1953986ee6bc221f555f4c53f8129f9c865f91e5
[sfrench/cifs-2.6.git] / fs / overlayfs / util.c
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/cred.h>
14 #include <linux/xattr.h>
15 #include <linux/sched/signal.h>
16 #include "overlayfs.h"
17 #include "ovl_entry.h"
18
19 int ovl_want_write(struct dentry *dentry)
20 {
21         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
22         return mnt_want_write(ofs->upper_mnt);
23 }
24
25 void ovl_drop_write(struct dentry *dentry)
26 {
27         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
28         mnt_drop_write(ofs->upper_mnt);
29 }
30
31 struct dentry *ovl_workdir(struct dentry *dentry)
32 {
33         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
34         return ofs->workdir;
35 }
36
37 const struct cred *ovl_override_creds(struct super_block *sb)
38 {
39         struct ovl_fs *ofs = sb->s_fs_info;
40
41         return override_creds(ofs->creator_cred);
42 }
43
44 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
45 {
46         size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
47         struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
48
49         if (oe)
50                 oe->numlower = numlower;
51
52         return oe;
53 }
54
55 bool ovl_dentry_remote(struct dentry *dentry)
56 {
57         return dentry->d_flags &
58                 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
59                  DCACHE_OP_REAL);
60 }
61
62 bool ovl_dentry_weird(struct dentry *dentry)
63 {
64         return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
65                                   DCACHE_MANAGE_TRANSIT |
66                                   DCACHE_OP_HASH |
67                                   DCACHE_OP_COMPARE);
68 }
69
70 enum ovl_path_type ovl_path_type(struct dentry *dentry)
71 {
72         struct ovl_entry *oe = dentry->d_fsdata;
73         enum ovl_path_type type = 0;
74
75         if (oe->__upperdentry) {
76                 type = __OVL_PATH_UPPER;
77
78                 /*
79                  * Non-dir dentry can hold lower dentry from previous
80                  * location.
81                  */
82                 if (oe->numlower && d_is_dir(dentry))
83                         type |= __OVL_PATH_MERGE;
84         } else {
85                 if (oe->numlower > 1)
86                         type |= __OVL_PATH_MERGE;
87         }
88         return type;
89 }
90
91 void ovl_path_upper(struct dentry *dentry, struct path *path)
92 {
93         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
94         struct ovl_entry *oe = dentry->d_fsdata;
95
96         path->mnt = ofs->upper_mnt;
97         path->dentry = ovl_upperdentry_dereference(oe);
98 }
99
100 void ovl_path_lower(struct dentry *dentry, struct path *path)
101 {
102         struct ovl_entry *oe = dentry->d_fsdata;
103
104         *path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
105 }
106
107 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
108 {
109         enum ovl_path_type type = ovl_path_type(dentry);
110
111         if (!OVL_TYPE_UPPER(type))
112                 ovl_path_lower(dentry, path);
113         else
114                 ovl_path_upper(dentry, path);
115
116         return type;
117 }
118
119 struct dentry *ovl_dentry_upper(struct dentry *dentry)
120 {
121         struct ovl_entry *oe = dentry->d_fsdata;
122
123         return ovl_upperdentry_dereference(oe);
124 }
125
126 static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
127 {
128         return oe->numlower ? oe->lowerstack[0].dentry : NULL;
129 }
130
131 struct dentry *ovl_dentry_lower(struct dentry *dentry)
132 {
133         struct ovl_entry *oe = dentry->d_fsdata;
134
135         return __ovl_dentry_lower(oe);
136 }
137
138 struct dentry *ovl_dentry_real(struct dentry *dentry)
139 {
140         struct ovl_entry *oe = dentry->d_fsdata;
141         struct dentry *realdentry;
142
143         realdentry = ovl_upperdentry_dereference(oe);
144         if (!realdentry)
145                 realdentry = __ovl_dentry_lower(oe);
146
147         return realdentry;
148 }
149
150 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
151 {
152         struct ovl_entry *oe = dentry->d_fsdata;
