Issue with DiskArbitration unmount approval callback - it is called multiple times

19 Feb 2010

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Hello darwin-devs!

I'm developing an application which should do some actions with removable disks before it's unmount. I've found out that this could be done with DiskArbitration unmount approval callback.
I use the following test code:

1. Registering approval callback
  <...>
   //create approval session
   DAApprovalSessionRef session = DAApprovalSessionCreate(kCFAllocatorDefault);
   //register unmount callback
   DARegisterDiskUnmountApprovalCallback(session,
                                         kDADiskDescriptionMatchVolumeMountable,
                                         unmountApprovalCallback,
                                         NULL); // context

   DAApprovalSessionScheduleWithRunLoop(session, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
   CFRunLoopRun();

2. Callback function itself - just log it was called and return success.

DADissenterRef unmountApprovalCallback(DADiskRef disk, void *context)
{
   //Just log and return success - this should allow unmounting
   <>
   NSLog(@"unmountApprovalCallback called");
   DADissenterRef dissenter = DADissenterCreate(kCFAllocatorDefault,
                                                kDAReturnSuccess,
                                                CFSTR("unmount allowed"));
   return dissenter;
}

Unmount callback is called, the application returns success and I thought that it will never be called again for this drive. But my tests show different: callback is called multiple times and it seems that system ignores returned value (e.g. Finder shows "Force Eject").
Additionally, in case of Network Volume Finder logs the following:
	e.g. "Feb 17 16:14:04 macaca /System/Library/CoreServices/Finder.app/Contents/MacOS/Finder[215]: NetworkNode::ejectCallBack returned -47"

Summarizing the problem: Why is callback called several times? Why system ignores my successful return code? Should I do something additionally to this?

Thanks in advance for your replies!

--
With regards,
Vera Tkachenko _______________________________________________
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