Am 05.08.2011 17:24, schrieb Stefan Hajnoczi: > On Fri, Aug 5, 2011 at 3:28 PM, Christoph Hellwig <h...@lst.de> wrote: >> On Fri, Aug 05, 2011 at 02:12:48PM +0100, Daniel P. Berrange wrote: >>>> Because you cannot change O_DIRECT on an open fd :(. This is why >>>> we're going through this pain. >>> >>> Hmm, I remember hearing that before, but looking at the current fcntl() >>> manpage, it claims you *can* change O_DIRECT using SET_FL. Perhaps this >>> is a newish feature, but it'd be nicer to use it if possible ? >> >> It's been there since day 1 of O_DIRECT support. > > Sorry, my bad. So for Linux we could just use fcntl for > block_set_hostcache and not bother with reopening. However, we will > need to reopen should we wish to support changing O_DSYNC.
We do wish to support that. Anthony thinks that allowing the guest to toggle WCE is a prerequisite for making cache=writeback the default. And this is something that I definitely want to do for 1.0. Kevin
