Re: bugs in handling of errors for SG_IO and SCSI_IOCT L_SEND_COMMAND ioctls to block device

[Mike Christie <michaelc@cs.wisc.edu>]

goggin, edward wrote:
> On Thu, 07 Jul 2005 23:19:57 -0500
> Mike Christie <michaelc@cs.wisc.edu> wrote
> 
> 
>>>...
>>>
>>>	The bio handling for these REQ_BLOCK_PC requests shouldn't be
>>>treated any
>>>	differently than the more typical REQ_CMD type block io request.
>>
> 
>>what is meant by this last comment specifically?
> 
> 
> Just trying to make a case that a device pass through read command
> issued to a block device should transfer to user space only the
> user requested number of bytes minus the residual from the transfer
> (as is done for block device read and write requests) and not always
> transfer the number of bytes requested by the user.
> 

ah ok, I thought it was referring to something else, nevermind.

Was the reason it does SG_IO reads becuase opens on the device were not 
allowed? Was not being able to open a dm device a bug or by design? For 
devices that do not support SG_IO like NBD, dasd and if you do 
dm-multipath with AOE, another solution may have to be found.