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;
236 struct kernfs_node *pos;
239 pos = rb_to_kn(*node);
241 result = kernfs_sd_compare(kn, pos);
243 node = &pos->rb.rb_left;
245 node = &pos->rb.rb_right;
250 /* add new node and rebalance the tree */
251 rb_link_node(&kn->rb, parent, node);
252 rb_insert_color(&kn->rb, &kn->parent->dir.children);
254 /* successfully added, account subdir number */
255 if (kernfs_type(kn) == KERNFS_DIR)
256 kn->parent->dir.subdirs++;
262 * kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
263 * @kn: kernfs_node of interest
265 * Try to unlink @kn from its sibling rbtree which starts from
266 * kn->parent->dir.children. Returns %true if @kn was actually
267 * removed, %false if @kn wasn't on the rbtree.
270 * mutex_lock(kernfs_mutex)
272 static bool kernfs_unlink_sibling(struct kernfs_node *kn)
274 if (RB_EMPTY_NODE(&kn->rb))
277 if (kernfs_type(kn) == KERNFS_DIR)
278 kn->parent->dir.subdirs--;
280 rb_erase(&kn->rb, &kn->parent->dir.children);
281 RB_CLEAR_NODE(&kn->rb);
286 * kernfs_get_active - get an active reference to kernfs_node
287 * @kn: kernfs_node to get an active reference to
289 * Get an active reference of @kn. This function is noop if @kn
293 * Pointer to @kn on success, NULL on failure.
295 struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
300 if (!atomic_inc_unless_negative(&kn->active))
303 if (kernfs_lockdep(kn))
304 rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
309 * kernfs_put_active - put an active reference to kernfs_node
310 * @kn: kernfs_node to put an active reference to
312 * Put an active reference to @kn. This function is noop if @kn
315 void kernfs_put_active(struct kernfs_node *kn)
317 struct kernfs_root *root = kernfs_root(kn);
323 if (kernfs_lockdep(kn))
324 rwsem_release(&kn->dep_map, 1, _RET_IP_);
325 v = atomic_dec_return(&kn->active);
326 if (likely(v != KN_DEACTIVATED_BIAS))
329 wake_up_all(&root->deactivate_waitq);
333 * kernfs_drain - drain kernfs_node
334 * @kn: kernfs_node to drain
336 * Drain existing usages and nuke all existing mmaps of @kn. Mutiple
337 * removers may invoke this function concurrently on @kn and all will
338 * return after draining is complete.
340 static void kernfs_drain(struct kernfs_node *kn)
341 __releases(&kernfs_mutex) __acquires(&kernfs_mutex)
343 struct kernfs_root *root = kernfs_root(kn);
345 lockdep_assert_held(&kernfs_mutex);
346 WARN_ON_ONCE(kernfs_active(kn));
348 mutex_unlock(&kernfs_mutex);
350 if (kernfs_lockdep(kn)) {
351 rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
352 if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
353 lock_contended(&kn->dep_map, _RET_IP_);
356 /* but everyone should wait for draining */
357 wait_event(root->deactivate_waitq,
358 atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
360 if (kernfs_lockdep(kn)) {
361 lock_acquired(&kn->dep_map, _RET_IP_);
362 rwsem_release(&kn->dep_map, 1, _RET_IP_);
365 kernfs_unmap_bin_file(kn);
367 mutex_lock(&kernfs_mutex);
371 * kernfs_get - get a reference count on a kernfs_node
372 * @kn: the target kernfs_node
374 void kernfs_get(struct kernfs_node *kn)
377 WARN_ON(!atomic_read(&kn->count));
378 atomic_inc(&kn->count);
381 EXPORT_SYMBOL_GPL(kernfs_get);
384 * kernfs_put - put a reference count on a kernfs_node
385 * @kn: the target kernfs_node
387 * Put a reference count of @kn and destroy it if it reached zero.
389 void kernfs_put(struct kernfs_node *kn)
391 struct kernfs_node *parent;
392 struct kernfs_root *root;
394 if (!kn || !atomic_dec_and_test(&kn->count))
396 root = kernfs_root(kn);
399 * Moving/renaming is always done while holding reference.
400 * kn->parent won't change beneath us.
