whiterose

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util.c (22156B)


      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 <linux/namei.h>
     18 #include <linux/ratelimit.h>
     19 #include "overlayfs.h"
     20 
     21 int ovl_want_write(struct dentry *dentry)
     22 {
     23 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
     24 	return mnt_want_write(ofs->upper_mnt);
     25 }
     26 
     27 void ovl_drop_write(struct dentry *dentry)
     28 {
     29 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
     30 	mnt_drop_write(ofs->upper_mnt);
     31 }
     32 
     33 struct dentry *ovl_workdir(struct dentry *dentry)
     34 {
     35 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
     36 	return ofs->workdir;
     37 }
     38 
     39 const struct cred *ovl_override_creds(struct super_block *sb)
     40 {
     41 	struct ovl_fs *ofs = sb->s_fs_info;
     42 
     43 	return override_creds(ofs->creator_cred);
     44 }
     45 
     46 struct super_block *ovl_same_sb(struct super_block *sb)
     47 {
     48 	struct ovl_fs *ofs = sb->s_fs_info;
     49 
     50 	if (!ofs->numlowerfs)
     51 		return ofs->upper_mnt->mnt_sb;
     52 	else if (ofs->numlowerfs == 1 && !ofs->upper_mnt)
     53 		return ofs->lower_fs[0].sb;
     54 	else
     55 		return NULL;
     56 }
     57 
     58 /*
     59  * Check if underlying fs supports file handles and try to determine encoding
     60  * type, in order to deduce maximum inode number used by fs.
     61  *
     62  * Return 0 if file handles are not supported.
     63  * Return 1 (FILEID_INO32_GEN) if fs uses the default 32bit inode encoding.
     64  * Return -1 if fs uses a non default encoding with unknown inode size.
     65  */
     66 int ovl_can_decode_fh(struct super_block *sb)
     67 {
     68 	if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry)
     69 		return 0;
     70 
     71 	return sb->s_export_op->encode_fh ? -1 : FILEID_INO32_GEN;
     72 }
     73 
     74 struct dentry *ovl_indexdir(struct super_block *sb)
     75 {
     76 	struct ovl_fs *ofs = sb->s_fs_info;
     77 
     78 	return ofs->indexdir;
     79 }
     80 
     81 /* Index all files on copy up. For now only enabled for NFS export */
     82 bool ovl_index_all(struct super_block *sb)
     83 {
     84 	struct ovl_fs *ofs = sb->s_fs_info;
     85 
     86 	return ofs->config.nfs_export && ofs->config.index;
     87 }
     88 
     89 /* Verify lower origin on lookup. For now only enabled for NFS export */
     90 bool ovl_verify_lower(struct super_block *sb)
     91 {
     92 	struct ovl_fs *ofs = sb->s_fs_info;
     93 
     94 	return ofs->config.nfs_export && ofs->config.index;
     95 }
     96 
     97 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
     98 {
     99 	size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
    100 	struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
    101 
    102 	if (oe)
    103 		oe->numlower = numlower;
    104 
    105 	return oe;
    106 }
    107 
    108 bool ovl_dentry_remote(struct dentry *dentry)
    109 {
    110 	return dentry->d_flags &
    111 		(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
    112 		 DCACHE_OP_REAL);
    113 }
    114 
    115 bool ovl_dentry_weird(struct dentry *dentry)
    116 {
    117 	return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
    118 				  DCACHE_MANAGE_TRANSIT |
    119 				  DCACHE_OP_HASH |
    120 				  DCACHE_OP_COMPARE);
    121 }
    122 
    123 enum ovl_path_type ovl_path_type(struct dentry *dentry)
    124 {
    125 	struct ovl_entry *oe = dentry->d_fsdata;
    126 	enum ovl_path_type type = 0;
    127 
    128 	if (ovl_dentry_upper(dentry)) {
    129 		type = __OVL_PATH_UPPER;
    130 
    131 		/*
    132 		 * Non-dir dentry can hold lower dentry of its copy up origin.
