fs/overlayfs/util.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
ovl_want_write
ovl_drop_write
ovl_workdir
ovl_override_creds
ovl_same_sb
ovl_can_decode_fh
ovl_indexdir
ovl_index_all
ovl_verify_lower
ovl_alloc_entry
ovl_dentry_remote
ovl_dentry_weird
ovl_path_upper
ovl_path_lower
ovl_path_lowerdata
ovl_path_real
ovl_dentry_upper
ovl_dentry_lower
ovl_layer_lower
ovl_dentry_lowerdata
ovl_dentry_real
ovl_i_dentry_upper
ovl_inode_upper
ovl_inode_lower
ovl_inode_real
ovl_inode_lowerdata
ovl_inode_realdata
ovl_set_dir_cache
ovl_dentry_set_flag
ovl_dentry_clear_flag
ovl_dentry_test_flag
ovl_dentry_is_opaque
ovl_dentry_is_whiteout
ovl_dentry_set_opaque
ovl_dentry_has_upper_alias
ovl_dentry_set_upper_alias
ovl_should_check_upperdata
ovl_has_upperdata
ovl_set_upperdata
ovl_dentry_needs_data_copy_up_locked
ovl_dentry_needs_data_copy_up
ovl_redirect_dir
ovl_dentry_get_redirect
ovl_dentry_set_redirect
ovl_inode_init
ovl_inode_update
ovl_dentry_version_inc
ovl_dir_modified
ovl_dentry_version_get
ovl_is_whiteout
ovl_path_open
ovl_already_copied_up_locked
ovl_already_copied_up
ovl_copy_up_start
ovl_copy_up_end
ovl_check_origin_xattr
ovl_check_dir_xattr
ovl_check_setxattr
ovl_set_impure
ovl_set_flag
ovl_clear_flag
ovl_test_flag
ovl_inuse_trylock
ovl_inuse_unlock
ovl_is_inuse
ovl_need_index
ovl_cleanup_index
ovl_nlink_start
ovl_nlink_end
ovl_lock_rename_workdir
ovl_check_metacopy_xattr
ovl_is_metacopy_dentry
ovl_getxattr
ovl_get_redirect_xattr
   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2011 Novell Inc.
   4  * Copyright (C) 2016 Red Hat, Inc.
   5  */
   6 
   7 #include <linux/fs.h>
   8 #include <linux/mount.h>
   9 #include <linux/slab.h>
  10 #include <linux/cred.h>
  11 #include <linux/xattr.h>
  12 #include <linux/exportfs.h>
  13 #include <linux/uuid.h>
  14 #include <linux/namei.h>
  15 #include <linux/ratelimit.h>
  16 #include "overlayfs.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         if (!ofs->numlowerfs)
  48                 return ofs->upper_mnt->mnt_sb;
  49         else if (ofs->numlowerfs == 1 && !ofs->upper_mnt)
  50                 return ofs->lower_fs[0].sb;
  51         else
  52                 return NULL;
  53 }
  54 
  55 /*
  56  * Check if underlying fs supports file handles and try to determine encoding
  57  * type, in order to deduce maximum inode number used by fs.
  58  *
  59  * Return 0 if file handles are not supported.
  60  * Return 1 (FILEID_INO32_GEN) if fs uses the default 32bit inode encoding.
  61  * Return -1 if fs uses a non default encoding with unknown inode size.
