xref: /openbmc/linux/fs/squashfs/super.c (revision fb40fe04)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Squashfs - a compressed read only filesystem for Linux
4  *
5  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
6  * Phillip Lougher <phillip@squashfs.org.uk>
7  *
8  * super.c
9  */
10 
11 /*
12  * This file implements code to read the superblock, read and initialise
13  * in-memory structures at mount time, and all the VFS glue code to register
14  * the filesystem.
15  */
16 
17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18 
19 #include <linux/blkdev.h>
20 #include <linux/fs.h>
21 #include <linux/fs_context.h>
22 #include <linux/fs_parser.h>
23 #include <linux/vfs.h>
24 #include <linux/slab.h>
25 #include <linux/mutex.h>
26 #include <linux/seq_file.h>
27 #include <linux/pagemap.h>
28 #include <linux/init.h>
29 #include <linux/module.h>
30 #include <linux/magic.h>
31 #include <linux/xattr.h>
32 
33 #include "squashfs_fs.h"
34 #include "squashfs_fs_sb.h"
35 #include "squashfs_fs_i.h"
36 #include "squashfs.h"
37 #include "decompressor.h"
38 #include "xattr.h"
39 
40 static struct file_system_type squashfs_fs_type;
41 static const struct super_operations squashfs_super_ops;
42 
43 enum Opt_errors {
44 	Opt_errors_continue,
45 	Opt_errors_panic,
46 };
47 
48 enum squashfs_param {
49 	Opt_errors,
50 	Opt_threads,
51 };
52 
53 struct squashfs_mount_opts {
54 	enum Opt_errors errors;
55 	const struct squashfs_decompressor_thread_ops *thread_ops;
56 	int thread_num;
57 };
58 
59 static const struct constant_table squashfs_param_errors[] = {
60 	{"continue",   Opt_errors_continue },
61 	{"panic",      Opt_errors_panic },
62 	{}
63 };
64 
65 static const struct fs_parameter_spec squashfs_fs_parameters[] = {
66 	fsparam_enum("errors", Opt_errors, squashfs_param_errors),
67 	fsparam_string("threads", Opt_threads),
68 	{}
69 };
70 
71 
72 static int squashfs_parse_param_threads_str(const char *str, struct squashfs_mount_opts *opts)
73 {
74 #ifdef CONFIG_SQUASHFS_CHOICE_DECOMP_BY_MOUNT
75 	if (strcmp(str, "single") == 0) {
76 		opts->thread_ops = &squashfs_decompressor_single;
77 		return 0;
78 	}
79 	if (strcmp(str, "multi") == 0) {
80 		opts->thread_ops = &squashfs_decompressor_multi;
81 		return 0;
82 	}
83 	if (strcmp(str, "percpu") == 0) {
84 		opts->thread_ops = &squashfs_decompressor_percpu;
85 		return 0;
86 	}
87 #endif
88 	return -EINVAL;
89 }
90 
91 static int squashfs_parse_param_threads_num(const char *str, struct squashfs_mount_opts *opts)
92 {
93 #ifdef CONFIG_SQUASHFS_MOUNT_DECOMP_THREADS
94 	int ret;
95 	unsigned long num;
96 
97 	ret = kstrtoul(str, 0, &num);
98 	if (ret != 0)
99 		return -EINVAL;
100 	if (num > 1) {
101 		opts->thread_ops = &squashfs_decompressor_multi;
102 		if (num > opts->thread_ops->max_decompressors())
103 			return -EINVAL;
104 		opts->thread_num = (int)num;
105 		return 0;
106 	}
107 #ifdef CONFIG_SQUASHFS_DECOMP_SINGLE
108 	if (num == 1) {
109 		opts->thread_ops = &squashfs_decompressor_single;
110 		opts->thread_num = 1;
111 		return 0;
112 	}
113 #endif
114 #endif /* !CONFIG_SQUASHFS_MOUNT_DECOMP_THREADS */
115 	return -EINVAL;
116 }
117 
118 static int squashfs_parse_param_threads(const char *str, struct squashfs_mount_opts *opts)
119 {
120 	int ret = squashfs_parse_param_threads_str(str, opts);
121 
122 	if (ret == 0)
123 		return ret;
