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Re: [dm-devel] SCSI's heuristics for enabling WRITE SAME still need work [was: dm mpath: disable WRITE SAME if it fails]



On Tue, 2013-09-24 at 11:37 +0200, Paolo Bonzini wrote:
> Il 21/09/2013 00:03, Martin K. Petersen ha scritto:
> > 
> > The major headache here of course is that WRITE SAME is inherently
> > destructive. We can't just fire off one during discovery and see if it
> > works. For WRITE you can issue a command with a transfer length of 0 to
> > see if things work. But unfortunately for WRITE SAME a transfer length
> > of zero means "wipe the entire device". Yikes!
> 
> What about WRITE SAME with an out-of-range lba?  Or lba equal to the
> size of the disk and #blocks equal to zero.

That's inviting undefined behaviour in a data destructive command ...
not something we really want to do.

James



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