  62  */
  63 int ovl_can_decode_fh(struct super_block *sb)
  64 {
  65         if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry)
  66                 return 0;
  67 
  68         return sb->s_export_op->encode_fh ? -1 : FILEID_INO32_GEN;
  69 }
  70 
  71 struct dentry *ovl_indexdir(struct super_block *sb)
  72 {
  73         struct ovl_fs *ofs = sb->s_fs_info;
  74 
  75         return ofs->indexdir;
  76 }
  77 
  78 /* Index all files on copy up. For now only enabled for NFS export */
  79 bool ovl_index_all(struct super_block *sb)
  80 {
  81         struct ovl_fs *ofs = sb->s_fs_info;
  82 
  83         return ofs->config.nfs_export && ofs->config.index;
  84 }
  85 
  86 /* Verify lower origin on lookup. For now only enabled for NFS export */
  87 bool ovl_verify_lower(struct super_block *sb)
  88 {
  89         struct ovl_fs *ofs = sb->s_fs_info;
  90 
  91         return ofs->config.nfs_export && ofs->config.index;
  92 }
  93 
  94 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
  95 {
  96         size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
  97         struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
  98 
  99         if (oe)
 100                 oe->numlower = numlower;
 101 
 102         return oe;
 103 }
 104 
 105 bool ovl_dentry_remote(struct dentry *dentry)
 106 {
 107         return dentry->d_flags &
 108                 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
 109                  DCACHE_OP_REAL);
 110 }
 111 
 112 bool ovl_dentry_weird(struct dentry *dentry)
 113 {
 114         return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
 115                                   DCACHE_MANAGE_TRANSIT |
 116                                   DCACHE_OP_HASH |
 117                                   DCACHE_OP_COMPARE);
 118 }
 119 
 120 enum ovl_path_type ovl_path_type(struct dentry *dentry)
 121 {
 122         struct ovl_entry *oe = dentry->d_fsdata;
 123         enum ovl_path_type type = 0;
 124 
 125         if (ovl_dentry_upper(dentry)) {
 126                 type = __OVL_PATH_UPPER;
 127 
 128                 /*
 129                  * Non-dir dentry can hold lower dentry of its copy up origin.
 130                  */
 131                 if (oe->numlower) {
 132                         if (ovl_test_flag(OVL_CONST_INO, d_inode(dentry)))
 133                                 type |= __OVL_PATH_ORIGIN;
 134                         if (d_is_dir(dentry) ||
 135                             !ovl_has_upperdata(d_inode(dentry)))
 136                                 type |= __OVL_PATH_MERGE;
 137                 }
 138         } else {
 139                 if (oe->numlower > 1)
 140                         type |= __OVL_PATH_MERGE;
 141         }
 142         return type;
 143 }
 144 
 145 void ovl_path_upper(struct dentry *dentry, struct path *path)
 146 {
 147         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 148 
 149         path->mnt = ofs->upper_mnt;
 150         path->dentry = ovl_dentry_upper(dentry);
 151 }
 152 
 153 void ovl_path_lower(struct dentry *dentry, struct path *path)
 154 {
 155         struct ovl_entry *oe = dentry->d_fsdata;
 156 
 157         if (oe->numlower) {
 158                 path->mnt = oe->lowerstack[0].layer->mnt;
 159                 path->dentry = oe->lowerstack[0].dentry;
 160         } else {
 161                 *path = (struct path) { };
 162         }
 163 }
 164 
 165 void ovl_path_lowerdata(struct dentry *dentry, struct path *path)
 166 {
 167         struct ovl_entry *oe = dentry->d_fsdata;
 168 
 169         if (oe->numlower) {
 170                 path->mnt = oe->lowerstack[oe->numlower - 1].layer->mnt;
 171                 path->dentry = oe->lowerstack[oe->numlower - 1].dentry;
 172         } else {
 173                 *path = (struct path) { };
 174         }
 175 }
 176 
 177 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
 178 {
 179         enum ovl_path_type type = ovl_path_type(dentry);
 180 
 181         if (!OVL_TYPE_UPPER(type))
 182                 ovl_path_lower(dentry, path);
 183         else
 184                 ovl_path_upper(dentry, path);
 185 
 186         return type;
 187 }
 188 
 189 struct dentry *ovl_dentry_upper(struct dentry *dentry)
 190 {
 191         return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
 192 }
 193 
 194 struct dentry *ovl_dentry_lower(struct dentry *dentry)
 195 {
 196         struct ovl_entry *oe = dentry->d_fsdata;
 197 
 198         return oe->numlower ? oe->lowerstack[0].dentry : NULL;
 199 }
 200 
 201 struct ovl_layer *ovl_layer_lower(struct dentry *dentry)
 202 {
 203         struct ovl_entry *oe = dentry->d_fsdata;
 204 
 205         return oe->numlower ? oe->lowerstack[0].layer : NULL;
 206 }
 207 
 208 /*
 209  * ovl_dentry_lower() could return either a data dentry or metacopy dentry
 210  * dependig on what is stored in lowerstack[0]. At times we need to find
 211  * lower dentry which has data (and not metacopy dentry). This helper
 212  * returns the lower data dentry.