    133 		 */
    134 		if (oe->numlower) {
    135 			if (ovl_test_flag(OVL_CONST_INO, d_inode(dentry)))
    136 				type |= __OVL_PATH_ORIGIN;
    137 			if (d_is_dir(dentry) ||
    138 			    !ovl_has_upperdata(d_inode(dentry)))
    139 				type |= __OVL_PATH_MERGE;
    140 		}
    141 	} else {
    142 		if (oe->numlower > 1)
    143 			type |= __OVL_PATH_MERGE;
    144 	}
    145 	return type;
    146 }
    147 
    148 void ovl_path_upper(struct dentry *dentry, struct path *path)
    149 {
    150 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
    151 
    152 	path->mnt = ofs->upper_mnt;
    153 	path->dentry = ovl_dentry_upper(dentry);
    154 }
    155 
    156 void ovl_path_lower(struct dentry *dentry, struct path *path)
    157 {
    158 	struct ovl_entry *oe = dentry->d_fsdata;
    159 
    160 	if (oe->numlower) {
    161 		path->mnt = oe->lowerstack[0].layer->mnt;
    162 		path->dentry = oe->lowerstack[0].dentry;
    163 	} else {
    164 		*path = (struct path) { };
    165 	}
    166 }
    167 
    168 void ovl_path_lowerdata(struct dentry *dentry, struct path *path)
    169 {
    170 	struct ovl_entry *oe = dentry->d_fsdata;
    171 
    172 	if (oe->numlower) {
    173 		path->mnt = oe->lowerstack[oe->numlower - 1].layer->mnt;
    174 		path->dentry = oe->lowerstack[oe->numlower - 1].dentry;
    175 	} else {
    176 		*path = (struct path) { };
    177 	}
    178 }
    179 
    180 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
    181 {
    182 	enum ovl_path_type type = ovl_path_type(dentry);
    183 
    184 	if (!OVL_TYPE_UPPER(type))
    185 		ovl_path_lower(dentry, path);
    186 	else
    187 		ovl_path_upper(dentry, path);
    188 
    189 	return type;
    190 }
    191 
    192 struct dentry *ovl_dentry_upper(struct dentry *dentry)
    193 {
    194 	return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
    195 }
    196 
    197 struct dentry *ovl_dentry_lower(struct dentry *dentry)
    198 {
    199 	struct ovl_entry *oe = dentry->d_fsdata;
    200 
    201 	return oe->numlower ? oe->lowerstack[0].dentry : NULL;
    202 }
    203 
    204 struct ovl_layer *ovl_layer_lower(struct dentry *dentry)
    205 {
    206 	struct ovl_entry *oe = dentry->d_fsdata;
    207 
    208 	return oe->numlower ? oe->lowerstack[0].layer : NULL;
    209 }
    210 
    211 /*
    212  * ovl_dentry_lower() could return either a data dentry or metacopy dentry
    213  * dependig on what is stored in lowerstack[0]. At times we need to find
    214  * lower dentry which has data (and not metacopy dentry). This helper
    215  * returns the lower data dentry.
