Re: [PATCH 32/32] target: Increase MAX_LUNS_PER_TPG to 16384

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On 12/16/2013 10:20 AM, Hannes Reinecke wrote:
> On 12/14/2013 12:59 AM, Andy Grover wrote:
>> Indicate support for hierarchical LUN addressing.
>>
>> Set address method field in each LUN reported by REPORT LUNS to 1, in
>> accordance with SCSI SAM specs.
>>
>> Signed-off-by: Andy Grover <agrover@xxxxxxxxxx>
>> ---
>>  drivers/target/target_core_spc.c  |    8 ++++++--
>>  include/target/target_core_base.h |    4 ++--
>>  2 files changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/target/target_core_spc.c b/drivers/target/target_core_spc.c
>> index 0b678fc..04690bf 100644
>> --- a/drivers/target/target_core_spc.c
>> +++ b/drivers/target/target_core_spc.c
>> @@ -79,7 +79,7 @@ spc_emulate_inquiry_std(struct se_cmd *cmd, unsigned char *buf)
>>  	buf[2] = 0x05; /* SPC-3 */
>>  
>>  	/*
>> -	 * NORMACA and HISUP = 0, RESPONSE DATA FORMAT = 2
>> +	 * NORMACA = 0, HISUP = 1, RESPONSE DATA FORMAT = 2
>>  	 *
>>  	 * SPC4 says:
>>  	 *   A RESPONSE DATA FORMAT field set to 2h indicates that the
>> @@ -88,7 +88,7 @@ spc_emulate_inquiry_std(struct se_cmd *cmd, unsigned char *buf)
>>  	 *   obsolete. Response data format values greater than 2h are
>>  	 *   reserved.
>>  	 */
>> -	buf[3] = 2;
>> +	buf[3] = 0x12;
>>  
>>  	/*
>>  	 * Enable SCCS and TPGS fields for Emulated ALUA
>> @@ -1164,6 +1164,10 @@ sense_reason_t spc_emulate_report_luns(struct se_cmd *cmd)
>>  			break;
>>  
>>  		int_to_scsilun(deve->mapped_lun, (struct scsi_lun *)&buf[offset]);
>> +
>> +		/* Address method 1 for hier flat-space address. see SAM-5 */
>> +		buf[offset] |= (1 << 6);
>> +
>>  		offset += 8;
>>  	}
>>  	spin_unlock_irq(&sess->se_node_acl->device_list_lock);
>> diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
>> index 08ecfed..537cc67 100644
>> --- a/include/target/target_core_base.h
>> +++ b/include/target/target_core_base.h
>> @@ -14,8 +14,8 @@
>>  #define TARGET_CORE_VERSION		TARGET_CORE_MOD_VERSION
>>  
>>  /* Maximum Number of LUNs per Target Portal Group */
>> -/* Don't raise above 511 or REPORT_LUNS needs to handle >1 page */
>> -#define TRANSPORT_MAX_LUNS_PER_TPG		256
>> +/* Don't raise above 16384 or a different format in report_luns is needed */
>> +#define TRANSPORT_MAX_LUNS_PER_TPG		16384
>>  /*
>>   * By default we use 32-byte CDBs in TCM Core and subsystem plugin code.
>>   *
>>
> NO WAY.
> 
> TCM is (currently) keeping the LUNs in a static array.
> Which is sort-of-okay if the number of LUNs is somewhat reasonable,
> as it was for 256.
> But 16k is way beyond any sensible number and will increase the
> memory footprint by a massive amount, irrespective whether someone
> will actually _use_ such a large number of LUNs.
> 
> Before attempting that one would need to convert the LUN array into
> something scalable, like a linked list or somesuch.
> 
Ouch.

Please ignore this mail.

One should _really_ read the entire patchset before jumping to
conclusions.
Monday morning and all that ...

Sorry for the noise.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@xxxxxxx			      +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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