name
, const void *ns
)
187 unsigned long hash
= init_name_hash();
188 unsigned int len
= strlen(name
);
190 hash
= partial_name_hash(*name
++, hash
);
191 hash
= (end_name_hash(hash
) ^ hash_ptr((void *)ns
, 31));
193 /* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
201 static int kernfs_name_compare(unsigned int hash
, const char *name
,
202 const void *ns
, const struct kernfs_node
*kn
)
204 if (hash
!= kn
->hash
)
205 return hash
- kn
->hash
;
208 return strcmp(name
, kn
->name
);
211 static int kernfs_sd_compare(const struct kernfs_node
*left
,
212 const struct kernfs_node
*right
)
214 return kernfs_name_compare(left
->hash
, left
->name
, left
->ns
, right
);
218 * kernfs_link_sibling - link kernfs_node into sibling rbtree
219 * @kn: kernfs_node of interest
221 * Link @kn into its sibling rbtree which starts from
222 * @kn->parent->dir.children.
225 * mutex_lock(kernfs_mutex)
228 * 0 on susccess -EEXIST on failure.
230 static int kernfs_link_sibling(struct kernfs_node
*kn
)
232 struct rb_node
**node
= &kn
->parent
->dir
.children
.rb_node
;
233 struct rb_node
*parent
= NULL
;
235 if (kernfs_type(kn
) == KERNFS_DIR
)
236 kn
->parent
->dir
.subdirs
++;
239 struct kernfs_node
*pos
;
242 pos
= rb_to_kn(*node
);
244 result
= kernfs_sd_compare(kn
, pos
);
246 node
= &pos
->rb
.rb_left
;
248 node
= &pos
->rb
.rb_right
;
252 /* add new node and rebalance the tree */
253 rb_link_node(&kn
->rb
, parent
, node
);
254 rb_insert_color(&kn
->rb
, &kn
->parent
->dir
.children
);
259 * kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
260 * @kn: kernfs_node of interest
262 * Try to unlink @kn from its sibling rbtree which starts from
263 * kn->parent->dir.children. Returns %true if @kn was actually
264 * removed, %false if @kn wasn't on the rbtree.
267 * mutex_lock(kernfs_mutex)
269 static bool kernfs_unlink_sibling(struct kernfs_node
*kn
)
271 if (RB_EMPTY_NODE(&kn
->rb
))
274 if (kernfs_type(kn
) == KERNFS_DIR
)
275 kn
->parent
->dir
.subdirs
--;
277 rb_erase(&kn
->rb
, &kn
->parent
->dir
.children
);
278 RB_CLEAR_NODE(&kn
->rb
);
283 * kernfs_get_active - get an active reference to kernfs_node
284 * @kn: kernfs_node to get an active reference to
286 * Get an active reference of @kn. This function is noop if @kn
290 * Pointer to @kn on success, NULL on failure.
292 struct kernfs_node
*kernfs_get_active(struct kernfs_node
*kn
)
297 if (!atomic_inc_unless_negative(&kn
->active
))
300 if (kernfs_lockdep(kn
))
301 rwsem_acquire_read(&kn
->dep_map
, 0, 1, _RET_IP_
);
306 * kernfs_put_active - put an active reference to kernfs_node
307 * @kn: kernfs_node to put an active reference to
309 * Put an active reference to @kn. This function is noop if @kn
312 void kernfs_put_active(struct kernfs_node
*kn
)
314 struct kernfs_root
*root
= kernfs_root(kn
);
320 if (kernfs_lockdep(kn
))
321 rwsem_release(&kn
->dep_map
, 1, _RET_IP_
);
322 v
= atomic_dec_return(&kn
->active
);
323 if (likely(v
!= KN_DEACTIVATED_BIAS
))
326 wake_up_all(&root
->deactivate_waitq
);
330 * kernfs_drain - drain kernfs_node
331 * @kn: kernfs_node to drain
333 * Drain existing usages and nuke all existing mmaps of @kn. Mutiple
334 * removers may invoke this function concurrently on @kn and all will
335 * return after draining is complete.
