fs/squashfs/super.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Squashfs - a compressed read only filesystem for Linux
  *
  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
  * Phillip Lougher <phillip@squashfs.org.uk>
  *
  * super.c
  */

 /*
  * This file implements code to read the superblock, read and initialise
  * in-memory structures at mount time, and all the VFS glue code to register
  * the filesystem.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/blkdev.h>
 #include <linux/fs.h>
 #include <linux/fs_context.h>
 #include <linux/fs_parser.h>
 #include <linux/vfs.h>
 #include <linux/slab.h>
 #include <linux/mutex.h>
 #include <linux/seq_file.h>
 #include <linux/pagemap.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/magic.h>
 #include <linux/xattr.h>
 #include <linux/backing-dev.h>

 #include "squashfs_fs.h"
 #include "squashfs_fs_sb.h"
 #include "squashfs_fs_i.h"
 #include "squashfs.h"
 #include "decompressor.h"
 #include "xattr.h"

 static struct file_system_type squashfs_fs_type;
 static const struct super_operations squashfs_super_ops;

 enum Opt_errors {
 	Opt_errors_continue,
 	Opt_errors_panic,
 };

 enum squashfs_param {
 	Opt_errors,
 };

 struct squashfs_mount_opts {
 	enum Opt_errors errors;
 };

 static const struct constant_table squashfs_param_errors[] = {
 	{"continue",   Opt_errors_continue },
 	{"panic",      Opt_errors_panic },
 	{}
 };

 static const struct fs_parameter_spec squashfs_fs_parameters[] = {
 	fsparam_enum("errors", Opt_errors, squashfs_param_errors),
 	{}
 };

 static int squashfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 {
 	struct squashfs_mount_opts *opts = fc->fs_private;
 	struct fs_parse_result result;
 	int opt;

 	opt = fs_parse(fc, squashfs_fs_parameters, param, &result);
 	if (opt < 0)
 		return opt;

 	switch (opt) {
 	case Opt_errors:
 		opts->errors = result.uint_32;
 		break;
 	default:
 		return -EINVAL;
 	}

 	return 0;
 }

 static const struct squashfs_decompressor *supported_squashfs_filesystem(
 	struct fs_context *fc,
 	short major, short minor, short id)
 {
 	const struct squashfs_decompressor *decompressor;

 	if (major < SQUASHFS_MAJOR) {
 		errorf(fc, "Major/Minor mismatch, older Squashfs %d.%d "
 		       "filesystems are unsupported", major, minor);
 		return NULL;
 	} else if (major > SQUASHFS_MAJOR || minor > SQUASHFS_MINOR) {
 		errorf(fc, "Major/Minor mismatch, trying to mount newer "
 		       "%d.%d filesystem", major, minor);
 		errorf(fc, "Please update your kernel");
 		return NULL;
 	}

 	decompressor = squashfs_lookup_decompressor(id);
 	if (!decompressor->supported) {
 		errorf(fc, "Filesystem uses \"%s\" compression. This is not supported",
 		       decompressor->name);
 		return NULL;
 	}

 	return decompressor;
 }

 static int squashfs_bdi_init(struct super_block *sb)
 {
 	int err;
 	unsigned int major = MAJOR(sb->s_dev);
 	unsigned int minor = MINOR(sb->s_dev);

 	bdi_put(sb->s_bdi);
 	sb->s_bdi = &noop_backing_dev_info;

 	err = super_setup_bdi_name(sb, "squashfs_%u_%u", major, minor);
 	if (err)
 		return err;

 	sb->s_bdi->ra_pages = 0;
 	sb->s_bdi->io_pages = 0;

 	return 0;
 }

 static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct squashfs_mount_opts *opts = fc->fs_private;
 	struct squashfs_sb_info *msblk;
 	struct squashfs_super_block *sblk = NULL;
 	struct inode *root;
 	long long root_inode;
 	unsigned short flags;
 	unsigned int fragments;
 	u64 lookup_table_start, xattr_id_table_start, next_table;
 	int err;

 	TRACE("Entered squashfs_fill_superblock\n");

 	/*
 	 * squashfs provides 'backing_dev_info' in order to disable read-ahead. For
 	 * squashfs, I/O is not deferred, it is done immediately in read_folio,
 	 * which means the user would always have to wait their own I/O. So the effect
 	 * of readahead is very weak for squashfs. squashfs_bdi_init will set
 	 * sb->s_bdi->ra_pages and sb->s_bdi->io_pages to 0 and close readahead for
 	 * squashfs.
 	 */
 	err = squashfs_bdi_init(sb);
 	if (err) {
 		errorf(fc, "squashfs init bdi failed");
 		return err;
 	}

 	sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
 	if (sb->s_fs_info == NULL) {
 		ERROR("Failed to allocate squashfs_sb_info\n");
 		return -ENOMEM;
 	}
 	msblk = sb->s_fs_info;

 	msblk->panic_on_errors = (opts->errors == Opt_errors_panic);

 	msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
 	msblk->devblksize_log2 = ffz(~msblk->devblksize);

 	mutex_init(&msblk->meta_index_mutex);