    216  */
    217 struct dentry *ovl_dentry_lowerdata(struct dentry *dentry)
    218 {
    219 	struct ovl_entry *oe = dentry->d_fsdata;
    220 
    221 	return oe->numlower ? oe->lowerstack[oe->numlower - 1].dentry : NULL;
    222 }
    223 
    224 struct dentry *ovl_dentry_real(struct dentry *dentry)
    225 {
    226 	return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
    227 }
    228 
    229 struct dentry *ovl_i_dentry_upper(struct inode *inode)
    230 {
    231 	return ovl_upperdentry_dereference(OVL_I(inode));
    232 }
    233 
    234 struct inode *ovl_inode_upper(struct inode *inode)
    235 {
    236 	struct dentry *upperdentry = ovl_i_dentry_upper(inode);
    237 
    238 	return upperdentry ? d_inode(upperdentry) : NULL;
    239 }
    240 
    241 struct inode *ovl_inode_lower(struct inode *inode)
    242 {
    243 	return OVL_I(inode)->lower;
    244 }
    245 
    246 struct inode *ovl_inode_real(struct inode *inode)
    247 {
    248 	return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
    249 }
    250 
    251 /* Return inode which contains lower data. Do not return metacopy */
    252 struct inode *ovl_inode_lowerdata(struct inode *inode)
    253 {
    254 	if (WARN_ON(!S_ISREG(inode->i_mode)))
    255 		return NULL;
    256 
    257 	return OVL_I(inode)->lowerdata ?: ovl_inode_lower(inode);
    258 }
    259 
    260 /* Return real inode which contains data. Does not return metacopy inode */
    261 struct inode *ovl_inode_realdata(struct inode *inode)
    262 {
    263 	struct inode *upperinode;
    264 
    265 	upperinode = ovl_inode_upper(inode);
    266 	if (upperinode && ovl_has_upperdata(inode))
    267 		return upperinode;
    268 
    269 	return ovl_inode_lowerdata(inode);
    270 }
    271 
    272 struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
    273 {
    274 	return OVL_I(inode)->cache;
    275 }
    276 
    277 void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
    278 {
    279 	OVL_I(inode)->cache = cache;
    280 }
    281 
    282 void ovl_dentry_set_flag(unsigned long flag, struct dentry *dentry)
    283 {
    284 	set_bit(flag, &OVL_E(dentry)->flags);
    285 }
    286 
    287 void ovl_dentry_clear_flag(unsigned long flag, struct dentry *dentry)
    288 {
    289 	clear_bit(flag, &OVL_E(dentry)->flags);
    290 }
    291 
    292 bool ovl_dentry_test_flag(unsigned long flag, struct dentry *dentry)
    293 {
    294 	return test_bit(flag, &OVL_E(dentry)->flags);
    295 }
    296 
    297 bool ovl_dentry_is_opaque(struct dentry *dentry)
    298 {
    299 	return ovl_dentry_test_flag(OVL_E_OPAQUE, dentry);
    300 }
    301 
    302 bool ovl_dentry_is_whiteout(struct dentry *dentry)
    303 {
    304 	return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
    305 }
    306 
    307 void ovl_dentry_set_opaque(struct dentry *dentry)
    308 {
    309 	ovl_dentry_set_flag(OVL_E_OPAQUE, dentry);
    310 }
    311 
    312 /*
    313  * For hard links and decoded file handles, it's possible for ovl_dentry_upper()
    314  * to return positive, while there's no actual upper alias for the inode.
    315  * Copy up code needs to know about the existence of the upper alias, so it
    316  * can't use ovl_dentry_upper().
    317  */
    318 bool ovl_dentry_has_upper_alias(struct dentry *dentry)
    319 {
    320 	return ovl_dentry_test_flag(OVL_E_UPPER_ALIAS, dentry);
    321 }
    322 
    323 void ovl_dentry_set_upper_alias(struct dentry *dentry)
    324 {
    325 	ovl_dentry_set_flag(OVL_E_UPPER_ALIAS, dentry);
    326 }
    327 
    328 static bool ovl_should_check_upperdata(struct inode *inode)
    329 {
    330 	if (!S_ISREG(inode->i_mode))
    331 		return false;
    332 
    333 	if (!ovl_inode_lower(inode))
    334 		return false;
    335 
    336 	return true;
    337 }
    338 
    339 bool ovl_has_upperdata(struct inode *inode)
    340 {
    341 	if (!ovl_should_check_upperdata(inode))
    342 		return true;
    343 
    344 	if (!ovl_test_flag(OVL_UPPERDATA, inode))
    345 		return false;
    346 	/*
    347 	 * Pairs with smp_wmb() in ovl_set_upperdata(). Main user of
    348 	 * ovl_has_upperdata() is ovl_copy_up_meta_inode_data(). Make sure
    349 	 * if setting of OVL_UPPERDATA is visible, then effects of writes
    350 	 * before that are visible too.
    351 	 */
    352 	smp_rmb();
    353 	return true;
    354 }
    355 
    356 void ovl_set_upperdata(struct inode *inode)
    357 {
    358 	/*
    359 	 * Pairs with smp_rmb() in ovl_has_upperdata(). Make sure
    360 	 * if OVL_UPPERDATA flag is visible, then effects of write operations
    361 	 * before it are visible as well.
