Code: static int ext4_fill_super(struct super_block *sb, void *data, int silent)
{
	char *orig_data = kstrdup(data, GFP_KERNEL);
	struct buffer_head *bh;
	struct ext4_super_block *es = NULL;
	struct ext4_sb_info *sbi;
	ext4_fsblk_t block;
	ext4_fsblk_t sb_block = get_sb_block(&data);
	ext4_fsblk_t logical_sb_block;
	unsigned long offset = 0;
	unsigned long journal_devnum = 0;
	unsigned long def_mount_opts;
	struct inode *root;
	const char *descr;
	int ret = -ENOMEM;
	int blocksize, clustersize;
	unsigned int db_count;
	unsigned int i;
	int needs_recovery, has_huge_files, has_bigalloc;
	__u64 blocks_count;
	int err = 0;
	unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
	ext4_group_t first_not_zeroed;

	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
	if (!sbi)
		goto out_free_orig;

	sbi->s_blockgroup_lock =
		kzalloc(sizeof(struct blockgroup_lock), GFP_KERNEL);
	if (!sbi->s_blockgroup_lock) {
		kfree(sbi);
		goto out_free_orig;
	}
	sb->s_fs_info = sbi;
	sbi->s_sb = sb;
	sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS;
	sbi->s_sb_block = sb_block;
	if (sb->s_bdev->bd_part)
		sbi->s_sectors_written_start =
			part_stat_read(sb->s_bdev->bd_part, sectors[1]);

	/* Cleanup superblock name */
	strreplace(sb->s_id, '/', '!');

	/* -EINVAL is default */
	ret = -EINVAL;
	blocksize = sb_min_blocksize(sb, EXT4_MIN_BLOCK_SIZE);
	if (!blocksize) {
		ext4_msg(sb, KERN_ERR, "unable to set blocksize");
		goto out_fail;
	}

	/*
	 * The ext4 superblock will not be buffer aligned for other than 1kB
	 * block sizes.  We need to calculate the offset from buffer start.
	 */
	if (blocksize != EXT4_MIN_BLOCK_SIZE) {
		logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
		offset = do_div(logical_sb_block, blocksize);
	} else {
		logical_sb_block = sb_block;
	}

	if (!(bh = sb_bread_unmovable(sb, logical_sb_block))) {
		ext4_msg(sb, KERN_ERR, "unable to read superblock");
		goto out_fail;
	}
	/*
	 * Note: s_es must be initialized as soon as possible because
	 *       some ext4 macro-instructions depend on its value
	 */
	es = (struct ext4_super_block *) (bh->b_data + offset);
	sbi->s_es = es;
	sb->s_magic = le16_to_cpu(es->s_magic);
	if (sb->s_magic != EXT4_SUPER_MAGIC)
		goto cantfind_ext4;
	sbi->s_kbytes_written = le64_to_cpu(es->s_kbytes_written);

	/* Warn if metadata_csum and gdt_csum are both set. */
	if (ext4_has_feature_metadata_csum(sb) &&
	    ext4_has_feature_gdt_csum(sb))
		ext4_warning(sb, "metadata_csum and uninit_bg are "
			     "redundant flags; please run fsck.");

	/* Check for a known checksum algorithm */
	if (!ext4_verify_csum_type(sb, es)) {
		ext4_msg(sb, KERN_ERR, "VFS: Found ext4 filesystem with "
			 "unknown checksum algorithm.");
		silent = 1;
		goto cantfind_ext4;
	}

	/* Load the checksum driver */
	if (ext4_has_feature_metadata_csum(sb)) {
		sbi->s_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
		if (IS_ERR(sbi->s_chksum_driver)) {
			ext4_msg(sb, KERN_ERR, "Cannot load crc32c driver.");
			ret = PTR_ERR(sbi->s_chksum_driver);
			sbi->s_chksum_driver = NULL;
			goto failed_mount;
		}
	}

	/* Check superblock checksum */
	if (!ext4_superblock_csum_verify(sb, es)) {
		ext4_msg(sb, KERN_ERR, "VFS: Found ext4 filesystem with "
			 "invalid superblock checksum.  Run e2fsck?");
		silent = 1;
		ret = -EFSBADCRC;
		goto cantfind_ext4;
	}

	/* Precompute checksum seed for all metadata */
	if (ext4_has_feature_csum_seed(sb))
		sbi->s_csum_seed = le32_to_cpu(es->s_checksum_seed);
	else if (ext4_has_metadata_csum(sb))
		sbi->s_csum_seed = ext4_chksum(sbi, ~0, es->s_uuid,
					       sizeof(es->s_uuid));