 213  */
 214 struct dentry *ovl_dentry_lowerdata(struct dentry *dentry)
 215 {
 216         struct ovl_entry *oe = dentry->d_fsdata;
 217 
 218         return oe->numlower ? oe->lowerstack[oe->numlower - 1].dentry : NULL;
 219 }
 220 
 221 struct dentry *ovl_dentry_real(struct dentry *dentry)
 222 {
 223         return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
 224 }
 225 
 226 struct dentry *ovl_i_dentry_upper(struct inode *inode)
 227 {
 228         return ovl_upperdentry_dereference(OVL_I(inode));
 229 }
 230 
 231 struct inode *ovl_inode_upper(struct inode *inode)
 232 {
 233         struct dentry *upperdentry = ovl_i_dentry_upper(inode);
 234 
 235         return upperdentry ? d_inode(upperdentry) : NULL;
 236 }
 237 
 238 struct inode *ovl_inode_lower(struct inode *inode)
 239 {
 240         return OVL_I(inode)->lower;
 241 }
 242 
 243 struct inode *ovl_inode_real(struct inode *inode)
 244 {
 245         return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
 246 }
 247 
 248 /* Return inode which contains lower data. Do not return metacopy */
 249 struct inode *ovl_inode_lowerdata(struct inode *inode)
 250 {
 251         if (WARN_ON(!S_ISREG(inode->i_mode)))
 252                 return NULL;
 253 
 254         return OVL_I(inode)->lowerdata ?: ovl_inode_lower(inode);
 255 }
 256 
 257 /* Return real inode which contains data. Does not return metacopy inode */
 258 struct inode *ovl_inode_realdata(struct inode *inode)
 259 {
 260         struct inode *upperinode;
 261 
 262         upperinode = ovl_inode_upper(inode);
 263         if (upperinode && ovl_has_upperdata(inode))
 264                 return upperinode;
 265 
 266         return ovl_inode_lowerdata(inode);
 267 }
 268 
 269 struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
 270 {
 271         return OVL_I(inode)->cache;
 272 }
 273 
 274 void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
 275 {
 276         OVL_I(inode)->cache = cache;
 277 }
 278 
 279 void ovl_dentry_set_flag(unsigned long flag, struct dentry *dentry)
 280 {
 281         set_bit(flag, &OVL_E(dentry)->flags);
 282 }
 283 
 284 void ovl_dentry_clear_flag(unsigned long flag, struct dentry *dentry)
 285 {
 286         clear_bit(flag, &OVL_E(dentry)->flags);
 287 }
 288 
 289 bool ovl_dentry_test_flag(unsigned long flag, struct dentry *dentry)
 290 {
 291         return test_bit(flag, &OVL_E(dentry)->flags);
 292 }
 293 
 294 bool ovl_dentry_is_opaque(struct dentry *dentry)
 295 {
 296         return ovl_dentry_test_flag(OVL_E_OPAQUE, dentry);
 297 }
 298 
 299 bool ovl_dentry_is_whiteout(struct dentry *dentry)
 300 {
 301         return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
 302 }
 303 
 304 void ovl_dentry_set_opaque(struct dentry *dentry)
 305 {
 306         ovl_dentry_set_flag(OVL_E_OPAQUE, dentry);
 307 }
 308 
 309 /*
 310  * For hard links and decoded file handles, it's possible for ovl_dentry_upper()
 311  * to return positive, while there's no actual upper alias for the inode.
 312  * Copy up code needs to know about the existence of the upper alias, so it
 313  * can't use ovl_dentry_upper().
