panic in ffs (Re: hangs in nbufkv)

[Kris Kennaway]

On Tue, Oct 12, 2004 at 11:18:16AM -0700, Matthew Dillon wrote:
> 
> :[...]
> :
> :>    But to be absolutely safe, I would follow Bruce's original suggestion
> :>    and increase BKVASIZE to 64K, for your particular system.
> :>  
> :>
> :After doing this and testing our backup script, the machine panicked two 
> :hours later (about half-way through the backup) with 
> :"initiate_write_inodeblock_ufs2: already started" (in 
> :ufs/ffs/ffs_softdep.c)... I guess, block sizes above 16Kb are just buggy 
> :and newfs(8) should be honest about it...
> :
> :    -mi
> 
>     Well, it's possible that UFS has bugs related to large block sizes.
>     People have gotten bitten on and off over the years but usually it 
>     works ok if you leave the 8:1 blocksize:fragsize ratio intact.  e.g.
>     if you have a 64KB block size then you should use a 8K frag size.
>     If you have a 32KB block size then you should use a 4K frag size.
> 
>     I think the buffer cache itself is is likely not the source of this
>     particular bug.

FYI, I ran the package build cluster with 4:1 ratios for a few months
and did not have problems.  If there are major bugs there I would have
expected to come across them.

Kris
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