124 	return squashfs_parse_param_threads_num(str, opts);
125 }
126 
127 static int squashfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
128 {
129 	struct squashfs_mount_opts *opts = fc->fs_private;
130 	struct fs_parse_result result;
131 	int opt;
132 
133 	opt = fs_parse(fc, squashfs_fs_parameters, param, &result);
134 	if (opt < 0)
135 		return opt;
136 
137 	switch (opt) {
138 	case Opt_errors:
139 		opts->errors = result.uint_32;
140 		break;
141 	case Opt_threads:
142 		if (squashfs_parse_param_threads(param->string, opts) != 0)
143 			return -EINVAL;
144 		break;
145 	default:
146 		return -EINVAL;
147 	}
148 
149 	return 0;
150 }
151 
152 static const struct squashfs_decompressor *supported_squashfs_filesystem(
153 	struct fs_context *fc,
154 	short major, short minor, short id)
155 {
156 	const struct squashfs_decompressor *decompressor;
157 
158 	if (major < SQUASHFS_MAJOR) {
159 		errorf(fc, "Major/Minor mismatch, older Squashfs %d.%d "
160 		       "filesystems are unsupported", major, minor);
161 		return NULL;
162 	} else if (major > SQUASHFS_MAJOR || minor > SQUASHFS_MINOR) {
163 		errorf(fc, "Major/Minor mismatch, trying to mount newer "
164 		       "%d.%d filesystem", major, minor);
165 		errorf(fc, "Please update your kernel");
166 		return NULL;
167 	}
168 
169 	decompressor = squashfs_lookup_decompressor(id);
170 	if (!decompressor->supported) {
171 		errorf(fc, "Filesystem uses \"%s\" compression. This is not supported",
172 		       decompressor->name);
173 		return NULL;
174 	}
175 
176 	return decompressor;
177 }
178 
179 
180 static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
181 {
182 	struct squashfs_mount_opts *opts = fc->fs_private;
183 	struct squashfs_sb_info *msblk;
184 	struct squashfs_super_block *sblk = NULL;
185 	struct inode *root;
186 	long long root_inode;
187 	unsigned short flags;
188 	unsigned int fragments;
189 	u64 lookup_table_start, xattr_id_table_start, next_table;
190 	int err;
191 
192 	TRACE("Entered squashfs_fill_superblock\n");
193 
194 	sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
195 	if (sb->s_fs_info == NULL) {
196 		ERROR("Failed to allocate squashfs_sb_info\n");
197 		return -ENOMEM;
198 	}
199 	msblk = sb->s_fs_info;
200 
201 	msblk->panic_on_errors = (opts->errors == Opt_errors_panic);
202 
203 	msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
204 	msblk->devblksize_log2 = ffz(~msblk->devblksize);
205 
206 	mutex_init(&msblk->meta_index_mutex);
207 
208 	/*
209 	 * msblk->bytes_used is checked in squashfs_read_table to ensure reads
210 	 * are not beyond filesystem end.  But as we're using
211 	 * squashfs_read_table here to read the superblock (including the value
212 	 * of bytes_used) we need to set it to an initial sensible dummy value
213 	 */
214 	msblk->bytes_used = sizeof(*sblk);
215 	sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));
216 
217 	if (IS_ERR(sblk)) {
218 		errorf(fc, "unable to read squashfs_super_block");
219 		err = PTR_ERR(sblk);
220 		sblk = NULL;
221 		goto failed_mount;
222 	}
223 
224 	err = -EINVAL;
225 
226 	/* Check it is a SQUASHFS superblock */
227 	sb->s_magic = le32_to_cpu(sblk->s_magic);
228 	if (sb->s_magic != SQUASHFS_MAGIC) {
229 		if (!(fc->sb_flags & SB_SILENT))
230 			errorf(fc, "Can't find a SQUASHFS superblock on %pg",
231 			       sb->s_bdev);
232 		goto failed_mount;
233 	}
