Re: [PATCH v11 6/9] Make scsi_remove_host() wait until error handling finished

[Bart Van Assche <bvanassche@acm.org>]

On 06/25/13 00:27, James Bottomley wrote:
> For a variety of reasons this patch set is incredibly hard to review:
> Almost every patch touches pieces in the mid layer where you have to be
> sure in minute detail you know what's going on (and what should be going
> on), so usually it's a couple of hours with the source code just making
> sure you do know this.  Plus it's code where the underlying usage model
> has evolved over the years meaning the original guarantees might have
> been violated silently somewhere and the ramifications spread out like
> tentacles everywhere.  Finally, it's not clear from the change logs why
> the changes are actually being made: for instance sentence one of this
> change log says "A SCSI LLD may start cleaning up host resources as soon
> as scsi_remove_host() returns." which causes my sanity checker to go off
> immediately because in a refcounted model, like we use for dev, target
> and host, nothing essential is supposed to be freed until the last put
> which may or may not happen in the remove function.

If the invocations of the eh_* callback functions would be visible to 
the block layer then blk_cleanup_queue() would wait until any such eh_* 
invocations have finished. Such an approach could simplify device 
removal in the SCSI mid-layer significantly. It also would avoid that an 
eh_* callback can be invoked via an ioctl after scsi_remove_device() has 
finished.

Bart.