    362 	 */
    363 	smp_wmb();
    364 	ovl_set_flag(OVL_UPPERDATA, inode);
    365 }
    366 
    367 /* Caller should hold ovl_inode->lock */
    368 bool ovl_dentry_needs_data_copy_up_locked(struct dentry *dentry, int flags)
    369 {
    370 	if (!ovl_open_flags_need_copy_up(flags))
    371 		return false;
    372 
    373 	return !ovl_test_flag(OVL_UPPERDATA, d_inode(dentry));
    374 }
    375 
    376 bool ovl_dentry_needs_data_copy_up(struct dentry *dentry, int flags)
    377 {
    378 	if (!ovl_open_flags_need_copy_up(flags))
    379 		return false;
    380 
    381 	return !ovl_has_upperdata(d_inode(dentry));
    382 }
    383 
    384 bool ovl_redirect_dir(struct super_block *sb)
    385 {
    386 	struct ovl_fs *ofs = sb->s_fs_info;
    387 
    388 	return ofs->config.redirect_dir && !ofs->noxattr;
    389 }
    390 
    391 const char *ovl_dentry_get_redirect(struct dentry *dentry)
    392 {
    393 	return OVL_I(d_inode(dentry))->redirect;
    394 }
    395 
    396 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
    397 {
    398 	struct ovl_inode *oi = OVL_I(d_inode(dentry));
    399 
    400 	kfree(oi->redirect);
    401 	oi->redirect = redirect;
    402 }
    403 
    404 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
    405 		    struct dentry *lowerdentry, struct dentry *lowerdata)
    406 {
    407 	struct inode *realinode = d_inode(upperdentry ?: lowerdentry);
    408 
    409 	if (upperdentry)
    410 		OVL_I(inode)->__upperdentry = upperdentry;
    411 	if (lowerdentry)
    412 		OVL_I(inode)->lower = igrab(d_inode(lowerdentry));
    413 	if (lowerdata)
    414 		OVL_I(inode)->lowerdata = igrab(d_inode(lowerdata));
    415 
    416 	ovl_copyattr(realinode, inode);
    417 	ovl_copyflags(realinode, inode);
    418 	if (!inode->i_ino)
    419 		inode->i_ino = realinode->i_ino;
    420 }
    421 
    422 void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
    423 {
    424 	struct inode *upperinode = d_inode(upperdentry);
    425 
    426 	WARN_ON(OVL_I(inode)->__upperdentry);
    427 
    428 	/*
    429 	 * Make sure upperdentry is consistent before making it visible
    430 	 */
    431 	smp_wmb();
    432 	OVL_I(inode)->__upperdentry = upperdentry;
    433 	if (inode_unhashed(inode)) {
    434 		if (!inode->i_ino)
    435 			inode->i_ino = upperinode->i_ino;
    436 		inode->i_private = upperinode;
    437 		__insert_inode_hash(inode, (unsigned long) upperinode);
    438 	}
    439 }
    440 
    441 static void ovl_dentry_version_inc(struct dentry *dentry, bool impurity)
    442 {
    443 	struct inode *inode = d_inode(dentry);
    444 
    445 	WARN_ON(!inode_is_locked(inode));
    446 	/*
    447 	 * Version is used by readdir code to keep cache consistent.  For merge
    448 	 * dirs all changes need to be noted.  For non-merge dirs, cache only
    449 	 * contains impure (ones which have been copied up and have origins)
    450 	 * entries, so only need to note changes to impure entries.