234 	msblk->thread_ops = opts->thread_ops;
235 	if (opts->thread_num == 0) {
236 		msblk->max_thread_num = msblk->thread_ops->max_decompressors();
237 	} else {
238 		msblk->max_thread_num = opts->thread_num;
239 	}
240 
241 	/* Check the MAJOR & MINOR versions and lookup compression type */
242 	msblk->decompressor = supported_squashfs_filesystem(
243 			fc,
244 			le16_to_cpu(sblk->s_major),
245 			le16_to_cpu(sblk->s_minor),
246 			le16_to_cpu(sblk->compression));
247 	if (msblk->decompressor == NULL)
248 		goto failed_mount;
249 
250 	/* Check the filesystem does not extend beyond the end of the
251 	   block device */
252 	msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
253 	if (msblk->bytes_used < 0 ||
254 	    msblk->bytes_used > bdev_nr_bytes(sb->s_bdev))
255 		goto failed_mount;
256 
257 	/* Check block size for sanity */
258 	msblk->block_size = le32_to_cpu(sblk->block_size);
259 	if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
260 		goto insanity;
261 
262 	/*
263 	 * Check the system page size is not larger than the filesystem
264 	 * block size (by default 128K).  This is currently not supported.
265 	 */
266 	if (PAGE_SIZE > msblk->block_size) {
267 		errorf(fc, "Page size > filesystem block size (%d).  This is "
268 		       "currently not supported!", msblk->block_size);
269 		goto failed_mount;
270 	}
271 
272 	/* Check block log for sanity */
273 	msblk->block_log = le16_to_cpu(sblk->block_log);
274 	if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
275 		goto failed_mount;
276 
277 	/* Check that block_size and block_log match */
278 	if (msblk->block_size != (1 << msblk->block_log))
279 		goto insanity;
280 
281 	/* Check the root inode for sanity */
282 	root_inode = le64_to_cpu(sblk->root_inode);
283 	if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
284 		goto insanity;
285 
286 	msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
287 	msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
288 	msblk->inodes = le32_to_cpu(sblk->inodes);
289 	msblk->fragments = le32_to_cpu(sblk->fragments);
290 	msblk->ids = le16_to_cpu(sblk->no_ids);
291 	flags = le16_to_cpu(sblk->flags);
292 
293 	TRACE("Found valid superblock on %pg\n", sb->s_bdev);
294 	TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
295 				? "un" : "");
296 	TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
297 				? "un" : "");
298 	TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
299 	TRACE("Block size %d\n", msblk->block_size);
300 	TRACE("Number of inodes %d\n", msblk->inodes);
301 	TRACE("Number of fragments %d\n", msblk->fragments);
302 	TRACE("Number of ids %d\n", msblk->ids);
303 	TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
304 	TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
305 	TRACE("sblk->fragment_table_start %llx\n",
306 		(u64) le64_to_cpu(sblk->fragment_table_start));
307 	TRACE("sblk->id_table_start %llx\n",
308 		(u64) le64_to_cpu(sblk->id_table_start));
309 
310 	sb->s_maxbytes = MAX_LFS_FILESIZE;
311 	sb->s_time_min = 0;
312 	sb->s_time_max = U32_MAX;
313 	sb->s_flags |= SB_RDONLY;
314 	sb->s_op = &squashfs_super_ops;
315 
316 	err = -ENOMEM;
317 
318 	msblk->block_cache = squashfs_cache_init("metadata",
319 			SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
320 	if (msblk->block_cache == NULL)
321 		goto failed_mount;
322 