 	/*
 	 * msblk->bytes_used is checked in squashfs_read_table to ensure reads
 	 * are not beyond filesystem end.  But as we're using
 	 * squashfs_read_table here to read the superblock (including the value
 	 * of bytes_used) we need to set it to an initial sensible dummy value
 	 */
 	msblk->bytes_used = sizeof(*sblk);
 	sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));

 	if (IS_ERR(sblk)) {
 		errorf(fc, "unable to read squashfs_super_block");
 		err = PTR_ERR(sblk);
 		sblk = NULL;
 		goto failed_mount;
 	}

 	err = -EINVAL;

 	/* Check it is a SQUASHFS superblock */
 	sb->s_magic = le32_to_cpu(sblk->s_magic);
 	if (sb->s_magic != SQUASHFS_MAGIC) {
 		if (!(fc->sb_flags & SB_SILENT))
 			errorf(fc, "Can't find a SQUASHFS superblock on %pg",
 			       sb->s_bdev);
 		goto failed_mount;
 	}

 	/* Check the MAJOR & MINOR versions and lookup compression type */
 	msblk->decompressor = supported_squashfs_filesystem(
 			fc,
 			le16_to_cpu(sblk->s_major),
 			le16_to_cpu(sblk->s_minor),
 			le16_to_cpu(sblk->compression));
 	if (msblk->decompressor == NULL)
 		goto failed_mount;

 	/* Check the filesystem does not extend beyond the end of the
 	   block device */
 	msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
 	if (msblk->bytes_used < 0 ||
 	    msblk->bytes_used > bdev_nr_bytes(sb->s_bdev))
 		goto failed_mount;

 	/* Check block size for sanity */
 	msblk->block_size = le32_to_cpu(sblk->block_size);
 	if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
 		goto insanity;

 	/*
 	 * Check the system page size is not larger than the filesystem
 	 * block size (by default 128K).  This is currently not supported.
 	 */
 	if (PAGE_SIZE > msblk->block_size) {
 		errorf(fc, "Page size > filesystem block size (%d).  This is "
 		       "currently not supported!", msblk->block_size);
 		goto failed_mount;
 	}

 	/* Check block log for sanity */
 	msblk->block_log = le16_to_cpu(sblk->block_log);
 	if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
 		goto failed_mount;

 	/* Check that block_size and block_log match */
 	if (msblk->block_size != (1 << msblk->block_log))
 		goto insanity;

 	/* Check the root inode for sanity */
 	root_inode = le64_to_cpu(sblk->root_inode);
 	if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
 		goto insanity;

 	msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
 	msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
 	msblk->inodes = le32_to_cpu(sblk->inodes);
 	msblk->fragments = le32_to_cpu(sblk->fragments);
 	msblk->ids = le16_to_cpu(sblk->no_ids);
 	flags = le16_to_cpu(sblk->flags);

 	TRACE("Found valid superblock on %pg\n", sb->s_bdev);
 	TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
 				? "un" : "");
 	TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
 				? "un" : "");
 	TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
 	TRACE("Block size %d\n", msblk->block_size);
 	TRACE("Number of inodes %d\n", msblk->inodes);
 	TRACE("Number of fragments %d\n", msblk->fragments);
 	TRACE("Number of ids %d\n", msblk->ids);
 	TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
 	TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
 	TRACE("sblk->fragment_table_start %llx\n",
 		(u64) le64_to_cpu(sblk->fragment_table_start));
 	TRACE("sblk->id_table_start %llx\n",
 		(u64) le64_to_cpu(sblk->id_table_start));

 	sb->s_maxbytes = MAX_LFS_FILESIZE;
 	sb->s_time_min = 0;
 	sb->s_time_max = U32_MAX;
 	sb->s_flags |= SB_RDONLY;
 	sb->s_op = &squashfs_super_ops;

 	err = -ENOMEM;

 	msblk->block_cache = squashfs_cache_init("metadata",
 			SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
 	if (msblk->block_cache == NULL)
 		goto failed_mount;

 	/* Allocate read_page block */
 	msblk->read_page = squashfs_cache_init("data",
 		squashfs_max_decompressors(), msblk->block_size);
 	if (msblk->read_page == NULL) {
 		errorf(fc, "Failed to allocate read_page block");
 		goto failed_mount;
 	}

 	msblk->stream = squashfs_decompressor_setup(sb, flags);
 	if (IS_ERR(msblk->stream)) {
 		err = PTR_ERR(msblk->stream);
 		msblk->stream = NULL;
 		goto insanity;
 	}

