super.c 24.3 KB
Newer Older
M
Miklos Szeredi 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
/*
 *
 * Copyright (C) 2011 Novell Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/xattr.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/parser.h>
#include <linux/module.h>
#include <linux/sched.h>
A
Andy Whitcroft 已提交
19
#include <linux/statfs.h>
E
Erez Zadok 已提交
20
#include <linux/seq_file.h>
M
Miklos Szeredi 已提交
21 22 23 24 25 26
#include "overlayfs.h"

MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
MODULE_DESCRIPTION("Overlay filesystem");
MODULE_LICENSE("GPL");

E
Erez Zadok 已提交
27 28 29 30
struct ovl_config {
	char *lowerdir;
	char *upperdir;
	char *workdir;
M
Miklos Szeredi 已提交
31
	bool default_permissions;
E
Erez Zadok 已提交
32 33
};

M
Miklos Szeredi 已提交
34 35 36
/* private information held for overlayfs's superblock */
struct ovl_fs {
	struct vfsmount *upper_mnt;
37 38
	unsigned numlower;
	struct vfsmount **lower_mnt;
M
Miklos Szeredi 已提交
39
	struct dentry *workdir;
A
Andy Whitcroft 已提交
40
	long lower_namelen;
E
Erez Zadok 已提交
41 42
	/* pathnames of lower and upper dirs, for show_options */
	struct ovl_config config;
M
Miklos Szeredi 已提交
43 44 45 46 47 48 49 50 51 52 53 54 55 56 57
};

struct ovl_dir_cache;

/* private information held for every overlayfs dentry */
struct ovl_entry {
	struct dentry *__upperdentry;
	struct ovl_dir_cache *cache;
	union {
		struct {
			u64 version;
			bool opaque;
		};
		struct rcu_head rcu;
	};
58 59
	unsigned numlower;
	struct path lowerstack[];
M
Miklos Szeredi 已提交
60 61
};

62 63
#define OVL_MAX_STACK 500

64 65 66 67
static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
{
	return oe->numlower ? oe->lowerstack[0].dentry : NULL;
}
M
Miklos Szeredi 已提交
68 69 70 71

enum ovl_path_type ovl_path_type(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;
M
Miklos Szeredi 已提交
72
	enum ovl_path_type type = 0;
M
Miklos Szeredi 已提交
73 74

	if (oe->__upperdentry) {
M
Miklos Szeredi 已提交
75 76
		type = __OVL_PATH_UPPER;

77
		if (oe->numlower) {
M
Miklos Szeredi 已提交
78
			if (S_ISDIR(dentry->d_inode->i_mode))
M
Miklos Szeredi 已提交
79 80 81
				type |= __OVL_PATH_MERGE;
		} else if (!oe->opaque) {
			type |= __OVL_PATH_PURE;
M
Miklos Szeredi 已提交
82
		}
M
Miklos Szeredi 已提交
83 84 85
	} else {
		if (oe->numlower > 1)
			type |= __OVL_PATH_MERGE;
M
Miklos Szeredi 已提交
86
	}
M
Miklos Szeredi 已提交
87
	return type;
M
Miklos Szeredi 已提交
88 89 90 91
}

static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
{
92
	return lockless_dereference(oe->__upperdentry);
M
Miklos Szeredi 已提交
93 94 95 96 97 98 99 100 101 102 103 104 105 106 107
}

void ovl_path_upper(struct dentry *dentry, struct path *path)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	struct ovl_entry *oe = dentry->d_fsdata;

	path->mnt = ofs->upper_mnt;
	path->dentry = ovl_upperdentry_dereference(oe);
}

enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
{
	enum ovl_path_type type = ovl_path_type(dentry);

M
Miklos Szeredi 已提交
108
	if (!OVL_TYPE_UPPER(type))
M
Miklos Szeredi 已提交
109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126
		ovl_path_lower(dentry, path);
	else
		ovl_path_upper(dentry, path);

	return type;
}

struct dentry *ovl_dentry_upper(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	return ovl_upperdentry_dereference(oe);
}

struct dentry *ovl_dentry_lower(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

127
	return __ovl_dentry_lower(oe);
M
Miklos Szeredi 已提交
128 129 130 131 132 133 134 135 136
}

struct dentry *ovl_dentry_real(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	struct dentry *realdentry;

	realdentry = ovl_upperdentry_dereference(oe);
	if (!realdentry)
137
		realdentry = __ovl_dentry_lower(oe);
M
Miklos Szeredi 已提交
138 139 140 141 142 143 144 145 146 147 148 149

	return realdentry;
}

struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
{
	struct dentry *realdentry;

	realdentry = ovl_upperdentry_dereference(oe);
	if (realdentry) {
		*is_upper = true;
	} else {
150
		realdentry = __ovl_dentry_lower(oe);
M
Miklos Szeredi 已提交
151 152 153 154 155
		*is_upper = false;
	}
	return realdentry;
}