 314  */
 315 bool ovl_dentry_has_upper_alias(struct dentry *dentry)
 316 {
 317         return ovl_dentry_test_flag(OVL_E_UPPER_ALIAS, dentry);
 318 }
 319 
 320 void ovl_dentry_set_upper_alias(struct dentry *dentry)
 321 {
 322         ovl_dentry_set_flag(OVL_E_UPPER_ALIAS, dentry);
 323 }
 324 
 325 static bool ovl_should_check_upperdata(struct inode *inode)
 326 {
 327         if (!S_ISREG(inode->i_mode))
 328                 return false;
 329 
 330         if (!ovl_inode_lower(inode))
 331                 return false;
 332 
 333         return true;
 334 }
 335 
 336 bool ovl_has_upperdata(struct inode *inode)
 337 {
 338         if (!ovl_should_check_upperdata(inode))
 339                 return true;
 340 
 341         if (!ovl_test_flag(OVL_UPPERDATA, inode))
 342                 return false;
 343         /*
 344          * Pairs with smp_wmb() in ovl_set_upperdata(). Main user of
 345          * ovl_has_upperdata() is ovl_copy_up_meta_inode_data(). Make sure
 346          * if setting of OVL_UPPERDATA is visible, then effects of writes
 347          * before that are visible too.
 348          */
 349         smp_rmb();
 350         return true;
 351 }
 352 
 353 void ovl_set_upperdata(struct inode *inode)
 354 {
 355         /*
 356          * Pairs with smp_rmb() in ovl_has_upperdata(). Make sure
 357          * if OVL_UPPERDATA flag is visible, then effects of write operations
 358          * before it are visible as well.
 359          */
 360         smp_wmb();
 361         ovl_set_flag(OVL_UPPERDATA, inode);
 362 }
 363 
 364 /* Caller should hold ovl_inode->lock */
 365 bool ovl_dentry_needs_data_copy_up_locked(struct dentry *dentry, int flags)
 366 {
 367         if (!ovl_open_flags_need_copy_up(flags))
 368                 return false;
 369 
 370         return !ovl_test_flag(OVL_UPPERDATA, d_inode(dentry));
 371 }
 372 
 373 bool ovl_dentry_needs_data_copy_up(struct dentry *dentry, int flags)
 374 {
 375         if (!ovl_open_flags_need_copy_up(flags))
 376                 return false;
 377 
 378         return !ovl_has_upperdata(d_inode(dentry));
 379 }
 380 
 381 bool ovl_redirect_dir(struct super_block *sb)
 382 {
 383         struct ovl_fs *ofs = sb->s_fs_info;
 384 
 385         return ofs->config.redirect_dir && !ofs->noxattr;
 386 }
 387 
 388 const char *ovl_dentry_get_redirect(struct dentry *dentry)
 389 {
 390         return OVL_I(d_inode(dentry))->redirect;
 391 }
 392 
 393 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
 394 {
 395         struct ovl_inode *oi = OVL_I(d_inode(dentry));
 396 
 397         kfree(oi->redirect);
 398         oi->redirect = redirect;
 399 }
 400 
 401 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
 402                     struct dentry *lowerdentry, struct dentry *lowerdata)
 403 {
 404         struct inode *realinode = d_inode(upperdentry ?: lowerdentry);
 405 
 406         if (upperdentry)
 407                 OVL_I(inode)->__upperdentry = upperdentry;
 408         if (lowerdentry)
 409                 OVL_I(inode)->lower = igrab(d_inode(lowerdentry));
 410         if (lowerdata)
 411                 OVL_I(inode)->lowerdata = igrab(d_inode(lowerdata));
 412 
 413         ovl_copyattr(realinode, inode);
 414         ovl_copyflags(realinode, inode);
 415         if (!inode->i_ino)
 416                 inode->i_ino = realinode->i_ino;
 417 }
 418 
 419 void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
 420 {
 421         struct inode *upperinode = d_inode(upperdentry);
 422 
 423         WARN_ON(OVL_I(inode)->__upperdentry);
 424 
 425         /*
 426          * Make sure upperdentry is consistent before making it visible
 427          */
 428         smp_wmb();
 429         OVL_I(inode)->__upperdentry = upperdentry;
 430         if (inode_unhashed(inode)) {
 431                 if (!inode->i_ino)
 432                         inode->i_ino = upperinode->i_ino;
 433                 inode->i_private = upperinode;
 434                 __insert_inode_hash(inode, (unsigned long) upperinode);
 435         }
 436 }
 437 
 438 static void ovl_dentry_version_inc(struct dentry *dentry, bool impurity)
 439 {
 440         struct inode *inode = d_inode(dentry);
 441 
 442         WARN_ON(!inode_is_locked(inode));
 443         /*
 444          * Version is used by readdir code to keep cache consistent.  For merge
 445          * dirs all changes need to be noted.  For non-merge dirs, cache only
 446          * contains impure (ones which have been copied up and have origins)
 447          * entries, so only need to note changes to impure entries.