 	/* Handle xattrs */
 	sb->s_xattr = squashfs_xattr_handlers;
 	xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
 	if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {
 		next_table = msblk->bytes_used;
 		goto allocate_id_index_table;
 	}

 	/* Allocate and read xattr id lookup table */
 	msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
 		xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
 	if (IS_ERR(msblk->xattr_id_table)) {
 		errorf(fc, "unable to read xattr id index table");
 		err = PTR_ERR(msblk->xattr_id_table);
 		msblk->xattr_id_table = NULL;
 		if (err != -ENOTSUPP)
 			goto failed_mount;
 	}
 	next_table = msblk->xattr_table;

 allocate_id_index_table:
 	/* Allocate and read id index table */
 	msblk->id_table = squashfs_read_id_index_table(sb,
 		le64_to_cpu(sblk->id_table_start), next_table, msblk->ids);
 	if (IS_ERR(msblk->id_table)) {
 		errorf(fc, "unable to read id index table");
 		err = PTR_ERR(msblk->id_table);
 		msblk->id_table = NULL;
 		goto failed_mount;
 	}
 	next_table = le64_to_cpu(msblk->id_table[0]);

 	/* Handle inode lookup table */
 	lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
 	if (lookup_table_start == SQUASHFS_INVALID_BLK)
 		goto handle_fragments;

 	/* Allocate and read inode lookup table */
 	msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
 		lookup_table_start, next_table, msblk->inodes);
 	if (IS_ERR(msblk->inode_lookup_table)) {
 		errorf(fc, "unable to read inode lookup table");
 		err = PTR_ERR(msblk->inode_lookup_table);
 		msblk->inode_lookup_table = NULL;
 		goto failed_mount;
 	}
 	next_table = le64_to_cpu(msblk->inode_lookup_table[0]);

 	sb->s_export_op = &squashfs_export_ops;

 handle_fragments:
 	fragments = msblk->fragments;
 	if (fragments == 0)
 		goto check_directory_table;

 	msblk->fragment_cache = squashfs_cache_init("fragment",
 		SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
 	if (msblk->fragment_cache == NULL) {
 		err = -ENOMEM;
 		goto failed_mount;
 	}

 	/* Allocate and read fragment index table */
 	msblk->fragment_index = squashfs_read_fragment_index_table(sb,
 		le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
 	if (IS_ERR(msblk->fragment_index)) {
 		errorf(fc, "unable to read fragment index table");
 		err = PTR_ERR(msblk->fragment_index);
 		msblk->fragment_index = NULL;
 		goto failed_mount;
 	}
 	next_table = le64_to_cpu(msblk->fragment_index[0]);

 check_directory_table:
 	/* Sanity check directory_table */
 	if (msblk->directory_table > next_table) {
 		err = -EINVAL;
 		goto insanity;
 	}

 	/* Sanity check inode_table */
 	if (msblk->inode_table >= msblk->directory_table) {
 		err = -EINVAL;
 		goto insanity;
 	}

 	/* allocate root */
 	root = new_inode(sb);
 	if (!root) {
 		err = -ENOMEM;
 		goto failed_mount;
 	}

 	err = squashfs_read_inode(root, root_inode);
 	if (err) {
 		make_bad_inode(root);
 		iput(root);
 		goto failed_mount;
 	}
 	insert_inode_hash(root);

 	sb->s_root = d_make_root(root);
 	if (sb->s_root == NULL) {
 		ERROR("Root inode create failed\n");
 		err = -ENOMEM;
 		goto failed_mount;
 	}

 	TRACE("Leaving squashfs_fill_super\n");
 	kfree(sblk);
 	return 0;

 insanity:
 	errorf(fc, "squashfs image failed sanity check");
 failed_mount:
 	squashfs_cache_delete(msblk->block_cache);
 	squashfs_cache_delete(msblk->fragment_cache);
 	squashfs_cache_delete(msblk->read_page);
 	squashfs_decompressor_destroy(msblk);
 	kfree(msblk->inode_lookup_table);
 	kfree(msblk->fragment_index);
 	kfree(msblk->id_table);
 	kfree(msblk->xattr_id_table);
 	kfree(sb->s_fs_info);
 	sb->s_fs_info = NULL;
 	kfree(sblk);
 	return err;
 }

 static int squashfs_get_tree(struct fs_context *fc)
 {
 	return get_tree_bdev(fc, squashfs_fill_super);
 }

 static int squashfs_reconfigure(struct fs_context *fc)
 {
 	struct super_block *sb = fc->root->d_sb;
 	struct squashfs_sb_info *msblk = sb->s_fs_info;
 	struct squashfs_mount_opts *opts = fc->fs_private;

