Re: AFFS fixes v1

From: Alexander Viro (viro@math.psu.edu)
Date: Sun Apr 02 2000 - 16:14:34 EST


On 2 Apr 2000, Rask Ingemann Lambertsen wrote:

> Den 31-Mar-00 04:23:46 skrev Matthias Andree følgende om "Re: AFFS fixes v1":
> > Nicholai Benalal <nicholai@chello.se> writes:
>
> >> AFFS works allright under AmigaOS.
>
> > Prove that. It blows itself off its very feet when crashing at the wrong
> > time and leaving a system behind that's corrupted beyond repair. This is
> > happening all over the place every now and then.
>
> AFFS is as good (or bad) as ext2 in this regard. Hopefully Reiserfs will
> save Linux users from such trouble the same way PFS/AFS/SFS has for Amiga
> users.

It is not. You need much more atomic operations to get from one valid
state of filesystem to another. And I mean _much_ more - as minimum twice.
Data structure is designed by complete loonie - just look at it and write
down the worst-case set of modifications to be done upon rename(). Pay
attention to the size of critical part - _some_ steps can be performed
without corrupting the structure if you fail after them, but there is a
nice lump that should be taken together or not at all. Now, do the same
for FFS (_real_ one, designed by sane people). Or its descendants - ext2,
ufs... Compare the results.

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