337 static void kernfs_drain(struct kernfs_node
*kn
)
338 __releases(&kernfs_mutex
) __acquires(&kernfs_mutex
)
340 struct kernfs_root
*root
= kernfs_root(kn
);
342 lockdep_assert_held(&kernfs_mutex
);
343 WARN_ON_ONCE(kernfs_active(kn
));
345 mutex_unlock(&kernfs_mutex
);
347 if (kernfs_lockdep(kn
)) {
348 rwsem_acquire(&kn
->dep_map
, 0, 0, _RET_IP_
);
349 if (atomic_read(&kn
->active
) != KN_DEACTIVATED_BIAS
)
350 lock_contended(&kn
->dep_map
, _RET_IP_
);
353 /* but everyone should wait for draining */
354 wait_event(root
->deactivate_waitq
,
355 atomic_read(&kn
->active
) == KN_DEACTIVATED_BIAS
);
357 if (kernfs_lockdep(kn
)) {
358 lock_acquired(&kn
->dep_map
, _RET_IP_
);
359 rwsem_release(&kn
->dep_map
, 1, _RET_IP_
);
362 kernfs_unmap_bin_file(kn
);
364 mutex_lock(&kernfs_mutex
);
368 * kernfs_get - get a reference count on a kernfs_node
369 * @kn: the target kernfs_node
371 void kernfs_get(struct kernfs_node
*kn
)
374 WARN_ON(!atomic_read(&kn
->count
));
375 atomic_inc(&kn
->count
);
378 EXPORT_SYMBOL_GPL(kernfs_get
);
381 * kernfs_put - put a reference count on a kernfs_node
382 * @kn: the target kernfs_node
384 * Put a reference count of @kn and destroy it if it reached zero.
386 void kernfs_put(struct kernfs_node
*kn
)
388 struct kernfs_node
*parent
;
389 struct kernfs_root
*root
;
391 if (!kn
|| !atomic_dec_and_test(&kn
->count
))
393 root
= kernfs_root(kn
);
396 * Moving/renaming is always done while holding reference.
397 * kn->parent won't change beneath us.
401 WARN_ONCE(atomic_read(&kn
->active
) != KN_DEACTIVATED_BIAS
,
402 "kernfs_put: %s/%s: released with incorrect active_ref %d\n",
403 parent
? parent
->name
: "", kn
->name
, atomic_read(&kn
->active
));
405 if (kernfs_type(kn
) == KERNFS_LINK
)
406 kernfs_put(kn
->symlink
.target_kn
);
407 if (!(kn
->flags
& KERNFS_STATIC_NAME
))
410 if (kn
->iattr
->ia_secdata
)
411 security_release_secctx(kn
->iattr
->ia_secdata
,
412 kn
->iattr
->ia_secdata_len
);
413 simple_xattrs_free(&kn
->iattr
->xattrs
);
416 ida_simple_remove(&root
->ino_ida
, kn
->ino
);
417 kmem_cache_free(kernfs_node_cache
, kn
);
421 if (atomic_dec_and_test(&kn
->count
))
424 /* just released the root kn, free @root too */
425 ida_destroy(&root
->ino_ida
);
429 EXPORT_SYMBOL_GPL(kernfs_put
);
431 static int kernfs_dop_revalidate(struct dentry
*dentry
, unsigned int flags
)
433 struct kernfs_node
*kn
;
435 if (flags
& LOOKUP_RCU
)
438 /* Always perform fresh lookup for negatives */
439 if (!dentry
->d_inode
)
440 goto out_bad_unlocked
;
442 kn
= dentry
->d_fsdata
;
443 mutex_lock(&kernfs_mutex
);
445 /* The kernfs node has been deactivated */
446 if (!kernfs_active(kn
))
449 /* The kernfs node has been moved? */
450 if (dentry
->d_parent
->d_fsdata
!= kn
->parent
)
453 /* The kernfs node has been renamed */
454 if (strcmp(dentry
->d_name
.name
, kn
->name
) != 0)
457 /* The kernfs node has been moved to a different namespace */
458 if (kn
->parent
&& kernfs_ns_enabled(kn
->parent
) &&
459 kernfs_info(dentry
->d_sb
)->ns
!= kn
->ns
)
462 mutex_unlock(&kernfs_mutex
);
466 mutex_unlock(&kernfs_mutex
);
469 * @dentry doesn't match the underlying kernfs node, drop the
470 * dentry and force lookup. If we have submounts we must allow the
471 * vfs caches to lie about the state of the filesystem to prevent
472 * leaks and other nasty things, so use check_submounts_and_drop()
473 * instead of d_drop().
475 if (check_submounts_and_drop(dentry
) != 0)
481 static void kernfs_dop_release(struct dentry
*dentry
)
483 kernfs_put(dentry
->d_fsdata
);
486 const struct dentry_operations kernfs_dops
= {
487 .d_revalidate
= kernfs_dop_revalidate
,
488 .d_release
= kernfs_dop_release
,
492 * kernfs_node_from_dentry - determine kernfs_node associated with a dentry
493 * @dentry: the dentry in question
495 * Return the kernfs_node associated with @dentry. If @dentry is not a
496 * kernfs one, %NULL is returned.