M
Miklos Szeredi 已提交
156 157 158 159 160 161 162 163 164 165 166 167
struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,
				    bool is_upper)
{
	if (is_upper) {
		struct ovl_fs *ofs = inode->i_sb->s_fs_info;

		return ofs->upper_mnt;
	} else {
		return oe->numlower ? oe->lowerstack[0].mnt : NULL;
	}
}

M
Miklos Szeredi 已提交
168 169 170 171 172 173 174
struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	return oe->cache;
}

M
Miklos Szeredi 已提交
175 176 177 178 179 180 181
bool ovl_is_default_permissions(struct inode *inode)
{
	struct ovl_fs *ofs = inode->i_sb->s_fs_info;

	return ofs->config.default_permissions;
}

M
Miklos Szeredi 已提交
182 183 184 185 186 187 188 189 190 191 192
void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	oe->cache = cache;
}

void ovl_path_lower(struct dentry *dentry, struct path *path)
{
	struct ovl_entry *oe = dentry->d_fsdata;

193
	*path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
M
Miklos Szeredi 已提交
194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272
}

int ovl_want_write(struct dentry *dentry)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	return mnt_want_write(ofs->upper_mnt);
}

void ovl_drop_write(struct dentry *dentry)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	mnt_drop_write(ofs->upper_mnt);
}

struct dentry *ovl_workdir(struct dentry *dentry)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	return ofs->workdir;
}

bool ovl_dentry_is_opaque(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	return oe->opaque;
}

void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	oe->opaque = opaque;
}

void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
	WARN_ON(oe->__upperdentry);
	BUG_ON(!upperdentry->d_inode);
	/*
	 * Make sure upperdentry is consistent before making it visible to
	 * ovl_upperdentry_dereference().
	 */
	smp_wmb();
	oe->__upperdentry = upperdentry;
}

void ovl_dentry_version_inc(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
	oe->version++;
}

u64 ovl_dentry_version_get(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
	return oe->version;
}

bool ovl_is_whiteout(struct dentry *dentry)
{
	struct inode *inode = dentry->d_inode;

	return inode && IS_WHITEOUT(inode);
}

static bool ovl_is_opaquedir(struct dentry *dentry)
{
	int res;
	char val;
	struct inode *inode = dentry->d_inode;

	if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr)
		return false;

H
hujianyang 已提交
273
	res = inode->i_op->getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
M
Miklos Szeredi 已提交
274 275 276 277 278 279 280 281 282 283 284
	if (res == 1 && val == 'y')
		return true;

	return false;
}

static void ovl_dentry_release(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	if (oe) {
285 286
		unsigned int i;

M
Miklos Szeredi 已提交
287
		dput(oe->__upperdentry);
288 289
		for (i = 0; i < oe->numlower; i++)
			dput(oe->lowerstack[i].dentry);
M
Miklos Szeredi 已提交
290 291 292 293
		kfree_rcu(oe, rcu);
	}
}

294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334
static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	unsigned int i;
	int ret = 1;

	for (i = 0; i < oe->numlower; i++) {
		struct dentry *d = oe->lowerstack[i].dentry;

		if (d->d_flags & DCACHE_OP_REVALIDATE) {
			ret = d->d_op->d_revalidate(d, flags);
			if (ret < 0)
				return ret;
			if (!ret) {
				if (!(flags & LOOKUP_RCU))
					d_invalidate(d);
				return -ESTALE;
			}
		}
	}
	return 1;
}

static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	unsigned int i;
	int ret = 1;

	for (i = 0; i < oe->numlower; i++) {
		struct dentry *d = oe->lowerstack[i].dentry;

		if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
			ret = d->d_op->d_weak_revalidate(d, flags);
			if (ret <= 0)
				break;
		}
	}
	return ret;
}

M
Miklos Szeredi 已提交
335 336
static const struct dentry_operations ovl_dentry_operations = {
	.d_release = ovl_dentry_release,
337
	.d_select_inode = ovl_d_select_inode,
M
Miklos Szeredi 已提交
338 339
};

340 341 342 343 344 345
static const struct dentry_operations ovl_reval_dentry_operations = {
	.d_release = ovl_dentry_release,
	.d_revalidate = ovl_dentry_revalidate,
	.d_weak_revalidate = ovl_dentry_weak_revalidate,
};