404 WARN_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS,
405 "kernfs_put: %s/%s: released with incorrect active_ref %d\n",
406 parent ? parent->name : "", kn->name, atomic_read(&kn->active));
408 if (kernfs_type(kn) == KERNFS_LINK)
409 kernfs_put(kn->symlink.target_kn);
410 if (!(kn->flags & KERNFS_STATIC_NAME))
413 if (kn->iattr->ia_secdata)
414 security_release_secctx(kn->iattr->ia_secdata,
415 kn->iattr->ia_secdata_len);
416 simple_xattrs_free(&kn->iattr->xattrs);
419 ida_simple_remove(&root->ino_ida, kn->ino);
420 kmem_cache_free(kernfs_node_cache, kn);
424 if (atomic_dec_and_test(&kn->count))
427 /* just released the root kn, free @root too */
428 ida_destroy(&root->ino_ida);
432 EXPORT_SYMBOL_GPL(kernfs_put);
434 static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
436 struct kernfs_node *kn;
438 if (flags & LOOKUP_RCU)
441 /* Always perform fresh lookup for negatives */
442 if (!dentry->d_inode)
443 goto out_bad_unlocked;
445 kn = dentry->d_fsdata;
446 mutex_lock(&kernfs_mutex);
448 /* The kernfs node has been deactivated */
449 if (!kernfs_active(kn))
452 /* The kernfs node has been moved? */
453 if (dentry->d_parent->d_fsdata != kn->parent)
456 /* The kernfs node has been renamed */
457 if (strcmp(dentry->d_name.name, kn->name) != 0)
460 /* The kernfs node has been moved to a different namespace */
461 if (kn->parent && kernfs_ns_enabled(kn->parent) &&
462 kernfs_info(dentry->d_sb)->ns != kn->ns)
465 mutex_unlock(&kernfs_mutex);
469 mutex_unlock(&kernfs_mutex);
472 * @dentry doesn't match the underlying kernfs node, drop the
473 * dentry and force lookup. If we have submounts we must allow the
474 * vfs caches to lie about the state of the filesystem to prevent
475 * leaks and other nasty things, so use check_submounts_and_drop()
476 * instead of d_drop().
478 if (check_submounts_and_drop(dentry) != 0)
484 static void kernfs_dop_release(struct dentry *dentry)
486 kernfs_put(dentry->d_fsdata);
489 const struct dentry_operations kernfs_dops = {
490 .d_revalidate = kernfs_dop_revalidate,
491 .d_release = kernfs_dop_release,
495 * kernfs_node_from_dentry - determine kernfs_node associated with a dentry
496 * @dentry: the dentry in question
498 * Return the kernfs_node associated with @dentry. If @dentry is not a
499 * kernfs one, %NULL is returned.
501 * While the returned kernfs_node will stay accessible as long as @dentry
502 * is accessible, the returned node can be in any state and the caller is
503 * fully responsible for determining what's accessible.
505 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
507 if (dentry->d_sb->s_op == &kernfs_sops)
508 return dentry->d_fsdata;
512 static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
513 const char *name, umode_t mode,
516 char *dup_name = NULL;
517 struct kernfs_node *kn;
520 if (!(flags & KERNFS_STATIC_NAME)) {
521 name = dup_name = kstrdup(name, GFP_KERNEL);
526 kn = kmem_cache_zalloc(kernfs_node_cache, GFP_KERNEL);
530 ret = ida_simple_get(&root->ino_ida, 1, 0, GFP_KERNEL);
535 atomic_set(&kn->count, 1);
536 atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
537 RB_CLEAR_NODE(&kn->rb);
546 kmem_cache_free(kernfs_node_cache, kn);
552 struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
553 const char *name, umode_t mode,
556 struct kernfs_node *kn;
558 kn = __kernfs_new_node(kernfs_root(parent), name, mode, flags);
567 * kernfs_add_one - add kernfs_node to parent without warning
568 * @kn: kernfs_node to be added
570 * The caller must already have initialized @kn->parent. This
571 * function increments nlink of the parent's inode if @kn is a
572 * directory and link into the children list of the parent.
