Re: clean unmount?

["H. Peter Anvin" <hpa@zytor.com>]

Followup to:  <20030310234800.GA4357@win.tue.nl>
By author:    Andries Brouwer <aebr@win.tue.nl>
In newsgroup: linux.dev.fs.devel
> 
> My docs say "high-order" instead of "low-order".
> Are there people with a Windows system so that they can check?
> 
> Andries
> 
> http://www.win.tue.nl/~aeb/linux/fs/fat/fat-1.html#ss1.3.1
> 

The FAT spec claims it's the high bits, which makes sense because
0x..FF8 and 0x..FFF are all technically valid EOCs (in fact, Linux for
a long time wrote 0x...FF8 instead of the correct 0x...FFF):

For FAT16 and FAT32, the file system driver may use the high two bits
of the FAT[1] entry for dirty volume flags (all other bits, are always
left set to 1). Note that the bit location is different for FAT16 and
FAT32, because they are the high 2 bits of the entry. For FAT16:
ClnShutBitMask = 0x8000; HrdErrBitMask = 0x4000; For FAT32:
ClnShutBitMask = 0x08000000; HrdErrBitMask = 0x04000000; Bit
ClnShutBitMask   If bit is 1, volume is  clean . If bit is 0, volume
is  dirty . This indicates that the file system driver did not
Dismount the volume properly the last time it had the volume
mounted. It would be a good idea to run a Chkdsk/Scandisk disk repair
utility on it, because it may be damaged. Bit HrdErrBitMask   If this
bit is 1, no disk read/write errors were encountered. If this bit is
0, the file system driver encountered a disk I/O error on the Volume
the last time it was mounted, which is an indicator that some sectors
may have gone bad on the volume. It would be a good idea to run a
Chkdsk/Scandisk disk repair utility that does surface analysis on it
to look for new bad sectors.
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