ffstest is the first stage of a disk repair program. It parses
a OFS/FFS/DCFS filesystem tree and reports inconsistencies. It
does not repair them.

Currently it checks

- meta-block checksum
- hash table entries
- hash chains
- parent links
- file names
- dircache blocks
- hard link chains
- usage of various 'reserved' fields
- allocation bitmap

it doesn't yet check for

- OFS data blocks
- consistent hard link types
- dircache contents
- soft link targets

usage:

    ffstest DISK/A,LIST/S,NOINHIBIT/S

DISK      - name of the drive/partition, the partition must be mounted
            but the filesystem handler doesn't need to loaded
            A trailing ':' is discarded from the name.
LIST      - lists every meta-block encountered.
NOINHIBIT - don't send an ACTION_INHIBIT to the filesystem, you can
            access the filesystem while it is checked, but obviously
            you must not modify it.
            Caveat: ACTION_INHIBIT may fail.

a small tool lets you also start the disk validator manually

    validate DISK/A

DISK      - name of the drive/partition, the partition must be mounted
            but the filesystem handler doesn't need to loaded


diagnostics:

"bad checksum for key"
  -  a meta block has a bad checksum, ignored
"need a root block to start"
  -  the calculated root block is not of type ST_ROOT, use something
     like DiskSalv to salvage the disk contents
"ERROR: long name"
  -  the name field in a block has a length > 30 chars      
"ERROR: tablesize = xxxx, hashsize = xxxx"
  -  invalid hash table size field in root block, ignored
"ERROR: invalid dircache chain xxxx=>xxxx"
  -  invalid key to next dir cache block
"ERROR: invalid dircache block type"
  -  dircache block is not of type ST_DIRCACHE
"ERROR: key xxx refers to itself as xxx"
  -  the OWNKEY field of a meta block doesn't contain its block number
"ERROR: key xxx with parent xxx doesn't match previous xxx"
  -  the PARENT field of a meta block doesn't match the parent block
"key xxx linked at bad hash position xxx (!= xxx)"
  -  the hash function for a meta block does not match the position
     in the parents hash table
"INVALID(xxx) type xxx (!= ST_LIST)"
  -  list block is not of type ST_LIST
"ERROR: LIST block xxx for file header xxx has different parent xxx"
  -  the PARENT field in a LIST block doesn't match the parent of the
     file header
"key xxx: unallocated xxx"
  -  the number of allocated blocks for a file doesn't match the size
     in the file header
"INVALID(xxx) type xxx"
  -  meta block not recognized
"Unsorted hash chain xxx => xxx"
  -  found a hash chain that isn't sorted by block number
"key xxx: invalid hash entry xxx = xxx"
  -  invalid entry in hash table
"key xxx: hash entry xxx = xxx already used for key xxx at xxx..xxx"
  -  a hash entry points to a block that is already allocated for
     a different disk object
"ERROR: zero bitmap pointer xxx"
  -  an entry in the table of bitmap block is zero
"bad checksum for bitmap key xxx"
  -  ...
"key xxx: allocation error"
  -  bitmap block xxx doesn't match with computed disk allocations"
"BitMap is not valid"
  -  validator did not complete, the bitmap isn't checked

"typeBlock xxx/xxx"
  -  unrecognized block of type/subtype encountered
"xxx: non-zero reserved fields"
  -  meta block contains non-zero data in reserved fields

"alloc(llist) failed"
  -  out of memory for storing hard link information
"link chain for target xxx unbalanced"
  -  multiple hard links to this target don't build a single list
"link chain for target xxx not terminated"
  -  the list of hard links for this target isn't terminated with 0
"bad link chain for target xxx: xxx -> xxx != xxx"
  -  multiple hard links to this target don't build a single list
"ST_FILE xxx doesn't point back to link xxx"
"ST_DIR xxx doesn't point back to link xxx"
  -  a file or directory object doesn't point back to the first hard link
"invalid target type xxx for link"
  -  the target of a hard link is neither a file nor a directory


"openMountedDisk("xxx") failed"
  -  the drive/partition xxx isn't found or the device driver couldn't
     be opened or the environment vector couldn't be found or the filesystem
     couldn't be inhibited
"FATAL: invalid environment vector"
  -  The environment vector was found, but contained invalid data"
"FATAL: unsupported huge disk"
  -  Sorry, no support for the 64bit disk APIs yet. Max disk size
     for standard exec drivers is 4GB.

"alloc(Extent) failed"
  -  out of memory for allocating Extent structure, computed disk allocation
     will be erroneous
"overlap key xxx: xxx..xxx"
"   with key xxx: xxx..xxx"
  -  two disk objects claim the same disk blocks (corresponds to validator
     messages 'key already set' or 'key used twice')
"key xxx outside of filesystem"
  -  tried to lookup a block number larger than the disk size (should never
     happen)

"allocated free block xxx"
  -  this block is missing in the bitmap
"xxx..xxx: xxxxxxxxxxx"
  -  this block range contains errors in the bitmap,
     either blocks missing or allocated while free,
     the right part is a bitmask, zeros represent errors

"ERROR: bounding circle in tree at xxx"
  -  a circular block chain was found, the repeated block isn't
     read again to avoid infinite loops
"ERROR: readDisk failed for key xxx"
  -  the disk driver returned an error reading this block
"ERROR: getBuffer failed for key xxx"
  -  sorry, out of memory for allocating a buffer for this block
"ERROR: alloc(bstack) failed for key xxx"
  -  sorry, out of memory for allocating a stack node


Michael van Elst

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                 8940   16464  54.3% -lh5- bb1b Nov 29  1997 ffstest
[generic]                 2141    5728  37.4% -lh5- db5f Nov 30  1997 ffstest.readme
[generic]                 3077    5276  58.3% -lh5- 0ab6 Nov 30  1997 validate
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         3 files   14158   27468  51.5%            Dec  1  1997