> -----Original Message----- > From: linux-scsi-ow...@vger.kernel.org [mailto:linux-scsi- > ow...@vger.kernel.org] On Behalf Of Hannes Reinecke > Sent: Thursday, 28 August, 2014 10:13 AM > To: Paolo Bonzini; Hans de Goede; Bart Van Assche; SCSI development > list > Subject: Re: Debugging scsi abort handling ? > > On 08/28/2014 04:56 PM, Paolo Bonzini wrote: > > Il 28/08/2014 16:17, Hannes Reinecke ha scritto: > >>> > >> As mentioned earlier, as soon as SCSI EH is invoked control > >> is assumed to be transferred back to the SCSI midlayer. > >> How the midlayer interprets any return value from the various > eh_XX > >> callbacks is immaterial to the LLDD. > >> > >> So even if the eh_abort returns FAILED control is still with the > SCSI > >> midlayer, so the earlier statements apply. > >> IE the command will be short-circuited by the block layer anyway > if > >> ->scsi_done() is called. > > > > As I parsed it, the question is not whether the short-circuiting > will > > happen. It's whether you will have use-after-free bugs or not if > you > > call ->scsi_done() after eh_abort returns FAILED. > > > > Paolo > > > No. Once eh_abort is called control is back with the SCSI midlayer. > (Read: REQ_ATOM_COMPLETE is set in req->atomic_flags). > So you can call ->scsi_done() at your hearts content and nothing will > happen. > What might happen, though, that the command is already dead and gone > by > the time you're calling ->scsi_done() (if you call it after > eh_abort). > So there might not _be_ a command upon which you can call - > >scsi_done() > to start with. > > Hence any LLDD need to clear up any internal references after a call > to > eh_XXX to ensure it doesn't call ->scsi_done() an in invalid command. > > So even if the LLDD returns 'FAILED' upon a call to eh_XXX it _still_ > needs to clear up the internal reference. > Either that or return 'FAILED' for any later eh_XXX function until > the > internal references can be cleared up. >
Is the block layer prevented from issuing a new command with the same tag before the error handling is finished? --- Rob Elliott HP Server Storage