346
static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
M
Miklos Szeredi 已提交
347
{
348 349 350 351 352 353 354
	size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
	struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);

	if (oe)
		oe->numlower = numlower;

	return oe;
M
Miklos Szeredi 已提交
355 356
}

357 358 359 360 361 362 363 364 365 366 367 368 369 370
static bool ovl_dentry_remote(struct dentry *dentry)
{
	return dentry->d_flags &
		(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
}

static bool ovl_dentry_weird(struct dentry *dentry)
{
	return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
				  DCACHE_MANAGE_TRANSIT |
				  DCACHE_OP_HASH |
				  DCACHE_OP_COMPARE);
}

M
Miklos Szeredi 已提交
371 372 373 374 375 376 377 378 379 380 381 382 383 384 385
static inline struct dentry *ovl_lookup_real(struct dentry *dir,
					     struct qstr *name)
{
	struct dentry *dentry;

	mutex_lock(&dir->d_inode->i_mutex);
	dentry = lookup_one_len(name->name, dir, name->len);
	mutex_unlock(&dir->d_inode->i_mutex);

	if (IS_ERR(dentry)) {
		if (PTR_ERR(dentry) == -ENOENT)
			dentry = NULL;
	} else if (!dentry->d_inode) {
		dput(dentry);
		dentry = NULL;
386
	} else if (ovl_dentry_weird(dentry)) {
387
		dput(dentry);
388
		/* Don't support traversing automounts and other weirdness */
389
		dentry = ERR_PTR(-EREMOTE);
M
Miklos Szeredi 已提交
390 391 392 393
	}
	return dentry;
}

M
Miklos Szeredi 已提交
394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414
/*
 * Returns next layer in stack starting from top.
 * Returns -1 if this is the last layer.
 */
int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	BUG_ON(idx < 0);
	if (idx == 0) {
		ovl_path_upper(dentry, path);
		if (path->dentry)
			return oe->numlower ? 1 : -1;
		idx++;
	}
	BUG_ON(idx > oe->numlower);
	*path = oe->lowerstack[idx - 1];

	return (idx < oe->numlower) ? idx + 1 : -1;
}

M
Miklos Szeredi 已提交
415 416 417 418
struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
			  unsigned int flags)
{
	struct ovl_entry *oe;
M
Miklos Szeredi 已提交
419 420 421 422
	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
	struct path *stack = NULL;
	struct dentry *upperdir, *upperdentry = NULL;
	unsigned int ctr = 0;
M
Miklos Szeredi 已提交
423
	struct inode *inode = NULL;
M
Miklos Szeredi 已提交
424 425 426
	bool upperopaque = false;
	struct dentry *this, *prev = NULL;
	unsigned int i;
M
Miklos Szeredi 已提交
427 428
	int err;

M
Miklos Szeredi 已提交
429
	upperdir = ovl_upperdentry_dereference(poe);
M
Miklos Szeredi 已提交
430
	if (upperdir) {
M
Miklos Szeredi 已提交
431 432 433 434 435
		this = ovl_lookup_real(upperdir, &dentry->d_name);
		err = PTR_ERR(this);
		if (IS_ERR(this))
			goto out;

436
		if (this) {
437 438 439 440 441
			if (unlikely(ovl_dentry_remote(this))) {
				dput(this);
				err = -EREMOTE;
				goto out;
			}
M
Miklos Szeredi 已提交
442 443 444 445
			if (ovl_is_whiteout(this)) {
				dput(this);
				this = NULL;
				upperopaque = true;
446
			} else if (poe->numlower && ovl_is_opaquedir(this)) {
M
Miklos Szeredi 已提交
447
				upperopaque = true;
M
Miklos Szeredi 已提交
448 449
			}
		}
M
Miklos Szeredi 已提交
450
		upperdentry = prev = this;
M
Miklos Szeredi 已提交
451
	}
M
Miklos Szeredi 已提交
452 453 454 455 456 457

	if (!upperopaque && poe->numlower) {
		err = -ENOMEM;
		stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
		if (!stack)
			goto out_put_upper;
M
Miklos Szeredi 已提交
458 459
	}