323 	/* Allocate read_page block */
324 	msblk->read_page = squashfs_cache_init("data",
325 		msblk->max_thread_num, msblk->block_size);
326 	if (msblk->read_page == NULL) {
327 		errorf(fc, "Failed to allocate read_page block");
328 		goto failed_mount;
329 	}
330 
331 	msblk->stream = squashfs_decompressor_setup(sb, flags);
332 	if (IS_ERR(msblk->stream)) {
333 		err = PTR_ERR(msblk->stream);
334 		msblk->stream = NULL;
335 		goto insanity;
336 	}
337 
338 	/* Handle xattrs */
339 	sb->s_xattr = squashfs_xattr_handlers;
340 	xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
341 	if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {
342 		next_table = msblk->bytes_used;
343 		goto allocate_id_index_table;
344 	}
345 
346 	/* Allocate and read xattr id lookup table */
347 	msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
348 		xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
349 	if (IS_ERR(msblk->xattr_id_table)) {
350 		errorf(fc, "unable to read xattr id index table");
351 		err = PTR_ERR(msblk->xattr_id_table);
352 		msblk->xattr_id_table = NULL;
353 		if (err != -ENOTSUPP)
354 			goto failed_mount;
355 	}
356 	next_table = msblk->xattr_table;
357 
358 allocate_id_index_table:
359 	/* Allocate and read id index table */
360 	msblk->id_table = squashfs_read_id_index_table(sb,
361 		le64_to_cpu(sblk->id_table_start), next_table, msblk->ids);
362 	if (IS_ERR(msblk->id_table)) {
363 		errorf(fc, "unable to read id index table");
364 		err = PTR_ERR(msblk->id_table);
365 		msblk->id_table = NULL;
366 		goto failed_mount;
367 	}
368 	next_table = le64_to_cpu(msblk->id_table[0]);
369 
370 	/* Handle inode lookup table */
371 	lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
372 	if (lookup_table_start == SQUASHFS_INVALID_BLK)
373 		goto handle_fragments;
374 
375 	/* Allocate and read inode lookup table */
376 	msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
377 		lookup_table_start, next_table, msblk->inodes);
378 	if (IS_ERR(msblk->inode_lookup_table)) {
379 		errorf(fc, "unable to read inode lookup table");
380 		err = PTR_ERR(msblk->inode_lookup_table);
381 		msblk->inode_lookup_table = NULL;
382 		goto failed_mount;
383 	}
384 	next_table = le64_to_cpu(msblk->inode_lookup_table[0]);
385 
386 	sb->s_export_op = &squashfs_export_ops;
387 
388 handle_fragments:
389 	fragments = msblk->fragments;
390 	if (fragments == 0)
391 		goto check_directory_table;
392 
393 	msblk->fragment_cache = squashfs_cache_init("fragment",
394 		SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
395 	if (msblk->fragment_cache == NULL) {
396 		err = -ENOMEM;
397 		goto failed_mount;
398 	}
399 
400 	/* Allocate and read fragment index table */
401 	msblk->fragment_index = squashfs_read_fragment_index_table(sb,
402 		le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
403 	if (IS_ERR(msblk->fragment_index)) {
404 		errorf(fc, "unable to read fragment index table");
405 		err = PTR_ERR(msblk->fragment_index);
406 		msblk->fragment_index = NULL;
407 		goto failed_mount;
408 	}
409 	next_table = le64_to_cpu(msblk->fragment_index[0]);
410 
411 check_directory_table:
412 	/* Sanity check directory_table */
413 	if (msblk->directory_table > next_table) {
414 		err = -EINVAL;
415 		goto insanity;
416 	}
417 
418 	/* Sanity check inode_table */
419 	if (msblk->inode_table >= msblk->directory_table) {