 	sync_filesystem(fc->root->d_sb);
 	fc->sb_flags |= SB_RDONLY;

 	msblk->panic_on_errors = (opts->errors == Opt_errors_panic);

 	return 0;
 }

 static void squashfs_free_fs_context(struct fs_context *fc)
 {
 	kfree(fc->fs_private);
 }

 static const struct fs_context_operations squashfs_context_ops = {
 	.get_tree	= squashfs_get_tree,
 	.free		= squashfs_free_fs_context,
 	.parse_param	= squashfs_parse_param,
 	.reconfigure	= squashfs_reconfigure,
 };

 static int squashfs_show_options(struct seq_file *s, struct dentry *root)
 {
 	struct super_block *sb = root->d_sb;
 	struct squashfs_sb_info *msblk = sb->s_fs_info;

 	if (msblk->panic_on_errors)
 		seq_puts(s, ",errors=panic");
 	else
 		seq_puts(s, ",errors=continue");

 	return 0;
 }

 static int squashfs_init_fs_context(struct fs_context *fc)
 {
 	struct squashfs_mount_opts *opts;

 	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
 	if (!opts)
 		return -ENOMEM;

 	fc->fs_private = opts;
 	fc->ops = &squashfs_context_ops;
 	return 0;
 }

 static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
 	u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);

 	TRACE("Entered squashfs_statfs\n");

 	buf->f_type = SQUASHFS_MAGIC;
 	buf->f_bsize = msblk->block_size;
 	buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
 	buf->f_bfree = buf->f_bavail = 0;
 	buf->f_files = msblk->inodes;
 	buf->f_ffree = 0;
 	buf->f_namelen = SQUASHFS_NAME_LEN;
 	buf->f_fsid = u64_to_fsid(id);

 	return 0;
 }


 static void squashfs_put_super(struct super_block *sb)
 {
 	if (sb->s_fs_info) {
 		struct squashfs_sb_info *sbi = sb->s_fs_info;
 		squashfs_cache_delete(sbi->block_cache);
 		squashfs_cache_delete(sbi->fragment_cache);
 		squashfs_cache_delete(sbi->read_page);
 		squashfs_decompressor_destroy(sbi);
 		kfree(sbi->id_table);
 		kfree(sbi->fragment_index);
 		kfree(sbi->meta_index);
 		kfree(sbi->inode_lookup_table);
 		kfree(sbi->xattr_id_table);
 		kfree(sb->s_fs_info);
 		sb->s_fs_info = NULL;
 	}
 }

 static struct kmem_cache *squashfs_inode_cachep;


 static void init_once(void *foo)
 {
 	struct squashfs_inode_info *ei = foo;

 	inode_init_once(&ei->vfs_inode);
 }


 static int __init init_inodecache(void)
 {
 	squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
 		sizeof(struct squashfs_inode_info), 0,
 		SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|SLAB_ACCOUNT,
 		init_once);

 	return squashfs_inode_cachep ? 0 : -ENOMEM;
 }


 static void destroy_inodecache(void)
 {
 	/*
 	 * Make sure all delayed rcu free inodes are flushed before we
 	 * destroy cache.
 	 */
 	rcu_barrier();
 	kmem_cache_destroy(squashfs_inode_cachep);
 }


 static int __init init_squashfs_fs(void)
 {
 	int err = init_inodecache();

 	if (err)
 		return err;

 	err = register_filesystem(&squashfs_fs_type);
 	if (err) {
 		destroy_inodecache();
 		return err;
 	}

 	pr_info("version 4.0 (2009/01/31) Phillip Lougher\n");

 	return 0;
 }


 static void __exit exit_squashfs_fs(void)
 {
 	unregister_filesystem(&squashfs_fs_type);
 	destroy_inodecache();
 }


 static struct inode *squashfs_alloc_inode(struct super_block *sb)
 {
 	struct squashfs_inode_info *ei =
 		alloc_inode_sb(sb, squashfs_inode_cachep, GFP_KERNEL);

 	return ei ? &ei->vfs_inode : NULL;
 }


 static void squashfs_free_inode(struct inode *inode)
 {
 	kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
 }

 static struct file_system_type squashfs_fs_type = {
 	.owner = THIS_MODULE,
 	.name = "squashfs",
 	.init_fs_context = squashfs_init_fs_context,
 	.parameters = squashfs_fs_parameters,
 	.kill_sb = kill_block_super,
 	.fs_flags = FS_REQUIRES_DEV
 };
 MODULE_ALIAS_FS("squashfs");

 static const struct super_operations squashfs_super_ops = {
 	.alloc_inode = squashfs_alloc_inode,
 	.free_inode = squashfs_free_inode,
 	.statfs = squashfs_statfs,
 	.put_super = squashfs_put_super,
 	.show_options = squashfs_show_options,
 };

 module_init(init_squashfs_fs);
 module_exit(exit_squashfs_fs);
 MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
 MODULE_AUTHOR("Phillip Lougher <phillip@squashfs.org.uk>");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Squashfs - a compressed read only filesystem for Linux
	*
	* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
	* Phillip Lougher <phillip@squashfs.org.uk>
	*
	* super.c
	*/