M
Miklos Szeredi 已提交
460 461 462 463 464 465
	for (i = 0; !upperopaque && i < poe->numlower; i++) {
		bool opaque = false;
		struct path lowerpath = poe->lowerstack[i];

		this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
		err = PTR_ERR(this);
466 467 468 469 470 471
		if (IS_ERR(this)) {
			/*
			 * If it's positive, then treat ENAMETOOLONG as ENOENT.
			 */
			if (err == -ENAMETOOLONG && (upperdentry || ctr))
				continue;
M
Miklos Szeredi 已提交
472
			goto out_put;
473
		}
M
Miklos Szeredi 已提交
474 475
		if (!this)
			continue;
476 477 478 479
		if (ovl_is_whiteout(this)) {
			dput(this);
			break;
		}
M
Miklos Szeredi 已提交
480
		/*
481 482
		 * Only makes sense to check opaque dir if this is not the
		 * lowermost layer.
M
Miklos Szeredi 已提交
483
		 */
484 485
		if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
			opaque = true;
486 487 488 489 490 491 492

		if (prev && (!S_ISDIR(prev->d_inode->i_mode) ||
			     !S_ISDIR(this->d_inode->i_mode))) {
			/*
			 * FIXME: check for upper-opaqueness maybe better done
			 * in remove code.
			 */
M
Miklos Szeredi 已提交
493 494 495 496 497
			if (prev == upperdentry)
				upperopaque = true;
			dput(this);
			break;
		}
498 499 500 501 502 503
		/*
		 * If this is a non-directory then stop here.
		 */
		if (!S_ISDIR(this->d_inode->i_mode))
			opaque = true;

M
Miklos Szeredi 已提交
504 505 506 507 508 509
		stack[ctr].dentry = this;
		stack[ctr].mnt = lowerpath.mnt;
		ctr++;
		prev = this;
		if (opaque)
			break;
M
Miklos Szeredi 已提交
510 511
	}

M
Miklos Szeredi 已提交
512 513 514 515 516 517
	oe = ovl_alloc_entry(ctr);
	err = -ENOMEM;
	if (!oe)
		goto out_put;

	if (upperdentry || ctr) {
M
Miklos Szeredi 已提交
518 519
		struct dentry *realdentry;

M
Miklos Szeredi 已提交
520 521
		realdentry = upperdentry ? upperdentry : stack[0].dentry;

M
Miklos Szeredi 已提交
522 523 524 525
		err = -ENOMEM;
		inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,
				      oe);
		if (!inode)
M
Miklos Szeredi 已提交
526
			goto out_free_oe;
M
Miklos Szeredi 已提交
527 528 529
		ovl_copyattr(realdentry->d_inode, inode);
	}

M
Miklos Szeredi 已提交
530
	oe->opaque = upperopaque;
M
Miklos Szeredi 已提交
531
	oe->__upperdentry = upperdentry;
M
Miklos Szeredi 已提交
532 533
	memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
	kfree(stack);
M
Miklos Szeredi 已提交
534 535 536 537 538
	dentry->d_fsdata = oe;
	d_add(dentry, inode);

	return NULL;

M
Miklos Szeredi 已提交
539
out_free_oe:
M
Miklos Szeredi 已提交
540
	kfree(oe);
M
Miklos Szeredi 已提交
541 542 543 544 545 546
out_put:
	for (i = 0; i < ctr; i++)
		dput(stack[i].dentry);
	kfree(stack);
out_put_upper:
	dput(upperdentry);
M
Miklos Szeredi 已提交
547 548 549 550 551 552 553 554 555 556 557 558
out:
	return ERR_PTR(err);
}

struct file *ovl_path_open(struct path *path, int flags)
{
	return dentry_open(path, flags, current_cred());
}

static void ovl_put_super(struct super_block *sb)
{
	struct ovl_fs *ufs = sb->s_fs_info;
559
	unsigned i;
M
Miklos Szeredi 已提交
560 561 562

	dput(ufs->workdir);
	mntput(ufs->upper_mnt);
563 564
	for (i = 0; i < ufs->numlower; i++)
		mntput(ufs->lower_mnt[i]);
565
	kfree(ufs->lower_mnt);
M
Miklos Szeredi 已提交
566

E
Erez Zadok 已提交
567 568 569
	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
M
Miklos Szeredi 已提交
570 571 572
	kfree(ufs);
}

A
Andy Whitcroft 已提交
573 574 575 576 577 578
/**
 * ovl_statfs
 * @sb: The overlayfs super block
 * @buf: The struct kstatfs to fill in with stats
 *
 * Get the filesystem statistics.  As writes always target the upper layer
579
 * filesystem pass the statfs to the upper filesystem (if it exists)
A
Andy Whitcroft 已提交
580 581 582 583 584 585 586 587
 */
static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	struct dentry *root_dentry = dentry->d_sb->s_root;
	struct path path;
	int err;