575 * 0 on success, -EEXIST if entry with the given name already
578 int kernfs_add_one(struct kernfs_node *kn)
580 struct kernfs_node *parent = kn->parent;
581 struct kernfs_iattrs *ps_iattr;
585 mutex_lock(&kernfs_mutex);
588 has_ns = kernfs_ns_enabled(parent);
589 if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
590 has_ns ? "required" : "invalid", parent->name, kn->name))
593 if (kernfs_type(parent) != KERNFS_DIR)
597 if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent))
600 kn->hash = kernfs_name_hash(kn->name, kn->ns);
602 ret = kernfs_link_sibling(kn);
606 /* Update timestamps on the parent */
607 ps_iattr = parent->iattr;
609 struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
610 ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
613 mutex_unlock(&kernfs_mutex);
616 * Activate the new node unless CREATE_DEACTIVATED is requested.
617 * If not activated here, the kernfs user is responsible for
618 * activating the node with kernfs_activate(). A node which hasn't
619 * been activated is not visible to userland and its removal won't
620 * trigger deactivation.
622 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
627 mutex_unlock(&kernfs_mutex);
632 * kernfs_find_ns - find kernfs_node with the given name
633 * @parent: kernfs_node to search under
634 * @name: name to look for
635 * @ns: the namespace tag to use
637 * Look for kernfs_node with name @name under @parent. Returns pointer to
638 * the found kernfs_node on success, %NULL on failure.
640 static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
641 const unsigned char *name,
644 struct rb_node *node = parent->dir.children.rb_node;
645 bool has_ns = kernfs_ns_enabled(parent);
648 lockdep_assert_held(&kernfs_mutex);
650 if (has_ns != (bool)ns) {
651 WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
652 has_ns ? "required" : "invalid", parent->name, name);
656 hash = kernfs_name_hash(name, ns);
658 struct kernfs_node *kn;
662 result = kernfs_name_compare(hash, name, ns, kn);
664 node = node->rb_left;
666 node = node->rb_right;
674 * kernfs_find_and_get_ns - find and get kernfs_node with the given name
675 * @parent: kernfs_node to search under
676 * @name: name to look for
677 * @ns: the namespace tag to use
679 * Look for kernfs_node with name @name under @parent and get a reference
680 * if found. This function may sleep and returns pointer to the found
681 * kernfs_node on success, %NULL on failure.
683 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
684 const char *name, const void *ns)
686 struct kernfs_node *kn;
688 mutex_lock(&kernfs_mutex);
689 kn = kernfs_find_ns(parent, name, ns);
691 mutex_unlock(&kernfs_mutex);
695 EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
698 * kernfs_create_root - create a new kernfs hierarchy
699 * @scops: optional syscall operations for the hierarchy
700 * @flags: KERNFS_ROOT_* flags
701 * @priv: opaque data associated with the new directory
703 * Returns the root of the new hierarchy on success, ERR_PTR() value on
706 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
707 unsigned int flags, void *priv)
709 struct kernfs_root *root;
710 struct kernfs_node *kn;
712 root = kzalloc(sizeof(*root), GFP_KERNEL);
714 return ERR_PTR(-ENOMEM);
716 ida_init(&root->ino_ida);
718 kn = __kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO,
721 ida_destroy(&root->ino_ida);
723 return ERR_PTR(-ENOMEM);
729 root->syscall_ops = scops;
732 init_waitqueue_head(&root->deactivate_waitq);
734 if (!(root->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
741 * kernfs_destroy_root - destroy a kernfs hierarchy
742 * @root: root of the hierarchy to destroy
744 * Destroy the hierarchy anchored at @root by removing all existing
745 * directories and destroying @root.
747 void kernfs_destroy_root(struct kernfs_root *root)
749 kernfs_remove(root->kn); /* will also free @root */
753 * kernfs_create_dir_ns - create a directory
754 * @parent: parent in which to create a new directory
755 * @name: name of the new directory
756 * @mode: mode of the new directory
757 * @priv: opaque data associated with the new directory
758 * @ns: optional namespace tag of the directory
760 * Returns the created node on success, ERR_PTR() value on failure.
