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/exportfs.h>
  16 #include <linux/uuid.h>
  17 #include "overlayfs.h"
  18 #include "ovl_entry.h"
  19
  20 int ovl_want_write(struct dentry *dentry)
  21 {
  22         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  23         return mnt_want_write(ofs->upper_mnt);
  24 }
  25
  26 void ovl_drop_write(struct dentry *dentry)
  27 {
  28         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  29         mnt_drop_write(ofs->upper_mnt);
  30 }
  31
  32 struct dentry *ovl_workdir(struct dentry *dentry)
  33 {
  34         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  35         return ofs->workdir;
  36 }
  37
  38 const struct cred *ovl_override_creds(struct super_block *sb)
  39 {
  40         struct ovl_fs *ofs = sb->s_fs_info;
  41
  42         return override_creds(ofs->creator_cred);
  43 }
  44
  45 struct super_block *ovl_same_sb(struct super_block *sb)
  46 {
  47         struct ovl_fs *ofs = sb->s_fs_info;
  48
  49         return ofs->same_sb;
  50 }
  51
  52 bool ovl_can_decode_fh(struct super_block *sb)
  53 {
  54         return (sb->s_export_op && sb->s_export_op->fh_to_dentry &&
  55                 !uuid_is_null(&sb->s_uuid));
  56 }
  57
  58 struct dentry *ovl_indexdir(struct super_block *sb)
  59 {
  60         struct ovl_fs *ofs = sb->s_fs_info;
  61
  62         return ofs->indexdir;
  63 }
  64
  65 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
  66 {
  67         size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
  68         struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
  69
  70         if (oe)
  71                 oe->numlower = numlower;
  72
  73         return oe;
  74 }
  75
  76 bool ovl_dentry_remote(struct dentry *dentry)
  77 {
  78         return dentry->d_flags &
  79                 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
  80                  DCACHE_OP_REAL);
  81 }
  82
  83 bool ovl_dentry_weird(struct dentry *dentry)
  84 {
  85         return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
  86                                   DCACHE_MANAGE_TRANSIT |
  87                                   DCACHE_OP_HASH |
  88                                   DCACHE_OP_COMPARE);
  89 }
  90
  91 enum ovl_path_type ovl_path_type(struct dentry *dentry)
  92 {
  93         struct ovl_entry *oe = dentry->d_fsdata;
  94         enum ovl_path_type type = 0;
  95
  96         if (ovl_dentry_upper(dentry)) {
  97                 type = __OVL_PATH_UPPER;
  98
  99                 /*
 100                  * Non-dir dentry can hold lower dentry of its copy up origin.
 101                  */
 102                 if (oe->numlower) {
 103                         type |= __OVL_PATH_ORIGIN;
 104                         if (d_is_dir(dentry))
 105                                 type |= __OVL_PATH_MERGE;
 106                 }
 107         } else {
 108                 if (oe->numlower > 1)
 109                         type |= __OVL_PATH_MERGE;
 110         }
 111         return type;
 112 }
 113
 114 void ovl_path_upper(struct dentry *dentry, struct path *path)
 115 {
 116         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 117
 118         path->mnt = ofs->upper_mnt;
 119         path->dentry = ovl_dentry_upper(dentry);
 120 }
 121
 122 void ovl_path_lower(struct dentry *dentry, struct path *path)
 123 {
 124         struct ovl_entry *oe = dentry->d_fsdata;
 125
 126         *path = oe->numlower ? oe->lowerstack[0] : (struct path) { };
 127 }
 128
 129 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
 130 {
 131         enum ovl_path_type type = ovl_path_type(dentry);
 132
 133         if (!OVL_TYPE_UPPER(type))
 134                 ovl_path_lower(dentry, path);
 135         else
 136                 ovl_path_upper(dentry, path);
 137
 138         return type;
 139 }
 140
 141 struct dentry *ovl_dentry_upper(struct dentry *dentry)
 142 {