588
	ovl_path_real(root_dentry, &path);
A
Andy Whitcroft 已提交
589 590 591 592 593 594 595 596 597 598

	err = vfs_statfs(&path, buf);
	if (!err) {
		buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen);
		buf->f_type = OVERLAYFS_SUPER_MAGIC;
	}

	return err;
}

E
Erez Zadok 已提交
599 600 601 602 603 604 605 606 607 608 609 610
/**
 * ovl_show_options
 *
 * Prints the mount options for a given superblock.
 * Returns zero; does not fail.
 */
static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
{
	struct super_block *sb = dentry->d_sb;
	struct ovl_fs *ufs = sb->s_fs_info;

	seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir);
M
Miklos Szeredi 已提交
611 612 613 614
	if (ufs->config.upperdir) {
		seq_printf(m, ",upperdir=%s", ufs->config.upperdir);
		seq_printf(m, ",workdir=%s", ufs->config.workdir);
	}
M
Miklos Szeredi 已提交
615 616
	if (ufs->config.default_permissions)
		seq_puts(m, ",default_permissions");
E
Erez Zadok 已提交
617 618 619
	return 0;
}

620 621 622 623
static int ovl_remount(struct super_block *sb, int *flags, char *data)
{
	struct ovl_fs *ufs = sb->s_fs_info;

624
	if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
625 626 627 628 629
		return -EROFS;

	return 0;
}

M
Miklos Szeredi 已提交
630 631
static const struct super_operations ovl_super_operations = {
	.put_super	= ovl_put_super,
A
Andy Whitcroft 已提交
632
	.statfs		= ovl_statfs,
E
Erez Zadok 已提交
633
	.show_options	= ovl_show_options,
634
	.remount_fs	= ovl_remount,
M
Miklos Szeredi 已提交
635 636 637 638 639 640
};

enum {
	OPT_LOWERDIR,
	OPT_UPPERDIR,
	OPT_WORKDIR,
M
Miklos Szeredi 已提交
641
	OPT_DEFAULT_PERMISSIONS,
M
Miklos Szeredi 已提交
642 643 644 645 646 647 648
	OPT_ERR,
};

static const match_table_t ovl_tokens = {
	{OPT_LOWERDIR,			"lowerdir=%s"},
	{OPT_UPPERDIR,			"upperdir=%s"},
	{OPT_WORKDIR,			"workdir=%s"},
M
Miklos Szeredi 已提交
649
	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
M
Miklos Szeredi 已提交
650 651 652
	{OPT_ERR,			NULL}
};

M
Miklos Szeredi 已提交
653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675
static char *ovl_next_opt(char **s)
{
	char *sbegin = *s;
	char *p;

	if (sbegin == NULL)
		return NULL;

	for (p = sbegin; *p; p++) {
		if (*p == '\\') {
			p++;
			if (!*p)
				break;
		} else if (*p == ',') {
			*p = '\0';
			*s = p + 1;
			return sbegin;
		}
	}
	*s = NULL;
	return sbegin;
}

M
Miklos Szeredi 已提交
676 677 678 679
static int ovl_parse_opt(char *opt, struct ovl_config *config)
{
	char *p;

M
Miklos Szeredi 已提交
680
	while ((p = ovl_next_opt(&opt)) != NULL) {
M
Miklos Szeredi 已提交
681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709
		int token;
		substring_t args[MAX_OPT_ARGS];

		if (!*p)
			continue;

		token = match_token(p, ovl_tokens, args);
		switch (token) {
		case OPT_UPPERDIR:
			kfree(config->upperdir);
			config->upperdir = match_strdup(&args[0]);
			if (!config->upperdir)
				return -ENOMEM;
			break;

		case OPT_LOWERDIR:
			kfree(config->lowerdir);
			config->lowerdir = match_strdup(&args[0]);
			if (!config->lowerdir)
				return -ENOMEM;
			break;

		case OPT_WORKDIR:
			kfree(config->workdir);
			config->workdir = match_strdup(&args[0]);
			if (!config->workdir)
				return -ENOMEM;
			break;

M
Miklos Szeredi 已提交
710 711 712 713
		case OPT_DEFAULT_PERMISSIONS:
			config->default_permissions = true;
			break;

M
Miklos Szeredi 已提交
714
		default:
715
			pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
M
Miklos Szeredi 已提交
716 717 718
			return -EINVAL;
		}
	}
H
hujianyang 已提交
719 720 721 722 723 724 725 726 727

	/* Workdir is useless in non-upper mount */
	if (!config->upperdir && config->workdir) {
		pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
			config->workdir);
		kfree(config->workdir);
		config->workdir = NULL;
	}

M
Miklos Szeredi 已提交
728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781
	return 0;
}