    451 	 */
    452 	if (OVL_TYPE_MERGE(ovl_path_type(dentry)) || impurity)
    453 		OVL_I(inode)->version++;
    454 }
    455 
    456 void ovl_dir_modified(struct dentry *dentry, bool impurity)
    457 {
    458 	/* Copy mtime/ctime */
    459 	ovl_copyattr(d_inode(ovl_dentry_upper(dentry)), d_inode(dentry));
    460 
    461 	ovl_dentry_version_inc(dentry, impurity);
    462 }
    463 
    464 u64 ovl_dentry_version_get(struct dentry *dentry)
    465 {
    466 	struct inode *inode = d_inode(dentry);
    467 
    468 	WARN_ON(!inode_is_locked(inode));
    469 	return OVL_I(inode)->version;
    470 }
    471 
    472 bool ovl_is_whiteout(struct dentry *dentry)
    473 {
    474 	struct inode *inode = dentry->d_inode;
    475 
    476 	return inode && IS_WHITEOUT(inode);
    477 }
    478 
    479 struct file *ovl_path_open(struct path *path, int flags)
    480 {
    481 	return dentry_open(path, flags | O_NOATIME, current_cred());
    482 }
    483 
    484 /* Caller should hold ovl_inode->lock */
    485 static bool ovl_already_copied_up_locked(struct dentry *dentry, int flags)
    486 {
    487 	bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;
    488 
    489 	if (ovl_dentry_upper(dentry) &&
    490 	    (ovl_dentry_has_upper_alias(dentry) || disconnected) &&
    491 	    !ovl_dentry_needs_data_copy_up_locked(dentry, flags))
    492 		return true;
    493 
    494 	return false;
    495 }
    496 
    497 bool ovl_already_copied_up(struct dentry *dentry, int flags)
    498 {
    499 	bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;
    500 
    501 	/*
    502 	 * Check if copy-up has happened as well as for upper alias (in
    503 	 * case of hard links) is there.
    504 	 *
    505 	 * Both checks are lockless:
    506 	 *  - false negatives: will recheck under oi->lock
    507 	 *  - false positives:
    508 	 *    + ovl_dentry_upper() uses memory barriers to ensure the
    509 	 *      upper dentry is up-to-date
    510 	 *    + ovl_dentry_has_upper_alias() relies on locking of
    511 	 *      upper parent i_rwsem to prevent reordering copy-up
    512 	 *      with rename.
    513 	 */
    514 	if (ovl_dentry_upper(dentry) &&
    515 	    (ovl_dentry_has_upper_alias(dentry) || disconnected) &&
    516 	    !ovl_dentry_needs_data_copy_up(dentry, flags))
    517 		return true;
    518 
    519 	return false;
    520 }
    521 
    522 int ovl_copy_up_start(struct dentry *dentry, int flags)
    523 {
    524 	struct inode *inode = d_inode(dentry);
    525 	int err;
    526 
    527 	err = ovl_inode_lock(inode);
    528 	if (!err && ovl_already_copied_up_locked(dentry, flags)) {
    529 		err = 1; /* Already copied up */
    530 		ovl_inode_unlock(inode);
    531 	}
    532 
    533 	return err;
    534 }
    535 
    536 void ovl_copy_up_end(struct dentry *dentry)
    537 {
    538 	ovl_inode_unlock(d_inode(dentry));
    539 }
    540 
    541 bool ovl_check_origin_xattr(struct dentry *dentry)
    542 {
    543 	int res;
    544 
    545 	res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
    546 
    547 	/* Zero size value means "copied up but origin unknown" */
    548 	if (res >= 0)
    549 		return true;
    550 
    551 	return false;
    552 }
    553 
    554 bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
    555 {
    556 	int res;
    557 	char val;
    558 
    559 	if (!d_is_dir(dentry))
    560 		return false;
    561 
    562 	res = vfs_getxattr(dentry, name, &val, 1);
    563 	if (res == 1 && val == 'y')
    564 		return true;
    565 
    566 	return false;
    567 }
    568 
    569 int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
    570 		       const char *name, const void *value, size_t size,
    571 		       int xerr)
    572 {
    573 	int err;
    574 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
    575 
    576 	if (ofs->noxattr)
    577 		return xerr;
    578 
    579 	err = ovl_do_setxattr(upperdentry, name, value, size, 0);
    580 
    581 	if (err == -EOPNOTSUPP) {
    582 		pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
    583 		ofs->noxattr = true;
    584 		return xerr;
    585 	}
    586 
    587 	return err;
    588 }
    589 
    590 int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
    591 {
    592 	int err;
    593 
    594 	if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
    595 		return 0;
    596 
    597 	/*
    598 	 * Do not fail when upper doesn't support xattrs.
