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

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2017-2018 HUAWEI, Inc.
  *             https://www.huawei.com/
  * Created by Gao Xiang <gaoxiang25@huawei.com>
  */
 #include <linux/module.h>
 #include <linux/buffer_head.h>
 #include <linux/statfs.h>
 #include <linux/parser.h>
 #include <linux/seq_file.h>
 #include <linux/crc32c.h>
 #include <linux/fs_context.h>
 #include <linux/fs_parser.h>
 #include "xattr.h"

 #define CREATE_TRACE_POINTS
 #include <trace/events/erofs.h>

 static struct kmem_cache *erofs_inode_cachep __read_mostly;

 void _erofs_err(struct super_block *sb, const char *function,
 		const char *fmt, ...)
 {
 	struct va_format vaf;
 	va_list args;

 	va_start(args, fmt);

 	vaf.fmt = fmt;
 	vaf.va = &args;

 	pr_err("(device %s): %s: %pV", sb->s_id, function, &vaf);
 	va_end(args);
 }

 void _erofs_info(struct super_block *sb, const char *function,
 		 const char *fmt, ...)
 {
 	struct va_format vaf;
 	va_list args;

 	va_start(args, fmt);

 	vaf.fmt = fmt;
 	vaf.va = &args;

 	pr_info("(device %s): %pV", sb->s_id, &vaf);
 	va_end(args);
 }

 static int erofs_superblock_csum_verify(struct super_block *sb, void *sbdata)
 {
 	struct erofs_super_block *dsb;
 	u32 expected_crc, crc;

 	dsb = kmemdup(sbdata + EROFS_SUPER_OFFSET,
 		      EROFS_BLKSIZ - EROFS_SUPER_OFFSET, GFP_KERNEL);
 	if (!dsb)
 		return -ENOMEM;

 	expected_crc = le32_to_cpu(dsb->checksum);
 	dsb->checksum = 0;
 	/* to allow for x86 boot sectors and other oddities. */
 	crc = crc32c(~0, dsb, EROFS_BLKSIZ - EROFS_SUPER_OFFSET);
 	kfree(dsb);

 	if (crc != expected_crc) {
 		erofs_err(sb, "invalid checksum 0x%08x, 0x%08x expected",
 			  crc, expected_crc);
 		return -EBADMSG;
 	}
 	return 0;
 }

 static void erofs_inode_init_once(void *ptr)
 {
 	struct erofs_inode *vi = ptr;

 	inode_init_once(&vi->vfs_inode);
 }

 static struct inode *erofs_alloc_inode(struct super_block *sb)
 {
 	struct erofs_inode *vi =
 		kmem_cache_alloc(erofs_inode_cachep, GFP_KERNEL);

 	if (!vi)
 		return NULL;

 	/* zero out everything except vfs_inode */
 	memset(vi, 0, offsetof(struct erofs_inode, vfs_inode));
 	return &vi->vfs_inode;
 }

 static void erofs_free_inode(struct inode *inode)
 {
 	struct erofs_inode *vi = EROFS_I(inode);

 	/* be careful of RCU symlink path */
 	if (inode->i_op == &erofs_fast_symlink_iops)
 		kfree(inode->i_link);
 	kfree(vi->xattr_shared_xattrs);

 	kmem_cache_free(erofs_inode_cachep, vi);
 }

 static bool check_layout_compatibility(struct super_block *sb,
 				       struct erofs_super_block *dsb)
 {
 	const unsigned int feature = le32_to_cpu(dsb->feature_incompat);

 	EROFS_SB(sb)->feature_incompat = feature;

 	/* check if current kernel meets all mandatory requirements */
 	if (feature & (~EROFS_ALL_FEATURE_INCOMPAT)) {
 		erofs_err(sb,
 			  "unidentified incompatible feature %x, please upgrade kernel version",
 			   feature & ~EROFS_ALL_FEATURE_INCOMPAT);
 		return false;
 	}
 	return true;
 }

 static int erofs_read_superblock(struct super_block *sb)
 {
 	struct erofs_sb_info *sbi;
 	struct page *page;
 	struct erofs_super_block *dsb;
 	unsigned int blkszbits;
 	void *data;
 	int ret;

 	page = read_mapping_page(sb->s_bdev->bd_inode->i_mapping, 0, NULL);
 	if (IS_ERR(page)) {
 		erofs_err(sb, "cannot read erofs superblock");
 		return PTR_ERR(page);
 	}

 	sbi = EROFS_SB(sb);

 	data = kmap(page);
 	dsb = (struct erofs_super_block *)(data + EROFS_SUPER_OFFSET);

 	ret = -EINVAL;
 	if (le32_to_cpu(dsb->magic) != EROFS_SUPER_MAGIC_V1) {
 		erofs_err(sb, "cannot find valid erofs superblock");
 		goto out;
 	}