#define OVL_WORKDIR_NAME "work"

static struct dentry *ovl_workdir_create(struct vfsmount *mnt,
					 struct dentry *dentry)
{
	struct inode *dir = dentry->d_inode;
	struct dentry *work;
	int err;
	bool retried = false;

	err = mnt_want_write(mnt);
	if (err)
		return ERR_PTR(err);

	mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
retry:
	work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
			      strlen(OVL_WORKDIR_NAME));

	if (!IS_ERR(work)) {
		struct kstat stat = {
			.mode = S_IFDIR | 0,
		};

		if (work->d_inode) {
			err = -EEXIST;
			if (retried)
				goto out_dput;

			retried = true;
			ovl_cleanup(dir, work);
			dput(work);
			goto retry;
		}

		err = ovl_create_real(dir, work, &stat, NULL, NULL, true);
		if (err)
			goto out_dput;
	}
out_unlock:
	mutex_unlock(&dir->i_mutex);
	mnt_drop_write(mnt);

	return work;

out_dput:
	dput(work);
	work = ERR_PTR(err);
	goto out_unlock;
}

M
Miklos Szeredi 已提交
782 783 784 785 786 787 788 789 790 791 792 793 794
static void ovl_unescape(char *s)
{
	char *d = s;

	for (;; s++, d++) {
		if (*s == '\\')
			s++;
		*d = *s;
		if (!*s)
			break;
	}
}

M
Miklos Szeredi 已提交
795 796
static int ovl_mount_dir_noesc(const char *name, struct path *path)
{
797
	int err = -EINVAL;
M
Miklos Szeredi 已提交
798

799 800 801 802
	if (!*name) {
		pr_err("overlayfs: empty lowerdir\n");
		goto out;
	}
M
Miklos Szeredi 已提交
803 804 805 806 807 808
	err = kern_path(name, LOOKUP_FOLLOW, path);
	if (err) {
		pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
		goto out;
	}
	err = -EINVAL;
809
	if (ovl_dentry_weird(path->dentry)) {
M
Miklos Szeredi 已提交
810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832
		pr_err("overlayfs: filesystem on '%s' not supported\n", name);
		goto out_put;
	}
	if (!S_ISDIR(path->dentry->d_inode->i_mode)) {
		pr_err("overlayfs: '%s' not a directory\n", name);
		goto out_put;
	}
	return 0;

out_put:
	path_put(path);
out:
	return err;
}

static int ovl_mount_dir(const char *name, struct path *path)
{
	int err = -ENOMEM;
	char *tmp = kstrdup(name, GFP_KERNEL);

	if (tmp) {
		ovl_unescape(tmp);
		err = ovl_mount_dir_noesc(tmp, path);
833 834 835 836 837 838 839 840

		if (!err)
			if (ovl_dentry_remote(path->dentry)) {
				pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
				       tmp);
				path_put(path);
				err = -EINVAL;
			}
M
Miklos Szeredi 已提交
841 842 843 844 845 846
		kfree(tmp);
	}
	return err;
}

static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
847
			 int *stack_depth, bool *remote)
M
Miklos Szeredi 已提交
848 849 850 851
{
	int err;
	struct kstatfs statfs;

852
	err = ovl_mount_dir_noesc(name, path);
M
Miklos Szeredi 已提交
853 854 855 856 857 858 859 860 861 862 863
	if (err)
		goto out;

	err = vfs_statfs(path, &statfs);
	if (err) {
		pr_err("overlayfs: statfs failed on '%s'\n", name);
		goto out_put;
	}
	*namelen = max(*namelen, statfs.f_namelen);
	*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);

864 865 866
	if (ovl_dentry_remote(path->dentry))
		*remote = true;

M
Miklos Szeredi 已提交
867 868 869 870 871 872 873 874
	return 0;

out_put:
	path_put(path);
out:
	return err;
}

M
Miklos Szeredi 已提交
875 876 877 878 879 880 881 882 883 884 885 886
/* Workdir should not be subdir of upperdir and vice versa */
static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
{
	bool ok = false;

	if (workdir != upperdir) {
		ok = (lock_rename(workdir, upperdir) == NULL);
		unlock_rename(workdir, upperdir);
	}
	return ok;
}

887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906
static unsigned int ovl_split_lowerdirs(char *str)
{
	unsigned int ctr = 1;
	char *s, *d;

	for (s = d = str;; s++, d++) {
		if (*s == '\\') {
			s++;
		} else if (*s == ':') {
			*d = '\0';
			ctr++;
			continue;
		}
		*d = *s;
		if (!*s)
			break;
	}
	return ctr;
}

M
Miklos Szeredi 已提交
907 908
static int ovl_fill_super(struct super_block *sb, void *data, int silent)
{
M
Miklos Szeredi 已提交
909 910
	struct path upperpath = { NULL, NULL };
	struct path workpath = { NULL, NULL };
M
Miklos Szeredi 已提交
911 912 913
	struct dentry *root_dentry;
	struct ovl_entry *oe;
	struct ovl_fs *ufs;
914 915 916 917 918
	struct path *stack = NULL;
	char *lowertmp;
	char *lower;
	unsigned int numlower;
	unsigned int stacklen = 0;
919
	unsigned int i;
920
	bool remote = false;
M
Miklos Szeredi 已提交
921 922
	int err;