153
154         return oe->cache;
155 }
156
157 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
158 {
159         struct ovl_entry *oe = dentry->d_fsdata;
160
161         oe->cache = cache;
162 }
163
164 bool ovl_dentry_is_opaque(struct dentry *dentry)
165 {
166         struct ovl_entry *oe = dentry->d_fsdata;
167         return oe->opaque;
168 }
169
170 bool ovl_dentry_is_whiteout(struct dentry *dentry)
171 {
172         return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
173 }
174
175 void ovl_dentry_set_opaque(struct dentry *dentry)
176 {
177         struct ovl_entry *oe = dentry->d_fsdata;
178
179         oe->opaque = true;
180 }
181
182 bool ovl_redirect_dir(struct super_block *sb)
183 {
184         struct ovl_fs *ofs = sb->s_fs_info;
185
186         return ofs->config.redirect_dir;
187 }
188
189 void ovl_clear_redirect_dir(struct super_block *sb)
190 {
191         struct ovl_fs *ofs = sb->s_fs_info;
192
193         ofs->config.redirect_dir = false;
194 }
195
196 const char *ovl_dentry_get_redirect(struct dentry *dentry)
197 {
198         struct ovl_entry *oe = dentry->d_fsdata;
199
200         return oe->redirect;
201 }
202
203 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
204 {
205         struct ovl_entry *oe = dentry->d_fsdata;
206
207         kfree(oe->redirect);
208         oe->redirect = redirect;
209 }
210
211 void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
212 {
213         struct ovl_entry *oe = dentry->d_fsdata;
214
215         WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
216         WARN_ON(oe->__upperdentry);
217         /*
218          * Make sure upperdentry is consistent before making it visible to
219          * ovl_upperdentry_dereference().
220          */
221         smp_wmb();
222         oe->__upperdentry = upperdentry;
223 }
224
225 void ovl_inode_init(struct inode *inode, struct inode *realinode, bool is_upper)
226 {
227         WRITE_ONCE(inode->i_private, (unsigned long) realinode |
228                    (is_upper ? OVL_ISUPPER_MASK : 0));
229 }
230
231 void ovl_inode_update(struct inode *inode, struct inode *upperinode)
232 {
233         WARN_ON(!upperinode);
234         WARN_ON(!inode_unhashed(inode));
235         WRITE_ONCE(inode->i_private,
236                    (unsigned long) upperinode | OVL_ISUPPER_MASK);
237         if (!S_ISDIR(upperinode->i_mode))
238                 __insert_inode_hash(inode, (unsigned long) upperinode);
239 }
240
241 void ovl_dentry_version_inc(struct dentry *dentry)
242 {
243         struct ovl_entry *oe = dentry->d_fsdata;
244
245         WARN_ON(!inode_is_locked(dentry->d_inode));
246         oe->version++;
247 }
248
249 u64 ovl_dentry_version_get(struct dentry *dentry)
250 {
251         struct ovl_entry *oe = dentry->d_fsdata;
252
253         WARN_ON(!inode_is_locked(dentry->d_inode));
254         return oe->version;
255 }
256
257 bool ovl_is_whiteout(struct dentry *dentry)
258 {
259         struct inode *inode = dentry->d_inode;
260
261         return inode && IS_WHITEOUT(inode);
262 }
263
264 struct file *ovl_path_open(struct path *path, int flags)
265 {
266         return dentry_open(path, flags | O_NOATIME, current_cred());
267 }
268
269 int ovl_copy_up_start(struct dentry *dentry)
270 {
271         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
272         struct ovl_entry *oe = dentry->d_fsdata;
273         int err;
274
275         spin_lock(&ofs->copyup_wq.lock);
276         err = wait_event_interruptible_locked(ofs->copyup_wq, !oe->copying);
277         if (!err) {
278                 if (oe->__upperdentry)
279                         err = 1; /* Already copied up */
280                 else
281                         oe->copying = true;
282         }
283         spin_unlock(&ofs->copyup_wq.lock);
284
285         return err;
286 }
287
288 void ovl_copy_up_end(struct dentry *dentry)
289 {
290         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
291         struct ovl_entry *oe = dentry->d_fsdata;
292
293         spin_lock(&ofs->copyup_wq.lock);
294         oe->copying = false;
295         wake_up_locked(&ofs->copyup_wq);
296         spin_unlock(&ofs->copyup_wq.lock);
297 }