Re: [PATCH 3/9] scsi: improved eh timeout handler

[Christoph Hellwig <hch@infradead.org>]

On Mon, Jun 10, 2013 at 09:40:52AM +0200, Hannes Reinecke wrote:
> When a command runs into a timeout we need to send an 'ABORT TASK'
> TMF. This is typically done by the 'eh_abort_handler' LLDD callback.
> 
> Conceptually, however, this function is a normal SCSI command, so
> there is no need to enter the error handler.
> 
> This patch implements a new scsi_abort_command() function which
> invokes an asynchronous function scsi_eh_abort_handler() to
> abort the commands via 'eh_abort_handler'.
> 
> If the 'eh_abort_handler' returns SUCCESS or FAST_IO_FAIL the
> command will be retried if possible. If no retries are allowed
> the command will be returned immediately, as we have to assume
> the TMF succeeded and the command is completed with the LLDD.
> If the TMF fails the command will be pushed back onto the
> list of failed commands and the SCSI EH handler will be
> called immediately for all timed-out commands.

Why can't we use a work item per command?  Linking things into a list
just to queue it up to workqueues missed half of the point of the
workqueue infrastructure.