struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
{
	struct ext4_iloc iloc;
	struct ext4_inode *raw_inode;
	struct ext4_inode_info *ei;
	struct inode *inode;
	journal_t *journal = EXT4_SB(sb)->s_journal;
	long ret;
	loff_t size;
	int block;
	uid_t i_uid;
	gid_t i_gid;
	projid_t i_projid;

	inode = iget_locked(sb, ino);
	if (!inode)
		return ERR_PTR(-ENOMEM);
	if (!(inode->i_state & I_NEW))
		return inode;

	ei = EXT4_I(inode);
	iloc.bh = NULL;

	ret = __ext4_get_inode_loc(inode, &iloc, 0);
	if (ret < 0)
		goto bad_inode;
	raw_inode = ext4_raw_inode(&iloc);

	if ((ino == EXT4_ROOT_INO) && (raw_inode->i_links_count == 0)) {
		EXT4_ERROR_INODE(inode, "root inode unallocated");
		ret = -EFSCORRUPTED;
		goto bad_inode;
	}

	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
		ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
		if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >
			EXT4_INODE_SIZE(inode->i_sb) ||
		    (ei->i_extra_isize & 3)) {
			EXT4_ERROR_INODE(inode,
					 "bad extra_isize %u (inode size %u)",
					 ei->i_extra_isize,
					 EXT4_INODE_SIZE(inode->i_sb));
			ret = -EFSCORRUPTED;
			goto bad_inode;
		}
	} else
		ei->i_extra_isize = 0;

	/* Precompute checksum seed for inode metadata */
	if (ext4_has_metadata_csum(sb)) {
		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
		__u32 csum;
		__le32 inum = cpu_to_le32(inode->i_ino);
		__le32 gen = raw_inode->i_generation;
		csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&inum,
				   sizeof(inum));
		ei->i_csum_seed = ext4_chksum(sbi, csum, (__u8 *)&gen,
					      sizeof(gen));
	}

	if (!ext4_inode_csum_verify(inode, raw_inode, ei)) {
		EXT4_ERROR_INODE(inode, "checksum invalid");
		ret = -EFSBADCRC;
		goto bad_inode;
	}

	inode->i_mode = le16_to_cpu(raw_inode->i_mode);
	i_uid = (uid_t)le16_to_cpu(raw_inode->i_uid_low);
	i_gid = (gid_t)le16_to_cpu(raw_inode->i_gid_low);
	if (ext4_has_feature_project(sb) &&
	    EXT4_INODE_SIZE(sb) > EXT4_GOOD_OLD_INODE_SIZE &&
	    EXT4_FITS_IN_INODE(raw_inode, ei, i_projid))
		i_projid = (projid_t)le32_to_cpu(raw_inode->i_projid);
	else
		i_projid = EXT4_DEF_PROJID;

	if (!(test_opt(inode->i_sb, NO_UID32))) {
		i_uid |= le16_to_cpu(raw_inode->i_uid_high) << 16;
		i_gid |= le16_to_cpu(raw_inode->i_gid_high) << 16;
	}
	i_uid_write(inode, i_uid);
	i_gid_write(inode, i_gid);
	ei->i_projid = make_kprojid(&init_user_ns, i_projid);
	set_nlink(inode, le16_to_cpu(raw_inode->i_links_count));

	ext4_clear_state_flags(ei);	/* Only relevant on 32-bit archs */
	ei->i_inline_off = 0;
	ei->i_dir_start_lookup = 0;
	ei->i_dtime = le32_to_cpu(raw_inode->i_dtime);
	/* We now have enough fields to check if the inode was active or not.
	 * This is needed because nfsd might try to access dead inodes
	 * the test is that same one that e2fsck uses
	 * NeilBrown 1999oct15
	 */
	if (inode->i_nlink == 0) {
		if ((inode->i_mode == 0 ||
		     !(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_ORPHAN_FS)) &&
		    ino != EXT4_BOOT_LOADER_INO) {
			/* this inode is deleted */
			ret = -ESTALE;
			goto bad_inode;
		}
		/* The only unlinked inodes we let through here have
		 * valid i_mode and are being read by the orphan
		 * recovery code: that's fine, we're about to complete
		 * the process of deleting those.
		 * OR it is the EXT4_BOOT_LOADER_INO which is
		 * not initialized on a new filesystem. */
	}
	ei->i_flags = le32_to_cpu(raw_inode->i_flags);
	inode->i_blocks = ext4_inode_blocks(raw_inode, ei);
	ei->i_file_acl = le32_to_cpu(raw_inode->i_file_acl_lo);
	if (ext4_has_feature_64bit(sb))
		ei->i_file_acl |=
			((__u64)le16_to_cpu(raw_inode->i_file_acl_high)) << 32;
	inode->i_size = ext4_isize(sb, raw_inode);
	if ((size = i_size_read(inode)) < 0) {
		EXT4_ERROR_INODE(inode, "bad i_size value: %lld", size);
		ret = -EFSCORRUPTED;
		goto bad_inode;
	}
	ei->i_disksize = inode->i_size;
#ifdef CONFIG_QUOTA
	ei->i_reserved_quota = 0;
#endif
	inode->i_generation = le32_to_cpu(raw_inode->i_generation);
	ei->i_block_group = iloc.block_group;
	ei->i_last_alloc_group = ~0;
	/*
	 * NOTE! The in-memory inode i_data array is in little-endian order
	 * even on big-endian machines: we do NOT byteswap the block numbers!
	 */
	for (block = 0; block < EXT4_N_BLOCKS; block++)
		ei->i_data[block] = raw_inode->i_block[block];
	INIT_LIST_HEAD(&ei->i_orphan);

