[dm-devel] [PATCH] DM MULTIPATH: Allow dm to send larger request if underlying device set to larger max_sectors value

[Chauhan, Vijay]

Hi Alasdair,

On July 09, 2012 6:32 AM, Alasdair Wrote:
>
>Why is this separate from dm_set_device_limits?
Ideally it should have been taken care in dm_set_device_limits but to find 
minimum of max_sectors value among physical paths in dm_set_device_limits  seems tricky. 
I will look into it to use dm_set_device_limits.

>Why is this not handled by blk-settings.c?
blk_stack_limits do compare max_sectors between dm & physical path and minimum 
between two values is then set to max_sectors of dm. But if underlying paths 
are set with higher value, dm's max_sectors will be always set to default being 
minimum. Rather objective is to set minimum of max_sectors among underlying paths but 
not exceeding dm's max_hw_max_sectors

>Should max_sectors be preserved across a table reload?
Intentions is to set max_sectors to maximum capable when dm device is created. Even if 
we reset max_sectors_kb from sysfs, restart of multipathd would again reset it to default. 
Not sure if I answered your question.



Thanks,
Vijay