On Fri, Apr 22, 2011 at 04:08:57PM +1000, ronnie sahlberg wrote:
> So I should set FUA when
> BDRV_O_CACHE_WB==0 or BDRV_O_NOCACHE==1
> right?
At this point you need to set it if either the BDRV_O_CACHE_WB and
BDRV_O_NOCACHE flags are set. And yes, the naming of the nocache
flag is rather confusing.
Take a look at block.c:bdrv_open_common():
/*
* Yes, BDRV_O_NOCACHE aka O_DIRECT means we have to present a
* write cache to the guest. We do need the fdatasync to flush
* out transactions for block allocations, and we maybe have a
* volatile write cache in our backing device to deal with.
*/
if (flags & (BDRV_O_CACHE_WB|BDRV_O_NOCACHE))
bs->enable_write_cache = 1;
