Open BSD raw disk with O_RDWR issue

Hi Everyone,

 

The suggestion that if application needs to perform block-level reads or writes, consider the BSD raw disk device instead.

And yes, now I could use BSD pread()/pwrite() APIs to read/write specified one sector in /dev/rdiskx.

But I have a problem is when I want to open the raw disk with O_RDWR (O_RDONLY is fine), the system report that “Resource Busy” and I need to unmount or eject this disk’s partitions first, than I could use O_RDWR for pwrite().

So here are my questions:

1.      Do I really need to unmount the all the partitions of the /dev/rdiskx, then I can successfully open disk with O_RDWR without “Resource Busy”?

2.      Is there any kind of methods or parameters that I could open the disk using O_RDWR flags but without “Resource Busy”?

3.      If the disk is busy reading or writing, could I force to unmount the partitions?

 

Any comments will be appreciated.

 

Thanks!

 

Mark