    599 	 * Upper inodes won't have origin nor redirect xattr anyway.
    600 	 */
    601 	err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
    602 				 "y", 1, 0);
    603 	if (!err)
    604 		ovl_set_flag(OVL_IMPURE, d_inode(dentry));
    605 
    606 	return err;
    607 }
    608 
    609 void ovl_set_flag(unsigned long flag, struct inode *inode)
    610 {
    611 	set_bit(flag, &OVL_I(inode)->flags);
    612 }
    613 
    614 void ovl_clear_flag(unsigned long flag, struct inode *inode)
    615 {
    616 	clear_bit(flag, &OVL_I(inode)->flags);
    617 }
    618 
    619 bool ovl_test_flag(unsigned long flag, struct inode *inode)
    620 {
    621 	return test_bit(flag, &OVL_I(inode)->flags);
    622 }
    623 
    624 /**
    625  * Caller must hold a reference to inode to prevent it from being freed while
    626  * it is marked inuse.
    627  */
    628 bool ovl_inuse_trylock(struct dentry *dentry)
    629 {
    630 	struct inode *inode = d_inode(dentry);
    631 	bool locked = false;
    632 
    633 	spin_lock(&inode->i_lock);
    634 	if (!(inode->i_state & I_OVL_INUSE)) {
    635 		inode->i_state |= I_OVL_INUSE;
    636 		locked = true;
    637 	}
    638 	spin_unlock(&inode->i_lock);
    639 
    640 	return locked;
    641 }
    642 
    643 void ovl_inuse_unlock(struct dentry *dentry)
    644 {
    645 	if (dentry) {
    646 		struct inode *inode = d_inode(dentry);
    647 
    648 		spin_lock(&inode->i_lock);
    649 		WARN_ON(!(inode->i_state & I_OVL_INUSE));
    650 		inode->i_state &= ~I_OVL_INUSE;
    651 		spin_unlock(&inode->i_lock);
    652 	}
    653 }
    654 
    655 /*
    656  * Does this overlay dentry need to be indexed on copy up?
    657  */
    658 bool ovl_need_index(struct dentry *dentry)
    659 {
    660 	struct dentry *lower = ovl_dentry_lower(dentry);
    661 
    662 	if (!lower || !ovl_indexdir(dentry->d_sb))
    663 		return false;
    664 
    665 	/* Index all files for NFS export and consistency verification */
    666 	if (ovl_index_all(dentry->d_sb))
    667 		return true;
    668 
    669 	/* Index only lower hardlinks on copy up */
    670 	if (!d_is_dir(lower) && d_inode(lower)->i_nlink > 1)
    671 		return true;
    672 
    673 	return false;
    674 }
    675 
    676 /* Caller must hold OVL_I(inode)->lock */
    677 static void ovl_cleanup_index(struct dentry *dentry)
    678 {
    679 	struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
    680 	struct inode *dir = indexdir->d_inode;
    681 	struct dentry *lowerdentry = ovl_dentry_lower(dentry);
    682 	struct dentry *upperdentry = ovl_dentry_upper(dentry);
    683 	struct dentry *index = NULL;
    684 	struct inode *inode;
    685 	struct qstr name = { };
    686 	int err;
    687 
    688 	err = ovl_get_index_name(lowerdentry, &name);
    689 	if (err)
    690 		goto fail;
    691 
    692 	inode = d_inode(upperdentry);
    693 	if (!S_ISDIR(inode->i_mode) && inode->i_nlink != 1) {
    694 		pr_warn_ratelimited("overlayfs: cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
    695 				    upperdentry, inode->i_ino, inode->i_nlink);
    696 		/*
    697 		 * We either have a bug with persistent union nlink or a lower
    698 		 * hardlink was added while overlay is mounted. Adding a lower
    699 		 * hardlink and then unlinking all overlay hardlinks would drop
    700 		 * overlay nlink to zero before all upper inodes are unlinked.
