Am 01.10.2013 um 17:41 hat Eric Blake geschrieben: > On 10/01/2013 07:20 AM, Kevin Wolf wrote: > > This series adds a blockdev-add QMP command and a row of cleanup patches to > > separate legacy -drive/drive_add behaviour from blockdev_init() to the > > wrapper > > function drive_init(). > > > > v2: > > > > - Removed I/O throttling and copy-on-read options from the schema: Both are > > candidates for becoming block filters instead. For the time being, you can > > use the existing QMP commands in order to enable I/O throttling on a > > device > > created with blockdev-add in a second step. > > Tolerable as a stop-gap; but doesn't that mean that there is a window > where throttling is not active? Anything that can restrict block > operations must ultimately be specified atomically up front to avoid a > non-deterministic burst during the race window. But in the interest of > incremental improvements, I can live with the approach used here, while > still waiting for throttling to be implemented as a true filter device.
Immediately after blockdev-add, the block device is still completely unused. You can set the throttling options before you do the corresponding device-add or block job command or whatever you're planning to do with the device. Kevin