 	sbi->feature_compat = le32_to_cpu(dsb->feature_compat);
 	if (sbi->feature_compat & EROFS_FEATURE_COMPAT_SB_CHKSUM) {
 		ret = erofs_superblock_csum_verify(sb, data);
 		if (ret)
 			goto out;
 	}

 	blkszbits = dsb->blkszbits;
 	/* 9(512 bytes) + LOG_SECTORS_PER_BLOCK == LOG_BLOCK_SIZE */
 	if (blkszbits != LOG_BLOCK_SIZE) {
 		erofs_err(sb, "blksize %u isn't supported on this platform",
 			  1 << blkszbits);
 		goto out;
 	}

 	if (!check_layout_compatibility(sb, dsb))
 		goto out;

 	sbi->blocks = le32_to_cpu(dsb->blocks);
 	sbi->meta_blkaddr = le32_to_cpu(dsb->meta_blkaddr);
 #ifdef CONFIG_EROFS_FS_XATTR
 	sbi->xattr_blkaddr = le32_to_cpu(dsb->xattr_blkaddr);
 #endif
 	sbi->islotbits = ilog2(sizeof(struct erofs_inode_compact));
 	sbi->root_nid = le16_to_cpu(dsb->root_nid);
 	sbi->inos = le64_to_cpu(dsb->inos);

 	sbi->build_time = le64_to_cpu(dsb->build_time);
 	sbi->build_time_nsec = le32_to_cpu(dsb->build_time_nsec);

 	memcpy(&sb->s_uuid, dsb->uuid, sizeof(dsb->uuid));

 	ret = strscpy(sbi->volume_name, dsb->volume_name,
 		      sizeof(dsb->volume_name));
 	if (ret < 0) {	/* -E2BIG */
 		erofs_err(sb, "bad volume name without NIL terminator");
 		ret = -EFSCORRUPTED;
 		goto out;
 	}
 	ret = 0;
 out:
 	kunmap(page);
 	put_page(page);
 	return ret;
 }

 /* set up default EROFS parameters */
 static void erofs_default_options(struct erofs_fs_context *ctx)
 {
 #ifdef CONFIG_EROFS_FS_ZIP
 	ctx->cache_strategy = EROFS_ZIP_CACHE_READAROUND;
 	ctx->max_sync_decompress_pages = 3;
 #endif
 #ifdef CONFIG_EROFS_FS_XATTR
 	set_opt(ctx, XATTR_USER);
 #endif
 #ifdef CONFIG_EROFS_FS_POSIX_ACL
 	set_opt(ctx, POSIX_ACL);
 #endif
 }

 enum {
 	Opt_user_xattr,
 	Opt_acl,
 	Opt_cache_strategy,
 	Opt_err
 };

 static const struct constant_table erofs_param_cache_strategy[] = {
 	{"disabled",	EROFS_ZIP_CACHE_DISABLED},
 	{"readahead",	EROFS_ZIP_CACHE_READAHEAD},
 	{"readaround",	EROFS_ZIP_CACHE_READAROUND},
 	{}
 };

 static const struct fs_parameter_spec erofs_fs_parameters[] = {
 	fsparam_flag_no("user_xattr",	Opt_user_xattr),
 	fsparam_flag_no("acl",		Opt_acl),
 	fsparam_enum("cache_strategy",	Opt_cache_strategy,
 		     erofs_param_cache_strategy),
 	{}
 };

 static int erofs_fc_parse_param(struct fs_context *fc,
 				struct fs_parameter *param)
 {
 	struct erofs_fs_context *ctx __maybe_unused = fc->fs_private;
 	struct fs_parse_result result;
 	int opt;

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

 	switch (opt) {
 	case Opt_user_xattr:
 #ifdef CONFIG_EROFS_FS_XATTR
 		if (result.boolean)
 			set_opt(ctx, XATTR_USER);
 		else
 			clear_opt(ctx, XATTR_USER);
 #else
 		errorfc(fc, "{,no}user_xattr options not supported");
 #endif
 		break;
 	case Opt_acl:
 #ifdef CONFIG_EROFS_FS_POSIX_ACL
 		if (result.boolean)
 			set_opt(ctx, POSIX_ACL);
 		else
 			clear_opt(ctx, POSIX_ACL);
 #else
 		errorfc(fc, "{,no}acl options not supported");
 #endif
 		break;
 	case Opt_cache_strategy:
 #ifdef CONFIG_EROFS_FS_ZIP
 		ctx->cache_strategy = result.uint_32;
 #else
 		errorfc(fc, "compression not supported, cache_strategy ignored");
 #endif
 		break;
 	default:
 		return -ENOPARAM;
 	}
 	return 0;
 }

 #ifdef CONFIG_EROFS_FS_ZIP
 static const struct address_space_operations managed_cache_aops;

 static int erofs_managed_cache_releasepage(struct page *page, gfp_t gfp_mask)
 {
 	int ret = 1;	/* 0 - busy */
 	struct address_space *const mapping = page->mapping;