498 * While the returned kernfs_node will stay accessible as long as @dentry
499 * is accessible, the returned node can be in any state and the caller is
500 * fully responsible for determining what's accessible.
502 struct kernfs_node
*kernfs_node_from_dentry(struct dentry
*dentry
)
504 if (dentry
->d_sb
->s_op
== &kernfs_sops
)
505 return dentry
->d_fsdata
;
509 static struct kernfs_node
*__kernfs_new_node(struct kernfs_root
*root
,
510 const char *name
, umode_t mode
,
513 char *dup_name
= NULL
;
514 struct kernfs_node
*kn
;
517 if (!(flags
& KERNFS_STATIC_NAME
)) {
518 name
= dup_name
= kstrdup(name
, GFP_KERNEL
);
523 kn
= kmem_cache_zalloc(kernfs_node_cache
, GFP_KERNEL
);
527 ret
= ida_simple_get(&root
->ino_ida
, 1, 0, GFP_KERNEL
);
532 atomic_set(&kn
->count
, 1);
533 atomic_set(&kn
->active
, KN_DEACTIVATED_BIAS
);
534 RB_CLEAR_NODE(&kn
->rb
);
543 kmem_cache_free(kernfs_node_cache
, kn
);
549 struct kernfs_node
*kernfs_new_node(struct kernfs_node
*parent
,
550 const char *name
, umode_t mode
,
553 struct kernfs_node
*kn
;
555 kn
= __kernfs_new_node(kernfs_root(parent
), name
, mode
, flags
);
564 * kernfs_add_one - add kernfs_node to parent without warning
565 * @kn: kernfs_node to be added
567 * The caller must already have initialized @kn->parent. This
568 * function increments nlink of the parent's inode if @kn is a
569 * directory and link into the children list of the parent.
572 * 0 on success, -EEXIST if entry with the given name already
575 int kernfs_add_one(struct kernfs_node
*kn
)
577 struct kernfs_node
*parent
= kn
->parent
;
578 struct kernfs_iattrs
*ps_iattr
;
582 mutex_lock(&kernfs_mutex
);
585 has_ns
= kernfs_ns_enabled(parent
);
586 if (WARN(has_ns
!= (bool)kn
->ns
, KERN_WARNING
"kernfs: ns %s in '%s' for '%s'\n",
587 has_ns
? "required" : "invalid", parent
->name
, kn
->name
))
590 if (kernfs_type(parent
) != KERNFS_DIR
)
594 if ((parent
->flags
& KERNFS_ACTIVATED
) && !kernfs_active(parent
))
597 kn
->hash
= kernfs_name_hash(kn
->name
, kn
->ns
);
599 ret
= kernfs_link_sibling(kn
);
603 /* Update timestamps on the parent */
604 ps_iattr
= parent
->iattr
;
606 struct iattr
*ps_iattrs
= &ps_iattr
->ia_iattr
;
607 ps_iattrs
->ia_ctime
= ps_iattrs
->ia_mtime
= CURRENT_TIME
;
610 mutex_unlock(&kernfs_mutex
);
613 * Activate the new node unless CREATE_DEACTIVATED is requested.
614 * If not activated here, the kernfs user is responsible for
615 * activating the node with kernfs_activate(). A node which hasn't
616 * been activated is not visible to userland and its removal won't
617 * trigger deactivation.
619 if (!(kernfs_root(kn
)->flags
& KERNFS_ROOT_CREATE_DEACTIVATED
))
624 mutex_unlock(&kernfs_mutex
);
629 * kernfs_find_ns - find kernfs_node with the given name
630 * @parent: kernfs_node to search under
631 * @name: name to look for
632 * @ns: the namespace tag to use
634 * Look for kernfs_node with name @name under @parent. Returns pointer to
635 * the found kernfs_node on success, %NULL on failure.
637 static struct kernfs_node
*kernfs_find_ns(struct kernfs_node
*parent
,
638 const unsigned char *name
,
641 struct rb_node
*node
= parent
->dir
.children
.rb_node
;
642 bool has_ns
= kernfs_ns_enabled(parent
);
645 lockdep_assert_held(&kernfs_mutex
);
647 if (has_ns
!= (bool)ns
) {
648 WARN(1, KERN_WARNING
"kernfs: ns %s in '%s' for '%s'\n",
649 has_ns
? "required" : "invalid", parent
->name
, name
);
653 hash
= kernfs_name_hash(name
, ns
);
655 struct kernfs_node
*kn
;
659 result
= kernfs_name_compare(hash
, name
, ns
, kn
);
661 node
= node
->rb_left
;
663 node
= node
->rb_right
;
671 * kernfs_find_and_get_ns - find and get kernfs_node with the given name
672 * @parent: kernfs_node to search under
673 * @name: name to look for
674 * @ns: the namespace tag to use
676 * Look for kernfs_node with name @name under @parent and get a reference
677 * if found. This function may sleep and returns pointer to the found
678 * kernfs_node on success, %NULL on failure.
