xref: /openbmc/linux/fs/overlayfs/util.c (revision 4e1a33b1)
1 /*
2  * Copyright (C) 2011 Novell Inc.
3  * Copyright (C) 2016 Red Hat, Inc.
4  *
5  * This program is free software; you can redistribute it and/or modify it
6  * under the terms of the GNU General Public License version 2 as published by
7  * the Free Software Foundation.
8  */
9 
10 #include <linux/fs.h>
11 #include <linux/mount.h>
12 #include <linux/slab.h>
13 #include <linux/xattr.h>
14 #include "overlayfs.h"
15 #include "ovl_entry.h"
16 
17 int ovl_want_write(struct dentry *dentry)
18 {
19 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
20 	return mnt_want_write(ofs->upper_mnt);
21 }
22 
23 void ovl_drop_write(struct dentry *dentry)
24 {
25 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
26 	mnt_drop_write(ofs->upper_mnt);
27 }
28 
29 struct dentry *ovl_workdir(struct dentry *dentry)
30 {
31 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
32 	return ofs->workdir;
33 }
34 
35 const struct cred *ovl_override_creds(struct super_block *sb)
36 {
37 	struct ovl_fs *ofs = sb->s_fs_info;
38 
39 	return override_creds(ofs->creator_cred);
40 }
41 
42 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
43 {
44 	size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
45 	struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
46 
47 	if (oe)
48 		oe->numlower = numlower;
49 
50 	return oe;
51 }
52 
53 bool ovl_dentry_remote(struct dentry *dentry)
54 {
55 	return dentry->d_flags &
56 		(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
57 		 DCACHE_OP_REAL);
58 }
59 
60 bool ovl_dentry_weird(struct dentry *dentry)
61 {
62 	return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
63 				  DCACHE_MANAGE_TRANSIT |
64 				  DCACHE_OP_HASH |
65 				  DCACHE_OP_COMPARE);
66 }
67 
68 enum ovl_path_type ovl_path_type(struct dentry *dentry)
69 {
70 	struct ovl_entry *oe = dentry->d_fsdata;
71 	enum ovl_path_type type = 0;
72 
73 	if (oe->__upperdentry) {
74 		type = __OVL_PATH_UPPER;
75 
76 		/*
77 		 * Non-dir dentry can hold lower dentry from previous
78 		 * location.
79 		 */
80 		if (oe->numlower && d_is_dir(dentry))
81 			type |= __OVL_PATH_MERGE;
82 	} else {
83 		if (oe->numlower > 1)
84 			type |= __OVL_PATH_MERGE;
85 	}
86 	return type;
87 }
88 
89 void ovl_path_upper(struct dentry *dentry, struct path *path)
90 {
91 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
92 	struct ovl_entry *oe = dentry->d_fsdata;
93 
94 	path->mnt = ofs->upper_mnt;
95 	path->dentry = ovl_upperdentry_dereference(oe);
96 }
97 
98 void ovl_path_lower(struct dentry *dentry, struct path *path)
99 {
100 	struct ovl_entry *oe = dentry->d_fsdata;
101 
102 	*path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
103 }
104 
105 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
106 {
107 	enum ovl_path_type type = ovl_path_type(dentry);
108 
109 	if (!OVL_TYPE_UPPER(type))
110 		ovl_path_lower(dentry, path);
111 	else
112 		ovl_path_upper(dentry, path);
113 
114 	return type;
115 }
116 
117 struct dentry *ovl_dentry_upper(struct dentry *dentry)
118 {
119 	struct ovl_entry *oe = dentry->d_fsdata;
120 
121 	return ovl_upperdentry_dereference(oe);
122 }
123 
124 static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
125 {
126 	return oe->numlower ? oe->lowerstack[0].dentry : NULL;
127 }
128 
129 struct dentry *ovl_dentry_lower(struct dentry *dentry)
130 {