 143         return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
 144 }
 145
 146 struct dentry *ovl_dentry_lower(struct dentry *dentry)
 147 {
 148         struct ovl_entry *oe = dentry->d_fsdata;
 149
 150         return oe->numlower ? oe->lowerstack[0].dentry : NULL;
 151 }
 152
 153 struct dentry *ovl_dentry_real(struct dentry *dentry)
 154 {
 155         return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
 156 }
 157
 158 struct inode *ovl_inode_upper(struct inode *inode)
 159 {
 160         struct dentry *upperdentry = ovl_upperdentry_dereference(OVL_I(inode));
 161
 162         return upperdentry ? d_inode(upperdentry) : NULL;
 163 }
 164
 165 struct inode *ovl_inode_lower(struct inode *inode)
 166 {
 167         return OVL_I(inode)->lower;
 168 }
 169
 170 struct inode *ovl_inode_real(struct inode *inode)
 171 {
 172         return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
 173 }
 174
 175
 176 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
 177 {
 178         return OVL_I(d_inode(dentry))->cache;
 179 }
 180
 181 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
 182 {
 183         OVL_I(d_inode(dentry))->cache = cache;
 184 }
 185
 186 bool ovl_dentry_is_opaque(struct dentry *dentry)
 187 {
 188         struct ovl_entry *oe = dentry->d_fsdata;
 189         return oe->opaque;
 190 }
 191
 192 bool ovl_dentry_is_whiteout(struct dentry *dentry)
 193 {
 194         return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
 195 }
 196
 197 void ovl_dentry_set_opaque(struct dentry *dentry)
 198 {
 199         struct ovl_entry *oe = dentry->d_fsdata;
 200
 201         oe->opaque = true;
 202 }
 203
 204 /*
 205  * For hard links it's possible for ovl_dentry_upper() to return positive, while
 206  * there's no actual upper alias for the inode.  Copy up code needs to know
 207  * about the existence of the upper alias, so it can't use ovl_dentry_upper().
 208  */
 209 bool ovl_dentry_has_upper_alias(struct dentry *dentry)
 210 {
 211         struct ovl_entry *oe = dentry->d_fsdata;
 212
 213         return oe->has_upper;
 214 }
 215
 216 void ovl_dentry_set_upper_alias(struct dentry *dentry)
 217 {
 218         struct ovl_entry *oe = dentry->d_fsdata;
 219
 220         oe->has_upper = true;
 221 }
 222
 223 bool ovl_redirect_dir(struct super_block *sb)
 224 {
 225         struct ovl_fs *ofs = sb->s_fs_info;
 226
 227         return ofs->config.redirect_dir && !ofs->noxattr;
 228 }
 229
 230 const char *ovl_dentry_get_redirect(struct dentry *dentry)
 231 {
 232         return OVL_I(d_inode(dentry))->redirect;
 233 }
 234
 235 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
 236 {
 237         struct ovl_inode *oi = OVL_I(d_inode(dentry));
 238
 239         kfree(oi->redirect);
 240         oi->redirect = redirect;
 241 }
 242
 243 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
 244                     struct dentry *lowerdentry)
 245 {
 246         if (upperdentry)
 247                 OVL_I(inode)->__upperdentry = upperdentry;
 248         if (lowerdentry)
 249                 OVL_I(inode)->lower = d_inode(lowerdentry);
 250
 251         ovl_copyattr(d_inode(upperdentry ?: lowerdentry), inode);
 252 }
 253
 254 void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
 255 {
 256         struct inode *upperinode = d_inode(upperdentry);
 257
 258         WARN_ON(OVL_I(inode)->__upperdentry);
 259
 260         /*
 261          * Make sure upperdentry is consistent before making it visible
 262          */
 263         smp_wmb();
 264         OVL_I(inode)->__upperdentry = upperdentry;
 265         if (!S_ISDIR(upperinode->i_mode) && inode_unhashed(inode)) {
 266                 inode->i_private = upperinode;
 267                 __insert_inode_hash(inode, (unsigned long) upperinode);
 268         }
 269 }
 270
 271 void ovl_dentry_version_inc(struct dentry *dentry)
 272 {
 273         struct inode *inode = d_inode(dentry);
 274
 275         WARN_ON(!inode_is_locked(inode));
 276         OVL_I(inode)->version++;