680 struct kernfs_node
*kernfs_find_and_get_ns(struct kernfs_node
*parent
,
681 const char *name
, const void *ns
)
683 struct kernfs_node
*kn
;
685 mutex_lock(&kernfs_mutex
);
686 kn
= kernfs_find_ns(parent
, name
, ns
);
688 mutex_unlock(&kernfs_mutex
);
692 EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns
);
695 * kernfs_create_root - create a new kernfs hierarchy
696 * @scops: optional syscall operations for the hierarchy
697 * @flags: KERNFS_ROOT_* flags
698 * @priv: opaque data associated with the new directory
700 * Returns the root of the new hierarchy on success, ERR_PTR() value on
703 struct kernfs_root
*kernfs_create_root(struct kernfs_syscall_ops
*scops
,
704 unsigned int flags
, void *priv
)
706 struct kernfs_root
*root
;
707 struct kernfs_node
*kn
;
709 root
= kzalloc(sizeof(*root
), GFP_KERNEL
);
711 return ERR_PTR(-ENOMEM
);
713 ida_init(&root
->ino_ida
);
715 kn
= __kernfs_new_node(root
, "", S_IFDIR
| S_IRUGO
| S_IXUGO
,
718 ida_destroy(&root
->ino_ida
);
720 return ERR_PTR(-ENOMEM
);
726 root
->syscall_ops
= scops
;
729 init_waitqueue_head(&root
->deactivate_waitq
);
731 if (!(root
->flags
& KERNFS_ROOT_CREATE_DEACTIVATED
))
738 * kernfs_destroy_root - destroy a kernfs hierarchy
739 * @root: root of the hierarchy to destroy
741 * Destroy the hierarchy anchored at @root by removing all existing
742 * directories and destroying @root.
744 void kernfs_destroy_root(struct kernfs_root
*root
)
746 kernfs_remove(root
->kn
); /* will also free @root */
750 * kernfs_create_dir_ns - create a directory
751 * @parent: parent in which to create a new directory
752 * @name: name of the new directory
753 * @mode: mode of the new directory
754 * @priv: opaque data associated with the new directory
755 * @ns: optional namespace tag of the directory
757 * Returns the created node on success, ERR_PTR() value on failure.
759 struct kernfs_node
*kernfs_create_dir_ns(struct kernfs_node
*parent
,
760 const char *name
, umode_t mode
,
761 void *priv
, const void *ns
)
763 struct kernfs_node
*kn
;
767 kn
= kernfs_new_node(parent
, name
, mode
| S_IFDIR
, KERNFS_DIR
);
769 return ERR_PTR(-ENOMEM
);
771 kn
->dir
.root
= parent
->dir
.root
;
776 rc
= kernfs_add_one(kn
);
784 static struct dentry
*kernfs_iop_lookup(struct inode
*dir
,
785 struct dentry
*dentry
,
789 struct kernfs_node
*parent
= dentry
->d_parent
->d_fsdata
;
790 struct kernfs_node
*kn
;
792 const void *ns
= NULL
;
794 mutex_lock(&kernfs_mutex
);
796 if (kernfs_ns_enabled(parent
))
797 ns
= kernfs_info(dir
->i_sb
)->ns
;
799 kn
= kernfs_find_ns(parent
, dentry
->d_name
.name
, ns
);
802 if (!kn
|| !kernfs_active(kn
)) {
807 dentry
->d_fsdata
= kn
;
809 /* attach dentry and inode */
810 inode
= kernfs_get_inode(dir
->i_sb
, kn
);
812 ret
= ERR_PTR(-ENOMEM
);
816 /* instantiate and hash dentry */
817 ret
= d_materialise_unique(dentry
, inode
);
819 mutex_unlock(&kernfs_mutex
);
823 static int kernfs_iop_mkdir(struct inode
*dir
, struct dentry
*dentry
,
826 struct kernfs_node
*parent
= dir
->i_private
;
827 struct kernfs_syscall_ops
*scops
= kernfs_root(parent
)->syscall_ops
;
830 if (!scops
|| !scops
->mkdir
)
833 if (!kernfs_get_active(parent
))
836 ret
= scops
->mkdir(parent
, dentry
->d_name
.name
, mode
);
838 kernfs_put_active(parent
);
842 static int kernfs_iop_rmdir(struct inode
*dir
, struct dentry
*dentry
)
844 struct kernfs_node
*kn
= dentry
->d_fsdata
;
845 struct kernfs_syscall_ops
*scops
= kernfs_root(kn
)->syscall_ops
;
848 if (!scops
|| !scops
->rmdir
)