 448          */
 449         if (OVL_TYPE_MERGE(ovl_path_type(dentry)) || impurity)
 450                 OVL_I(inode)->version++;
 451 }
 452 
 453 void ovl_dir_modified(struct dentry *dentry, bool impurity)
 454 {
 455         /* Copy mtime/ctime */
 456         ovl_copyattr(d_inode(ovl_dentry_upper(dentry)), d_inode(dentry));
 457 
 458         ovl_dentry_version_inc(dentry, impurity);
 459 }
 460 
 461 u64 ovl_dentry_version_get(struct dentry *dentry)
 462 {
 463         struct inode *inode = d_inode(dentry);
 464 
 465         WARN_ON(!inode_is_locked(inode));
 466         return OVL_I(inode)->version;
 467 }
 468 
 469 bool ovl_is_whiteout(struct dentry *dentry)
 470 {
 471         struct inode *inode = dentry->d_inode;
 472 
 473         return inode && IS_WHITEOUT(inode);
 474 }
 475 
 476 struct file *ovl_path_open(struct path *path, int flags)
 477 {
 478         return dentry_open(path, flags | O_NOATIME, current_cred());
 479 }
 480 
 481 /* Caller should hold ovl_inode->lock */
 482 static bool ovl_already_copied_up_locked(struct dentry *dentry, int flags)
 483 {
 484         bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;
 485 
 486         if (ovl_dentry_upper(dentry) &&
 487             (ovl_dentry_has_upper_alias(dentry) || disconnected) &&
 488             !ovl_dentry_needs_data_copy_up_locked(dentry, flags))
 489                 return true;
 490 
 491         return false;
 492 }
 493 
 494 bool ovl_already_copied_up(struct dentry *dentry, int flags)
 495 {
 496         bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;
 497 
 498         /*
 499          * Check if copy-up has happened as well as for upper alias (in
 500          * case of hard links) is there.
 501          *
 502          * Both checks are lockless:
 503          *  - false negatives: will recheck under oi->lock
 504          *  - false positives:
 505          *    + ovl_dentry_upper() uses memory barriers to ensure the
 506          *      upper dentry is up-to-date
 507          *    + ovl_dentry_has_upper_alias() relies on locking of
 508          *      upper parent i_rwsem to prevent reordering copy-up
 509          *      with rename.
 510          */
 511         if (ovl_dentry_upper(dentry) &&
 512             (ovl_dentry_has_upper_alias(dentry) || disconnected) &&
 513             !ovl_dentry_needs_data_copy_up(dentry, flags))
 514                 return true;
 515 
 516         return false;
 517 }
 518 
 519 int ovl_copy_up_start(struct dentry *dentry, int flags)
 520 {
 521         struct inode *inode = d_inode(dentry);
 522         int err;
 523 
 524         err = ovl_inode_lock(inode);
 525         if (!err && ovl_already_copied_up_locked(dentry, flags)) {
 526                 err = 1; /* Already copied up */
 527                 ovl_inode_unlock(inode);
 528         }
 529 
 530         return err;
 531 }
 532 
 533 void ovl_copy_up_end(struct dentry *dentry)
 534 {
 535         ovl_inode_unlock(d_inode(dentry));
 536 }
 537 
 538 bool ovl_check_origin_xattr(struct dentry *dentry)
 539 {
 540         int res;
 541 
 542         res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
 543 
 544         /* Zero size value means "copied up but origin unknown" */
 545         if (res >= 0)
 546                 return true;
 547 
 548         return false;
 549 }
 550 
 551 bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
 552 {
 553         int res;
 554         char val;
 555 
 556         if (!d_is_dir(dentry))
 557                 return false;
 558 
 559         res = vfs_getxattr(dentry, name, &val, 1);
 560         if (res == 1 && val == 'y')
 561                 return true;
 562 
 563         return false;
 564 }
 565 
 566 int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
 567                        const char *name, const void *value, size_t size,
 568                        int xerr)
 569 {
 570         int err;
 571         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 572 
 573         if (ofs->noxattr)
 574                 return xerr;
 575 
 576         err = ovl_do_setxattr(upperdentry, name, value, size, 0);
 577 
 578         if (err == -EOPNOTSUPP) {
 579                 pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
 580                 ofs->noxattr = true;
 581                 return xerr;
 582         }
 583 
 584         return err;
 585 }
 586 
 587 int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
 588 {
 589         int err;
 590 
 591         if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
 592                 return 0;
 593 
 594         /*
 595          * Do not fail when upper doesn't support xattrs.
