Re: [PATCH] make the SCSI mid-layer obey the device online flag

[Mike Anderson <andmike@us.ibm.com>]

James Bottomley [James.Bottomley@steeleye.com] wrote:
> It has been pointed out by the USB people that the mid-layer doesn't
> obey its own online flag.
> 
> The attached patch should fix this.  However, there are a few caveats to
> offlining (read that as devices should still be prepared to process
> commands).
> 
> 1. Any special command will still be accepted (that's a command either
> via the SCSI_IOCTL_SEND_COMMAND, or an internally generated command).
> 2. Outstanding already processed commands in the queue (i.e. commands
> which have already been through the upper layer drivers but needed
> requeuing for some reason like QUEUE_FULL or device busy).
> 
> I'm willing to consider changing 2., it just requires more speciallised
> logic to distinguish between a command that has been prepared by the
> upper level drivers and a command sent via 1.
> 
> However, not that LLDs may not assume they will receive no commands just
> because scsi_device->online is zero.
> 
> James
> 

Doesn't this patch just re-implement in the prep_fn what is already
being done by sd and sr in there init_command functions.

Why allow io after online goes to zero. The user could bring the device
back online if they needed to send IO. I was counting on no IO so we could
do faster cleanup in the scsi_remove_host function.

I having been looking at this, but it is not very clean. To use existing
common functionality and avoid deadlock from calling back into the
request_fn the command needs wasted preparation just to use common
interfaces.

-andmike
--
Michael Anderson
andmike@us.ibm.com