851 if (!kernfs_get_active(kn
))
854 ret
= scops
->rmdir(kn
);
856 kernfs_put_active(kn
);
860 static int kernfs_iop_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
861 struct inode
*new_dir
, struct dentry
*new_dentry
)
863 struct kernfs_node
*kn
= old_dentry
->d_fsdata
;
864 struct kernfs_node
*new_parent
= new_dir
->i_private
;
865 struct kernfs_syscall_ops
*scops
= kernfs_root(kn
)->syscall_ops
;
868 if (!scops
|| !scops
->rename
)
871 if (!kernfs_get_active(kn
))
874 if (!kernfs_get_active(new_parent
)) {
875 kernfs_put_active(kn
);
879 ret
= scops
->rename(kn
, new_parent
, new_dentry
->d_name
.name
);
881 kernfs_put_active(new_parent
);
882 kernfs_put_active(kn
);
886 const struct inode_operations kernfs_dir_iops
= {
887 .lookup
= kernfs_iop_lookup
,
888 .permission
= kernfs_iop_permission
,
889 .setattr
= kernfs_iop_setattr
,
890 .getattr
= kernfs_iop_getattr
,
891 .setxattr
= kernfs_iop_setxattr
,
892 .removexattr
= kernfs_iop_removexattr
,
893 .getxattr
= kernfs_iop_getxattr
,
894 .listxattr
= kernfs_iop_listxattr
,
896 .mkdir
= kernfs_iop_mkdir
,
897 .rmdir
= kernfs_iop_rmdir
,
898 .rename
= kernfs_iop_rename
,
901 static struct kernfs_node
*kernfs_leftmost_descendant(struct kernfs_node
*pos
)
903 struct kernfs_node
*last
;
910 if (kernfs_type(pos
) != KERNFS_DIR
)
913 rbn
= rb_first(&pos
->dir
.children
);
924 * kernfs_next_descendant_post - find the next descendant for post-order walk
925 * @pos: the current position (%NULL to initiate traversal)
926 * @root: kernfs_node whose descendants to walk
928 * Find the next descendant to visit for post-order traversal of @root's
929 * descendants. @root is included in the iteration and the last node to be
932 static struct kernfs_node
*kernfs_next_descendant_post(struct kernfs_node
*pos
,
933 struct kernfs_node
*root
)
937 lockdep_assert_held(&kernfs_mutex
);
939 /* if first iteration, visit leftmost descendant which may be root */
941 return kernfs_leftmost_descendant(root
);
943 /* if we visited @root, we're done */
947 /* if there's an unvisited sibling, visit its leftmost descendant */
948 rbn
= rb_next(&pos
->rb
);
950 return kernfs_leftmost_descendant(rb_to_kn(rbn
));
952 /* no sibling left, visit parent */
957 * kernfs_activate - activate a node which started deactivated
958 * @kn: kernfs_node whose subtree is to be activated
960 * If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node
961 * needs to be explicitly activated. A node which hasn't been activated
962 * isn't visible to userland and deactivation is skipped during its
963 * removal. This is useful to construct atomic init sequences where
964 * creation of multiple nodes should either succeed or fail atomically.
966 * The caller is responsible for ensuring that this function is not called
967 * after kernfs_remove*() is invoked on @kn.
969 void kernfs_activate(struct kernfs_node
*kn
)
971 struct kernfs_node
*pos
;
973 mutex_lock(&kernfs_mutex
);
976 while ((pos
= kernfs_next_descendant_post(pos
, kn
))) {
977 if (!pos
|| (pos
->flags
& KERNFS_ACTIVATED
))
980 WARN_ON_ONCE(pos
->parent
&& RB_EMPTY_NODE(&pos
->rb
));
981 WARN_ON_ONCE(atomic_read(&pos
->active
) != KN_DEACTIVATED_BIAS
);
983 atomic_sub(KN_DEACTIVATED_BIAS
, &pos
->active
);
984 pos
->flags
|= KERNFS_ACTIVATED
;
987 mutex_unlock(&kernfs_mutex
);
990 static void __kernfs_remove(struct kernfs_node
*kn
)
992 struct kernfs_node
*pos
;
994 lockdep_assert_held(&kernfs_mutex
);
997 * Short-circuit if non-root @kn has already finished removal.