 	DBG_BUGON(!PageLocked(page));
 	DBG_BUGON(mapping->a_ops != &managed_cache_aops);

 	if (PagePrivate(page))
 		ret = erofs_try_to_free_cached_page(mapping, page);

 	return ret;
 }

 static void erofs_managed_cache_invalidatepage(struct page *page,
 					       unsigned int offset,
 					       unsigned int length)
 {
 	const unsigned int stop = length + offset;

 	DBG_BUGON(!PageLocked(page));

 	/* Check for potential overflow in debug mode */
 	DBG_BUGON(stop > PAGE_SIZE || stop < length);

 	if (offset == 0 && stop == PAGE_SIZE)
 		while (!erofs_managed_cache_releasepage(page, GFP_NOFS))
 			cond_resched();
 }

 static const struct address_space_operations managed_cache_aops = {
 	.releasepage = erofs_managed_cache_releasepage,
 	.invalidatepage = erofs_managed_cache_invalidatepage,
 };

 static int erofs_init_managed_cache(struct super_block *sb)
 {
 	struct erofs_sb_info *const sbi = EROFS_SB(sb);
 	struct inode *const inode = new_inode(sb);

 	if (!inode)
 		return -ENOMEM;

 	set_nlink(inode, 1);
 	inode->i_size = OFFSET_MAX;

 	inode->i_mapping->a_ops = &managed_cache_aops;
 	mapping_set_gfp_mask(inode->i_mapping,
 			     GFP_NOFS | __GFP_HIGHMEM | __GFP_MOVABLE);
 	sbi->managed_cache = inode;
 	return 0;
 }
 #else
 static int erofs_init_managed_cache(struct super_block *sb) { return 0; }
 #endif

 static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct inode *inode;
 	struct erofs_sb_info *sbi;
 	struct erofs_fs_context *ctx = fc->fs_private;
 	int err;

 	sb->s_magic = EROFS_SUPER_MAGIC;

 	if (!sb_set_blocksize(sb, EROFS_BLKSIZ)) {
 		erofs_err(sb, "failed to set erofs blksize");
 		return -EINVAL;
 	}

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

 	sb->s_fs_info = sbi;
 	err = erofs_read_superblock(sb);
 	if (err)
 		return err;

 	sb->s_flags |= SB_RDONLY | SB_NOATIME;
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
 	sb->s_time_gran = 1;

 	sb->s_op = &erofs_sops;
 	sb->s_xattr = erofs_xattr_handlers;

 	if (test_opt(ctx, POSIX_ACL))
 		sb->s_flags |= SB_POSIXACL;
 	else
 		sb->s_flags &= ~SB_POSIXACL;

 	sbi->ctx = *ctx;

 #ifdef CONFIG_EROFS_FS_ZIP
 	xa_init(&sbi->managed_pslots);
 #endif

 	/* get the root inode */
 	inode = erofs_iget(sb, ROOT_NID(sbi), true);
 	if (IS_ERR(inode))
 		return PTR_ERR(inode);

 	if (!S_ISDIR(inode->i_mode)) {
 		erofs_err(sb, "rootino(nid %llu) is not a directory(i_mode %o)",
 			  ROOT_NID(sbi), inode->i_mode);
 		iput(inode);
 		return -EINVAL;
 	}

 	sb->s_root = d_make_root(inode);
 	if (!sb->s_root)
 		return -ENOMEM;

 	erofs_shrinker_register(sb);
 	/* sb->s_umount is already locked, SB_ACTIVE and SB_BORN are not set */
 	err = erofs_init_managed_cache(sb);
 	if (err)
 		return err;

 	erofs_info(sb, "mounted with root inode @ nid %llu.", ROOT_NID(sbi));
 	return 0;
 }

 static int erofs_fc_get_tree(struct fs_context *fc)
 {
 	return get_tree_bdev(fc, erofs_fc_fill_super);
 }

 static int erofs_fc_reconfigure(struct fs_context *fc)
 {
 	struct super_block *sb = fc->root->d_sb;
 	struct erofs_sb_info *sbi = EROFS_SB(sb);
 	struct erofs_fs_context *ctx = fc->fs_private;

 	DBG_BUGON(!sb_rdonly(sb));

 	if (test_opt(ctx, POSIX_ACL))
 		fc->sb_flags |= SB_POSIXACL;
 	else
 		fc->sb_flags &= ~SB_POSIXACL;

 	sbi->ctx = *ctx;

 	fc->sb_flags |= SB_RDONLY;
 	return 0;
 }

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

 static const struct fs_context_operations erofs_context_ops = {
 	.parse_param	= erofs_fc_parse_param,
 	.get_tree       = erofs_fc_get_tree,
 	.reconfigure    = erofs_fc_reconfigure,
 	.free		= erofs_fc_free,
 };

 static int erofs_init_fs_context(struct fs_context *fc)
 {
 	fc->fs_private = kzalloc(sizeof(struct erofs_fs_context), GFP_KERNEL);
 	if (!fc->fs_private)
 		return -ENOMEM;

