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 }