998 * This is for kernfs_remove_self() which plays with active ref
1001 if (!kn
|| (kn
->parent
&& RB_EMPTY_NODE(&kn
->rb
)))
1004 pr_debug("kernfs %s: removing\n", kn
->name
);
1006 /* prevent any new usage under @kn by deactivating all nodes */
1008 while ((pos
= kernfs_next_descendant_post(pos
, kn
)))
1009 if (kernfs_active(pos
))
1010 atomic_add(KN_DEACTIVATED_BIAS
, &pos
->active
);
1012 /* deactivate and unlink the subtree node-by-node */
1014 pos
= kernfs_leftmost_descendant(kn
);
1017 * kernfs_drain() drops kernfs_mutex temporarily and @pos's
1018 * base ref could have been put by someone else by the time
1019 * the function returns. Make sure it doesn't go away
1025 * Drain iff @kn was activated. This avoids draining and
1026 * its lockdep annotations for nodes which have never been
1027 * activated and allows embedding kernfs_remove() in create
1028 * error paths without worrying about draining.
1030 if (kn
->flags
& KERNFS_ACTIVATED
)
1033 WARN_ON_ONCE(atomic_read(&kn
->active
) != KN_DEACTIVATED_BIAS
);
1036 * kernfs_unlink_sibling() succeeds once per node. Use it
1037 * to decide who's responsible for cleanups.
1039 if (!pos
->parent
|| kernfs_unlink_sibling(pos
)) {
1040 struct kernfs_iattrs
*ps_iattr
=
1041 pos
->parent
? pos
->parent
->iattr
: NULL
;
1043 /* update timestamps on the parent */
1045 ps_iattr
->ia_iattr
.ia_ctime
= CURRENT_TIME
;
1046 ps_iattr
->ia_iattr
.ia_mtime
= CURRENT_TIME
;
1053 } while (pos
!= kn
);
1057 * kernfs_remove - remove a kernfs_node recursively
1058 * @kn: the kernfs_node to remove
1060 * Remove @kn along with all its subdirectories and files.
1062 void kernfs_remove(struct kernfs_node
*kn
)
1064 mutex_lock(&kernfs_mutex
);
1065 __kernfs_remove(kn
);
1066 mutex_unlock(&kernfs_mutex
);
1070 * kernfs_break_active_protection - break out of active protection
1071 * @kn: the self kernfs_node
1073 * The caller must be running off of a kernfs operation which is invoked
1074 * with an active reference - e.g. one of kernfs_ops. Each invocation of
1075 * this function must also be matched with an invocation of
1076 * kernfs_unbreak_active_protection().
1078 * This function releases the active reference of @kn the caller is
1079 * holding. Once this function is called, @kn may be removed at any point
1080 * and the caller is solely responsible for ensuring that the objects it
1081 * dereferences are accessible.
1083 void kernfs_break_active_protection(struct kernfs_node
*kn
)
1086 * Take out ourself out of the active ref dependency chain. If
1087 * we're called without an active ref, lockdep will complain.
1089 kernfs_put_active(kn
);
1093 * kernfs_unbreak_active_protection - undo kernfs_break_active_protection()
1094 * @kn: the self kernfs_node
1096 * If kernfs_break_active_protection() was called, this function must be
1097 * invoked before finishing the kernfs operation. Note that while this
1098 * function restores the active reference, it doesn't and can't actually
1099 * restore the active protection - @kn may already or be in the process of
1100 * being removed. Once kernfs_break_active_protection() is invoked, that
1101 * protection is irreversibly gone for the kernfs operation instance.
1103 * While this function may be called at any point after
1104 * kernfs_break_active_protection() is invoked, its most useful location
1105 * would be right before the enclosing kernfs operation returns.
1107 void kernfs_unbreak_active_protection(struct kernfs_node
*kn
)
1110 * @kn->active could be in any state; however, the increment we do
1111 * here will be undone as soon as the enclosing kernfs operation
1112 * finishes and this temporary bump can't break anything. If @kn
1113 * is alive, nothing changes. If @kn is being deactivated, the
1114 * soon-to-follow put will either finish deactivation or restore
1115 * deactivated state. If @kn is already removed, the temporary
1116 * bump is guaranteed to be gone before @kn is released.
1118 atomic_inc(&kn
->active
);
1119 if (kernfs_lockdep(kn
))
1120 rwsem_acquire(&kn
->dep_map
, 0, 1, _RET_IP_
);
1124 * kernfs_remove_self - remove a kernfs_node from its own method
1125 * @kn: the self kernfs_node to remove
1127 * The caller must be running off of a kernfs operation which is invoked
1128 * with an active reference - e.g. one of kernfs_ops. This can be used to
1129 * implement a file operation which deletes itself.