	/* Set defaults before we parse the mount options */
	def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
	set_opt(sb, INIT_INODE_TABLE);
	if (def_mount_opts & EXT4_DEFM_DEBUG)
		set_opt(sb, DEBUG);
	if (def_mount_opts & EXT4_DEFM_BSDGROUPS)
		set_opt(sb, GRPID);
	if (def_mount_opts & EXT4_DEFM_UID16)
		set_opt(sb, NO_UID32);
	/* xattr user namespace & acls are now defaulted on */
	set_opt(sb, XATTR_USER);
#ifdef CONFIG_EXT4_FS_POSIX_ACL
	set_opt(sb, POSIX_ACL);
#endif
	/* don't forget to enable journal_csum when metadata_csum is enabled. */
	if (ext4_has_metadata_csum(sb))
		set_opt(sb, JOURNAL_CHECKSUM);

	if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_DATA)
		set_opt(sb, JOURNAL_DATA);
	else if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_ORDERED)
		set_opt(sb, ORDERED_DATA);
	else if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_WBACK)
		set_opt(sb, WRITEBACK_DATA);

	if (le16_to_cpu(sbi->s_es->s_errors) == EXT4_ERRORS_PANIC)
		set_opt(sb, ERRORS_PANIC);
	else if (le16_to_cpu(sbi->s_es->s_errors) == EXT4_ERRORS_CONTINUE)
		set_opt(sb, ERRORS_CONT);
	else
		set_opt(sb, ERRORS_RO);
	/* block_validity enabled by default; disable with noblock_validity */
	set_opt(sb, BLOCK_VALIDITY);
	if (def_mount_opts & EXT4_DEFM_DISCARD)
		set_opt(sb, DISCARD);

	sbi->s_resuid = make_kuid(&init_user_ns, le16_to_cpu(es->s_def_resuid));
	sbi->s_resgid = make_kgid(&init_user_ns, le16_to_cpu(es->s_def_resgid));
	sbi->s_commit_interval = JBD2_DEFAULT_MAX_COMMIT_AGE * HZ;
	sbi->s_min_batch_time = EXT4_DEF_MIN_BATCH_TIME;
	sbi->s_max_batch_time = EXT4_DEF_MAX_BATCH_TIME;

	if ((def_mount_opts & EXT4_DEFM_NOBARRIER) == 0)
		set_opt(sb, BARRIER);

	/*
	 * enable delayed allocation by default
	 * Use -o nodelalloc to turn it off
	 */
	if (!IS_EXT3_SB(sb) && !IS_EXT2_SB(sb) &&
	    ((def_mount_opts & EXT4_DEFM_NODELALLOC) == 0))
		set_opt(sb, DELALLOC);

	/*
	 * set default s_li_wait_mult for lazyinit, for the case there is
	 * no mount option specified.
	 */
	sbi->s_li_wait_mult = EXT4_DEF_LI_WAIT_MULT;

	if (!parse_options((char *) sbi->s_es->s_mount_opts, sb,
			   &journal_devnum, &journal_ioprio, 0)) {
		ext4_msg(sb, KERN_WARNING,
			 "failed to parse options in superblock: %s",
			 sbi->s_es->s_mount_opts);
	}
	sbi->s_def_mount_opt = sbi->s_mount_opt;
	if (!parse_options((char *) data, sb, &journal_devnum,
			   &journal_ioprio, 0))
		goto failed_mount;

	if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA) {
		printk_once(KERN_WARNING "EXT4-fs: Warning: mounting "
			    "with data=journal disables delayed "
			    "allocation and O_DIRECT support!\n");
		if (test_opt2(sb, EXPLICIT_DELALLOC)) {
			ext4_msg(sb, KERN_ERR, "can't mount with "
				 "both data=journal and delalloc");
			goto failed_mount;
		}
		if (test_opt(sb, DIOREAD_NOLOCK)) {
			ext4_msg(sb, KERN_ERR, "can't mount with "
				 "both data=journal and dioread_nolock");
			goto failed_mount;
		}
		if (test_opt(sb, DAX)) {
			ext4_msg(sb, KERN_ERR, "can't mount with "
				 "both data=journal and dax");
			goto failed_mount;
		}
		if (test_opt(sb, DELALLOC))
			clear_opt(sb, DELALLOC);
	} else {
		sb->s_iflags |= SB_I_CGROUPWB;
	}

	sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
		(test_opt(sb, POSIX_ACL) ? MS_POSIXACL : 0);

	if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV &&
	    (ext4_has_compat_features(sb) ||
	     ext4_has_ro_compat_features(sb) ||
	     ext4_has_incompat_features(sb)))
		ext4_msg(sb, KERN_WARNING,
		       "feature flags set on rev 0 fs, "
		       "running e2fsck is recommended");

	if (es->s_creator_os == cpu_to_le32(EXT4_OS_HURD)) {
		set_opt2(sb, HURD_COMPAT);
		if (ext4_has_feature_64bit(sb)) {
			ext4_msg(sb, KERN_ERR,
				 "The Hurd can't support 64-bit file systems");
			goto failed_mount;
		}
	}