 596          * Upper inodes won't have origin nor redirect xattr anyway.
 597          */
 598         err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
 599                                  "y", 1, 0);
 600         if (!err)
 601                 ovl_set_flag(OVL_IMPURE, d_inode(dentry));
 602 
 603         return err;
 604 }
 605 
 606 void ovl_set_flag(unsigned long flag, struct inode *inode)
 607 {
 608         set_bit(flag, &OVL_I(inode)->flags);
 609 }
 610 
 611 void ovl_clear_flag(unsigned long flag, struct inode *inode)
 612 {
 613         clear_bit(flag, &OVL_I(inode)->flags);
 614 }
 615 
 616 bool ovl_test_flag(unsigned long flag, struct inode *inode)
 617 {
 618         return test_bit(flag, &OVL_I(inode)->flags);
 619 }
 620 
 621 /**
 622  * Caller must hold a reference to inode to prevent it from being freed while
 623  * it is marked inuse.
 624  */
 625 bool ovl_inuse_trylock(struct dentry *dentry)
 626 {
 627         struct inode *inode = d_inode(dentry);
 628         bool locked = false;
 629 
 630         spin_lock(&inode->i_lock);
 631         if (!(inode->i_state & I_OVL_INUSE)) {
 632                 inode->i_state |= I_OVL_INUSE;
 633                 locked = true;
 634         }
 635         spin_unlock(&inode->i_lock);
 636 
 637         return locked;
 638 }
 639 
 640 void ovl_inuse_unlock(struct dentry *dentry)
 641 {
 642         if (dentry) {
 643                 struct inode *inode = d_inode(dentry);
 644 
 645                 spin_lock(&inode->i_lock);
 646                 WARN_ON(!(inode->i_state & I_OVL_INUSE));
 647                 inode->i_state &= ~I_OVL_INUSE;
 648                 spin_unlock(&inode->i_lock);
 649         }
 650 }
 651 
 652 bool ovl_is_inuse(struct dentry *dentry)
 653 {
 654         struct inode *inode = d_inode(dentry);
 655         bool inuse;
 656 
 657         spin_lock(&inode->i_lock);
 658         inuse = (inode->i_state & I_OVL_INUSE);
 659         spin_unlock(&inode->i_lock);
 660 
 661         return inuse;
 662 }
 663 
 664 /*
 665  * Does this overlay dentry need to be indexed on copy up?
 666  */
 667 bool ovl_need_index(struct dentry *dentry)
 668 {
 669         struct dentry *lower = ovl_dentry_lower(dentry);
 670 
 671         if (!lower || !ovl_indexdir(dentry->d_sb))
 672                 return false;
 673 
 674         /* Index all files for NFS export and consistency verification */
 675         if (ovl_index_all(dentry->d_sb))
 676                 return true;
 677 
 678         /* Index only lower hardlinks on copy up */
 679         if (!d_is_dir(lower) && d_inode(lower)->i_nlink > 1)
 680                 return true;
 681 
 682         return false;
 683 }
 684 
 685 /* Caller must hold OVL_I(inode)->lock */
 686 static void ovl_cleanup_index(struct dentry *dentry)
 687 {
 688         struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
 689         struct inode *dir = indexdir->d_inode;
 690         struct dentry *lowerdentry = ovl_dentry_lower(dentry);
 691         struct dentry *upperdentry = ovl_dentry_upper(dentry);
 692         struct dentry *index = NULL;
 693         struct inode *inode;
 694         struct qstr name = { };
 695         int err;
 696 
 697         err = ovl_get_index_name(lowerdentry, &name);
 698         if (err)
 699                 goto fail;
 700 
 701         inode = d_inode(upperdentry);
 702         if (!S_ISDIR(inode->i_mode) && inode->i_nlink != 1) {
 703                 pr_warn_ratelimited("overlayfs: cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
 704                                     upperdentry, inode->i_ino, inode->i_nlink);
 705                 /*
 706                  * We either have a bug with persistent union nlink or a lower
 707                  * hardlink was added while overlay is mounted. Adding a lower
 708                  * hardlink and then unlinking all overlay hardlinks would drop
 709                  * overlay nlink to zero before all upper inodes are unlinked.
