BAH! I get this ZBC/ZAC thing wrong still. mentally replace ATA with SCSI in my comments below.... ________________________________________ From: [email protected] [[email protected]] on behalf of John Utz [[email protected]] Sent: Monday, July 21, 2014 9:18 AM To: Hannes Reinecke; Christoph Hellwig Cc: [email protected]; [email protected]; James Bottomely Subject: RE: [PATCH 4/4] sd: Handle ZBC drives correctly
If I read Hanne's patch correctly, he is checking for the ZBC signature when the drives are probed. Thus, the only circumstance where adding zbc handling would lead to unexpected bad behavior in sd would be if a ZBC drive reported itself as a standard ATA drive or an ATA drive reported itself as a ZBC drive. ________________________________________ From: [email protected] [[email protected]] on behalf of Hannes Reinecke [[email protected]] Sent: Monday, July 21, 2014 4:51 AM To: Christoph Hellwig Cc: [email protected]; [email protected]; James Bottomely Subject: Re: [PATCH 4/4] sd: Handle ZBC drives correctly On 07/21/2014 01:29 PM, Christoph Hellwig wrote: > On Mon, Jul 21, 2014 at 10:27:21AM +0200, Hannes Reinecke wrote: >> ZBC drives are close to disk devices, so update sd.c to handle >> ZBC drives correctly. > > While the other patches all look fine with me I strongly disagree with > this one. Devices reporting the ZBC device type must have sequential > required zones, so they are _not_ anywhere close to disk devices, > and writes to them will cause errors that we aren't evenable able to > handle yet. > > If it makes some sort of experiment easier for you we can add a way to > force ZBC devices to use sd.c conditionally. Do you have a test device > that this works with? > Yes, I have. I was actually considering implementing a module option for sd (eg attach_zbc) to allow zac/zbc devices to be attached to the sd driver. Which will be off per default, so your concern should be addressed. However, zbc devices _are_ similar to normal 'sd' devices; it's only that some commands might fail unexpectedly. But all the usual commands from sbc are supported, so I found it a bit odd having to implement my own device driver (which would be a clone of 'sd' anyway). Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage [email protected] +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