	/*
	* This file implements code to read the superblock, read and initialise
	* in-memory structures at mount time, and all the VFS glue code to register
	* the filesystem.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/blkdev.h>
	#include <linux/fs.h>
	#include <linux/fs_context.h>
	#include <linux/fs_parser.h>
	#include <linux/vfs.h>
	#include <linux/slab.h>
	#include <linux/mutex.h>
	#include <linux/seq_file.h>
	#include <linux/pagemap.h>
	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/magic.h>
	#include <linux/xattr.h>
	#include <linux/backing-dev.h>

	#include "squashfs_fs.h"
	#include "squashfs_fs_sb.h"
	#include "squashfs_fs_i.h"
	#include "squashfs.h"
	#include "decompressor.h"
	#include "xattr.h"

	static struct file_system_type squashfs_fs_type;
	static const struct super_operations squashfs_super_ops;

	enum Opt_errors {
	Opt_errors_continue,
	Opt_errors_panic,
	};

	enum squashfs_param {
	Opt_errors,
	};

	struct squashfs_mount_opts {
	enum Opt_errors errors;
	};

	static const struct constant_table squashfs_param_errors[] = {
	{"continue", Opt_errors_continue },
	{"panic", Opt_errors_panic },
	{}
	};

	static const struct fs_parameter_spec squashfs_fs_parameters[] = {
	fsparam_enum("errors", Opt_errors, squashfs_param_errors),
	{}
	};

	static int squashfs_parse_param(struct fs_context fc, struct fs_parameter param)
	{
	struct squashfs_mount_opts *opts = fc->fs_private;
	struct fs_parse_result result;
	int opt;

	opt = fs_parse(fc, squashfs_fs_parameters, param, &result);
	if (opt < 0)
	return opt;

	switch (opt) {
	case Opt_errors:
	opts->errors = result.uint_32;
	break;
	default:
	return -EINVAL;
	}

	return 0;
	}

	static const struct squashfs_decompressor *supported_squashfs_filesystem(
	struct fs_context *fc,
	short major, short minor, short id)
	{
	const struct squashfs_decompressor *decompressor;

	if (major < SQUASHFS_MAJOR) {
	errorf(fc, "Major/Minor mismatch, older Squashfs %d.%d "
	"filesystems are unsupported", major, minor);
	return NULL;
	} else if (major > SQUASHFS_MAJOR \|\| minor > SQUASHFS_MINOR) {
	errorf(fc, "Major/Minor mismatch, trying to mount newer "
	"%d.%d filesystem", major, minor);
	errorf(fc, "Please update your kernel");
	return NULL;
	}

	decompressor = squashfs_lookup_decompressor(id);
	if (!decompressor->supported) {
	errorf(fc, "Filesystem uses \"%s\" compression. This is not supported",
	decompressor->name);
	return NULL;
	}

	return decompressor;
	}

	static int squashfs_bdi_init(struct super_block *sb)
	{
	int err;
	unsigned int major = MAJOR(sb->s_dev);
	unsigned int minor = MINOR(sb->s_dev);

	bdi_put(sb->s_bdi);
	sb->s_bdi = &noop_backing_dev_info;

	err = super_setup_bdi_name(sb, "squashfs_%u_%u", major, minor);
	if (err)
	return err;

	sb->s_bdi->ra_pages = 0;
	sb->s_bdi->io_pages = 0;

	return 0;
	}

	static int squashfs_fill_super(struct super_block sb, struct fs_context fc)
	{
	struct squashfs_mount_opts *opts = fc->fs_private;
	struct squashfs_sb_info *msblk;
	struct squashfs_super_block *sblk = NULL;
	struct inode *root;
	long long root_inode;
	unsigned short flags;
	unsigned int fragments;
	u64 lookup_table_start, xattr_id_table_start, next_table;
	int err;

	TRACE("Entered squashfs_fill_superblock\n");

