Re: [Q] FAT driver enhancement

[OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>]

Jos Hulzink <josh@stack.nl> writes:

> On Wed, 3 Apr 2002, OGAWA Hirofumi wrote:
> 
> > Mike Fedyk <mfedyk@matchmail.com> writes:
> >
> > > > I mean I/O error, not data damage.
> > >
> > > It is the block layer's responsibility to retry such soft errors and recover.
> >
> > Yes.
> 
> But what about the data damage errors ?
> 
> > > Probably the best you can do, is retry the read a few times if there
> > > is an error reported, and then fail if it persists.
> >
> > Umm, there is a `copy of FAT table' for this kind of error. If the I/O
> > error occurs, the FAT driver should use the other FAT table.
> 
> How should the FAT driver know that the first FAT is bad if it doesn't
> scan the FAT ? You don't want the second FAT to be used, you want the
> mount to fail, and fsck.xxx to fix the mess. Who tells you that the second
> copy of the FAT is the correct one, and not the first ?

FAT16/FAT32 use the second entry of FAT table for data damage.
The 1 bit of second entry is a clean/dirty unmount flag.

But, it's not perfect. Furthermore, currently not implemented.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>