fix a braino in compat_sys_getrlimit()
[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 "overlayfs.h"
16 #include "ovl_entry.h"
17
18 int ovl_want_write(struct dentry *dentry)
19 {
20         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
21         return mnt_want_write(ofs->upper_mnt);
22 }
23
24 void ovl_drop_write(struct dentry *dentry)
25 {
26         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
27         mnt_drop_write(ofs->upper_mnt);
28 }
29
30 struct dentry *ovl_workdir(struct dentry *dentry)
31 {
32         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
33         return ofs->workdir;
34 }
35
36 const struct cred *ovl_override_creds(struct super_block *sb)
37 {
38         struct ovl_fs *ofs = sb->s_fs_info;
39
40         return override_creds(ofs->creator_cred);
41 }
42
43 struct super_block *ovl_same_sb(struct super_block *sb)
44 {
45         struct ovl_fs *ofs = sb->s_fs_info;
46
47         return ofs->same_sb;
48 }
49
50 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
51 {
52         size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
53         struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
54
55         if (oe)
56                 oe->numlower = numlower;
57
58         return oe;
59 }
60
61 bool ovl_dentry_remote(struct dentry *dentry)
62 {
63         return dentry->d_flags &
64                 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
65                  DCACHE_OP_REAL);
66 }
67
68 bool ovl_dentry_weird(struct dentry *dentry)
69 {
70         return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
71                                   DCACHE_MANAGE_TRANSIT |
72                                   DCACHE_OP_HASH |
73                                   DCACHE_OP_COMPARE);
74 }
75
76 enum ovl_path_type ovl_path_type(struct dentry *dentry)
77 {
78         struct ovl_entry *oe = dentry->d_fsdata;
79         enum ovl_path_type type = 0;
80
81         if (oe->__upperdentry) {
82                 type = __OVL_PATH_UPPER;
83
84                 /*
85                  * Non-dir dentry can hold lower dentry of its copy up origin.
86                  */
87                 if (oe->numlower) {
88                         type |= __OVL_PATH_ORIGIN;
89                         if (d_is_dir(dentry))
90                                 type |= __OVL_PATH_MERGE;
91                 }
92         } else {
93                 if (oe->numlower > 1)
94                         type |= __OVL_PATH_MERGE;
95         }
96         return type;
97 }
98
99 void ovl_path_upper(struct dentry *dentry, struct path *path)
100 {
101         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
102         struct ovl_entry *oe = dentry->d_fsdata;
103
104         path->mnt = ofs->upper_mnt;
105         path->dentry = ovl_upperdentry_dereference(oe);
106 }
107
108 void ovl_path_lower(struct dentry *dentry, struct path *path)
109 {
110         struct ovl_entry *oe = dentry->d_fsdata;
111
112         *path = oe->numlower ? oe->lowerstack[0] : (struct path) { };
113 }
114
115 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
116 {
117         enum ovl_path_type type = ovl_path_type(dentry);
118
119         if (!OVL_TYPE_UPPER(type))
120                 ovl_path_lower(dentry, path);
121         else
122                 ovl_path_upper(dentry, path);
123
124         return type;
125 }
126
127 struct dentry *ovl_dentry_upper(struct dentry *dentry)
128 {
129         struct ovl_entry *oe = dentry->d_fsdata;
130
131         return ovl_upperdentry_dereference(oe);
132 }
133
134 static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
135 {
136         return oe->numlower ? oe->lowerstack[0].dentry : NULL;
137 }
138
139 struct dentry *ovl_dentry_lower(struct dentry *dentry)
140 {
141         struct ovl_entry *oe = dentry->d_fsdata;
142
143         return __ovl_dentry_lower(oe);
144 }
145
146 struct dentry *ovl_dentry_real(struct dentry *dentry)
147 {
148         struct ovl_entry *oe = dentry->d_fsdata;
149         struct dentry *realdentry;
150
151         realdentry = ovl_upperdentry_dereference(oe);
152         if (!realdentry)
153                 realdentry = __ovl_dentry_lower(oe);
154
155         return realdentry;
156 }
157
158 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
159 {
160         struct ovl_entry *oe = dentry->d_fsdata;
161
162         return oe->cache;
163 }
164
165 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
166 {
167         struct ovl_entry *oe = dentry->d_fsdata;
168
169         oe->cache = cache;
170 }
171
172 bool ovl_dentry_is_opaque(struct dentry *dentry)
173 {
174         struct ovl_entry *oe = dentry->d_fsdata;
175         return oe->opaque;
176 }
177
178 bool ovl_dentry_is_impure(struct dentry *dentry)
179 {
180         struct ovl_entry *oe = dentry->d_fsdata;
181
182         return oe->impure;
183 }
184
185 bool ovl_dentry_is_whiteout(struct dentry *dentry)
186 {
187         return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
188 }
189
190 void ovl_dentry_set_opaque(struct dentry *dentry)
191 {
192         struct ovl_entry *oe = dentry->d_fsdata;
193
194         oe->opaque = true;
195 }
196
197 bool ovl_redirect_dir(struct super_block *sb)
198 {
199         struct ovl_fs *ofs = sb->s_fs_info;
200
201         return ofs->config.redirect_dir && !ofs->noxattr;
202 }
203
204 const char *ovl_dentry_get_redirect(struct dentry *dentry)
205 {
206         struct ovl_entry *oe = dentry->d_fsdata;
207
208         return oe->redirect;
209 }
210
211 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
212 {
213         struct ovl_entry *oe = dentry->d_fsdata;
214
215         kfree(oe->redirect);
216         oe->redirect = redirect;
217 }
218
219 void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
220 {
221         struct ovl_entry *oe = dentry->d_fsdata;
222
223         WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
224         WARN_ON(oe->__upperdentry);
225         /*
226          * Make sure upperdentry is consistent before making it visible to
227          * ovl_upperdentry_dereference().