762 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
763 const char *name, umode_t mode,
764 void *priv, const void *ns)
766 struct kernfs_node *kn;
770 kn = kernfs_new_node(parent, name, mode | S_IFDIR, KERNFS_DIR);
772 return ERR_PTR(-ENOMEM);
774 kn->dir.root = parent->dir.root;
779 rc = kernfs_add_one(kn);
787 static struct dentry *kernfs_iop_lookup(struct inode *dir,
788 struct dentry *dentry,
792 struct kernfs_node *parent = dentry->d_parent->d_fsdata;
793 struct kernfs_node *kn;
795 const void *ns = NULL;
797 mutex_lock(&kernfs_mutex);
799 if (kernfs_ns_enabled(parent))
800 ns = kernfs_info(dir->i_sb)->ns;
802 kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
805 if (!kn || !kernfs_active(kn)) {
810 dentry->d_fsdata = kn;
812 /* attach dentry and inode */
813 inode = kernfs_get_inode(dir->i_sb, kn);
815 ret = ERR_PTR(-ENOMEM);
819 /* instantiate and hash dentry */
820 ret = d_materialise_unique(dentry, inode);
822 mutex_unlock(&kernfs_mutex);
826 static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,
829 struct kernfs_node *parent = dir->i_private;
830 struct kernfs_syscall_ops *scops = kernfs_root(parent)->syscall_ops;
833 if (!scops || !scops->mkdir)
836 if (!kernfs_get_active(parent))
839 ret = scops->mkdir(parent, dentry->d_name.name, mode);
841 kernfs_put_active(parent);
845 static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
847 struct kernfs_node *kn = dentry->d_fsdata;
848 struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
851 if (!scops || !scops->rmdir)
854 if (!kernfs_get_active(kn))
857 ret = scops->rmdir(kn);
859 kernfs_put_active(kn);
863 static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
864 struct inode *new_dir, struct dentry *new_dentry)
866 struct kernfs_node *kn = old_dentry->d_fsdata;
867 struct kernfs_node *new_parent = new_dir->i_private;
868 struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
871 if (!scops || !scops->rename)
874 if (!kernfs_get_active(kn))
877 if (!kernfs_get_active(new_parent)) {
878 kernfs_put_active(kn);
882 ret = scops->rename(kn, new_parent, new_dentry->d_name.name);
884 kernfs_put_active(new_parent);
885 kernfs_put_active(kn);
889 const struct inode_operations kernfs_dir_iops = {
890 .lookup = kernfs_iop_lookup,
891 .permission = kernfs_iop_permission,
892 .setattr = kernfs_iop_setattr,
893 .getattr = kernfs_iop_getattr,
894 .setxattr = kernfs_iop_setxattr,
895 .removexattr = kernfs_iop_removexattr,
896 .getxattr = kernfs_iop_getxattr,
897 .listxattr = kernfs_iop_listxattr,
899 .mkdir = kernfs_iop_mkdir,
900 .rmdir = kernfs_iop_rmdir,
901 .rename = kernfs_iop_rename,
904 static struct kernfs_node *kernfs_leftmost_descendant(struct kernfs_node *pos)
906 struct kernfs_node *last;
913 if (kernfs_type(pos) != KERNFS_DIR)
916 rbn = rb_first(&pos->dir.children);
927 * kernfs_next_descendant_post - find the next descendant for post-order walk
928 * @pos: the current position (%NULL to initiate traversal)
929 * @root: kernfs_node whose descendants to walk
931 * Find the next descendant to visit for post-order traversal of @root's
932 * descendants. @root is included in the iteration and the last node to be
935 static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
936 struct kernfs_node *root)
940 lockdep_assert_held(&kernfs_mutex);
942 /* if first iteration, visit leftmost descendant which may be root */
944 return kernfs_leftmost_descendant(root);
946 /* if we visited @root, we're done */
950 /* if there's an unvisited sibling, visit its leftmost descendant */
951 rbn = rb_next(&pos->rb);
953 return kernfs_leftmost_descendant(rb_to_kn(rbn));
955 /* no sibling left, visit parent */
960 * kernfs_activate - activate a node which started deactivated
961 * @kn: kernfs_node whose subtree is to be activated
963 * If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node
964 * needs to be explicitly activated. A node which hasn't been activated
965 * isn't visible to userland and deactivation is skipped during its
966 * removal. This is useful to construct atomic init sequences where
967 * creation of multiple nodes should either succeed or fail atomically.
969 * The caller is responsible for ensuring that this function is not called
970 * after kernfs_remove*() is invoked on @kn.
