[dm-devel] dm_calculate_queue_limits and default values

[benoit.welterlen at bull.net]

Hi,

I'm a newbie on dm and all this stuff, but I'm wondering why 
"max_segments" of all dm's queue is always 128 (cat 
/sys/block/dm-*/queue/max_segments), even if all devices used in the dm 
have another value (cat 
/sys/devices/pci0000:00/0000:00:1f.2/host0/scsi_host/host0/sg_tablesize : 
168).

I looked over the source code of dm_calculate_queue_limits, and saw that 
limits of all devices are combined with default limits 
(blk_set_default_limits(limits);). But, the value used is always the 
min_not_zero, so always 128, the default value.

As I understand, even if all devices have big limits, default values will 
be used.
Is my understanding wrong or there is a bug ?

Thank you to explain me the dm operation.

Regards

Benoit Welterlen
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listman.redhat.com/archives/dm-devel/attachments/20110729/c77b97ad/attachment.htm>