1131 * For example, the "delete" file for a sysfs device directory can be
1132 * implemented by invoking kernfs_remove_self() on the "delete" file
1133 * itself. This function breaks the circular dependency of trying to
1134 * deactivate self while holding an active ref itself. It isn't necessary
1135 * to modify the usual removal path to use kernfs_remove_self(). The
1136 * "delete" implementation can simply invoke kernfs_remove_self() on self
1137 * before proceeding with the usual removal path. kernfs will ignore later
1138 * kernfs_remove() on self.
1140 * kernfs_remove_self() can be called multiple times concurrently on the
1141 * same kernfs_node. Only the first one actually performs removal and
1142 * returns %true. All others will wait until the kernfs operation which
1143 * won self-removal finishes and return %false. Note that the losers wait
1144 * for the completion of not only the winning kernfs_remove_self() but also
1145 * the whole kernfs_ops which won the arbitration. This can be used to
1146 * guarantee, for example, all concurrent writes to a "delete" file to
1147 * finish only after the whole operation is complete.
1149 bool kernfs_remove_self(struct kernfs_node
*kn
)
1153 mutex_lock(&kernfs_mutex
);
1154 kernfs_break_active_protection(kn
);
1157 * SUICIDAL is used to arbitrate among competing invocations. Only
1158 * the first one will actually perform removal. When the removal
1159 * is complete, SUICIDED is set and the active ref is restored
1160 * while holding kernfs_mutex. The ones which lost arbitration
1161 * waits for SUICDED && drained which can happen only after the
1162 * enclosing kernfs operation which executed the winning instance
1163 * of kernfs_remove_self() finished.
1165 if (!(kn
->flags
& KERNFS_SUICIDAL
)) {
1166 kn
->flags
|= KERNFS_SUICIDAL
;
1167 __kernfs_remove(kn
);
1168 kn
->flags
|= KERNFS_SUICIDED
;
1171 wait_queue_head_t
*waitq
= &kernfs_root(kn
)->deactivate_waitq
;
1175 prepare_to_wait(waitq
, &wait
, TASK_UNINTERRUPTIBLE
);
1177 if ((kn
->flags
& KERNFS_SUICIDED
) &&
1178 atomic_read(&kn
->active
) == KN_DEACTIVATED_BIAS
)
1181 mutex_unlock(&kernfs_mutex
);
1183 mutex_lock(&kernfs_mutex
);
1185 finish_wait(waitq
, &wait
);
1186 WARN_ON_ONCE(!RB_EMPTY_NODE(&kn
->rb
));
1191 * This must be done while holding kernfs_mutex; otherwise, waiting
1192 * for SUICIDED && deactivated could finish prematurely.
1194 kernfs_unbreak_active_protection(kn
);
1196 mutex_unlock(&kernfs_mutex
);
1201 * kernfs_remove_by_name_ns - find a kernfs_node by name and remove it
1202 * @parent: parent of the target
1203 * @name: name of the kernfs_node to remove
1204 * @ns: namespace tag of the kernfs_node to remove
1206 * Look for the kernfs_node with @name and @ns under @parent and remove it.
1207 * Returns 0 on success, -ENOENT if such entry doesn't exist.
1209 int kernfs_remove_by_name_ns(struct kernfs_node
*parent
, const char *name
,
1212 struct kernfs_node
*kn
;
1215 WARN(1, KERN_WARNING
"kernfs: can not remove '%s', no directory\n",
1220 mutex_lock(&kernfs_mutex
);
1222 kn
= kernfs_find_ns(parent
, name
, ns
);
1224 __kernfs_remove(kn
);
1226 mutex_unlock(&kernfs_mutex
);
1235 * kernfs_rename_ns - move and rename a kernfs_node
1237 * @new_parent: new parent to put @sd under
1238 * @new_name: new name
1239 * @new_ns: new namespace tag
1241 int kernfs_rename_ns(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
1242 const char *new_name
, const void *new_ns
)
1244 struct kernfs_node
*old_parent
;
1245 const char *old_name
= NULL
;
1248 /* can't move or rename root */
1252 mutex_lock(&kernfs_mutex
);
1255 if (!kernfs_active(kn
) || !kernfs_active(new_parent
))
1259 if ((kn
->parent
== new_parent
) && (kn
->ns
== new_ns
) &&
1260 (strcmp(kn
->name
, new_name
) == 0))
1261 goto out
; /* nothing to rename */
1264 if (kernfs_find_ns(new_parent
, new_name
, new_ns
))
1267 /* rename kernfs_node */
1268 if (strcmp(kn
->name
, new_name
) != 0) {
1270 new_name
= kstrdup(new_name
, GFP_KERNEL
);
1278 * Move to the appropriate place in the appropriate directories rbtree.