972 void kernfs_activate(struct kernfs_node *kn)
974 struct kernfs_node *pos;
976 mutex_lock(&kernfs_mutex);
979 while ((pos = kernfs_next_descendant_post(pos, kn))) {
980 if (!pos || (pos->flags & KERNFS_ACTIVATED))
983 WARN_ON_ONCE(pos->parent && RB_EMPTY_NODE(&pos->rb));
984 WARN_ON_ONCE(atomic_read(&pos->active) != KN_DEACTIVATED_BIAS);
986 atomic_sub(KN_DEACTIVATED_BIAS, &pos->active);
987 pos->flags |= KERNFS_ACTIVATED;
990 mutex_unlock(&kernfs_mutex);
993 static void __kernfs_remove(struct kernfs_node *kn)
995 struct kernfs_node *pos;
997 lockdep_assert_held(&kernfs_mutex);
1000 * Short-circuit if non-root @kn has already finished removal.
1001 * This is for kernfs_remove_self() which plays with active ref
1004 if (!kn || (kn->parent && RB_EMPTY_NODE(&kn->rb)))
1007 pr_debug("kernfs %s: removing\n", kn->name);
1009 /* prevent any new usage under @kn by deactivating all nodes */
1011 while ((pos = kernfs_next_descendant_post(pos, kn)))
1012 if (kernfs_active(pos))
1013 atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
1015 /* deactivate and unlink the subtree node-by-node */
1017 pos = kernfs_leftmost_descendant(kn);
1020 * kernfs_drain() drops kernfs_mutex temporarily and @pos's
1021 * base ref could have been put by someone else by the time
1022 * the function returns. Make sure it doesn't go away
1028 * Drain iff @kn was activated. This avoids draining and
1029 * its lockdep annotations for nodes which have never been
1030 * activated and allows embedding kernfs_remove() in create
1031 * error paths without worrying about draining.
1033 if (kn->flags & KERNFS_ACTIVATED)
1036 WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
1039 * kernfs_unlink_sibling() succeeds once per node. Use it
1040 * to decide who's responsible for cleanups.
1042 if (!pos->parent || kernfs_unlink_sibling(pos)) {
1043 struct kernfs_iattrs *ps_iattr =
1044 pos->parent ? pos->parent->iattr : NULL;
1046 /* update timestamps on the parent */
1048 ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
1049 ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
1056 } while (pos != kn);
1060 * kernfs_remove - remove a kernfs_node recursively
1061 * @kn: the kernfs_node to remove
1063 * Remove @kn along with all its subdirectories and files.
1065 void kernfs_remove(struct kernfs_node *kn)
1067 mutex_lock(&kernfs_mutex);
1068 __kernfs_remove(kn);
1069 mutex_unlock(&kernfs_mutex);
1073 * kernfs_break_active_protection - break out of active protection
1074 * @kn: the self kernfs_node
1076 * The caller must be running off of a kernfs operation which is invoked
1077 * with an active reference - e.g. one of kernfs_ops. Each invocation of
1078 * this function must also be matched with an invocation of
1079 * kernfs_unbreak_active_protection().
1081 * This function releases the active reference of @kn the caller is
1082 * holding. Once this function is called, @kn may be removed at any point
1083 * and the caller is solely responsible for ensuring that the objects it
1084 * dereferences are accessible.
1086 void kernfs_break_active_protection(struct kernfs_node *kn)
1089 * Take out ourself out of the active ref dependency chain. If
1090 * we're called without an active ref, lockdep will complain.
1092 kernfs_put_active(kn);
1096 * kernfs_unbreak_active_protection - undo kernfs_break_active_protection()
1097 * @kn: the self kernfs_node
1099 * If kernfs_break_active_protection() was called, this function must be
1100 * invoked before finishing the kernfs operation. Note that while this
1101 * function restores the active reference, it doesn't and can't actually
1102 * restore the active protection - @kn may already or be in the process of
1103 * being removed. Once kernfs_break_active_protection() is invoked, that
1104 * protection is irreversibly gone for the kernfs operation instance.
1106 * While this function may be called at any point after
1107 * kernfs_break_active_protection() is invoked, its most useful location
1108 * would be right before the enclosing kernfs operation returns.