	if (IS_EXT2_SB(sb)) {
		if (ext2_feature_set_ok(sb))
			ext4_msg(sb, KERN_INFO, "mounting ext2 file system "
				 "using the ext4 subsystem");
		else {
			ext4_msg(sb, KERN_ERR, "couldn't mount as ext2 due "
				 "to feature incompatibilities");
			goto failed_mount;
		}
	}

	if (IS_EXT3_SB(sb)) {
		if (ext3_feature_set_ok(sb))
			ext4_msg(sb, KERN_INFO, "mounting ext3 file system "
				 "using the ext4 subsystem");
		else {
			ext4_msg(sb, KERN_ERR, "couldn't mount as ext3 due "
				 "to feature incompatibilities");
			goto failed_mount;
		}
	}

	/*
	 * Check feature flags regardless of the revision level, since we
	 * previously didn't change the revision level when setting the flags,
	 * so there is a chance incompat flags are set on a rev 0 filesystem.
	 */
	if (!ext4_feature_set_ok(sb, (sb->s_flags & MS_RDONLY)))
		goto failed_mount;

	blocksize = BLOCK_SIZE << le32_to_cpu(es->s_log_block_size);
	if (blocksize < EXT4_MIN_BLOCK_SIZE ||
	    blocksize > EXT4_MAX_BLOCK_SIZE) {
		ext4_msg(sb, KERN_ERR,
		       "Unsupported filesystem blocksize %d", blocksize);
		goto failed_mount;
	}

	if (sbi->s_mount_opt & EXT4_MOUNT_DAX) {
		if (blocksize != PAGE_SIZE) {
			ext4_msg(sb, KERN_ERR,
					"error: unsupported blocksize for dax");
			goto failed_mount;
		}
		if (!sb->s_bdev->bd_disk->fops->direct_access) {
			ext4_msg(sb, KERN_ERR,
					"error: device does not support dax");
			goto failed_mount;
		}
	}

	if (ext4_has_feature_encrypt(sb) && es->s_encryption_level) {
		ext4_msg(sb, KERN_ERR, "Unsupported encryption level %d",
			 es->s_encryption_level);
		goto failed_mount;
	}

	if (sb->s_blocksize != blocksize) {
		/* Validate the filesystem blocksize */
		if (!sb_set_blocksize(sb, blocksize)) {
			ext4_msg(sb, KERN_ERR, "bad block size %d",
					blocksize);
			goto failed_mount;
		}

		brelse(bh);
		logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
		offset = do_div(logical_sb_block, blocksize);
		bh = sb_bread_unmovable(sb, logical_sb_block);
		if (!bh) {
			ext4_msg(sb, KERN_ERR,
			       "Can't read superblock on 2nd try");
			goto failed_mount;
		}
		es = (struct ext4_super_block *)(bh->b_data + offset);
		sbi->s_es = es;
		if (es->s_magic != cpu_to_le16(EXT4_SUPER_MAGIC)) {
			ext4_msg(sb, KERN_ERR,
			       "Magic mismatch, very weird!");
			goto failed_mount;
		}
	}

	has_huge_files = ext4_has_feature_huge_file(sb);
	sbi->s_bitmap_maxbytes = ext4_max_bitmap_size(sb->s_blocksize_bits,
						      has_huge_files);
	sb->s_maxbytes = ext4_max_size(sb->s_blocksize_bits, has_huge_files);

	if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV) {
		sbi->s_inode_size = EXT4_GOOD_OLD_INODE_SIZE;
		sbi->s_first_ino = EXT4_GOOD_OLD_FIRST_INO;
	} else {
		sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
		sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
		if ((sbi->s_inode_size < EXT4_GOOD_OLD_INODE_SIZE) ||
		    (!is_power_of_2(sbi->s_inode_size)) ||
		    (sbi->s_inode_size > blocksize)) {
			ext4_msg(sb, KERN_ERR,
			       "unsupported inode size: %d",
			       sbi->s_inode_size);
			goto failed_mount;
		}
		if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE)
			sb->s_time_gran = 1 << (EXT4_EPOCH_BITS - 2);
	}

	sbi->s_desc_size = le16_to_cpu(es->s_desc_size);
	if (ext4_has_feature_64bit(sb)) {
		if (sbi->s_desc_size < EXT4_MIN_DESC_SIZE_64BIT ||
		    sbi->s_desc_size > EXT4_MAX_DESC_SIZE ||
		    !is_power_of_2(sbi->s_desc_size)) {
			ext4_msg(sb, KERN_ERR,
			       "unsupported descriptor size %lu",
			       sbi->s_desc_size);
			goto failed_mount;
		}
	} else
		sbi->s_desc_size = EXT4_MIN_DESC_SIZE;

	sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);
	sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);
	if (EXT4_INODE_SIZE(sb) == 0 || EXT4_INODES_PER_GROUP(sb) == 0)
		goto cantfind_ext4;

	sbi->s_inodes_per_block = blocksize / EXT4_INODE_SIZE(sb);
	if (sbi->s_inodes_per_block == 0)
		goto cantfind_ext4;
	sbi->s_itb_per_group = sbi->s_inodes_per_group /
					sbi->s_inodes_per_block;
	sbi->s_desc_per_block = blocksize / EXT4_DESC_SIZE(sb);
	sbi->s_sbh = bh;
	sbi->s_mount_state = le16_to_cpu(es->s_state);
	sbi->s_addr_per_block_bits = ilog2(EXT4_ADDR_PER_BLOCK(sb));
	sbi->s_desc_per_block_bits = ilog2(EXT4_DESC_PER_BLOCK(sb));

	for (i = 0; i < 4; i++)
		sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]);
	sbi->s_def_hash_version = es->s_def_hash_version;
	if (ext4_has_feature_dir_index(sb)) {
		i = le32_to_cpu(es->s_flags);
		if (i & EXT2_FLAGS_UNSIGNED_HASH)
			sbi->s_hash_unsigned = 3;
		else if ((i & EXT2_FLAGS_SIGNED_HASH) == 0) {
#ifdef __CHAR_UNSIGNED__
			if (!(sb->s_flags & MS_RDONLY))
				es->s_flags |=
					cpu_to_le32(EXT2_FLAGS_UNSIGNED_HASH);
			sbi->s_hash_unsigned = 3;
#else
			if (!(sb->s_flags & MS_RDONLY))
				es->s_flags |=
					cpu_to_le32(EXT2_FLAGS_SIGNED_HASH);
#endif
		}
	}

	/* Handle clustersize */
	clustersize = BLOCK_SIZE << le32_to_cpu(es->s_log_cluster_size);
	has_bigalloc = ext4_has_feature_bigalloc(sb);
	if (has_bigalloc) {
		if (clustersize < blocksize) {
			ext4_msg(sb, KERN_ERR,
				 "cluster size (%d) smaller than "
				 "block size (%d)", clustersize, blocksize);
			goto failed_mount;
		}
		sbi->s_cluster_bits = le32_to_cpu(es->s_log_cluster_size) -
			le32_to_cpu(es->s_log_block_size);
		sbi->s_clusters_per_group =
			le32_to_cpu(es->s_clusters_per_group);
		if (sbi->s_clusters_per_group > blocksize * 8) {
			ext4_msg(sb, KERN_ERR,
				 "#clusters per group too big: %lu",
				 sbi->s_clusters_per_group);
			goto failed_mount;
		}
		if (sbi->s_blocks_per_group !=
		    (sbi->s_clusters_per_group * (clustersize / blocksize))) {
			ext4_msg(sb, KERN_ERR, "blocks per group (%lu) and "
				 "clusters per group (%lu) inconsistent",
				 sbi->s_blocks_per_group,
				 sbi->s_clusters_per_group);
			goto failed_mount;
		}
	} else {
		if (clustersize != blocksize) {
			ext4_warning(sb, "fragment/cluster size (%d) != "
				     "block size (%d)", clustersize,
				     blocksize);
			clustersize = blocksize;
		}
		if (sbi->s_blocks_per_group > blocksize * 8) {
			ext4_msg(sb, KERN_ERR,
				 "#blocks per group too big: %lu",
				 sbi->s_blocks_per_group);
			goto failed_mount;
		}
		sbi->s_clusters_per_group = sbi->s_blocks_per_group;
		sbi->s_cluster_bits = 0;
	}
	sbi->s_cluster_ratio = clustersize / blocksize;

	if (sbi->s_inodes_per_group > blocksize * 8) {
		ext4_msg(sb, KERN_ERR,
		       "#inodes per group too big: %lu",
		       sbi->s_inodes_per_group);
		goto failed_mount;
	}

	/* Do we have standard group size of clustersize * 8 blocks ? */
	if (sbi->s_blocks_per_group == clustersize << 3)
		set_opt2(sb, STD_GROUP_SIZE);

	/*
	 * Test whether we have more sectors than will fit in sector_t,
	 * and whether the max offset is addressable by the page cache.
	 */
	err = generic_check_addressable(sb->s_blocksize_bits,
					ext4_blocks_count(es));
	if (err) {
		ext4_msg(sb, KERN_ERR, "filesystem"
			 " too large to mount safely on this system");
		if (sizeof(sector_t) < 8)
			ext4_msg(sb, KERN_WARNING, "CONFIG_LBDAF not enabled");
		goto failed_mount;
	}

	if (EXT4_BLOCKS_PER_GROUP(sb) == 0)
		goto cantfind_ext4;