 277 }
 278
 279 u64 ovl_dentry_version_get(struct dentry *dentry)
 280 {
 281         struct inode *inode = d_inode(dentry);
 282
 283         WARN_ON(!inode_is_locked(inode));
 284         return OVL_I(inode)->version;
 285 }
 286
 287 bool ovl_is_whiteout(struct dentry *dentry)
 288 {
 289         struct inode *inode = dentry->d_inode;
 290
 291         return inode && IS_WHITEOUT(inode);
 292 }
 293
 294 struct file *ovl_path_open(struct path *path, int flags)
 295 {
 296         return dentry_open(path, flags | O_NOATIME, current_cred());
 297 }
 298
 299 int ovl_copy_up_start(struct dentry *dentry)
 300 {
 301         struct ovl_inode *oi = OVL_I(d_inode(dentry));
 302         int err;
 303
 304         err = mutex_lock_interruptible(&oi->lock);
 305         if (!err && ovl_dentry_has_upper_alias(dentry)) {
 306                 err = 1; /* Already copied up */
 307                 mutex_unlock(&oi->lock);
 308         }
 309
 310         return err;
 311 }
 312
 313 void ovl_copy_up_end(struct dentry *dentry)
 314 {
 315         mutex_unlock(&OVL_I(d_inode(dentry))->lock);
 316 }
 317
 318 bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
 319 {
 320         int res;
 321         char val;
 322
 323         if (!d_is_dir(dentry))
 324                 return false;
 325
 326         res = vfs_getxattr(dentry, name, &val, 1);
 327         if (res == 1 && val == 'y')
 328                 return true;
 329
 330         return false;
 331 }
 332
 333 int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
 334                        const char *name, const void *value, size_t size,
 335                        int xerr)
 336 {
 337         int err;
 338         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 339
 340         if (ofs->noxattr)
 341                 return xerr;
 342
 343         err = ovl_do_setxattr(upperdentry, name, value, size, 0);
 344
 345         if (err == -EOPNOTSUPP) {
 346                 pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
 347                 ofs->noxattr = true;
 348                 return xerr;
 349         }
 350
 351         return err;
 352 }
 353
 354 int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
 355 {
 356         int err;
 357
 358         if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
 359                 return 0;
 360
 361         /*
 362          * Do not fail when upper doesn't support xattrs.
 363          * Upper inodes won't have origin nor redirect xattr anyway.
 364          */
 365         err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
 366                                  "y", 1, 0);
 367         if (!err)
 368                 ovl_set_flag(OVL_IMPURE, d_inode(dentry));
 369
 370         return err;
 371 }
 372
 373 void ovl_set_flag(unsigned long flag, struct inode *inode)
 374 {
 375         set_bit(flag, &OVL_I(inode)->flags);
 376 }
 377
 378 bool ovl_test_flag(unsigned long flag, struct inode *inode)
 379 {
 380         return test_bit(flag, &OVL_I(inode)->flags);
 381 }
 382
 383 /**
 384  * Caller must hold a reference to inode to prevent it from being freed while
 385  * it is marked inuse.
 386  */
 387 bool ovl_inuse_trylock(struct dentry *dentry)
 388 {
 389         struct inode *inode = d_inode(dentry);
 390         bool locked = false;
 391
 392         spin_lock(&inode->i_lock);
 393         if (!(inode->i_state & I_OVL_INUSE)) {
 394                 inode->i_state |= I_OVL_INUSE;
 395                 locked = true;
 396         }
 397         spin_unlock(&inode->i_lock);
 398
 399         return locked;
 400 }
 401
 402 void ovl_inuse_unlock(struct dentry *dentry)
 403 {
 404         if (dentry) {
 405                 struct inode *inode = d_inode(dentry);
 406
 407                 spin_lock(&inode->i_lock);
 408                 WARN_ON(!(inode->i_state & I_OVL_INUSE));
 409                 inode->i_state &= ~I_OVL_INUSE;
 410                 spin_unlock(&inode->i_lock);
 411         }
 412 }