    701 		 * As a safety measure, when that situation is detected, set
    702 		 * the overlay nlink to the index inode nlink minus one for the
    703 		 * index entry itself.
    704 		 */
    705 		set_nlink(d_inode(dentry), inode->i_nlink - 1);
    706 		ovl_set_nlink_upper(dentry);
    707 		goto out;
    708 	}
    709 
    710 	inode_lock_nested(dir, I_MUTEX_PARENT);
    711 	index = lookup_one_len(name.name, indexdir, name.len);
    712 	err = PTR_ERR(index);
    713 	if (IS_ERR(index)) {
    714 		index = NULL;
    715 	} else if (ovl_index_all(dentry->d_sb)) {
    716 		/* Whiteout orphan index to block future open by handle */
    717 		err = ovl_cleanup_and_whiteout(indexdir, dir, index);
    718 	} else {
    719 		/* Cleanup orphan index entries */
    720 		err = ovl_cleanup(dir, index);
    721 	}
    722 
    723 	inode_unlock(dir);
    724 	if (err)
    725 		goto fail;
    726 
    727 out:
    728 	kfree(name.name);
    729 	dput(index);
    730 	return;
    731 
    732 fail:
    733 	pr_err("overlayfs: cleanup index of '%pd2' failed (%i)\n", dentry, err);
    734 	goto out;
    735 }
    736 
    737 /*
    738  * Operations that change overlay inode and upper inode nlink need to be
    739  * synchronized with copy up for persistent nlink accounting.
    740  */
    741 int ovl_nlink_start(struct dentry *dentry)
    742 {
    743 	struct inode *inode = d_inode(dentry);
    744 	const struct cred *old_cred;
    745 	int err;
    746 
    747 	if (WARN_ON(!inode))
    748 		return -ENOENT;
    749 
    750 	/*
    751 	 * With inodes index is enabled, we store the union overlay nlink
    752 	 * in an xattr on the index inode. When whiting out an indexed lower,
    753 	 * we need to decrement the overlay persistent nlink, but before the
    754 	 * first copy up, we have no upper index inode to store the xattr.
    755 	 *
    756 	 * As a workaround, before whiteout/rename over an indexed lower,
    757 	 * copy up to create the upper index. Creating the upper index will
    758 	 * initialize the overlay nlink, so it could be dropped if unlink
    759 	 * or rename succeeds.
    760 	 *
    761 	 * TODO: implement metadata only index copy up when called with
    762 	 *       ovl_copy_up_flags(dentry, O_PATH).
    763 	 */
    764 	if (ovl_need_index(dentry) && !ovl_dentry_has_upper_alias(dentry)) {
    765 		err = ovl_copy_up(dentry);
    766 		if (err)
    767 			return err;
    768 	}
    769 
    770 	err = ovl_inode_lock(inode);
    771 	if (err)
    772 		return err;
    773 
    774 	if (d_is_dir(dentry) || !ovl_test_flag(OVL_INDEX, inode))
    775 		goto out;
    776 
    777 	old_cred = ovl_override_creds(dentry->d_sb);
    778 	/*
    779 	 * The overlay inode nlink should be incremented/decremented IFF the
    780 	 * upper operation succeeds, along with nlink change of upper inode.
    781 	 * Therefore, before link/unlink/rename, we store the union nlink
    782 	 * value relative to the upper inode nlink in an upper inode xattr.