 710                  * As a safety measure, when that situation is detected, set
 711                  * the overlay nlink to the index inode nlink minus one for the
 712                  * index entry itself.
 713                  */
 714                 set_nlink(d_inode(dentry), inode->i_nlink - 1);
 715                 ovl_set_nlink_upper(dentry);
 716                 goto out;
 717         }
 718 
 719         inode_lock_nested(dir, I_MUTEX_PARENT);
 720         index = lookup_one_len(name.name, indexdir, name.len);
 721         err = PTR_ERR(index);
 722         if (IS_ERR(index)) {
 723                 index = NULL;
 724         } else if (ovl_index_all(dentry->d_sb)) {
 725                 /* Whiteout orphan index to block future open by handle */
 726                 err = ovl_cleanup_and_whiteout(indexdir, dir, index);
 727         } else {
 728                 /* Cleanup orphan index entries */
 729                 err = ovl_cleanup(dir, index);
 730         }
 731 
 732         inode_unlock(dir);
 733         if (err)
 734                 goto fail;
 735 
 736 out:
 737         kfree(name.name);
 738         dput(index);
 739         return;
 740 
 741 fail:
 742         pr_err("overlayfs: cleanup index of '%pd2' failed (%i)\n", dentry, err);
 743         goto out;
 744 }
 745 
 746 /*
 747  * Operations that change overlay inode and upper inode nlink need to be
 748  * synchronized with copy up for persistent nlink accounting.
 749  */
 750 int ovl_nlink_start(struct dentry *dentry)
 751 {
 752         struct inode *inode = d_inode(dentry);
 753         const struct cred *old_cred;
 754         int err;
 755 
 756         if (WARN_ON(!inode))
 757                 return -ENOENT;
 758 
 759         /*
 760          * With inodes index is enabled, we store the union overlay nlink
 761          * in an xattr on the index inode. When whiting out an indexed lower,
 762          * we need to decrement the overlay persistent nlink, but before the
 763          * first copy up, we have no upper index inode to store the xattr.
 764          *
 765          * As a workaround, before whiteout/rename over an indexed lower,
 766          * copy up to create the upper index. Creating the upper index will
 767          * initialize the overlay nlink, so it could be dropped if unlink
 768          * or rename succeeds.
 769          *
 770          * TODO: implement metadata only index copy up when called with
 771          *       ovl_copy_up_flags(dentry, O_PATH).
 772          */
 773         if (ovl_need_index(dentry) && !ovl_dentry_has_upper_alias(dentry)) {
 774                 err = ovl_copy_up(dentry);
 775                 if (err)
 776                         return err;
 777         }
 778 
 779         err = ovl_inode_lock(inode);
 780         if (err)
 781                 return err;
 782 
 783         if (d_is_dir(dentry) || !ovl_test_flag(OVL_INDEX, inode))
 784                 goto out;
 785 
 786         old_cred = ovl_override_creds(dentry->d_sb);
 787         /*
 788          * The overlay inode nlink should be incremented/decremented IFF the
 789          * upper operation succeeds, along with nlink change of upper inode.
 790          * Therefore, before link/unlink/rename, we store the union nlink
 791          * value relative to the upper inode nlink in an upper inode xattr.