228          */
229         smp_wmb();
230         oe->__upperdentry = upperdentry;
231 }
232
233 void ovl_inode_init(struct inode *inode, struct inode *realinode, bool is_upper)
234 {
235         WRITE_ONCE(inode->i_private, (unsigned long) realinode |
236                    (is_upper ? OVL_ISUPPER_MASK : 0));
237 }
238
239 void ovl_inode_update(struct inode *inode, struct inode *upperinode)
240 {
241         WARN_ON(!upperinode);
242         WARN_ON(!inode_unhashed(inode));
243         WRITE_ONCE(inode->i_private,
244                    (unsigned long) upperinode | OVL_ISUPPER_MASK);
245         if (!S_ISDIR(upperinode->i_mode))
246                 __insert_inode_hash(inode, (unsigned long) upperinode);
247 }
248
249 void ovl_dentry_version_inc(struct dentry *dentry)
250 {
251         struct ovl_entry *oe = dentry->d_fsdata;
252
253         WARN_ON(!inode_is_locked(dentry->d_inode));
254         oe->version++;
255 }
256
257 u64 ovl_dentry_version_get(struct dentry *dentry)
258 {
259         struct ovl_entry *oe = dentry->d_fsdata;
260
261         WARN_ON(!inode_is_locked(dentry->d_inode));
262         return oe->version;
263 }
264
265 bool ovl_is_whiteout(struct dentry *dentry)
266 {
267         struct inode *inode = dentry->d_inode;
268
269         return inode && IS_WHITEOUT(inode);
270 }
271
272 struct file *ovl_path_open(struct path *path, int flags)
273 {
274         return dentry_open(path, flags | O_NOATIME, current_cred());
275 }
276
277 int ovl_copy_up_start(struct dentry *dentry)
278 {
279         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
280         struct ovl_entry *oe = dentry->d_fsdata;
281         int err;
282
283         spin_lock(&ofs->copyup_wq.lock);
284         err = wait_event_interruptible_locked(ofs->copyup_wq, !oe->copying);
285         if (!err) {
286                 if (oe->__upperdentry)
287                         err = 1; /* Already copied up */
288                 else
289                         oe->copying = true;
290         }
291         spin_unlock(&ofs->copyup_wq.lock);
292
293         return err;
294 }
295
296 void ovl_copy_up_end(struct dentry *dentry)
297 {
298         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
299         struct ovl_entry *oe = dentry->d_fsdata;
300
301         spin_lock(&ofs->copyup_wq.lock);
302         oe->copying = false;
303         wake_up_locked(&ofs->copyup_wq);
304         spin_unlock(&ofs->copyup_wq.lock);
305 }
306
307 bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
308 {
309         int res;
310         char val;
311
312         if (!d_is_dir(dentry))
313                 return false;
314
315         res = vfs_getxattr(dentry, name, &val, 1);
316         if (res == 1 && val == 'y')
317                 return true;
318
319         return false;
320 }
321
322 int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
323                        const char *name, const void *value, size_t size,
324                        int xerr)
325 {
326         int err;
327         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
328
329         if (ofs->noxattr)
330                 return xerr;
331
332         err = ovl_do_setxattr(upperdentry, name, value, size, 0);
333
334         if (err == -EOPNOTSUPP) {
335                 pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
336                 ofs->noxattr = true;
337                 return xerr;
338         }
339
340         return err;
341 }
342
343 int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
344 {
345         int err;
346         struct ovl_entry *oe = dentry->d_fsdata;
347
348         if (oe->impure)
349                 return 0;
350
351         /*
352          * Do not fail when upper doesn't support xattrs.
353          * Upper inodes won't have origin nor redirect xattr anyway.
354          */
355         err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
356                                  "y", 1, 0);
357         if (!err)
358                 oe->impure = true;
359
360         return err;
361 }