1110 void kernfs_unbreak_active_protection(struct kernfs_node *kn)
1113 * @kn->active could be in any state; however, the increment we do
1114 * here will be undone as soon as the enclosing kernfs operation
1115 * finishes and this temporary bump can't break anything. If @kn
1116 * is alive, nothing changes. If @kn is being deactivated, the
1117 * soon-to-follow put will either finish deactivation or restore
1118 * deactivated state. If @kn is already removed, the temporary
1119 * bump is guaranteed to be gone before @kn is released.
1121 atomic_inc(&kn->active);
1122 if (kernfs_lockdep(kn))
1123 rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_);
1127 * kernfs_remove_self - remove a kernfs_node from its own method
1128 * @kn: the self kernfs_node to remove
1130 * The caller must be running off of a kernfs operation which is invoked
1131 * with an active reference - e.g. one of kernfs_ops. This can be used to
1132 * implement a file operation which deletes itself.
1134 * For example, the "delete" file for a sysfs device directory can be
1135 * implemented by invoking kernfs_remove_self() on the "delete" file
1136 * itself. This function breaks the circular dependency of trying to
1137 * deactivate self while holding an active ref itself. It isn't necessary
1138 * to modify the usual removal path to use kernfs_remove_self(). The
1139 * "delete" implementation can simply invoke kernfs_remove_self() on self
1140 * before proceeding with the usual removal path. kernfs will ignore later
1141 * kernfs_remove() on self.
1143 * kernfs_remove_self() can be called multiple times concurrently on the
1144 * same kernfs_node. Only the first one actually performs removal and
1145 * returns %true. All others will wait until the kernfs operation which
1146 * won self-removal finishes and return %false. Note that the losers wait
1147 * for the completion of not only the winning kernfs_remove_self() but also
1148 * the whole kernfs_ops which won the arbitration. This can be used to
1149 * guarantee, for example, all concurrent writes to a "delete" file to
1150 * finish only after the whole operation is complete.
1152 bool kernfs_remove_self(struct kernfs_node *kn)
1156 mutex_lock(&kernfs_mutex);
1157 kernfs_break_active_protection(kn);
1160 * SUICIDAL is used to arbitrate among competing invocations. Only
1161 * the first one will actually perform removal. When the removal
1162 * is complete, SUICIDED is set and the active ref is restored
1163 * while holding kernfs_mutex. The ones which lost arbitration
1164 * waits for SUICDED && drained which can happen only after the
1165 * enclosing kernfs operation which executed the winning instance
1166 * of kernfs_remove_self() finished.
1168 if (!(kn->flags & KERNFS_SUICIDAL)) {
1169 kn->flags |= KERNFS_SUICIDAL;
1170 __kernfs_remove(kn);
1171 kn->flags |= KERNFS_SUICIDED;
1174 wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
1178 prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE);
1180 if ((kn->flags & KERNFS_SUICIDED) &&
1181 atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
1184 mutex_unlock(&kernfs_mutex);
1186 mutex_lock(&kernfs_mutex);
1188 finish_wait(waitq, &wait);
1189 WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
1194 * This must be done while holding kernfs_mutex; otherwise, waiting
1195 * for SUICIDED && deactivated could finish prematurely.
1197 kernfs_unbreak_active_protection(kn);
1199 mutex_unlock(&kernfs_mutex);
1204 * kernfs_remove_by_name_ns - find a kernfs_node by name and remove it
1205 * @parent: parent of the target
1206 * @name: name of the kernfs_node to remove
1207 * @ns: namespace tag of the kernfs_node to remove
1209 * Look for the kernfs_node with @name and @ns under @parent and remove it.
1210 * Returns 0 on success, -ENOENT if such entry doesn't exist.
1212 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
1215 struct kernfs_node *kn;
1218 WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
1223 mutex_lock(&kernfs_mutex);
1225 kn = kernfs_find_ns(parent, name, ns);
1227 __kernfs_remove(kn);
1229 mutex_unlock(&kernfs_mutex);
1238 * kernfs_rename_ns - move and rename a kernfs_node
1240 * @new_parent: new parent to put @sd under
1241 * @new_name: new name
1242 * @new_ns: new namespace tag
1244 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
1245 const char *new_name, const void *new_ns)
1247 struct kernfs_node *old_parent;
1248 const char *old_name = NULL;
1251 /* can't move or rename root */
1255 mutex_lock(&kernfs_mutex);
1258 if (!kernfs_active(kn) || !kernfs_active(new_parent))
1262 if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
1263 (strcmp(kn->name, new_name) == 0))
1264 goto out; /* nothing to rename */
1267 if (kernfs_find_ns(new_parent, new_name, new_ns))
1270 /* rename kernfs_node */
1271 if (strcmp(kn->name, new_name) != 0) {
1273 new_name = kstrdup(new_name, GFP_KERNEL);
1281 * Move to the appropriate place in the appropriate directories rbtree.