131 	struct ovl_entry *oe = dentry->d_fsdata;
132 
133 	return __ovl_dentry_lower(oe);
134 }
135 
136 struct dentry *ovl_dentry_real(struct dentry *dentry)
137 {
138 	struct ovl_entry *oe = dentry->d_fsdata;
139 	struct dentry *realdentry;
140 
141 	realdentry = ovl_upperdentry_dereference(oe);
142 	if (!realdentry)
143 		realdentry = __ovl_dentry_lower(oe);
144 
145 	return realdentry;
146 }
147 
148 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
149 {
150 	struct ovl_entry *oe = dentry->d_fsdata;
151 
152 	return oe->cache;
153 }
154 
155 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
156 {
157 	struct ovl_entry *oe = dentry->d_fsdata;
158 
159 	oe->cache = cache;
160 }
161 
162 bool ovl_dentry_is_opaque(struct dentry *dentry)
163 {
164 	struct ovl_entry *oe = dentry->d_fsdata;
165 	return oe->opaque;
166 }
167 
168 bool ovl_dentry_is_whiteout(struct dentry *dentry)
169 {
170 	return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
171 }
172 
173 void ovl_dentry_set_opaque(struct dentry *dentry)
174 {
175 	struct ovl_entry *oe = dentry->d_fsdata;
176 
177 	oe->opaque = true;
178 }
179 
180 bool ovl_redirect_dir(struct super_block *sb)
181 {
182 	struct ovl_fs *ofs = sb->s_fs_info;
183 
184 	return ofs->config.redirect_dir;
185 }
186 
187 void ovl_clear_redirect_dir(struct super_block *sb)
188 {
189 	struct ovl_fs *ofs = sb->s_fs_info;
190 
191 	ofs->config.redirect_dir = false;
192 }
193 
194 const char *ovl_dentry_get_redirect(struct dentry *dentry)
195 {
196 	struct ovl_entry *oe = dentry->d_fsdata;
197 
198 	return oe->redirect;
199 }
200 
201 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
202 {
203 	struct ovl_entry *oe = dentry->d_fsdata;
204 
205 	kfree(oe->redirect);
206 	oe->redirect = redirect;
207 }
208 
209 void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
210 {
211 	struct ovl_entry *oe = dentry->d_fsdata;
212 
213 	WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
214 	WARN_ON(oe->__upperdentry);
215 	/*
216 	 * Make sure upperdentry is consistent before making it visible to
217 	 * ovl_upperdentry_dereference().
218 	 */
219 	smp_wmb();
220 	oe->__upperdentry = upperdentry;
221 }
222 
223 void ovl_inode_init(struct inode *inode, struct inode *realinode, bool is_upper)
224 {
225 	WRITE_ONCE(inode->i_private, (unsigned long) realinode |
226 		   (is_upper ? OVL_ISUPPER_MASK : 0));
227 }
228 
229 void ovl_inode_update(struct inode *inode, struct inode *upperinode)
230 {
231 	WARN_ON(!upperinode);
232 	WARN_ON(!inode_unhashed(inode));
233 	WRITE_ONCE(inode->i_private,
234 		   (unsigned long) upperinode | OVL_ISUPPER_MASK);
235 	if (!S_ISDIR(upperinode->i_mode))
236 		__insert_inode_hash(inode, (unsigned long) upperinode);
237 }
238 
239 void ovl_dentry_version_inc(struct dentry *dentry)
240 {
241 	struct ovl_entry *oe = dentry->d_fsdata;
242 
243 	WARN_ON(!inode_is_locked(dentry->d_inode));
244 	oe->version++;
245 }
246 
247 u64 ovl_dentry_version_get(struct dentry *dentry)
248 {
249 	struct ovl_entry *oe = dentry->d_fsdata;
250 
251 	WARN_ON(!inode_is_locked(dentry->d_inode));
252 	return oe->version;
253 }
254 
255 bool ovl_is_whiteout(struct dentry *dentry)
256 {
257 	struct inode *inode = dentry->d_inode;
258 
259 	return inode && IS_WHITEOUT(inode);
260 }
261 
262 struct file *ovl_path_open(struct path *path, int flags)
263 {
264 	return dentry_open(path, flags | O_NOATIME, current_cred());
265 }
266