Re: New filesystem for Linux

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On Fri, 3 Nov 2006, Nikita Danilov wrote:

Mikulas Patocka writes:
> > Mikulas Patocka <[email protected]> writes:
> >
> >> new method to keep data consistent in case of crashes (instead
> >> of journaling),
> >
> > What is that method?
>
> Some tricks to avoid journal --- see
> http://artax.karlin.mff.cuni.cz/~mikulas/spadfs/download/INTERNALS
>
> --- unlike journaling it survives only 65536 crashes :)

What happens when hard-linked file is accessed, and it is found that
last fnode (one in fixed_fnode_block), has wrong "crash count"?

Nikita.

Fixed fnode block contains (txc,cc) pair describing which fnode and nlink count is valid. --- currently two fnodes are superflous (there could be just one), they are reserved for the possibility to atomically modify extended attributes --- but there is no code currently that does it.

The fnodes live on their own with their own (txc,cc) pair --- it is a bit confusing to have pair on both fixed_fnode_block and fnode --- the reason is that the code for handling fnodes in directories can be reused to handle fnodes in fixed_fnode_blocks and I can avoid many
if (is_fnode_fixed()) branches.

If the fnode in fixed_fnode_block has invalid crash count, fixed_fnode_block's (cc,txc) pair should never point to it. Or did it happen to you?

Mikulas
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