	/* check blocks count against device size */
	blocks_count = sb->s_bdev->bd_inode->i_size >> sb->s_blocksize_bits;
	if (blocks_count && ext4_blocks_count(es) > blocks_count) {
		ext4_msg(sb, KERN_WARNING, "bad geometry: block count %llu "
		       "exceeds size of device (%llu blocks)",
		       ext4_blocks_count(es), blocks_count);
		goto failed_mount;
	}

	/*
	 * It makes no sense for the first data block to be beyond the end
	 * of the filesystem.
	 */
	if (le32_to_cpu(es->s_first_data_block) >= ext4_blocks_count(es)) {
		ext4_msg(sb, KERN_WARNING, "bad geometry: first data "
			 "block %u is beyond end of filesystem (%llu)",
			 le32_to_cpu(es->s_first_data_block),
			 ext4_blocks_count(es));
		goto failed_mount;
	}
	blocks_count = (ext4_blocks_count(es) -
			le32_to_cpu(es->s_first_data_block) +
			EXT4_BLOCKS_PER_GROUP(sb) - 1);
	do_div(blocks_count, EXT4_BLOCKS_PER_GROUP(sb));
	if (blocks_count > ((uint64_t)1<<32) - EXT4_DESC_PER_BLOCK(sb)) {
		ext4_msg(sb, KERN_WARNING, "groups count too large: %u "
		       "(block count %llu, first data block %u, "
		       "blocks per group %lu)", sbi->s_groups_count,
		       ext4_blocks_count(es),
		       le32_to_cpu(es->s_first_data_block),
		       EXT4_BLOCKS_PER_GROUP(sb));
		goto failed_mount;
	}
	sbi->s_groups_count = blocks_count;
	sbi->s_blockfile_groups = min_t(ext4_group_t, sbi->s_groups_count,
			(EXT4_MAX_BLOCK_FILE_PHYS / EXT4_BLOCKS_PER_GROUP(sb)));
	db_count = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
		   EXT4_DESC_PER_BLOCK(sb);
	sbi->s_group_desc = ext4_kvmalloc(db_count *
					  sizeof(struct buffer_head *),
					  GFP_KERNEL);
	if (sbi->s_group_desc == NULL) {
		ext4_msg(sb, KERN_ERR, "not enough memory");
		ret = -ENOMEM;
		goto failed_mount;
	}

	bgl_lock_init(sbi->s_blockgroup_lock);

	for (i = 0; i < db_count; i++) {
		block = descriptor_loc(sb, logical_sb_block, i);
		sbi->s_group_desc[i] = sb_bread_unmovable(sb, block);
		if (!sbi->s_group_desc[i]) {
			ext4_msg(sb, KERN_ERR,
			       "can't read group descriptor %d", i);
			db_count = i;
			goto failed_mount2;
		}
	}
	if (!ext4_check_descriptors(sb, &first_not_zeroed)) {
		ext4_msg(sb, KERN_ERR, "group descriptors corrupted!");
		ret = -EFSCORRUPTED;
		goto failed_mount2;
	}

	sbi->s_gdb_count = db_count;
	get_random_bytes(&sbi->s_next_generation, sizeof(u32));
	spin_lock_init(&sbi->s_next_gen_lock);

	setup_timer(&sbi->s_err_report, print_daily_error_info,
		(unsigned long) sb);

	/* Register extent status tree shrinker */
	if (ext4_es_register_shrinker(sbi))
		goto failed_mount3;

	sbi->s_stripe = ext4_get_stripe_size(sbi);
	sbi->s_extent_max_zeroout_kb = 32;

	/*
	 * set up enough so that it can read an inode
	 */
	sb->s_op = &ext4_sops;
	sb->s_export_op = &ext4_export_ops;
	sb->s_xattr = ext4_xattr_handlers;
#ifdef CONFIG_QUOTA
	sb->dq_op = &ext4_quota_operations;
	if (ext4_has_feature_quota(sb))
		sb->s_qcop = &dquot_quotactl_sysfile_ops;
	else
		sb->s_qcop = &ext4_qctl_operations;
	sb->s_quota_types = QTYPE_MASK_USR | QTYPE_MASK_GRP | QTYPE_MASK_PRJ;
#endif
	memcpy(sb->s_uuid, es->s_uuid, sizeof(es->s_uuid));

	INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
	mutex_init(&sbi->s_orphan_lock);

	sb->s_root = NULL;

	needs_recovery = (es->s_last_orphan != 0 ||
			  ext4_has_feature_journal_needs_recovery(sb));

	if (ext4_has_feature_mmp(sb) && !(sb->s_flags & MS_RDONLY))
		if (ext4_multi_mount_protect(sb, le64_to_cpu(es->s_mmp_block)))
			goto failed_mount3a;