    783 	 */
    784 	err = ovl_set_nlink_upper(dentry);
    785 	revert_creds(old_cred);
    786 
    787 out:
    788 	if (err)
    789 		ovl_inode_unlock(inode);
    790 
    791 	return err;
    792 }
    793 
    794 void ovl_nlink_end(struct dentry *dentry)
    795 {
    796 	struct inode *inode = d_inode(dentry);
    797 
    798 	if (ovl_test_flag(OVL_INDEX, inode) && inode->i_nlink == 0) {
    799 		const struct cred *old_cred;
    800 
    801 		old_cred = ovl_override_creds(dentry->d_sb);
    802 		ovl_cleanup_index(dentry);
    803 		revert_creds(old_cred);
    804 	}
    805 
    806 	ovl_inode_unlock(inode);
    807 }
    808 
    809 int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
    810 {
    811 	/* Workdir should not be the same as upperdir */
    812 	if (workdir == upperdir)
    813 		goto err;
    814 
    815 	/* Workdir should not be subdir of upperdir and vice versa */
    816 	if (lock_rename(workdir, upperdir) != NULL)
    817 		goto err_unlock;
    818 
    819 	return 0;
    820 
    821 err_unlock:
    822 	unlock_rename(workdir, upperdir);
    823 err:
    824 	pr_err("overlayfs: failed to lock workdir+upperdir\n");
    825 	return -EIO;
    826 }
    827 
    828 /* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */
    829 int ovl_check_metacopy_xattr(struct dentry *dentry)
    830 {
    831 	int res;
    832 
    833 	/* Only regular files can have metacopy xattr */
    834 	if (!S_ISREG(d_inode(dentry)->i_mode))
    835 		return 0;
    836 
    837 	res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);
    838 	if (res < 0) {
    839 		if (res == -ENODATA || res == -EOPNOTSUPP)
    840 			return 0;
    841 		goto out;
    842 	}
    843 
    844 	return 1;
    845 out:
    846 	pr_warn_ratelimited("overlayfs: failed to get metacopy (%i)\n", res);
    847 	return res;
    848 }
    849 
    850 bool ovl_is_metacopy_dentry(struct dentry *dentry)
    851 {
    852 	struct ovl_entry *oe = dentry->d_fsdata;
    853 
    854 	if (!d_is_reg(dentry))
    855 		return false;
    856 
    857 	if (ovl_dentry_upper(dentry)) {
    858 		if (!ovl_has_upperdata(d_inode(dentry)))
    859 			return true;
    860 		return false;
    861 	}
    862 
    863 	return (oe->numlower > 1);
    864 }
    865 
    866 ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value,
    867 		     size_t padding)
    868 {
    869 	ssize_t res;
    870 	char *buf = NULL;
    871 
    872 	res = vfs_getxattr(dentry, name, NULL, 0);
    873 	if (res < 0) {
    874 		if (res == -ENODATA || res == -EOPNOTSUPP)
    875 			return -ENODATA;
    876 		goto fail;
    877 	}
    878 
    879 	if (res != 0) {
    880 		buf = kzalloc(res + padding, GFP_KERNEL);
    881 		if (!buf)
    882 			return -ENOMEM;
    883 
    884 		res = vfs_getxattr(dentry, name, buf, res);
    885 		if (res < 0)
    886 			goto fail;
    887 	}
    888 	*value = buf;
    889 
    890 	return res;
    891 
    892 fail:
    893 	pr_warn_ratelimited("overlayfs: failed to get xattr %s: err=%zi)\n",
    894 			    name, res);
    895 	kfree(buf);
    896 	return res;
    897 }
    898 
    899 char *ovl_get_redirect_xattr(struct dentry *dentry, int padding)
    900 {
    901 	int res;
    902 	char *s, *next, *buf = NULL;
    903 
    904 	res = ovl_getxattr(dentry, OVL_XATTR_REDIRECT, &buf, padding + 1);
    905 	if (res == -ENODATA)
    906 		return NULL;
    907 	if (res < 0)
    908 		return ERR_PTR(res);
    909 	if (res == 0)
    910 		goto invalid;
    911 
    912 	if (buf[0] == '/') {
    913 		for (s = buf; *s++ == '/'; s = next) {
    914 			next = strchrnul(s, '/');
    915 			if (s == next)
    916 				goto invalid;
    917 		}
    918 	} else {
    919 		if (strchr(buf, '/') != NULL)
    920 			goto invalid;
    921 	}
    922 
    923 	return buf;
    924 invalid:
    925 	pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf);
    926 	res = -EINVAL;
    927 	kfree(buf);
    928 	return ERR_PTR(res);
    929 }