 	/* set default mount options */
 	erofs_default_options(fc->fs_private);

 	fc->ops = &erofs_context_ops;

 	return 0;
 }

 /*
  * could be triggered after deactivate_locked_super()
  * is called, thus including umount and failed to initialize.
  */
 static void erofs_kill_sb(struct super_block *sb)
 {
 	struct erofs_sb_info *sbi;

 	WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);

 	kill_block_super(sb);

 	sbi = EROFS_SB(sb);
 	if (!sbi)
 		return;
 	kfree(sbi);
 	sb->s_fs_info = NULL;
 }

 /* called when ->s_root is non-NULL */
 static void erofs_put_super(struct super_block *sb)
 {
 	struct erofs_sb_info *const sbi = EROFS_SB(sb);

 	DBG_BUGON(!sbi);

 	erofs_shrinker_unregister(sb);
 #ifdef CONFIG_EROFS_FS_ZIP
 	iput(sbi->managed_cache);
 	sbi->managed_cache = NULL;
 #endif
 }

 static struct file_system_type erofs_fs_type = {
 	.owner          = THIS_MODULE,
 	.name           = "erofs",
 	.init_fs_context = erofs_init_fs_context,
 	.kill_sb        = erofs_kill_sb,
 	.fs_flags       = FS_REQUIRES_DEV,
 };
 MODULE_ALIAS_FS("erofs");

 static int __init erofs_module_init(void)
 {
 	int err;

 	erofs_check_ondisk_layout_definitions();

 	erofs_inode_cachep = kmem_cache_create("erofs_inode",
 					       sizeof(struct erofs_inode), 0,
 					       SLAB_RECLAIM_ACCOUNT,
 					       erofs_inode_init_once);
 	if (!erofs_inode_cachep) {
 		err = -ENOMEM;
 		goto icache_err;
 	}

 	err = erofs_init_shrinker();
 	if (err)
 		goto shrinker_err;

 	err = z_erofs_init_zip_subsystem();
 	if (err)
 		goto zip_err;

 	err = register_filesystem(&erofs_fs_type);
 	if (err)
 		goto fs_err;

 	return 0;

 fs_err:
 	z_erofs_exit_zip_subsystem();
 zip_err:
 	erofs_exit_shrinker();
 shrinker_err:
 	kmem_cache_destroy(erofs_inode_cachep);
 icache_err:
 	return err;
 }

 static void __exit erofs_module_exit(void)
 {
 	unregister_filesystem(&erofs_fs_type);
 	z_erofs_exit_zip_subsystem();
 	erofs_exit_shrinker();

 	/* Ensure all RCU free inodes are safe before cache is destroyed. */
 	rcu_barrier();
 	kmem_cache_destroy(erofs_inode_cachep);
 }

 /* get filesystem statistics */
 static int erofs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct super_block *sb = dentry->d_sb;
 	struct erofs_sb_info *sbi = EROFS_SB(sb);
 	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);

 	buf->f_type = sb->s_magic;
 	buf->f_bsize = EROFS_BLKSIZ;
 	buf->f_blocks = sbi->blocks;
 	buf->f_bfree = buf->f_bavail = 0;

 	buf->f_files = ULLONG_MAX;
 	buf->f_ffree = ULLONG_MAX - sbi->inos;

 	buf->f_namelen = EROFS_NAME_LEN;

 	buf->f_fsid    = u64_to_fsid(id);
 	return 0;
 }

 static int erofs_show_options(struct seq_file *seq, struct dentry *root)
 {
 	struct erofs_sb_info *sbi __maybe_unused = EROFS_SB(root->d_sb);
 	struct erofs_fs_context *ctx __maybe_unused = &sbi->ctx;

 #ifdef CONFIG_EROFS_FS_XATTR
 	if (test_opt(ctx, XATTR_USER))
 		seq_puts(seq, ",user_xattr");
 	else
 		seq_puts(seq, ",nouser_xattr");
 #endif
 #ifdef CONFIG_EROFS_FS_POSIX_ACL
 	if (test_opt(ctx, POSIX_ACL))
 		seq_puts(seq, ",acl");
 	else
 		seq_puts(seq, ",noacl");
 #endif
 #ifdef CONFIG_EROFS_FS_ZIP
 	if (ctx->cache_strategy == EROFS_ZIP_CACHE_DISABLED)
 		seq_puts(seq, ",cache_strategy=disabled");
 	else if (ctx->cache_strategy == EROFS_ZIP_CACHE_READAHEAD)
 		seq_puts(seq, ",cache_strategy=readahead");
 	else if (ctx->cache_strategy == EROFS_ZIP_CACHE_READAROUND)
 		seq_puts(seq, ",cache_strategy=readaround");
 #endif
 	return 0;
 }

 const struct super_operations erofs_sops = {
 	.put_super = erofs_put_super,
 	.alloc_inode = erofs_alloc_inode,
 	.free_inode = erofs_free_inode,
 	.statfs = erofs_statfs,
 	.show_options = erofs_show_options,
 };

 module_init(erofs_module_init);
 module_exit(erofs_module_exit);