	/*
	* squashfs provides 'backing_dev_info' in order to disable read-ahead. For
	* squashfs, I/O is not deferred, it is done immediately in read_folio,
	* which means the user would always have to wait their own I/O. So the effect
	* of readahead is very weak for squashfs. squashfs_bdi_init will set
	* sb->s_bdi->ra_pages and sb->s_bdi->io_pages to 0 and close readahead for
	* squashfs.
	*/
	err = squashfs_bdi_init(sb);
	if (err) {
	errorf(fc, "squashfs init bdi failed");
	return err;
	}

	sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
	if (sb->s_fs_info == NULL) {
	ERROR("Failed to allocate squashfs_sb_info\n");
	return -ENOMEM;
	}
	msblk = sb->s_fs_info;

	msblk->panic_on_errors = (opts->errors == Opt_errors_panic);

	msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
	msblk->devblksize_log2 = ffz(~msblk->devblksize);

	mutex_init(&msblk->meta_index_mutex);

	/*
	* msblk->bytes_used is checked in squashfs_read_table to ensure reads
	* are not beyond filesystem end. But as we're using
	* squashfs_read_table here to read the superblock (including the value
	* of bytes_used) we need to set it to an initial sensible dummy value
	*/
	msblk->bytes_used = sizeof(*sblk);
	sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));

	if (IS_ERR(sblk)) {
	errorf(fc, "unable to read squashfs_super_block");
	err = PTR_ERR(sblk);
	sblk = NULL;
	goto failed_mount;
	}

	err = -EINVAL;

	/* Check it is a SQUASHFS superblock */
	sb->s_magic = le32_to_cpu(sblk->s_magic);
	if (sb->s_magic != SQUASHFS_MAGIC) {
	if (!(fc->sb_flags & SB_SILENT))
	errorf(fc, "Can't find a SQUASHFS superblock on %pg",
	sb->s_bdev);
	goto failed_mount;
	}

	/* Check the MAJOR & MINOR versions and lookup compression type */
	msblk->decompressor = supported_squashfs_filesystem(
	fc,
	le16_to_cpu(sblk->s_major),
	le16_to_cpu(sblk->s_minor),
	le16_to_cpu(sblk->compression));
	if (msblk->decompressor == NULL)
	goto failed_mount;

	/* Check the filesystem does not extend beyond the end of the
	block device */
	msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
	if (msblk->bytes_used < 0 \|\|
	msblk->bytes_used > bdev_nr_bytes(sb->s_bdev))
	goto failed_mount;

	/* Check block size for sanity */
	msblk->block_size = le32_to_cpu(sblk->block_size);
	if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
	goto insanity;

	/*
	* Check the system page size is not larger than the filesystem
	* block size (by default 128K). This is currently not supported.
	*/
	if (PAGE_SIZE > msblk->block_size) {
	errorf(fc, "Page size > filesystem block size (%d). This is "
	"currently not supported!", msblk->block_size);
	goto failed_mount;
	}

	/* Check block log for sanity */
	msblk->block_log = le16_to_cpu(sblk->block_log);
	if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
	goto failed_mount;

	/* Check that block_size and block_log match */
	if (msblk->block_size != (1 << msblk->block_log))
	goto insanity;

	/* Check the root inode for sanity */
	root_inode = le64_to_cpu(sblk->root_inode);
	if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
	goto insanity;

	msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
	msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
	msblk->inodes = le32_to_cpu(sblk->inodes);
	msblk->fragments = le32_to_cpu(sblk->fragments);
	msblk->ids = le16_to_cpu(sblk->no_ids);
	flags = le16_to_cpu(sblk->flags);

	TRACE("Found valid superblock on %pg\n", sb->s_bdev);
	TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
	? "un" : "");
	TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
	? "un" : "");
	TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
	TRACE("Block size %d\n", msblk->block_size);
	TRACE("Number of inodes %d\n", msblk->inodes);
	TRACE("Number of fragments %d\n", msblk->fragments);
	TRACE("Number of ids %d\n", msblk->ids);
	TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
	TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
	TRACE("sblk->fragment_table_start %llx\n",
	(u64) le64_to_cpu(sblk->fragment_table_start));
	TRACE("sblk->id_table_start %llx\n",
	(u64) le64_to_cpu(sblk->id_table_start));

	sb->s_maxbytes = MAX_LFS_FILESIZE;
	sb->s_time_min = 0;
	sb->s_time_max = U32_MAX;
	sb->s_flags \|= SB_RDONLY;
	sb->s_op = &squashfs_super_ops;

	err = -ENOMEM;

	msblk->block_cache = squashfs_cache_init("metadata",
	SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
	if (msblk->block_cache == NULL)
	goto failed_mount;

	/* Allocate read_page block */
	msblk->read_page = squashfs_cache_init("data",
	squashfs_max_decompressors(), msblk->block_size);
	if (msblk->read_page == NULL) {
	errorf(fc, "Failed to allocate read_page block");
	goto failed_mount;
	}

	msblk->stream = squashfs_decompressor_setup(sb, flags);
	if (IS_ERR(msblk->stream)) {
	err = PTR_ERR(msblk->stream);
	msblk->stream = NULL;
	goto insanity;
	}