420 		err = -EINVAL;
421 		goto insanity;
422 	}
423 
424 	/* allocate root */
425 	root = new_inode(sb);
426 	if (!root) {
427 		err = -ENOMEM;
428 		goto failed_mount;
429 	}
430 
431 	err = squashfs_read_inode(root, root_inode);
432 	if (err) {
433 		make_bad_inode(root);
434 		iput(root);
435 		goto failed_mount;
436 	}
437 	insert_inode_hash(root);
438 
439 	sb->s_root = d_make_root(root);
440 	if (sb->s_root == NULL) {
441 		ERROR("Root inode create failed\n");
442 		err = -ENOMEM;
443 		goto failed_mount;
444 	}
445 
446 	TRACE("Leaving squashfs_fill_super\n");
447 	kfree(sblk);
448 	return 0;
449 
450 insanity:
451 	errorf(fc, "squashfs image failed sanity check");
452 failed_mount:
453 	squashfs_cache_delete(msblk->block_cache);
454 	squashfs_cache_delete(msblk->fragment_cache);
455 	squashfs_cache_delete(msblk->read_page);
456 	msblk->thread_ops->destroy(msblk);
457 	kfree(msblk->inode_lookup_table);
458 	kfree(msblk->fragment_index);
459 	kfree(msblk->id_table);
460 	kfree(msblk->xattr_id_table);
461 	kfree(sb->s_fs_info);
462 	sb->s_fs_info = NULL;
463 	kfree(sblk);
464 	return err;
465 }
466 
467 static int squashfs_get_tree(struct fs_context *fc)
468 {
469 	return get_tree_bdev(fc, squashfs_fill_super);
470 }
471 
472 static int squashfs_reconfigure(struct fs_context *fc)
473 {
474 	struct super_block *sb = fc->root->d_sb;
475 	struct squashfs_sb_info *msblk = sb->s_fs_info;
476 	struct squashfs_mount_opts *opts = fc->fs_private;
477 
478 	sync_filesystem(fc->root->d_sb);
479 	fc->sb_flags |= SB_RDONLY;
480 
481 	msblk->panic_on_errors = (opts->errors == Opt_errors_panic);
482 
483 	return 0;
484 }
485 
486 static void squashfs_free_fs_context(struct fs_context *fc)
487 {
488 	kfree(fc->fs_private);
489 }
490 
491 static const struct fs_context_operations squashfs_context_ops = {
492 	.get_tree	= squashfs_get_tree,
493 	.free		= squashfs_free_fs_context,
494 	.parse_param	= squashfs_parse_param,
495 	.reconfigure	= squashfs_reconfigure,
496 };
497 
498 static int squashfs_show_options(struct seq_file *s, struct dentry *root)
499 {
500 	struct super_block *sb = root->d_sb;
501 	struct squashfs_sb_info *msblk = sb->s_fs_info;
502 
503 	if (msblk->panic_on_errors)
504 		seq_puts(s, ",errors=panic");
505 	else
506 		seq_puts(s, ",errors=continue");
507 
508 #ifdef CONFIG_SQUASHFS_CHOICE_DECOMP_BY_MOUNT
509 	if (msblk->thread_ops == &squashfs_decompressor_single) {
510 		seq_puts(s, ",threads=single");
511 		return 0;
512 	}
513 	if (msblk->thread_ops == &squashfs_decompressor_percpu) {
514 		seq_puts(s, ",threads=percpu");
515 		return 0;
516 	}
517 #endif
518 #ifdef CONFIG_SQUASHFS_MOUNT_DECOMP_THREADS
519 	seq_printf(s, ",threads=%d", msblk->max_thread_num);
520 #endif
521 	return 0;
522 }
523 
524 static int squashfs_init_fs_context(struct fs_context *fc)
525 {
526 	struct squashfs_mount_opts *opts;
527 
528 	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
529 	if (!opts)
530 		return -ENOMEM;
531 
532 #ifdef CONFIG_SQUASHFS_DECOMP_SINGLE
533 	opts->thread_ops = &squashfs_decompressor_single;
534 #elif defined(CONFIG_SQUASHFS_DECOMP_MULTI)
535 	opts->thread_ops = &squashfs_decompressor_multi;
536 #elif defined(CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU)
537 	opts->thread_ops = &squashfs_decompressor_percpu;
538 #else
539 #error "fail: unknown squashfs decompression thread mode?"