 MODULE_DESCRIPTION("Enhanced ROM File System");
 MODULE_AUTHOR("Gao Xiang, Chao Yu, Miao Xie, CONSUMER BG, HUAWEI Inc.");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2017-2018 HUAWEI, Inc.
	* https://www.huawei.com/
	* Created by Gao Xiang <gaoxiang25@huawei.com>
	*/
	#include <linux/module.h>
	#include <linux/buffer_head.h>
	#include <linux/statfs.h>
	#include <linux/parser.h>
	#include <linux/seq_file.h>
	#include <linux/crc32c.h>
	#include <linux/fs_context.h>
	#include <linux/fs_parser.h>
	#include "xattr.h"

	#define CREATE_TRACE_POINTS
	#include <trace/events/erofs.h>

	static struct kmem_cache *erofs_inode_cachep __read_mostly;

	void _erofs_err(struct super_block sb, const char function,
	const char *fmt, ...)
	{
	struct va_format vaf;
	va_list args;

	va_start(args, fmt);

	vaf.fmt = fmt;
	vaf.va = &args;

	pr_err("(device %s): %s: %pV", sb->s_id, function, &vaf);
	va_end(args);
	}

	void _erofs_info(struct super_block sb, const char function,
	const char *fmt, ...)
	{
	struct va_format vaf;
	va_list args;

	va_start(args, fmt);

	vaf.fmt = fmt;
	vaf.va = &args;

	pr_info("(device %s): %pV", sb->s_id, &vaf);
	va_end(args);
	}

	static int erofs_superblock_csum_verify(struct super_block sb, void sbdata)
	{
	struct erofs_super_block *dsb;
	u32 expected_crc, crc;

	dsb = kmemdup(sbdata + EROFS_SUPER_OFFSET,
	EROFS_BLKSIZ - EROFS_SUPER_OFFSET, GFP_KERNEL);
	if (!dsb)
	return -ENOMEM;

	expected_crc = le32_to_cpu(dsb->checksum);
	dsb->checksum = 0;
	/* to allow for x86 boot sectors and other oddities. */
	crc = crc32c(~0, dsb, EROFS_BLKSIZ - EROFS_SUPER_OFFSET);
	kfree(dsb);

	if (crc != expected_crc) {
	erofs_err(sb, "invalid checksum 0x%08x, 0x%08x expected",
	crc, expected_crc);
	return -EBADMSG;
	}
	return 0;
	}

	static void erofs_inode_init_once(void *ptr)
	{
	struct erofs_inode *vi = ptr;

	inode_init_once(&vi->vfs_inode);
	}

	static struct inode erofs_alloc_inode(struct super_block sb)
	{
	struct erofs_inode *vi =
	kmem_cache_alloc(erofs_inode_cachep, GFP_KERNEL);

	if (!vi)
	return NULL;

	/* zero out everything except vfs_inode */
	memset(vi, 0, offsetof(struct erofs_inode, vfs_inode));
	return &vi->vfs_inode;
	}

	static void erofs_free_inode(struct inode *inode)
	{
	struct erofs_inode *vi = EROFS_I(inode);

	/* be careful of RCU symlink path */
	if (inode->i_op == &erofs_fast_symlink_iops)
	kfree(inode->i_link);
	kfree(vi->xattr_shared_xattrs);

	kmem_cache_free(erofs_inode_cachep, vi);
	}

	static bool check_layout_compatibility(struct super_block *sb,
	struct erofs_super_block *dsb)
	{
	const unsigned int feature = le32_to_cpu(dsb->feature_incompat);

	EROFS_SB(sb)->feature_incompat = feature;

	/* check if current kernel meets all mandatory requirements */
	if (feature & (~EROFS_ALL_FEATURE_INCOMPAT)) {
	erofs_err(sb,
	"unidentified incompatible feature %x, please upgrade kernel version",
	feature & ~EROFS_ALL_FEATURE_INCOMPAT);
	return false;
	}
	return true;
	}

	static int erofs_read_superblock(struct super_block *sb)
	{
	struct erofs_sb_info *sbi;
	struct page *page;
	struct erofs_super_block *dsb;
	unsigned int blkszbits;
	void *data;
	int ret;

	page = read_mapping_page(sb->s_bdev->bd_inode->i_mapping, 0, NULL);
	if (IS_ERR(page)) {
	erofs_err(sb, "cannot read erofs superblock");
	return PTR_ERR(page);
	}

	sbi = EROFS_SB(sb);

	data = kmap(page);
	dsb = (struct erofs_super_block *)(data + EROFS_SUPER_OFFSET);

	ret = -EINVAL;
	if (le32_to_cpu(dsb->magic) != EROFS_SUPER_MAGIC_V1) {
	erofs_err(sb, "cannot find valid erofs superblock");
	goto out;
	}