	/* Handle xattrs */
	sb->s_xattr = squashfs_xattr_handlers;
	xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
	if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {
	next_table = msblk->bytes_used;
	goto allocate_id_index_table;
	}

	/* Allocate and read xattr id lookup table */
	msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
	xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
	if (IS_ERR(msblk->xattr_id_table)) {
	errorf(fc, "unable to read xattr id index table");
	err = PTR_ERR(msblk->xattr_id_table);
	msblk->xattr_id_table = NULL;
	if (err != -ENOTSUPP)
	goto failed_mount;
	}
	next_table = msblk->xattr_table;

	allocate_id_index_table:
	/* Allocate and read id index table */
	msblk->id_table = squashfs_read_id_index_table(sb,
	le64_to_cpu(sblk->id_table_start), next_table, msblk->ids);
	if (IS_ERR(msblk->id_table)) {
	errorf(fc, "unable to read id index table");
	err = PTR_ERR(msblk->id_table);
	msblk->id_table = NULL;
	goto failed_mount;
	}
	next_table = le64_to_cpu(msblk->id_table[0]);

	/* Handle inode lookup table */
	lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
	if (lookup_table_start == SQUASHFS_INVALID_BLK)
	goto handle_fragments;

	/* Allocate and read inode lookup table */
	msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
	lookup_table_start, next_table, msblk->inodes);
	if (IS_ERR(msblk->inode_lookup_table)) {
	errorf(fc, "unable to read inode lookup table");
	err = PTR_ERR(msblk->inode_lookup_table);
	msblk->inode_lookup_table = NULL;
	goto failed_mount;
	}
	next_table = le64_to_cpu(msblk->inode_lookup_table[0]);

	sb->s_export_op = &squashfs_export_ops;

	handle_fragments:
	fragments = msblk->fragments;
	if (fragments == 0)
	goto check_directory_table;

	msblk->fragment_cache = squashfs_cache_init("fragment",
	SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
	if (msblk->fragment_cache == NULL) {
	err = -ENOMEM;
	goto failed_mount;
	}

	/* Allocate and read fragment index table */
	msblk->fragment_index = squashfs_read_fragment_index_table(sb,
	le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
	if (IS_ERR(msblk->fragment_index)) {
	errorf(fc, "unable to read fragment index table");
	err = PTR_ERR(msblk->fragment_index);
	msblk->fragment_index = NULL;
	goto failed_mount;
	}
	next_table = le64_to_cpu(msblk->fragment_index[0]);

	check_directory_table:
	/* Sanity check directory_table */
	if (msblk->directory_table > next_table) {
	err = -EINVAL;
	goto insanity;
	}

	/* Sanity check inode_table */
	if (msblk->inode_table >= msblk->directory_table) {
	err = -EINVAL;
	goto insanity;
	}

	/* allocate root */
	root = new_inode(sb);
	if (!root) {
	err = -ENOMEM;
	goto failed_mount;
	}

	err = squashfs_read_inode(root, root_inode);
	if (err) {
	make_bad_inode(root);
	iput(root);
	goto failed_mount;
	}
	insert_inode_hash(root);

	sb->s_root = d_make_root(root);
	if (sb->s_root == NULL) {
	ERROR("Root inode create failed\n");
	err = -ENOMEM;
	goto failed_mount;
	}

	TRACE("Leaving squashfs_fill_super\n");
	kfree(sblk);
	return 0;

	insanity:
	errorf(fc, "squashfs image failed sanity check");
	failed_mount:
	squashfs_cache_delete(msblk->block_cache);
	squashfs_cache_delete(msblk->fragment_cache);
	squashfs_cache_delete(msblk->read_page);
	squashfs_decompressor_destroy(msblk);
	kfree(msblk->inode_lookup_table);
	kfree(msblk->fragment_index);
	kfree(msblk->id_table);
	kfree(msblk->xattr_id_table);
	kfree(sb->s_fs_info);
	sb->s_fs_info = NULL;
	kfree(sblk);
	return err;
	}

	static int squashfs_get_tree(struct fs_context *fc)
	{
	return get_tree_bdev(fc, squashfs_fill_super);
	}

	static int squashfs_reconfigure(struct fs_context *fc)
	{
	struct super_block *sb = fc->root->d_sb;
	struct squashfs_sb_info *msblk = sb->s_fs_info;
	struct squashfs_mount_opts *opts = fc->fs_private;

	sync_filesystem(fc->root->d_sb);
	fc->sb_flags \|= SB_RDONLY;

	msblk->panic_on_errors = (opts->errors == Opt_errors_panic);

