1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * fs/kernfs/kernfs-internal.h - kernfs internal header file
4 *
5 * Copyright (c) 2001-3 Patrick Mochel
6 * Copyright (c) 2007 SUSE Linux Products GmbH
7 * Copyright (c) 2007, 2013 Tejun Heo <teheo@suse.de>
8 */
9
10 #ifndef __KERNFS_INTERNAL_H
11 #define __KERNFS_INTERNAL_H
12
13 #include <linux/lockdep.h>
14 #include <linux/fs.h>
15 #include <linux/mutex.h>
16 #include <linux/rwsem.h>
17 #include <linux/xattr.h>
18
19 #include <linux/kernfs.h>
20 #include <linux/fs_context.h>
21
22 struct kernfs_iattrs {
23 kuid_t ia_uid;
24 kgid_t ia_gid;
25 struct timespec64 ia_atime;
26 struct timespec64 ia_mtime;
27 struct timespec64 ia_ctime;
28
29 struct list_head xattrs;
30 struct simple_xattr_limits xattr_limits;
31 };
32
33 struct kernfs_root {
34 /* published fields */
35 struct kernfs_node *kn;
36 unsigned int flags; /* KERNFS_ROOT_* flags */
37
38 /* private fields, do not use outside kernfs proper */
39 struct idr ino_idr;
40 spinlock_t kernfs_idr_lock; /* root->ino_idr */
41 u32 last_id_lowbits;
42 u32 id_highbits;
43 struct kernfs_syscall_ops *syscall_ops;
44
45 /* list of kernfs_super_info of this root, protected by kernfs_rwsem */
46 struct list_head supers;
47
48 wait_queue_head_t deactivate_waitq;
49 struct rw_semaphore kernfs_rwsem;
50 struct rw_semaphore kernfs_iattr_rwsem;
51 struct rw_semaphore kernfs_supers_rwsem;
52
53 /* kn->parent and kn->name */
54 rwlock_t kernfs_rename_lock;
55
56 struct rcu_head rcu;
57
58 struct simple_xattr_cache xa_cache;
59 };
60
61 /* +1 to avoid triggering overflow warning when negating it */
62 #define KN_DEACTIVATED_BIAS (INT_MIN + 1)
63
64 /* KERNFS_TYPE_MASK and types are defined in include/linux/kernfs.h */
65
66 /**
67 * kernfs_root - find out the kernfs_root a kernfs_node belongs to
68 * @kn: kernfs_node of interest
69 *
70 * Return: the kernfs_root @kn belongs to.
71 */
kernfs_root(const struct kernfs_node * kn)72 static inline struct kernfs_root *kernfs_root(const struct kernfs_node *kn)
73 {
74 const struct kernfs_node *knp;
75 /* if parent exists, it's always a dir; otherwise, @sd is a dir */
76 guard(rcu)();
77 knp = rcu_dereference(kn->__parent);
78 if (knp)
79 kn = knp;
80 return kn->dir.root;
81 }
82
83 /*
84 * mount.c
85 */
86 struct kernfs_super_info {
87 struct super_block *sb;
88
89 /*
90 * The root associated with this super_block. Each super_block is
91 * identified by the root and ns it's associated with.
92 */
93 struct kernfs_root *root;
94
95 /*
96 * Each sb is associated with one namespace tag, currently the
97 * network namespace of the task which mounted this kernfs
98 * instance. If multiple tags become necessary, make the following
99 * an array and compare kernfs_node tag against every entry.
100 */
101 const struct ns_common *ns;
102
103 /* anchored at kernfs_root->supers, protected by kernfs_rwsem */
104 struct list_head node;
105 };
106 #define kernfs_info(SB) ((struct kernfs_super_info *)(SB->s_fs_info))
107
kernfs_root_is_locked(const struct kernfs_node * kn)108 static inline bool kernfs_root_is_locked(const struct kernfs_node *kn)
109 {
110 return lockdep_is_held(&kernfs_root(kn)->kernfs_rwsem);
111 }
112
kernfs_rename_is_locked(const struct kernfs_node * kn)113 static inline bool kernfs_rename_is_locked(const struct kernfs_node *kn)
114 {
115 return lockdep_is_held(&kernfs_root(kn)->kernfs_rename_lock);
116 }
117
kernfs_rcu_name(const struct kernfs_node * kn)118 static inline const char *kernfs_rcu_name(const struct kernfs_node *kn)
119 {
120 /*
121 * Like kernfs_node::__parent below, the name is only replaced under
122 * both kernfs_root::kernfs_rwsem and kernfs_root::kernfs_rename_lock,
123 * so either one keeps it, and the string it points at, stable.
