dm_calculate_queue_limits and default values
 

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--
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