> -----Original Message----- > From: Christoph Hellwig [mailto:hch@xxxxxxxxxxxxx] > Sent: Friday, July 01, 2011 4:22 AM > To: KY Srinivasan > Cc: Christoph Hellwig; gregkh@xxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > devel@xxxxxxxxxxxxxxxxxxxxxx; virtualization@xxxxxxxxxxxxxx > Subject: Re: [PATCH 00/40] Staging: hv: Driver cleanup > > On Thu, Jun 30, 2011 at 11:28:27PM +0000, KY Srinivasan wrote: > > > On Wed, Jun 29, 2011 at 07:38:21AM -0700, K. Y. Srinivasan wrote: > > > > Further cleanup of the hv drivers: > > > > > > > > 1) Cleanup the reference counting mess for both stor and net devices. > > > > > > I really don't understand the need for reference counting on the storage > > > side, especially now that you only have a SCSI driver. The SCSI > > > midlayer does proper counting on it's objects (Scsi_Host, scsi_device, > > > scsi_cmnd), so you'll get that for free given that SCSI drivers just > > > piggyback on the midlayer lifetime rules. > > > > The reference counting allows us to properly deal with messages coming back > from the host > > to the guest with a racing remove of the device. I am told these messages could > potentially be > > not a response to a message sent from the guest. > > To deal with that the scsi subsystem has a two stage teardown for the > SCSI host. First you call scsi_remove_host, at which point no new I/O > to it can be started. After that you can wait for all outstanding > messages, and finally you do a scsi_host_put to drop the long-term > reference to it, and eventually free it. That is what I have currently implemented both on the stor as well as the net side with regards to the device specific objects hanging off of struct hv_device (the ext field). If it is ok with you, I want to do what you had suggested earlier. Keep the patches as they are with regards to reference counting for now. We can always simplify the code later. Regards, K. Y _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