124 */
125 return rcu_dereference_check(kn->name,
126 kernfs_root_is_locked(kn) ||
127 kernfs_rename_is_locked(kn));
128 }
129
kernfs_parent(const struct kernfs_node * kn)130 static inline struct kernfs_node *kernfs_parent(const struct kernfs_node *kn)
131 {
132 /*
133 * The kernfs_node::__parent remains valid within a RCU section. The kn
134 * can be reparented (and renamed) which changes the entry. This can be
135 * avoided by locking kernfs_root::kernfs_rwsem or
136 * kernfs_root::kernfs_rename_lock.
137 * Both locks can be used to obtain a reference on __parent. Once the
138 * reference count reaches 0 then the node is about to be freed
139 * and can not be renamed (or become a different parent) anymore.
140 */
141 return rcu_dereference_check(kn->__parent,
142 kernfs_root_is_locked(kn) ||
143 kernfs_rename_is_locked(kn) ||
144 !atomic_read(&kn->count));
145 }
146
kernfs_dentry_node(struct dentry * dentry)147 static inline struct kernfs_node *kernfs_dentry_node(struct dentry *dentry)
148 {
149 if (d_really_is_negative(dentry))
150 return NULL;
151 return d_inode(dentry)->i_private;
152 }
153
kernfs_set_rev(struct kernfs_node * parent,struct dentry * dentry)154 static inline void kernfs_set_rev(struct kernfs_node *parent,
155 struct dentry *dentry)
156 {
157 WRITE_ONCE(dentry->d_time, READ_ONCE(parent->dir.rev));
158 }
159
kernfs_inc_rev(struct kernfs_node * parent)160 static inline void kernfs_inc_rev(struct kernfs_node *parent)
161 {
162 lockdep_assert_held_write(&parent->dir.root->kernfs_rwsem);
163 WRITE_ONCE(parent->dir.rev, parent->dir.rev + 1);
164 }
165
kernfs_dir_changed(struct kernfs_node * parent,struct dentry * dentry)166 static inline bool kernfs_dir_changed(struct kernfs_node *parent,
167 struct dentry *dentry)
168 {
169 return READ_ONCE(parent->dir.rev) != READ_ONCE(dentry->d_time);
170 }
171
172 extern const struct super_operations kernfs_sops;
173 extern struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;
174
175 /*
176 * inode.c
177 */
178 extern const struct xattr_handler * const kernfs_xattr_handlers[];
179 void kernfs_evict_inode(struct inode *inode);
180 int kernfs_iop_permission(const struct mnt_idmap *idmap,
181 struct inode *inode, int mask);
182 int kernfs_iop_setattr(const struct mnt_idmap *idmap, struct dentry *dentry,
183 struct iattr *iattr);
184 int kernfs_iop_getattr(const struct mnt_idmap *idmap,
185 const struct path *path, struct kstat *stat,
186 u32 request_mask, unsigned int query_flags);
187 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size);
188 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
189
190 /*
191 * dir.c
192 */
193 extern const struct dentry_operations kernfs_dops;
194 extern const struct file_operations kernfs_dir_fops;
195 extern const struct inode_operations kernfs_dir_iops;
196
197 struct kernfs_node *kernfs_get_active(struct kernfs_node *kn);
198 void kernfs_put_active(struct kernfs_node *kn);
199 int kernfs_add_one(struct kernfs_node *kn);
200 struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
201 const char *name, umode_t mode,
202 kuid_t uid, kgid_t gid,
203 unsigned flags);
204
205 /*
206 * file.c
207 */
208 extern const struct file_operations kernfs_file_fops;
209
210 bool kernfs_should_drain_open_files(struct kernfs_node *kn);
211 void kernfs_drain_open_files(struct kernfs_node *kn);
212
213 /*
214 * symlink.c
215 */
216 extern const struct inode_operations kernfs_symlink_iops;
217
218 /*
219 * kernfs locks
220 */
221 extern struct kernfs_global_locks *kernfs_locks;
222
223 /* Hashed mutex helpers - protect per-node data structures */
kernfs_node_lock_ptr(struct kernfs_node * kn)224 static inline struct mutex *kernfs_node_lock_ptr(struct kernfs_node *kn)
225 {
226 int idx = hash_ptr(kn, NR_KERNFS_LOCK_BITS);
227
228 return &kernfs_locks->node_mutex[idx];
229 }
230
kernfs_node_lock(struct kernfs_node * kn)231 static inline struct mutex *kernfs_node_lock(struct kernfs_node *kn)
232 {
233 struct mutex *lock = kernfs_node_lock_ptr(kn);
234
235 mutex_lock(lock);
236 return lock;
237 }
238
239 DEFINE_CLASS(kernfs_node_lock, struct mutex *,
240 mutex_unlock(_T), kernfs_node_lock(kn), struct kernfs_node *kn)
241
242 #endif /* __KERNFS_INTERNAL_H */
243