block/iscsi: optimize WRITE10/16 if cache.writeback is not set
SCSI allowes to tell the target to not return from a write command if the date is not written to the disk. Use this so called FUA bit if it is supported to optimize WRITE commands if writeback is not allowed. In this case qemu always issues a WRITE followed by a FLUSH. This is 2 round trip times. If we set the FUA bit we can ignore the following FLUSH. Signed-off-by: NPeter Lieven <pl@kamp.de> Message-id: 1429193313-4263-6-git-send-email-pl@kamp.de Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com> Signed-off-by: NKevin Wolf <kwolf@redhat.com>
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