 792          */
 793         err = ovl_set_nlink_upper(dentry);
 794         revert_creds(old_cred);
 795 
 796 out:
 797         if (err)
 798                 ovl_inode_unlock(inode);
 799 
 800         return err;
 801 }
 802 
 803 void ovl_nlink_end(struct dentry *dentry)
 804 {
 805         struct inode *inode = d_inode(dentry);
 806 
 807         if (ovl_test_flag(OVL_INDEX, inode) && inode->i_nlink == 0) {
 808                 const struct cred *old_cred;
 809 
 810                 old_cred = ovl_override_creds(dentry->d_sb);
 811                 ovl_cleanup_index(dentry);
 812                 revert_creds(old_cred);
 813         }
 814 
 815         ovl_inode_unlock(inode);
 816 }
 817 
 818 int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
 819 {
 820         /* Workdir should not be the same as upperdir */
 821         if (workdir == upperdir)
 822                 goto err;
 823 
 824         /* Workdir should not be subdir of upperdir and vice versa */
 825         if (lock_rename(workdir, upperdir) != NULL)
 826                 goto err_unlock;
 827 
 828         return 0;
 829 
 830 err_unlock:
 831         unlock_rename(workdir, upperdir);
 832 err:
 833         pr_err("overlayfs: failed to lock workdir+upperdir\n");
 834         return -EIO;
 835 }
 836 
 837 /* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */
 838 int ovl_check_metacopy_xattr(struct dentry *dentry)
 839 {
 840         int res;
 841 
 842         /* Only regular files can have metacopy xattr */
 843         if (!S_ISREG(d_inode(dentry)->i_mode))
 844                 return 0;
 845 
 846         res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);
 847         if (res < 0) {
 848                 if (res == -ENODATA || res == -EOPNOTSUPP)
 849                         return 0;
 850                 goto out;
 851         }
 852 
 853         return 1;
 854 out:
 855         pr_warn_ratelimited("overlayfs: failed to get metacopy (%i)\n", res);
 856         return res;
 857 }
 858 
 859 bool ovl_is_metacopy_dentry(struct dentry *dentry)
 860 {
 861         struct ovl_entry *oe = dentry->d_fsdata;
 862 
 863         if (!d_is_reg(dentry))
 864                 return false;
 865 
 866         if (ovl_dentry_upper(dentry)) {
 867                 if (!ovl_has_upperdata(d_inode(dentry)))
 868                         return true;
 869                 return false;
 870         }
 871 
 872         return (oe->numlower > 1);
 873 }
 874 
 875 ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value,
 876                      size_t padding)
 877 {
 878         ssize_t res;
 879         char *buf = NULL;
 880 
 881         res = vfs_getxattr(dentry, name, NULL, 0);
 882         if (res < 0) {
 883                 if (res == -ENODATA || res == -EOPNOTSUPP)
 884                         return -ENODATA;
 885                 goto fail;
 886         }
 887 
 888         if (res != 0) {
 889                 buf = kzalloc(res + padding, GFP_KERNEL);
 890                 if (!buf)
 891                         return -ENOMEM;
 892 
 893                 res = vfs_getxattr(dentry, name, buf, res);
 894                 if (res < 0)
 895                         goto fail;
 896         }
 897         *value = buf;
 898 
 899         return res;
 900 
 901 fail:
 902         pr_warn_ratelimited("overlayfs: failed to get xattr %s: err=%zi)\n",
 903                             name, res);
 904         kfree(buf);
 905         return res;
 906 }
 907 
 908 char *ovl_get_redirect_xattr(struct dentry *dentry, int padding)
 909 {
 910         int res;
 911         char *s, *next, *buf = NULL;
 912 
 913         res = ovl_getxattr(dentry, OVL_XATTR_REDIRECT, &buf, padding + 1);
 914         if (res == -ENODATA)
 915                 return NULL;
 916         if (res < 0)
 917                 return ERR_PTR(res);
 918         if (res == 0)
 919                 goto invalid;
 920 
 921         if (buf[0] == '/') {
 922                 for (s = buf; *s++ == '/'; s = next) {
 923                         next = strchrnul(s, '/');
 924                         if (s == next)
 925                                 goto invalid;
 926                 }
 927         } else {
 928                 if (strchr(buf, '/') != NULL)
 929                         goto invalid;
 930         }
 931 
 932         return buf;
 933 invalid:
 934         pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf);
 935         res = -EINVAL;
 936         kfree(buf);
 937         return ERR_PTR(res);
 938 }
/* [<][>][^][v][top][bottom][index][help] */
root/fs/overlayfs/util.c

DEFINITIONS