E
Erez Zadok 已提交
923 924 925
	err = -ENOMEM;
	ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
	if (!ufs)
M
Miklos Szeredi 已提交
926 927
		goto out;

E
Erez Zadok 已提交
928 929 930 931
	err = ovl_parse_opt((char *) data, &ufs->config);
	if (err)
		goto out_free_config;

M
Miklos Szeredi 已提交
932
	err = -EINVAL;
M
Miklos Szeredi 已提交
933 934
	if (!ufs->config.lowerdir) {
		pr_err("overlayfs: missing 'lowerdir'\n");
M
Miklos Szeredi 已提交
935 936 937
		goto out_free_config;
	}

M
Miklos Szeredi 已提交
938 939 940 941 942 943
	sb->s_stack_depth = 0;
	if (ufs->config.upperdir) {
		if (!ufs->config.workdir) {
			pr_err("overlayfs: missing 'workdir'\n");
			goto out_free_config;
		}
M
Miklos Szeredi 已提交
944

M
Miklos Szeredi 已提交
945 946 947
		err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
		if (err)
			goto out_free_config;
M
Miklos Szeredi 已提交
948

H
hujianyang 已提交
949 950 951 952 953 954 955
		/* Upper fs should not be r/o */
		if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {
			pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
			err = -EINVAL;
			goto out_put_upperpath;
		}

M
Miklos Szeredi 已提交
956 957 958 959
		err = ovl_mount_dir(ufs->config.workdir, &workpath);
		if (err)
			goto out_put_upperpath;

960
		err = -EINVAL;
M
Miklos Szeredi 已提交
961 962 963 964 965 966 967 968 969
		if (upperpath.mnt != workpath.mnt) {
			pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
			goto out_put_workpath;
		}
		if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
			pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
			goto out_put_workpath;
		}
		sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
A
Andy Whitcroft 已提交
970
	}
971 972 973
	err = -ENOMEM;
	lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
	if (!lowertmp)
M
Miklos Szeredi 已提交
974
		goto out_put_workpath;
975

976 977
	err = -EINVAL;
	stacklen = ovl_split_lowerdirs(lowertmp);
978 979 980
	if (stacklen > OVL_MAX_STACK) {
		pr_err("overlayfs: too many lower directries, limit is %d\n",
		       OVL_MAX_STACK);
981
		goto out_free_lowertmp;
982 983 984 985
	} else if (!ufs->config.upperdir && stacklen == 1) {
		pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
		goto out_free_lowertmp;
	}
986 987 988 989 990 991 992 993

	stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
	if (!stack)
		goto out_free_lowertmp;

	lower = lowertmp;
	for (numlower = 0; numlower < stacklen; numlower++) {
		err = ovl_lower_dir(lower, &stack[numlower],
994 995
				    &ufs->lower_namelen, &sb->s_stack_depth,
				    &remote);
996 997 998 999 1000 1001
		if (err)
			goto out_put_lowerpath;

		lower = strchr(lower, '\0') + 1;
	}

1002
	err = -EINVAL;
M
Miklos Szeredi 已提交
1003
	sb->s_stack_depth++;
1004 1005
	if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
		pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1006
		goto out_put_lowerpath;
1007 1008
	}

M
Miklos Szeredi 已提交
1009 1010 1011 1012 1013 1014 1015
	if (ufs->config.upperdir) {
		ufs->upper_mnt = clone_private_mount(&upperpath);
		err = PTR_ERR(ufs->upper_mnt);
		if (IS_ERR(ufs->upper_mnt)) {
			pr_err("overlayfs: failed to clone upperpath\n");
			goto out_put_lowerpath;
		}
1016

M
Miklos Szeredi 已提交
1017 1018 1019
		ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
		err = PTR_ERR(ufs->workdir);
		if (IS_ERR(ufs->workdir)) {
1020 1021 1022 1023
			pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
				ufs->config.workdir, OVL_WORKDIR_NAME, -err);
			sb->s_flags |= MS_RDONLY;
			ufs->workdir = NULL;
M
Miklos Szeredi 已提交
1024
		}
M
Miklos Szeredi 已提交
1025 1026
	}

1027
	err = -ENOMEM;
1028
	ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
1029
	if (ufs->lower_mnt == NULL)
1030
		goto out_put_workdir;
1031 1032
	for (i = 0; i < numlower; i++) {
		struct vfsmount *mnt = clone_private_mount(&stack[i]);
1033