	/*
	 * The first inode we look at is the journal inode.  Don't try
	 * root first: it may be modified in the journal!
	 */
	if (!test_opt(sb, NOLOAD) && ext4_has_feature_journal(sb)) {
		if (ext4_load_journal(sb, es, journal_devnum))
			goto failed_mount3a;
	} else if (test_opt(sb, NOLOAD) && !(sb->s_flags & MS_RDONLY) &&
		   ext4_has_feature_journal_needs_recovery(sb)) {
		ext4_msg(sb, KERN_ERR, "required journal recovery "
		       "suppressed and not mounted read-only");
		goto failed_mount_wq;
	} else {
		/* Nojournal mode, all journal mount options are illegal */
		if (test_opt2(sb, EXPLICIT_JOURNAL_CHECKSUM)) {
			ext4_msg(sb, KERN_ERR, "can't mount with "
				 "journal_checksum, fs mounted w/o journal");
			goto failed_mount_wq;
		}
		if (test_opt(sb, JOURNAL_ASYNC_COMMIT)) {
			ext4_msg(sb, KERN_ERR, "can't mount with "
				 "journal_async_commit, fs mounted w/o journal");
			goto failed_mount_wq;
		}
		if (sbi->s_commit_interval != JBD2_DEFAULT_MAX_COMMIT_AGE*HZ) {
			ext4_msg(sb, KERN_ERR, "can't mount with "
				 "commit=%lu, fs mounted w/o journal",
				 sbi->s_commit_interval / HZ);
			goto failed_mount_wq;
		}
		if (EXT4_MOUNT_DATA_FLAGS &
		    (sbi->s_mount_opt ^ sbi->s_def_mount_opt)) {
			ext4_msg(sb, KERN_ERR, "can't mount with "
				 "data=, fs mounted w/o journal");
			goto failed_mount_wq;
		}
		sbi->s_def_mount_opt &= EXT4_MOUNT_JOURNAL_CHECKSUM;
		clear_opt(sb, JOURNAL_CHECKSUM);
		clear_opt(sb, DATA_FLAGS);
		sbi->s_journal = NULL;
		needs_recovery = 0;
		goto no_journal;
	}

	if (ext4_has_feature_64bit(sb) &&
	    !jbd2_journal_set_features(EXT4_SB(sb)->s_journal, 0, 0,
				       JBD2_FEATURE_INCOMPAT_64BIT)) {
		ext4_msg(sb, KERN_ERR, "Failed to set 64-bit journal feature");
		goto failed_mount_wq;
	}

	if (!set_journal_csum_feature_set(sb)) {
		ext4_msg(sb, KERN_ERR, "Failed to set journal checksum "
			 "feature set");
		goto failed_mount_wq;
	}

	/* We have now updated the journal if required, so we can
	 * validate the data journaling mode. */
	switch (test_opt(sb, DATA_FLAGS)) {
	case 0:
		/* No mode set, assume a default based on the journal
		 * capabilities: ORDERED_DATA if the journal can
		 * cope, else JOURNAL_DATA
		 */
		if (jbd2_journal_check_available_features
		    (sbi->s_journal, 0, 0, JBD2_FEATURE_INCOMPAT_REVOKE))
			set_opt(sb, ORDERED_DATA);
		else
			set_opt(sb, JOURNAL_DATA);
		break;

	case EXT4_MOUNT_ORDERED_DATA:
	case EXT4_MOUNT_WRITEBACK_DATA:
		if (!jbd2_journal_check_available_features
		    (sbi->s_journal, 0, 0, JBD2_FEATURE_INCOMPAT_REVOKE)) {
			ext4_msg(sb, KERN_ERR, "Journal does not support "
			       "requested data journaling mode");
			goto failed_mount_wq;
		}
	default:
		break;
	}
	set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);

	sbi->s_journal->j_commit_callback = ext4_journal_commit_callback;
 
 no_journal:
 	if (ext4_mballoc_ready) {
		sbi->s_mb_cache = ext4_xattr_create_cache(sb->s_id);
 		if (!sbi->s_mb_cache) {
 			ext4_msg(sb, KERN_ERR, "Failed to create an mb_cache");
 			goto failed_mount_wq;
		}
	}

	if ((DUMMY_ENCRYPTION_ENABLED(sbi) || ext4_has_feature_encrypt(sb)) &&
	    (blocksize != PAGE_CACHE_SIZE)) {
		ext4_msg(sb, KERN_ERR,
			 "Unsupported blocksize for fs encryption");
		goto failed_mount_wq;
	}

	if (DUMMY_ENCRYPTION_ENABLED(sbi) && !(sb->s_flags & MS_RDONLY) &&
	    !ext4_has_feature_encrypt(sb)) {
		ext4_set_feature_encrypt(sb);
		ext4_commit_super(sb, 1);
	}

