Silicon Graphics IRIS Workstation, User Manual

Page: 56 / 170

52 IRIS WORKSTATION GUIDE
Version 1.0
Appendix B:
If the stored link count is non-zero and the actual link count is zero, fsck may
link the disconnected file to the lost+found directory. If the stored and actual link
counts are non-zero and unequal, fsck may replace the stored link count by the
actual link count.
Duplicate Blocks.
Contained in each inode is a list or pointers to lists (indirect blocks) of all the
blocks claimed by the inode.
Fsck compares each block number claimed by an inode to a list of already
allocated blocks. If a block number is already claimed by another inode, the
block number is added to a list of duplicate blocks. Otherwise, the list of
allocated blocks is updated to include the block number. If there are any
duplicate blocks, fsck will make a partial second pass of the inode list to find
the inode of the duplicated block, because without examining the files
associated with these inodes for correct content, there is not enough
information available to decide which inode is corrupted and should be
cleared. Most times, the inode with the earliest modify time is incorrect, and
should be cleared.
This condition can occur by using a file system with blocks claimed by both the
free-block list and by other parts of the file system.
If there is a large number of duplicate blocks in an inode, this may be due to
an indirect block not being written to the file system.
Fsck will prompt the operator to clear both inodes.
Bad Blocks.
Contained in each inode is a list or pointer to lists of all the blocks claimed by
the inode.
Fsck checks each block number claimed by an inode for a value lower than that
of the first data block, or greater than the last block in the file system. If the
block number is outside this range, the block number is a bad block number.
If there is a large number of bad blocks in an inode, this may be due to an
indirect block not being written to the file system.
Fsck will prompt the operator to clear both inodes.
Size Checks.
Each inode contains a thirty-two bit (four-byte) size field. This size indicates
the number of characters in. the file associated with the inode. This size can
be checked for inconsistencies, e.g., directory sizes that are not a multiple of
sixteen characters, or the number of blocks actually used not matching that
indicated by the inode size.