1283 kernfs_unlink_sibling(kn);
1284 kernfs_get(new_parent);
1286 /* rename_lock protects ->parent and ->name accessors */
1287 spin_lock_irq(&kernfs_rename_lock);
1289 old_parent = kn->parent;
1290 kn->parent = new_parent;
1294 if (!(kn->flags & KERNFS_STATIC_NAME))
1295 old_name = kn->name;
1296 kn->flags &= ~KERNFS_STATIC_NAME;
1297 kn->name = new_name;
1300 spin_unlock_irq(&kernfs_rename_lock);
1302 kn->hash = kernfs_name_hash(kn->name, kn->ns);
1303 kernfs_link_sibling(kn);
1305 kernfs_put(old_parent);
1310 mutex_unlock(&kernfs_mutex);
1314 /* Relationship between s_mode and the DT_xxx types */
1315 static inline unsigned char dt_type(struct kernfs_node *kn)
1317 return (kn->mode >> 12) & 15;
1320 static int kernfs_dir_fop_release(struct inode *inode, struct file *filp)
1322 kernfs_put(filp->private_data);
1326 static struct kernfs_node *kernfs_dir_pos(const void *ns,
1327 struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos)
1330 int valid = kernfs_active(pos) &&
1331 pos->parent == parent && hash == pos->hash;
1336 if (!pos && (hash > 1) && (hash < INT_MAX)) {
1337 struct rb_node *node = parent->dir.children.rb_node;
1339 pos = rb_to_kn(node);
1341 if (hash < pos->hash)
1342 node = node->rb_left;
1343 else if (hash > pos->hash)
1344 node = node->rb_right;
1349 /* Skip over entries which are dying/dead or in the wrong namespace */
1350 while (pos && (!kernfs_active(pos) || pos->ns != ns)) {
1351 struct rb_node *node = rb_next(&pos->rb);
1355 pos = rb_to_kn(node);
1360 static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
1361 struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
1363 pos = kernfs_dir_pos(ns, parent, ino, pos);
1366 struct rb_node *node = rb_next(&pos->rb);
1370 pos = rb_to_kn(node);
1371 } while (pos && (!kernfs_active(pos) || pos->ns != ns));
1376 static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
1378 struct dentry *dentry = file->f_path.dentry;
1379 struct kernfs_node *parent = dentry->d_fsdata;
1380 struct kernfs_node *pos = file->private_data;
1381 const void *ns = NULL;
1383 if (!dir_emit_dots(file, ctx))
1385 mutex_lock(&kernfs_mutex);
1387 if (kernfs_ns_enabled(parent))
1388 ns = kernfs_info(dentry->d_sb)->ns;
1390 for (pos = kernfs_dir_pos(ns, parent, ctx->pos, pos);
1392 pos = kernfs_dir_next_pos(ns, parent, ctx->pos, pos)) {
1393 const char *name = pos->name;
1394 unsigned int type = dt_type(pos);
1395 int len = strlen(name);
1396 ino_t ino = pos->ino;
1398 ctx->pos = pos->hash;
1399 file->private_data = pos;
1402 mutex_unlock(&kernfs_mutex);
1403 if (!dir_emit(ctx, name, len, ino, type))
1405 mutex_lock(&kernfs_mutex);
1407 mutex_unlock(&kernfs_mutex);
1408 file->private_data = NULL;
1413 static loff_t kernfs_dir_fop_llseek(struct file *file, loff_t offset,
1416 struct inode *inode = file_inode(file);
1419 mutex_lock(&inode->i_mutex);
1420 ret = generic_file_llseek(file, offset, whence);
1421 mutex_unlock(&inode->i_mutex);
1426 const struct file_operations kernfs_dir_fops = {
1427 .read = generic_read_dir,
1428 .iterate = kernfs_fop_readdir,
1429 .release = kernfs_dir_fop_release,
1430 .llseek = kernfs_dir_fop_llseek,