Re: [PATCH 1/3] Remove two cancel_delayed_work() calls from the error handler

[James Bottomley <jbottomley@parallels.com>]

On Mon, 2014-05-26 at 17:23 +0200, Paolo Bonzini wrote:
> Il 26/05/2014 17:14, Bart Van Assche ha scritto:
> > scsi_put_command() is either invoked before a command is queued or
> > after a command has completed. scsi_cmnd.abort_work is scheduled
> > after a command has timed out and before it is finished. The block
> > layer guarantees that either the softirq_done_fn() or the
> > rq_timed_out_fn() function is invoked but not both. This means that
> > scsi_put_command() is never invoked while abort_work is scheduled.
> > Hence remove the cancel_delayed_work() call from scsi_put_command().
> >
> > Similarly, scsi_abort_command() is only invoked from the SCSI
> > timeout handler. If scsi_abort_command() is invoked for a SCSI
> > command with the SCSI_EH_ABORT_SCHEDULED flag set this means that
> > scmd_eh_abort_handler() has already invoked scsi_queue_insert() and
> > hence that scsi_cmnd.abort_work is no longer pending. Hence also
> > remove the cancel_delayed_work() call from scsi_abort_command().
> >
> > Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> > Cc: Hannes Reinecke <hare@suse.de>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Christoph Hellwig <hch@infradead.org>
> > Cc: Jens Axboe <axboe@fb.com>
> > Cc: Joe Lawrence <joe.lawrence@stratus.com>
> > ---
> >  drivers/scsi/scsi.c       | 2 +-
> >  drivers/scsi/scsi_error.c | 2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
> > index 88d46fe..c972eab 100644
> > --- a/drivers/scsi/scsi.c
> > +++ b/drivers/scsi/scsi.c
> > @@ -334,7 +334,7 @@ void scsi_put_command(struct scsi_cmnd *cmd)
> >  	list_del_init(&cmd->list);
> >  	spin_unlock_irqrestore(&cmd->device->list_lock, flags);
> >
> > -	cancel_delayed_work(&cmd->abort_work);
> > +	WARN_ON_ONCE(delayed_work_pending(&cmd->abort_work));
> >
> >  	__scsi_put_command(cmd->device->host, cmd);
> >  }
> > diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> > index f17aa7a..5232583 100644
> > --- a/drivers/scsi/scsi_error.c
> > +++ b/drivers/scsi/scsi_error.c
> > @@ -193,7 +193,7 @@ scsi_abort_command(struct scsi_cmnd *scmd)
> >  		SCSI_LOG_ERROR_RECOVERY(3,
> >  			scmd_printk(KERN_INFO, scmd,
> >  				    "scmd %p previous abort failed\n", scmd));
> > -		cancel_delayed_work(&scmd->abort_work);
> > +		WARN_ON_ONCE(delayed_work_pending(&scmd->abort_work));
> >  		return FAILED;
> >  	}
> >
> >
> 
> I still prefer a BUG_ON in scsi_put_command, but anyway: series

Me too, since this is supposed to be an impossible condition that would
induce corruption in the cmd free lists and hence make the system
unusable.

James