Re: Device Mapper Query

Vineet Agarwal <checkout.vineet@xxxxxxxxx> · Sat, 21 Jul 2012 01:31:11 +0530

Hello Satyajeet,

On Fri, Jul 20, 2012 at 7:52 PM, Satyajeet <satya.unplugged@xxxxxxxxx> wrote:

Does the dmsetup <dm-dev> <table-file> command, calls the constructor dm_ctr_fn??

If yes what are the argv passed in the dm_ctr_fn, are they the args you pass to dmsetup??

Is this constructor a callback from dm layer? when it is invoked and how it is invoked?

As i understand, dmsetup create calls DM_DEVICE_CREATE which fire two ioctls

1) DM_DEV_CREATE
2) DM_TABLE_LOAD

This first ioctl basically create the dev mapper device.
dev_create ()
	|

	-> dm_create ()

The second ioctl basically first creates an empty dm_table and later populate it. During the population it calls the target constructor.

table_load ()
	| dm_table_create ()
	| populate_table ()

		|
		->dm_table_add_target ()
			|

                        -> ctr ()

For further details i would suggest you refer to dm-ioctl.c, dm.c and dm-table.c

Hope it helps.

-- 
Regards:
Vineet Agarwal

Replies will be appreciated.

Regards,

satyajeet

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