	/*
	 * Get the # of file system overhead blocks from the
	 * superblock if present.
	 */
	if (es->s_overhead_clusters)
		sbi->s_overhead = le32_to_cpu(es->s_overhead_clusters);
	else {
		err = ext4_calculate_overhead(sb);
		if (err)
			goto failed_mount_wq;
	}

	/*
	 * The maximum number of concurrent works can be high and
	 * concurrency isn't really necessary.  Limit it to 1.
	 */
	EXT4_SB(sb)->rsv_conversion_wq =
		alloc_workqueue("ext4-rsv-conversion", WQ_MEM_RECLAIM | WQ_UNBOUND, 1);
	if (!EXT4_SB(sb)->rsv_conversion_wq) {
		printk(KERN_ERR "EXT4-fs: failed to create workqueue\n");
		ret = -ENOMEM;
		goto failed_mount4;
	}

	/*
	 * The jbd2_journal_load will have done any necessary log recovery,
	 * so we can safely mount the rest of the filesystem now.
	 */

	root = ext4_iget(sb, EXT4_ROOT_INO);
	if (IS_ERR(root)) {
		ext4_msg(sb, KERN_ERR, "get root inode failed");
		ret = PTR_ERR(root);
		root = NULL;
		goto failed_mount4;
	}
	if (!S_ISDIR(root->i_mode) || !root->i_blocks || !root->i_size) {
		ext4_msg(sb, KERN_ERR, "corrupt root inode, run e2fsck");
		iput(root);
		goto failed_mount4;
	}
	sb->s_root = d_make_root(root);
	if (!sb->s_root) {
		ext4_msg(sb, KERN_ERR, "get root dentry failed");
		ret = -ENOMEM;
		goto failed_mount4;
	}

	if (ext4_setup_super(sb, es, sb->s_flags & MS_RDONLY))
		sb->s_flags |= MS_RDONLY;

	/* determine the minimum size of new large inodes, if present */
	if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE) {
		sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
						     EXT4_GOOD_OLD_INODE_SIZE;
		if (ext4_has_feature_extra_isize(sb)) {
			if (sbi->s_want_extra_isize <
			    le16_to_cpu(es->s_want_extra_isize))
				sbi->s_want_extra_isize =
					le16_to_cpu(es->s_want_extra_isize);
			if (sbi->s_want_extra_isize <
			    le16_to_cpu(es->s_min_extra_isize))
				sbi->s_want_extra_isize =
					le16_to_cpu(es->s_min_extra_isize);
		}
	}
	/* Check if enough inode space is available */
	if (EXT4_GOOD_OLD_INODE_SIZE + sbi->s_want_extra_isize >
							sbi->s_inode_size) {
		sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
						       EXT4_GOOD_OLD_INODE_SIZE;
		ext4_msg(sb, KERN_INFO, "required extra inode space not"
			 "available");
	}

	ext4_set_resv_clusters(sb);

	err = ext4_setup_system_zone(sb);
	if (err) {
		ext4_msg(sb, KERN_ERR, "failed to initialize system "
			 "zone (%d)", err);
		goto failed_mount4a;
	}

	ext4_ext_init(sb);
	err = ext4_mb_init(sb);
	if (err) {
		ext4_msg(sb, KERN_ERR, "failed to initialize mballoc (%d)",
			 err);
		goto failed_mount5;
	}

	block = ext4_count_free_clusters(sb);
	ext4_free_blocks_count_set(sbi->s_es, 
				   EXT4_C2B(sbi, block));
	err = percpu_counter_init(&sbi->s_freeclusters_counter, block,
				  GFP_KERNEL);
	if (!err) {
		unsigned long freei = ext4_count_free_inodes(sb);
		sbi->s_es->s_free_inodes_count = cpu_to_le32(freei);
		err = percpu_counter_init(&sbi->s_freeinodes_counter, freei,
					  GFP_KERNEL);
	}
	if (!err)
		err = percpu_counter_init(&sbi->s_dirs_counter,
					  ext4_count_dirs(sb), GFP_KERNEL);
	if (!err)
		err = percpu_counter_init(&sbi->s_dirtyclusters_counter, 0,
					  GFP_KERNEL);
	if (err) {
		ext4_msg(sb, KERN_ERR, "insufficient memory");
		goto failed_mount6;
	}

	if (ext4_has_feature_flex_bg(sb))
		if (!ext4_fill_flex_info(sb)) {
			ext4_msg(sb, KERN_ERR,
			       "unable to initialize "
			       "flex_bg meta info!");
			goto failed_mount6;
		}

	err = ext4_register_li_request(sb, first_not_zeroed);
	if (err)
		goto failed_mount6;

	err = ext4_register_sysfs(sb);
	if (err)
		goto failed_mount7;

#ifdef CONFIG_QUOTA
	/* Enable quota usage during mount. */
	if (ext4_has_feature_quota(sb) && !(sb->s_flags & MS_RDONLY)) {
		err = ext4_enable_quotas(sb);
		if (err)
			goto failed_mount8;
	}
#endif  /* CONFIG_QUOTA */