540 #endif
541 	opts->thread_num = 0;
542 	fc->fs_private = opts;
543 	fc->ops = &squashfs_context_ops;
544 	return 0;
545 }
546 
547 static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
548 {
549 	struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
550 	u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);
551 
552 	TRACE("Entered squashfs_statfs\n");
553 
554 	buf->f_type = SQUASHFS_MAGIC;
555 	buf->f_bsize = msblk->block_size;
556 	buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
557 	buf->f_bfree = buf->f_bavail = 0;
558 	buf->f_files = msblk->inodes;
559 	buf->f_ffree = 0;
560 	buf->f_namelen = SQUASHFS_NAME_LEN;
561 	buf->f_fsid = u64_to_fsid(id);
562 
563 	return 0;
564 }
565 
566 
567 static void squashfs_put_super(struct super_block *sb)
568 {
569 	if (sb->s_fs_info) {
570 		struct squashfs_sb_info *sbi = sb->s_fs_info;
571 		squashfs_cache_delete(sbi->block_cache);
572 		squashfs_cache_delete(sbi->fragment_cache);
573 		squashfs_cache_delete(sbi->read_page);
574 		sbi->thread_ops->destroy(sbi);
575 		kfree(sbi->id_table);
576 		kfree(sbi->fragment_index);
577 		kfree(sbi->meta_index);
578 		kfree(sbi->inode_lookup_table);
579 		kfree(sbi->xattr_id_table);
580 		kfree(sb->s_fs_info);
581 		sb->s_fs_info = NULL;
582 	}
583 }
584 
585 static struct kmem_cache *squashfs_inode_cachep;
586 
587 
588 static void init_once(void *foo)
589 {
590 	struct squashfs_inode_info *ei = foo;
591 
592 	inode_init_once(&ei->vfs_inode);
593 }
594 
595 
596 static int __init init_inodecache(void)
597 {
598 	squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
599 		sizeof(struct squashfs_inode_info), 0,
600 		SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|SLAB_ACCOUNT,
601 		init_once);
602 
603 	return squashfs_inode_cachep ? 0 : -ENOMEM;
604 }
605 
606 
607 static void destroy_inodecache(void)
608 {
609 	/*
610 	 * Make sure all delayed rcu free inodes are flushed before we
611 	 * destroy cache.
612 	 */
613 	rcu_barrier();
614 	kmem_cache_destroy(squashfs_inode_cachep);
615 }
616 
617 
618 static int __init init_squashfs_fs(void)
619 {
620 	int err = init_inodecache();
621 
622 	if (err)
623 		return err;
624 
625 	err = register_filesystem(&squashfs_fs_type);
626 	if (err) {
627 		destroy_inodecache();
628 		return err;
629 	}
630 
631 	pr_info("version 4.0 (2009/01/31) Phillip Lougher\n");
632 
633 	return 0;
634 }
635 
636 
637 static void __exit exit_squashfs_fs(void)
638 {
639 	unregister_filesystem(&squashfs_fs_type);
640 	destroy_inodecache();
641 }
642 
643 
644 static struct inode *squashfs_alloc_inode(struct super_block *sb)
645 {
646 	struct squashfs_inode_info *ei =
647 		alloc_inode_sb(sb, squashfs_inode_cachep, GFP_KERNEL);
648 
649 	return ei ? &ei->vfs_inode : NULL;
650 }
651 
652 
653 static void squashfs_free_inode(struct inode *inode)
654 {
655 	kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
656 }
657 
658 static struct file_system_type squashfs_fs_type = {
659 	.owner = THIS_MODULE,
660 	.name = "squashfs",
661 	.init_fs_context = squashfs_init_fs_context,
662 	.parameters = squashfs_fs_parameters,
663 	.kill_sb = kill_block_super,
664 	.fs_flags = FS_REQUIRES_DEV
665 };
666 MODULE_ALIAS_FS("squashfs");
667 
668 static const struct super_operations squashfs_super_ops = {
669 	.alloc_inode = squashfs_alloc_inode,
670 	.free_inode = squashfs_free_inode,
671 	.statfs = squashfs_statfs,
672 	.put_super = squashfs_put_super,
673 	.show_options = squashfs_show_options,
674 };
675 
676 module_init(init_squashfs_fs);
677 module_exit(exit_squashfs_fs);
678 MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
679 MODULE_AUTHOR("Phillip Lougher <phillip@squashfs.org.uk>");
680 MODULE_LICENSE("GPL");
681