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 simple_xattrs	xattrs;
30 	atomic_t		nr_user_xattrs;
31 	atomic_t		user_xattr_size;
32 };
33 
34 struct kernfs_root {
35 	/* published fields */
36 	struct kernfs_node	*kn;
37 	unsigned int		flags;	/* KERNFS_ROOT_* flags */
38 
39 	/* private fields, do not use outside kernfs proper */
40 	struct idr		ino_idr;
41 	spinlock_t		kernfs_idr_lock;	/* root->ino_idr */
42 	u32			last_id_lowbits;
43 	u32			id_highbits;
44 	struct kernfs_syscall_ops *syscall_ops;
45 
46 	/* list of kernfs_super_info of this root, protected by kernfs_rwsem */
47 	struct list_head	supers;
48 
49 	wait_queue_head_t	deactivate_waitq;
50 	struct rw_semaphore	kernfs_rwsem;
51 	struct rw_semaphore	kernfs_iattr_rwsem;
52 	struct rw_semaphore	kernfs_supers_rwsem;
53 
54 	/* kn->parent and kn->name */
55 	rwlock_t		kernfs_rename_lock;
56 
57 	struct rcu_head		rcu;
58 };
59 
60 /* +1 to avoid triggering overflow warning when negating it */
61 #define KN_DEACTIVATED_BIAS		(INT_MIN + 1)
62 
63 /* KERNFS_TYPE_MASK and types are defined in include/linux/kernfs.h */
64 
65 /**
66  * kernfs_root - find out the kernfs_root a kernfs_node belongs to
67  * @kn: kernfs_node of interest
68  *
69  * Return: the kernfs_root @kn belongs to.
70  */
71 static inline struct kernfs_root *kernfs_root(const struct kernfs_node *kn)
72 {
73 	const struct kernfs_node *knp;
74 	/* if parent exists, it's always a dir; otherwise, @sd is a dir */
75 	guard(rcu)();
76 	knp = rcu_dereference(kn->__parent);
77 	if (knp)
78 		kn = knp;
79 	return kn->dir.root;
80 }
81 
82 /*
83  * mount.c
84  */
85 struct kernfs_super_info {
86 	struct super_block	*sb;
87 
88 	/*
89 	 * The root associated with this super_block.  Each super_block is
90 	 * identified by the root and ns it's associated with.
91 	 */
92 	struct kernfs_root	*root;
93 
94 	/*
95 	 * Each sb is associated with one namespace tag, currently the
96 	 * network namespace of the task which mounted this kernfs
97 	 * instance.  If multiple tags become necessary, make the following
98 	 * an array and compare kernfs_node tag against every entry.
99 	 */
100 	const void		*ns;
101 
102 	/* anchored at kernfs_root->supers, protected by kernfs_rwsem */
103 	struct list_head	node;
104 };
105 #define kernfs_info(SB) ((struct kernfs_super_info *)(SB->s_fs_info))
106 
107 static inline bool kernfs_root_is_locked(const struct kernfs_node *kn)
108 {
109 	return lockdep_is_held(&kernfs_root(kn)->kernfs_rwsem);
110 }
111 
112 static inline bool kernfs_rename_is_locked(const struct kernfs_node *kn)
113 {
114 	return lockdep_is_held(&kernfs_root(kn)->kernfs_rename_lock);
115 }
116 
117 static inline const char *kernfs_rcu_name(const struct kernfs_node *kn)
118 {
119 	return rcu_dereference_check(kn->name, kernfs_root_is_locked(kn));
120 }
121 
122 static inline struct kernfs_node *kernfs_parent(const struct kernfs_node *kn)
123 {
124 	/*
125 	 * The kernfs_node::__parent remains valid within a RCU section. The kn
126 	 * can be reparented (and renamed) which changes the entry. This can be
127 	 * avoided by locking kernfs_root::kernfs_rwsem or
128 	 * kernfs_root::kernfs_rename_lock.
129 	 * Both locks can be used to obtain a reference on __parent. Once the
130 	 * reference count reaches 0 then the node is about to be freed
131 	 * and can not be renamed (or become a different parent) anymore.
132 	 */
133 	return rcu_dereference_check(kn->__parent,
134 				     kernfs_root_is_locked(kn) ||
135 				     kernfs_rename_is_locked(kn) ||
136 				     !atomic_read(&kn->count));
137 }
138 
139 static inline struct kernfs_node *kernfs_dentry_node(struct dentry *dentry)
140 {
141 	if (d_really_is_negative(dentry))
142 		return NULL;
143 	return d_inode(dentry)->i_private;
144 }
145 
146 static inline void kernfs_set_rev(struct kernfs_node *parent,
147 				  struct dentry *dentry)
148 {
149 	dentry->d_time = parent->dir.rev;
150 }
151 
152 static inline void kernfs_inc_rev(struct kernfs_node *parent)
153 {
154 	parent->dir.rev++;
155 }
156 
157 static inline bool kernfs_dir_changed(struct kernfs_node *parent,
158 				      struct dentry *dentry)
159 {
160 	if (parent->dir.rev != dentry->d_time)
161 		return true;
162 	return false;
163 }
164 
165 extern const struct super_operations kernfs_sops;
166 extern struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;
167 
168 /*
169  * inode.c
170  */
171 extern const struct xattr_handler * const kernfs_xattr_handlers[];
172 void kernfs_evict_inode(struct inode *inode);
173 int kernfs_iop_permission(struct mnt_idmap *idmap,
174 			  struct inode *inode, int mask);
175 int kernfs_iop_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
176 		       struct iattr *iattr);
177 int kernfs_iop_getattr(struct mnt_idmap *idmap,
178 		       const struct path *path, struct kstat *stat,
179 		       u32 request_mask, unsigned int query_flags);
180 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size);
181 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
182 
183 /*
184  * dir.c
185  */
186 extern const struct dentry_operations kernfs_dops;
187 extern const struct file_operations kernfs_dir_fops;
188 extern const struct inode_operations kernfs_dir_iops;
189 
190 struct kernfs_node *kernfs_get_active(struct kernfs_node *kn);
191 void kernfs_put_active(struct kernfs_node *kn);
192 int kernfs_add_one(struct kernfs_node *kn);
193 struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
194 				    const char *name, umode_t mode,
195 				    kuid_t uid, kgid_t gid,
196 				    unsigned flags);
197 
198 /*
199  * file.c
200  */
201 extern const struct file_operations kernfs_file_fops;
202 
203 bool kernfs_should_drain_open_files(struct kernfs_node *kn);
204 void kernfs_drain_open_files(struct kernfs_node *kn);
205 
206 /*
207  * symlink.c
208  */
209 extern const struct inode_operations kernfs_symlink_iops;
210 
211 /*
212  * kernfs locks
213  */
214 extern struct kernfs_global_locks *kernfs_locks;
215 #endif	/* __KERNFS_INTERNAL_H */
216