Re: filesystem bug?

[viro]

On Wed, Dec 17, 2003 at 08:31:55AM +0900, Tsuchiya Yoshihiro wrote:
> Hi,
> 
> Stephen, I don't have anything helpful for debuging at this point. We 
> noticed the problem
> by debuging our SCSI driver. Then we found that the same thing happens 
> on generic
> SCSI disk and IDE also.  The problem we observed in our driver was that 
> while it is
> processing a buffer, which should be locked by BH_LOCK,  the contents of 
> the buffer were
> overwritten. The amount of overwrite is a few byte to 1KB out of 4KB, 
> which cannot be done
> in our driver. Then, we tried a generic SCSI and I reproduced the problem.
> I think it is not because of a broken pointer because overwrites only 
> happen in data buffers
> and other parts of memory seem ok.
 
Umm...  You do realize that if you have a shared writable mapping, the
buffer contents _can_ change during the IO?  Legitimately.  When dirty
page is being written to disk, it remains mapped.  So process can change
its contents just fine.

BH_LOCK does not prevent that and it was never supposed to...
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