	sbi->feature_compat = le32_to_cpu(dsb->feature_compat);
	if (sbi->feature_compat & EROFS_FEATURE_COMPAT_SB_CHKSUM) {
	ret = erofs_superblock_csum_verify(sb, data);
	if (ret)
	goto out;
	}

	blkszbits = dsb->blkszbits;
	/* 9(512 bytes) + LOG_SECTORS_PER_BLOCK == LOG_BLOCK_SIZE */
	if (blkszbits != LOG_BLOCK_SIZE) {
	erofs_err(sb, "blksize %u isn't supported on this platform",
	1 << blkszbits);
	goto out;
	}

	if (!check_layout_compatibility(sb, dsb))
	goto out;

	sbi->blocks = le32_to_cpu(dsb->blocks);
	sbi->meta_blkaddr = le32_to_cpu(dsb->meta_blkaddr);
	#ifdef CONFIG_EROFS_FS_XATTR
	sbi->xattr_blkaddr = le32_to_cpu(dsb->xattr_blkaddr);
	#endif
	sbi->islotbits = ilog2(sizeof(struct erofs_inode_compact));
	sbi->root_nid = le16_to_cpu(dsb->root_nid);
	sbi->inos = le64_to_cpu(dsb->inos);

	sbi->build_time = le64_to_cpu(dsb->build_time);
	sbi->build_time_nsec = le32_to_cpu(dsb->build_time_nsec);

	memcpy(&sb->s_uuid, dsb->uuid, sizeof(dsb->uuid));

	ret = strscpy(sbi->volume_name, dsb->volume_name,
	sizeof(dsb->volume_name));
	if (ret < 0) { /* -E2BIG */
	erofs_err(sb, "bad volume name without NIL terminator");
	ret = -EFSCORRUPTED;
	goto out;
	}
	ret = 0;
	out:
	kunmap(page);
	put_page(page);
	return ret;
	}

	/* set up default EROFS parameters */
	static void erofs_default_options(struct erofs_fs_context *ctx)
	{
	#ifdef CONFIG_EROFS_FS_ZIP
	ctx->cache_strategy = EROFS_ZIP_CACHE_READAROUND;
	ctx->max_sync_decompress_pages = 3;
	#endif
	#ifdef CONFIG_EROFS_FS_XATTR
	set_opt(ctx, XATTR_USER);
	#endif
	#ifdef CONFIG_EROFS_FS_POSIX_ACL
	set_opt(ctx, POSIX_ACL);
	#endif
	}

	enum {
	Opt_user_xattr,
	Opt_acl,
	Opt_cache_strategy,
	Opt_err
	};

	static const struct constant_table erofs_param_cache_strategy[] = {
	{"disabled", EROFS_ZIP_CACHE_DISABLED},
	{"readahead", EROFS_ZIP_CACHE_READAHEAD},
	{"readaround", EROFS_ZIP_CACHE_READAROUND},
	{}
	};

	static const struct fs_parameter_spec erofs_fs_parameters[] = {
	fsparam_flag_no("user_xattr", Opt_user_xattr),
	fsparam_flag_no("acl", Opt_acl),
	fsparam_enum("cache_strategy", Opt_cache_strategy,
	erofs_param_cache_strategy),
	{}
	};

	static int erofs_fc_parse_param(struct fs_context *fc,
	struct fs_parameter *param)
	{
	struct erofs_fs_context *ctx __maybe_unused = fc->fs_private;
	struct fs_parse_result result;
	int opt;

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

	switch (opt) {
	case Opt_user_xattr:
	#ifdef CONFIG_EROFS_FS_XATTR
	if (result.boolean)
	set_opt(ctx, XATTR_USER);
	else
	clear_opt(ctx, XATTR_USER);
	#else
	errorfc(fc, "{,no}user_xattr options not supported");
	#endif
	break;
	case Opt_acl:
	#ifdef CONFIG_EROFS_FS_POSIX_ACL
	if (result.boolean)
	set_opt(ctx, POSIX_ACL);
	else
	clear_opt(ctx, POSIX_ACL);
	#else
	errorfc(fc, "{,no}acl options not supported");
	#endif
	break;
	case Opt_cache_strategy:
	#ifdef CONFIG_EROFS_FS_ZIP
	ctx->cache_strategy = result.uint_32;
	#else
	errorfc(fc, "compression not supported, cache_strategy ignored");
	#endif
	break;
	default:
	return -ENOPARAM;
	}
	return 0;
	}

	#ifdef CONFIG_EROFS_FS_ZIP
	static const struct address_space_operations managed_cache_aops;

	static int erofs_managed_cache_releasepage(struct page *page, gfp_t gfp_mask)
	{
	int ret = 1; /* 0 - busy */
	struct address_space *const mapping = page->mapping;

