RE: Question about dmevents

* Question about dmevents
@ 2007-07-20 16:02 Wood, Brian J
  2007-07-20 16:16 ` Alasdair G Kergon
                   ` (2 more replies)
  0 siblings, 3 replies; 14+ messages in thread
From: Wood, Brian J @ 2007-07-20 16:02 UTC (permalink / raw)
  To: device-mapper development

Hello everyone, I have a question about something in the
"libdevmapper-event.c" code. I'm building a test application that I can
use to setup events I would like to register with dmeventd. As suggested
by Jonathan Brassow I've used the framework from lib/mirror/mirrored.c
in LVM2 as a template to creating my setup code in the test application.
Right now I'm hard coding in the name of the dso and the name of the
device I would like to register as a watch point. Here is how I get
things going: 

Create a structure "dm_event_handler"
Set char *dso to a stub dso (created for testing).
Set char *name to "/dev/mapper/XXXXX_Volume0p1" (one of my dm device
names) 
Call "dm_event_handler_create()"
Call "dm_event_handler_set_dso()"
Call "dm_event_handler_set_dev_name()"

After setting all this up I call "dm_event_register_handler()" passing
in the "dm_event_handler" structure. Inside this call the first thing is
a call to "_get_device_info()" that sets up my "dm_task" structure.
Inside this function I noticed the "dm_task_create()" function sets up
the dm_task structure, but leaves uuid as null. We then test uuid (since
its null it jumps past the first "if" statement heading into
dm_task_set_name()). In here it cuts off the "/dev/mapper/" and sets
dev_name to XXXXX and returns as it should.

After this long setup here's the problem I'm having. I run through the
remaining function calls in _get_device_info() and my uuid for the
dm_task is still null. The last call before sending this message off to
dmeventd using the "_do_event()" is a call to dm_task_get_uuid() that is
passed my dm_task struct. This should return a uuid string, but returns
null since my dm_task is never getting a uuid set. Without this I get a
failure on the dmeventd side stating I passed a null pointer into
dm_strdup via the function _alloc_thread_status (where it checks the
uuid field). 

Just as a test, in my gdb session I set the uuid to some text string,
"blah" for example, and I'm able to register my event and get a
"SUCCESS" message back in the FIFO. 

My one clue is that I noticed back in _get_device_info() a line that
says
 	/* FIXME Add name or uuid or devno to messages */
Does this mean that there needs to be code added to setup the dm_task
uuid? Or is there another call in libdevmapper.h that I'm missing that I
can use to set this up?

Thank you for any help you might be able to offer; I'm hoping I just
missed calling a libdevmapper* initialization function :)

Brian Wood
Intel Corporation 
Digital Enterprise Group
Manageability & Platform Software Division
brian.j.wood@intel.com

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