On 05/08/2017 05:02 PM, Denis V. Lunev wrote: > On 05/08/2017 10:35 PM, Stefan Hajnoczi wrote: >> On Thu, May 04, 2017 at 12:54:40PM +0200, Daniel Kucera wrote: >> >> Seems like a logical extension along the same lines as the backup block >> job's dirty bitmap sync mode. >> >>> parameter bitmap chooses existing dirtymap instead of newly created >>> in mirror_start_job >>> >>> Signed-off-by: Daniel Kucera <daniel.kuc...@gmail.com> > Can you pls describe the use case pls in a bit more details. > > For now this could be a bit strange: > - dirty bitmap, which can be found via bdrv_create_dirty_bitmap > could be read-only or read-write, i.e. being modified by writes > or be read-only, which should not be modified. Thus adding > r/o bitmap to the mirror could result in interesting things. >
This patch as it was submitted does not put the bitmap into a read-only mode; it leaves it RW and modifies it as it processes the mirror command. Though you do raise a good point; this bitmap is now in-use by a job and should not be allowed to be deleted by the user, but our existing mechanism treats a locked bitmap as one that is also in R/O mode. This would be a different use case. > Minimally we should prohibit usage of r/o bitmaps this way. > > So, why to use mirror, not backup for the case? > My guess is for pivot semantics. > Den >