	/*
	 * Set transaction id's of transactions that have to be committed
	 * to finish f[data]sync. We set them to currently running transaction
	 * as we cannot be sure that the inode or some of its metadata isn't
	 * part of the transaction - the inode could have been reclaimed and
	 * now it is reread from disk.
	 */
	if (journal) {
		transaction_t *transaction;
		tid_t tid;

		read_lock(&journal->j_state_lock);
		if (journal->j_running_transaction)
			transaction = journal->j_running_transaction;
		else
			transaction = journal->j_committing_transaction;
		if (transaction)
			tid = transaction->t_tid;
		else
			tid = journal->j_commit_sequence;
		read_unlock(&journal->j_state_lock);
		ei->i_sync_tid = tid;
		ei->i_datasync_tid = tid;
	}

	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
		if (ei->i_extra_isize == 0) {
			/* The extra space is currently unused. Use it. */
			BUILD_BUG_ON(sizeof(struct ext4_inode) & 3);
			ei->i_extra_isize = sizeof(struct ext4_inode) -
					    EXT4_GOOD_OLD_INODE_SIZE;
		} else {
			ext4_iget_extra_inode(inode, raw_inode, ei);
		}
	}

	EXT4_INODE_GET_XTIME(i_ctime, inode, raw_inode);
	EXT4_INODE_GET_XTIME(i_mtime, inode, raw_inode);
	EXT4_INODE_GET_XTIME(i_atime, inode, raw_inode);
	EXT4_EINODE_GET_XTIME(i_crtime, ei, raw_inode);

	if (likely(!test_opt2(inode->i_sb, HURD_COMPAT))) {
		u64 ivers = le32_to_cpu(raw_inode->i_disk_version);

		if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
			if (EXT4_FITS_IN_INODE(raw_inode, ei, i_version_hi))
				ivers |=
		    (__u64)(le32_to_cpu(raw_inode->i_version_hi)) << 32;
		}
		inode_set_iversion_queried(inode, ivers);
	}

	ret = 0;
	if (ei->i_file_acl &&
	    !ext4_data_block_valid(EXT4_SB(sb), ei->i_file_acl, 1)) {
		EXT4_ERROR_INODE(inode, "bad extended attribute block %llu",
				 ei->i_file_acl);
		ret = -EFSCORRUPTED;
		goto bad_inode;
	} else if (!ext4_has_inline_data(inode)) {
		if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
			if ((S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
			    (S_ISLNK(inode->i_mode) &&
			     !ext4_inode_is_fast_symlink(inode))))
				/* Validate extent which is part of inode */
				ret = ext4_ext_check_inode(inode);
		} else if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
			   (S_ISLNK(inode->i_mode) &&
			    !ext4_inode_is_fast_symlink(inode))) {
			/* Validate block references which are part of inode */
			ret = ext4_ind_check_inode(inode);
		}
	}
	if (ret)
		goto bad_inode;

	if (S_ISREG(inode->i_mode)) {
		inode->i_op = &ext4_file_inode_operations;
		inode->i_fop = &ext4_file_operations;
		ext4_set_aops(inode);
	} else if (S_ISDIR(inode->i_mode)) {
		inode->i_op = &ext4_dir_inode_operations;
		inode->i_fop = &ext4_dir_operations;
	} else if (S_ISLNK(inode->i_mode)) {
		if (ext4_encrypted_inode(inode)) {
			inode->i_op = &ext4_encrypted_symlink_inode_operations;
			ext4_set_aops(inode);
		} else if (ext4_inode_is_fast_symlink(inode)) {
			inode->i_link = (char *)ei->i_data;
			inode->i_op = &ext4_fast_symlink_inode_operations;
			nd_terminate_link(ei->i_data, inode->i_size,
				sizeof(ei->i_data) - 1);
		} else {
			inode->i_op = &ext4_symlink_inode_operations;
			ext4_set_aops(inode);
		}
		inode_nohighmem(inode);
	} else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode) ||
	      S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
		inode->i_op = &ext4_special_inode_operations;
		if (raw_inode->i_block[0])
			init_special_inode(inode, inode->i_mode,
			   old_decode_dev(le32_to_cpu(raw_inode->i_block[0])));
		else
			init_special_inode(inode, inode->i_mode,
			   new_decode_dev(le32_to_cpu(raw_inode->i_block[1])));
	} else if (ino == EXT4_BOOT_LOADER_INO) {
		make_bad_inode(inode);
	} else {
		ret = -EFSCORRUPTED;
		EXT4_ERROR_INODE(inode, "bogus i_mode (%o)", inode->i_mode);
		goto bad_inode;
	}
	brelse(iloc.bh);
	ext4_set_inode_flags(inode);

	unlock_new_inode(inode);
	return inode;

bad_inode:
	brelse(iloc.bh);
	iget_failed(inode);
	return ERR_PTR(ret);
}
Unknown