	EXT4_SB(sb)->s_mount_state |= EXT4_ORPHAN_FS;
	ext4_orphan_cleanup(sb, es);
	EXT4_SB(sb)->s_mount_state &= ~EXT4_ORPHAN_FS;
	if (needs_recovery) {
		ext4_msg(sb, KERN_INFO, "recovery complete");
		ext4_mark_recovery_complete(sb, es);
	}
	if (EXT4_SB(sb)->s_journal) {
		if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA)
			descr = " journalled data mode";
		else if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_ORDERED_DATA)
			descr = " ordered data mode";
		else
			descr = " writeback data mode";
	} else
		descr = "out journal";

	if (test_opt(sb, DISCARD)) {
		struct request_queue *q = bdev_get_queue(sb->s_bdev);
		if (!blk_queue_discard(q))
			ext4_msg(sb, KERN_WARNING,
				 "mounting with \"discard\" option, but "
				 "the device does not support discard");
	}

	if (___ratelimit(&ext4_mount_msg_ratelimit, "EXT4-fs mount"))
		ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. "
			 "Opts: %s%s%s", descr, sbi->s_es->s_mount_opts,
			 *sbi->s_es->s_mount_opts ? "; " : "", orig_data);

	if (es->s_error_count)
		mod_timer(&sbi->s_err_report, jiffies + 300*HZ); /* 5 minutes */

	/* Enable message ratelimiting. Default is 10 messages per 5 secs. */
	ratelimit_state_init(&sbi->s_err_ratelimit_state, 5 * HZ, 10);
	ratelimit_state_init(&sbi->s_warning_ratelimit_state, 5 * HZ, 10);
	ratelimit_state_init(&sbi->s_msg_ratelimit_state, 5 * HZ, 10);

	kfree(orig_data);
	return 0;

cantfind_ext4:
	if (!silent)
		ext4_msg(sb, KERN_ERR, "VFS: Can't find ext4 filesystem");
	goto failed_mount;

#ifdef CONFIG_QUOTA
failed_mount8:
	ext4_unregister_sysfs(sb);
#endif
failed_mount7:
	ext4_unregister_li_request(sb);
failed_mount6:
	ext4_mb_release(sb);
	if (sbi->s_flex_groups)
		kvfree(sbi->s_flex_groups);
	percpu_counter_destroy(&sbi->s_freeclusters_counter);
	percpu_counter_destroy(&sbi->s_freeinodes_counter);
	percpu_counter_destroy(&sbi->s_dirs_counter);
	percpu_counter_destroy(&sbi->s_dirtyclusters_counter);
failed_mount5:
	ext4_ext_release(sb);
	ext4_release_system_zone(sb);
failed_mount4a:
	dput(sb->s_root);
	sb->s_root = NULL;
failed_mount4:
	ext4_msg(sb, KERN_ERR, "mount failed");
 	if (EXT4_SB(sb)->rsv_conversion_wq)
 		destroy_workqueue(EXT4_SB(sb)->rsv_conversion_wq);
 failed_mount_wq:
 	if (sbi->s_journal) {
 		jbd2_journal_destroy(sbi->s_journal);
 		sbi->s_journal = NULL;
	}
failed_mount3a:
	ext4_es_unregister_shrinker(sbi);
failed_mount3:
	del_timer_sync(&sbi->s_err_report);
	if (sbi->s_mmp_tsk)
		kthread_stop(sbi->s_mmp_tsk);
failed_mount2:
	for (i = 0; i < db_count; i++)
		brelse(sbi->s_group_desc[i]);
	kvfree(sbi->s_group_desc);
failed_mount:
	if (sbi->s_chksum_driver)
		crypto_free_shash(sbi->s_chksum_driver);
#ifdef CONFIG_QUOTA
	for (i = 0; i < EXT4_MAXQUOTAS; i++)
		kfree(sbi->s_qf_names[i]);
#endif
	ext4_blkdev_remove(sbi);
	brelse(bh);
out_fail:
	sb->s_fs_info = NULL;
	kfree(sbi->s_blockgroup_lock);
	kfree(sbi);
out_free_orig:
	kfree(orig_data);
	return err ? err : ret;
}

Vulnerability Type: DoS 
CWE ID: CWE-19
Summary: The mbcache feature in the ext2 and ext4 filesystem implementations in the Linux kernel before 4.6 mishandles xattr block caching, which allows local users to cause a denial of service (soft lockup) via filesystem operations in environments that use many attributes, as demonstrated by Ceph and Samba.
Commit Message: ext4: convert to mbcache2

The conversion is generally straightforward. The only tricky part is
that xattr block corresponding to found mbcache entry can get freed
before we get buffer lock for that block. So we have to check whether
the entry is still valid after getting buffer lock.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>