1034
		err = PTR_ERR(mnt);
1035 1036 1037 1038 1039 1040 1041 1042 1043
		if (IS_ERR(mnt)) {
			pr_err("overlayfs: failed to clone lowerpath\n");
			goto out_put_lower_mnt;
		}
		/*
		 * Make lower_mnt R/O.  That way fchmod/fchown on lower file
		 * will fail instead of modifying lower fs.
		 */
		mnt->mnt_flags |= MNT_READONLY;
1044

1045 1046 1047
		ufs->lower_mnt[ufs->numlower] = mnt;
		ufs->numlower++;
	}
M
Miklos Szeredi 已提交
1048

H
hujianyang 已提交
1049 1050
	/* If the upper fs is nonexistent, we mark overlayfs r/o too */
	if (!ufs->upper_mnt)
M
Miklos Szeredi 已提交
1051 1052
		sb->s_flags |= MS_RDONLY;

1053 1054 1055 1056
	if (remote)
		sb->s_d_op = &ovl_reval_dentry_operations;
	else
		sb->s_d_op = &ovl_dentry_operations;
M
Miklos Szeredi 已提交
1057 1058

	err = -ENOMEM;
1059
	oe = ovl_alloc_entry(numlower);
1060 1061
	if (!oe)
		goto out_put_lower_mnt;
M
Miklos Szeredi 已提交
1062

1063
	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, oe));
M
Miklos Szeredi 已提交
1064
	if (!root_dentry)
1065
		goto out_free_oe;
M
Miklos Szeredi 已提交
1066 1067

	mntput(upperpath.mnt);
1068 1069
	for (i = 0; i < numlower; i++)
		mntput(stack[i].mnt);
M
Miklos Szeredi 已提交
1070
	path_put(&workpath);
1071
	kfree(lowertmp);
M
Miklos Szeredi 已提交
1072 1073

	oe->__upperdentry = upperpath.dentry;
1074 1075 1076 1077
	for (i = 0; i < numlower; i++) {
		oe->lowerstack[i].dentry = stack[i].dentry;
		oe->lowerstack[i].mnt = ufs->lower_mnt[i];
	}
1078
	kfree(stack);
M
Miklos Szeredi 已提交
1079 1080 1081

	root_dentry->d_fsdata = oe;

M
Miklos Szeredi 已提交
1082 1083 1084
	ovl_copyattr(ovl_dentry_real(root_dentry)->d_inode,
		     root_dentry->d_inode);

A
Andy Whitcroft 已提交
1085
	sb->s_magic = OVERLAYFS_SUPER_MAGIC;
M
Miklos Szeredi 已提交
1086 1087 1088 1089 1090 1091
	sb->s_op = &ovl_super_operations;
	sb->s_root = root_dentry;
	sb->s_fs_info = ufs;

	return 0;

1092 1093
out_free_oe:
	kfree(oe);
M
Miklos Szeredi 已提交
1094
out_put_lower_mnt:
1095 1096 1097
	for (i = 0; i < ufs->numlower; i++)
		mntput(ufs->lower_mnt[i]);
	kfree(ufs->lower_mnt);
1098 1099
out_put_workdir:
	dput(ufs->workdir);
M
Miklos Szeredi 已提交
1100 1101
	mntput(ufs->upper_mnt);
out_put_lowerpath:
1102 1103 1104 1105 1106
	for (i = 0; i < numlower; i++)
		path_put(&stack[i]);
	kfree(stack);
out_free_lowertmp:
	kfree(lowertmp);
1107 1108
out_put_workpath:
	path_put(&workpath);
M
Miklos Szeredi 已提交
1109 1110 1111
out_put_upperpath:
	path_put(&upperpath);
out_free_config:
E
Erez Zadok 已提交
1112 1113 1114 1115
	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
	kfree(ufs);
M
Miklos Szeredi 已提交
1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127
out:
	return err;
}

static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
				const char *dev_name, void *raw_data)
{
	return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
}

static struct file_system_type ovl_fs_type = {
	.owner		= THIS_MODULE,
1128
	.name		= "overlay",
M
Miklos Szeredi 已提交
1129 1130 1131
	.mount		= ovl_mount,
	.kill_sb	= kill_anon_super,
};
1132
MODULE_ALIAS_FS("overlay");
M
Miklos Szeredi 已提交
1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145

static int __init ovl_init(void)
{
	return register_filesystem(&ovl_fs_type);
}

static void __exit ovl_exit(void)
{
	unregister_filesystem(&ovl_fs_type);
}

module_init(ovl_init);
module_exit(ovl_exit);