1280 kernfs_unlink_sibling(kn
);
1281 kernfs_get(new_parent
);
1283 /* rename_lock protects ->parent and ->name accessors */
1284 spin_lock_irq(&kernfs_rename_lock
);
1286 old_parent
= kn
->parent
;
1287 kn
->parent
= new_parent
;
1291 if (!(kn
->flags
& KERNFS_STATIC_NAME
))
1292 old_name
= kn
->name
;
1293 kn
->flags
&= ~KERNFS_STATIC_NAME
;
1294 kn
->name
= new_name
;
1297 spin_unlock_irq(&kernfs_rename_lock
);
1299 kn
->hash
= kernfs_name_hash(kn
->name
, kn
->ns
);
1300 kernfs_link_sibling(kn
);
1302 kernfs_put(old_parent
);
1307 mutex_unlock(&kernfs_mutex
);
1311 /* Relationship between s_mode and the DT_xxx types */
1312 static inline unsigned char dt_type(struct kernfs_node
*kn
)
1314 return (kn
->mode
>> 12) & 15;
1317 static int kernfs_dir_fop_release(struct inode
*inode
, struct file
*filp
)
1319 kernfs_put(filp
->private_data
);
1323 static struct kernfs_node
*kernfs_dir_pos(const void *ns
,
1324 struct kernfs_node
*parent
, loff_t hash
, struct kernfs_node
*pos
)
1327 int valid
= kernfs_active(pos
) &&
1328 pos
->parent
== parent
&& hash
== pos
->hash
;
1333 if (!pos
&& (hash
> 1) && (hash
< INT_MAX
)) {
1334 struct rb_node
*node
= parent
->dir
.children
.rb_node
;
1336 pos
= rb_to_kn(node
);
1338 if (hash
< pos
->hash
)
1339 node
= node
->rb_left
;
1340 else if (hash
> pos
->hash
)
1341 node
= node
->rb_right
;
1346 /* Skip over entries which are dying/dead or in the wrong namespace */
1347 while (pos
&& (!kernfs_active(pos
) || pos
->ns
!= ns
)) {
1348 struct rb_node
*node
= rb_next(&pos
->rb
);
1352 pos
= rb_to_kn(node
);
1357 static struct kernfs_node
*kernfs_dir_next_pos(const void *ns
,
1358 struct kernfs_node
*parent
, ino_t ino
, struct kernfs_node
*pos
)
1360 pos
= kernfs_dir_pos(ns
, parent
, ino
, pos
);
1363 struct rb_node
*node
= rb_next(&pos
->rb
);
1367 pos
= rb_to_kn(node
);
1368 } while (pos
&& (!kernfs_active(pos
) || pos
->ns
!= ns
));
1373 static int kernfs_fop_readdir(struct file
*file
, struct dir_context
*ctx
)
1375 struct dentry
*dentry
= file
->f_path
.dentry
;
1376 struct kernfs_node
*parent
= dentry
->d_fsdata
;
1377 struct kernfs_node
*pos
= file
->private_data
;
1378 const void *ns
= NULL
;
1380 if (!dir_emit_dots(file
, ctx
))
1382 mutex_lock(&kernfs_mutex
);
1384 if (kernfs_ns_enabled(parent
))
1385 ns
= kernfs_info(dentry
->d_sb
)->ns
;
1387 for (pos
= kernfs_dir_pos(ns
, parent
, ctx
->pos
, pos
);
1389 pos
= kernfs_dir_next_pos(ns
, parent
, ctx
->pos
, pos
)) {
1390 const char *name
= pos
->name
;
1391 unsigned int type
= dt_type(pos
);
1392 int len
= strlen(name
);
1393 ino_t ino
= pos
->ino
;
1395 ctx
->pos
= pos
->hash
;
1396 file
->private_data
= pos
;
1399 mutex_unlock(&kernfs_mutex
);
1400 if (!dir_emit(ctx
, name
, len
, ino
, type
))
1402 mutex_lock(&kernfs_mutex
);
1404 mutex_unlock(&kernfs_mutex
);
1405 file
->private_data
= NULL
;
1410 static loff_t
kernfs_dir_fop_llseek(struct file
*file
, loff_t offset
,
1413 struct inode
*inode
= file_inode(file
);
1416 mutex_lock(&inode
->i_mutex
);
1417 ret
= generic_file_llseek(file
, offset
, whence
);
1418 mutex_unlock(&inode
->i_mutex
);
1423 const struct file_operations kernfs_dir_fops
= {
1424 .read
= generic_read_dir
,
1425 .iterate
= kernfs_fop_readdir
,
1426 .release
= kernfs_dir_fop_release
,
1427 .llseek
= kernfs_dir_fop_llseek
,