panic in ffs (Re: hangs in nbufkv)
scottl at freebsd.org
Tue Oct 12 14:48:07 PDT 2004
Kris Kennaway wrote:
> 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...
>> 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.
IIRC, the fragment allocation code in FFS allocates in terms of bits
withing a byte, so anything that is 8:1 or less should work.
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