From: Hannes Reinecke <hare@suse.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: James Bottomley <jbottomley@parallels.com>, linux-scsi@vger.kernel.org
Subject: Re: [PATCH 2/5] scsi_scan: Restrict sequential scan to 256 LUNs
Date: Fri, 28 Mar 2014 01:22:15 -0700 [thread overview]
Message-ID: <53353137.2050603@suse.de> (raw)
In-Reply-To: <20140327144926.GB16958@infradead.org>
On 03/27/2014 07:49 AM, Christoph Hellwig wrote:
> On Tue, Dec 10, 2013 at 12:05:12PM +0100, Hannes Reinecke wrote:
>> Sequential scan for more than 256 LUNs is very fragile as
>> LUNs might not be numbered sequentially after that point.
>>
>> SAM revisions later than SCSI-3 impose a structure on
>> LUNs larger than 256, making LUN numbers between 256
>> and 16384 illegal.
>> SCSI-3, however allows for plain 64-bit numbers with
>> no internal structure.
>>
>> So restrict sequential LUN scan to 256 LUNs and add a
>> new blacklist flag 'BLIST_SCSI3LUN' to scan up to
>> max_lun devices.
>
> What do you need the blacklist flag for? There's no user of it, and
> supporting that many LUNs without REPORT LUNS support doesn't sound very
> practical anyway.
>
Because there is no guarantee that pre-SCSI-3 devices (or devices
announcing to be pre-SCSI-3) will not allow to scan more than 256 devices.
Thinking of older Symmetrix here with their weird 'SPC-3 masking as
SCSI-2' habit.
Also currently we're allowing to scan beyond 256 without any
restrictions there might be installations out there which rely on this
behaviour.
Hence this flag.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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next prev parent reply other threads:[~2014-03-28 8:22 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-10 11:05 [PATCH 0/5][RFC] Support 64-bit LUNs Hannes Reinecke
2013-12-10 11:05 ` [PATCH 1/5] scsi: Remove CONFIG_SCSI_MULTI_LUN Hannes Reinecke
2014-03-27 14:47 ` Christoph Hellwig
2013-12-10 11:05 ` [PATCH 2/5] scsi_scan: Restrict sequential scan to 256 LUNs Hannes Reinecke
2014-03-27 14:49 ` Christoph Hellwig
2014-03-28 8:22 ` Hannes Reinecke [this message]
2014-03-28 12:47 ` Christoph Hellwig
2014-03-28 13:19 ` Hannes Reinecke
2013-12-10 11:05 ` [PATCH 3/5] qla2xxx: Restrict max_luns to 16-bit for older HBAs Hannes Reinecke
2013-12-10 18:26 ` Chad Dupuis
2014-05-15 6:38 ` Christoph Hellwig
2014-05-15 8:47 ` Hannes Reinecke
2013-12-10 11:05 ` [PATCH 4/5] scsi: use 64-bit LUNs Hannes Reinecke
2014-03-27 14:52 ` Christoph Hellwig
2013-12-10 11:05 ` [PATCH 5/5] scsi: use 64-bit value for 'max_luns' Hannes Reinecke
2014-03-27 14:52 ` Christoph Hellwig
2014-05-15 6:38 ` [PATCH 0/5][RFC] Support 64-bit LUNs Christoph Hellwig
2014-05-15 6:57 ` Hannes Reinecke
-- strict thread matches above, loose matches on Subject: below --
2014-05-20 11:03 [PATCHv2 0/5] " Hannes Reinecke
2014-05-20 11:03 ` [PATCH 2/5] scsi_scan: Restrict sequential scan to 256 LUNs Hannes Reinecke
2014-05-22 9:08 ` Christoph Hellwig
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