	return 0;
	}

	static void squashfs_free_fs_context(struct fs_context *fc)
	{
	kfree(fc->fs_private);
	}

	static const struct fs_context_operations squashfs_context_ops = {
	.get_tree = squashfs_get_tree,
	.free = squashfs_free_fs_context,
	.parse_param = squashfs_parse_param,
	.reconfigure = squashfs_reconfigure,
	};

	static int squashfs_show_options(struct seq_file s, struct dentry root)
	{
	struct super_block *sb = root->d_sb;
	struct squashfs_sb_info *msblk = sb->s_fs_info;

	if (msblk->panic_on_errors)
	seq_puts(s, ",errors=panic");
	else
	seq_puts(s, ",errors=continue");

	return 0;
	}

	static int squashfs_init_fs_context(struct fs_context *fc)
	{
	struct squashfs_mount_opts *opts;

	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
	if (!opts)
	return -ENOMEM;

	fc->fs_private = opts;
	fc->ops = &squashfs_context_ops;
	return 0;
	}

	static int squashfs_statfs(struct dentry dentry, struct kstatfs buf)
	{
	struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
	u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);

	TRACE("Entered squashfs_statfs\n");

	buf->f_type = SQUASHFS_MAGIC;
	buf->f_bsize = msblk->block_size;
	buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
	buf->f_bfree = buf->f_bavail = 0;
	buf->f_files = msblk->inodes;
	buf->f_ffree = 0;
	buf->f_namelen = SQUASHFS_NAME_LEN;
	buf->f_fsid = u64_to_fsid(id);

	return 0;
	}


	static void squashfs_put_super(struct super_block *sb)
	{
	if (sb->s_fs_info) {
	struct squashfs_sb_info *sbi = sb->s_fs_info;
	squashfs_cache_delete(sbi->block_cache);
	squashfs_cache_delete(sbi->fragment_cache);
	squashfs_cache_delete(sbi->read_page);
	squashfs_decompressor_destroy(sbi);
	kfree(sbi->id_table);
	kfree(sbi->fragment_index);
	kfree(sbi->meta_index);
	kfree(sbi->inode_lookup_table);
	kfree(sbi->xattr_id_table);
	kfree(sb->s_fs_info);
	sb->s_fs_info = NULL;
	}
	}

	static struct kmem_cache *squashfs_inode_cachep;


	static void init_once(void *foo)
	{
	struct squashfs_inode_info *ei = foo;

	inode_init_once(&ei->vfs_inode);
	}


	static int __init init_inodecache(void)
	{
	squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
	sizeof(struct squashfs_inode_info), 0,
	SLAB_HWCACHE_ALIGN\|SLAB_RECLAIM_ACCOUNT\|SLAB_ACCOUNT,
	init_once);

	return squashfs_inode_cachep ? 0 : -ENOMEM;
	}


	static void destroy_inodecache(void)
	{
	/*
	* Make sure all delayed rcu free inodes are flushed before we
	* destroy cache.
	*/
	rcu_barrier();
	kmem_cache_destroy(squashfs_inode_cachep);
	}


	static int __init init_squashfs_fs(void)
	{
	int err = init_inodecache();

	if (err)
	return err;

	err = register_filesystem(&squashfs_fs_type);
	if (err) {
	destroy_inodecache();
	return err;
	}

	pr_info("version 4.0 (2009/01/31) Phillip Lougher\n");

	return 0;
	}


	static void __exit exit_squashfs_fs(void)
	{
	unregister_filesystem(&squashfs_fs_type);
	destroy_inodecache();
	}


	static struct inode squashfs_alloc_inode(struct super_block sb)
	{
	struct squashfs_inode_info *ei =
	alloc_inode_sb(sb, squashfs_inode_cachep, GFP_KERNEL);

	return ei ? &ei->vfs_inode : NULL;
	}


	static void squashfs_free_inode(struct inode *inode)
	{
	kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
	}

	static struct file_system_type squashfs_fs_type = {
	.owner = THIS_MODULE,
	.name = "squashfs",
	.init_fs_context = squashfs_init_fs_context,
	.parameters = squashfs_fs_parameters,
	.kill_sb = kill_block_super,
	.fs_flags = FS_REQUIRES_DEV
	};
	MODULE_ALIAS_FS("squashfs");

	static const struct super_operations squashfs_super_ops = {
	.alloc_inode = squashfs_alloc_inode,
	.free_inode = squashfs_free_inode,
	.statfs = squashfs_statfs,
	.put_super = squashfs_put_super,
	.show_options = squashfs_show_options,
	};

	module_init(init_squashfs_fs);
	module_exit(exit_squashfs_fs);
	MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
	MODULE_AUTHOR("Phillip Lougher <phillip@squashfs.org.uk>");
	MODULE_LICENSE("GPL");