	DBG_BUGON(!PageLocked(page));
	DBG_BUGON(mapping->a_ops != &managed_cache_aops);

	if (PagePrivate(page))
	ret = erofs_try_to_free_cached_page(mapping, page);

	return ret;
	}

	static void erofs_managed_cache_invalidatepage(struct page *page,
	unsigned int offset,
	unsigned int length)
	{
	const unsigned int stop = length + offset;

	DBG_BUGON(!PageLocked(page));

	/* Check for potential overflow in debug mode */
	DBG_BUGON(stop > PAGE_SIZE \|\| stop < length);

	if (offset == 0 && stop == PAGE_SIZE)
	while (!erofs_managed_cache_releasepage(page, GFP_NOFS))
	cond_resched();
	}

	static const struct address_space_operations managed_cache_aops = {
	.releasepage = erofs_managed_cache_releasepage,
	.invalidatepage = erofs_managed_cache_invalidatepage,
	};

	static int erofs_init_managed_cache(struct super_block *sb)
	{
	struct erofs_sb_info *const sbi = EROFS_SB(sb);
	struct inode *const inode = new_inode(sb);

	if (!inode)
	return -ENOMEM;

	set_nlink(inode, 1);
	inode->i_size = OFFSET_MAX;

	inode->i_mapping->a_ops = &managed_cache_aops;
	mapping_set_gfp_mask(inode->i_mapping,
	GFP_NOFS \| __GFP_HIGHMEM \| __GFP_MOVABLE);
	sbi->managed_cache = inode;
	return 0;
	}
	#else
	static int erofs_init_managed_cache(struct super_block *sb) { return 0; }
	#endif

	static int erofs_fc_fill_super(struct super_block sb, struct fs_context fc)
	{
	struct inode *inode;
	struct erofs_sb_info *sbi;
	struct erofs_fs_context *ctx = fc->fs_private;
	int err;

	sb->s_magic = EROFS_SUPER_MAGIC;

	if (!sb_set_blocksize(sb, EROFS_BLKSIZ)) {
	erofs_err(sb, "failed to set erofs blksize");
	return -EINVAL;
	}

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

	sb->s_fs_info = sbi;
	err = erofs_read_superblock(sb);
	if (err)
	return err;

	sb->s_flags \|= SB_RDONLY \| SB_NOATIME;
	sb->s_maxbytes = MAX_LFS_FILESIZE;
	sb->s_time_gran = 1;

	sb->s_op = &erofs_sops;
	sb->s_xattr = erofs_xattr_handlers;

	if (test_opt(ctx, POSIX_ACL))
	sb->s_flags \|= SB_POSIXACL;
	else
	sb->s_flags &= ~SB_POSIXACL;

	sbi->ctx = *ctx;

	#ifdef CONFIG_EROFS_FS_ZIP
	xa_init(&sbi->managed_pslots);
	#endif

	/* get the root inode */
	inode = erofs_iget(sb, ROOT_NID(sbi), true);
	if (IS_ERR(inode))
	return PTR_ERR(inode);

	if (!S_ISDIR(inode->i_mode)) {
	erofs_err(sb, "rootino(nid %llu) is not a directory(i_mode %o)",
	ROOT_NID(sbi), inode->i_mode);
	iput(inode);
	return -EINVAL;
	}

	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
	return -ENOMEM;

	erofs_shrinker_register(sb);
	/* sb->s_umount is already locked, SB_ACTIVE and SB_BORN are not set */
	err = erofs_init_managed_cache(sb);
	if (err)
	return err;

	erofs_info(sb, "mounted with root inode @ nid %llu.", ROOT_NID(sbi));
	return 0;
	}

	static int erofs_fc_get_tree(struct fs_context *fc)
	{
	return get_tree_bdev(fc, erofs_fc_fill_super);
	}

	static int erofs_fc_reconfigure(struct fs_context *fc)
	{
	struct super_block *sb = fc->root->d_sb;
	struct erofs_sb_info *sbi = EROFS_SB(sb);
	struct erofs_fs_context *ctx = fc->fs_private;

	DBG_BUGON(!sb_rdonly(sb));

	if (test_opt(ctx, POSIX_ACL))
	fc->sb_flags \|= SB_POSIXACL;
	else
	fc->sb_flags &= ~SB_POSIXACL;

	sbi->ctx = *ctx;

	fc->sb_flags \|= SB_RDONLY;
	return 0;
	}

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

	static const struct fs_context_operations erofs_context_ops = {
	.parse_param = erofs_fc_parse_param,
	.get_tree = erofs_fc_get_tree,
	.reconfigure = erofs_fc_reconfigure,
	.free = erofs_fc_free,
	};

	static int erofs_init_fs_context(struct fs_context *fc)
	{
	fc->fs_private = kzalloc(sizeof(struct erofs_fs_context), GFP_KERNEL);
	if (!fc->fs_private)
	return -ENOMEM;

	/* set default mount options */
	erofs_default_options(fc->fs_private);

	fc->ops = &erofs_context_ops;

	return 0;
	}

	/*
	* could be triggered after deactivate_locked_super()
	* is called, thus including umount and failed to initialize.
	*/
	static void erofs_kill_sb(struct super_block *sb)
	{
	struct erofs_sb_info *sbi;

	WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);

	kill_block_super(sb);

	sbi = EROFS_SB(sb);
	if (!sbi)
	return;
	kfree(sbi);
	sb->s_fs_info = NULL;
	}

	/* called when ->s_root is non-NULL */
	static void erofs_put_super(struct super_block *sb)
	{
	struct erofs_sb_info *const sbi = EROFS_SB(sb);

	DBG_BUGON(!sbi);

	erofs_shrinker_unregister(sb);
	#ifdef CONFIG_EROFS_FS_ZIP
	iput(sbi->managed_cache);
	sbi->managed_cache = NULL;
	#endif
	}

	static struct file_system_type erofs_fs_type = {
	.owner = THIS_MODULE,
	.name = "erofs",
	.init_fs_context = erofs_init_fs_context,
	.kill_sb = erofs_kill_sb,
	.fs_flags = FS_REQUIRES_DEV,
	};
	MODULE_ALIAS_FS("erofs");

	static int __init erofs_module_init(void)
	{
	int err;

	erofs_check_ondisk_layout_definitions();

	erofs_inode_cachep = kmem_cache_create("erofs_inode",
	sizeof(struct erofs_inode), 0,
	SLAB_RECLAIM_ACCOUNT,
	erofs_inode_init_once);
	if (!erofs_inode_cachep) {
	err = -ENOMEM;
	goto icache_err;
	}

	err = erofs_init_shrinker();
	if (err)
	goto shrinker_err;

	err = z_erofs_init_zip_subsystem();
	if (err)
	goto zip_err;

	err = register_filesystem(&erofs_fs_type);
	if (err)
	goto fs_err;

	return 0;

	fs_err:
	z_erofs_exit_zip_subsystem();
	zip_err:
	erofs_exit_shrinker();
	shrinker_err:
	kmem_cache_destroy(erofs_inode_cachep);
	icache_err:
	return err;
	}

	static void __exit erofs_module_exit(void)
	{
	unregister_filesystem(&erofs_fs_type);
	z_erofs_exit_zip_subsystem();
	erofs_exit_shrinker();

	/* Ensure all RCU free inodes are safe before cache is destroyed. */
	rcu_barrier();
	kmem_cache_destroy(erofs_inode_cachep);
	}

	/* get filesystem statistics */
	static int erofs_statfs(struct dentry dentry, struct kstatfs buf)
	{
	struct super_block *sb = dentry->d_sb;
	struct erofs_sb_info *sbi = EROFS_SB(sb);
	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);

	buf->f_type = sb->s_magic;
	buf->f_bsize = EROFS_BLKSIZ;
	buf->f_blocks = sbi->blocks;
	buf->f_bfree = buf->f_bavail = 0;

	buf->f_files = ULLONG_MAX;
	buf->f_ffree = ULLONG_MAX - sbi->inos;

	buf->f_namelen = EROFS_NAME_LEN;

	buf->f_fsid = u64_to_fsid(id);
	return 0;
	}

	static int erofs_show_options(struct seq_file seq, struct dentry root)
	{
	struct erofs_sb_info *sbi __maybe_unused = EROFS_SB(root->d_sb);
	struct erofs_fs_context *ctx __maybe_unused = &sbi->ctx;

	#ifdef CONFIG_EROFS_FS_XATTR
	if (test_opt(ctx, XATTR_USER))
	seq_puts(seq, ",user_xattr");
	else
	seq_puts(seq, ",nouser_xattr");
	#endif
	#ifdef CONFIG_EROFS_FS_POSIX_ACL
	if (test_opt(ctx, POSIX_ACL))
	seq_puts(seq, ",acl");
	else
	seq_puts(seq, ",noacl");
	#endif
	#ifdef CONFIG_EROFS_FS_ZIP
	if (ctx->cache_strategy == EROFS_ZIP_CACHE_DISABLED)
	seq_puts(seq, ",cache_strategy=disabled");
	else if (ctx->cache_strategy == EROFS_ZIP_CACHE_READAHEAD)
	seq_puts(seq, ",cache_strategy=readahead");
	else if (ctx->cache_strategy == EROFS_ZIP_CACHE_READAROUND)
	seq_puts(seq, ",cache_strategy=readaround");
	#endif
	return 0;
	}

	const struct super_operations erofs_sops = {
	.put_super = erofs_put_super,
	.alloc_inode = erofs_alloc_inode,
	.free_inode = erofs_free_inode,
	.statfs = erofs_statfs,
	.show_options = erofs_show_options,
	};

	module_init(erofs_module_init);
	module_exit(erofs_module_exit);

	MODULE_DESCRIPTION("Enhanced ROM File System");
	MODULE_AUTHOR("Gao Xiang, Chao Yu, Miao Xie, CONSUMER BG, HUAWEI Inc.");
	MODULE_LICENSE("GPL");