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Re: [dm-devel] racing libdevmapper calls



On Thu, Oct 20, 2005 at 03:38:12PM +0100, Alasdair G Kergon wrote:
> Neither libdevmapper nor dmsetup does any locking.
> 
> It's easy to make the case for dmsetup to include locking - but
> dmsetup is only meant as a diagnostic tool so it's hardly an 
> important feature to add.
> 
> DM_DEVICE_CREATE with a table supplied is *not* an atomic
> operation.  It only exists to provide backwards-compatibility for
> the original version of the ioctls (when it *was* atomic).  It's 
> perfectly OK still to use it when convenient, but you have to 
> remember it's actually performing *two* ioctls:
> 
>   DM_DEV_CREATE
>   DM_TABLE_LOAD
> 
> If you need finer-level control, you may be better off calling
> those two separately i.e. DM_DEVICE_CREATE without a table 
> (if the device doesn't already exist) then DM_DEVICE_RELOAD.
> 
Thanks, this information is very valuable and to the point.

Regards,
cvaroqui


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