Am 11.04.2012 12:33, schrieb Kevin Wolf: > Am 11.04.2012 12:05, schrieb Liu Yuan: >> On 04/11/2012 03:49 PM, Kevin Wolf wrote: >> >>> I don't agree with this patch. If the documentation says that qemu-img >>> always uses writeback, then the documentation must be fixed. >>> >>> We really don't care about flushes during an image conversion. It should >>> just go as fast as it can. If any error happens in the middle, you'll >>> have to throw the image away anyway, because it contains only half of >>> what you need. So not having flushed doesn't really make any difference. >>> >>> As soon as a guest begins using the image with data that we really care >>> about, it's probably running in a VM with non-unsafe mode, and then it >>> gets flushed. >> >> >> But we can set cache mode for qemu-img convert. So at least if we set >> explicitly with other modes(for e.g, writeback) that ask to flush the >> dirty bits, I think we should call brdv_flush(). >> >> If you agree, I'll update the patch with this modification. > > Yes, adding the flush is fine, I just wouldn't change the default cache > mode.
On second thought, wouldn't make it more sense to add the flush in bdrv_close(), so that all callers get it? Kevin
