On 08/05/2011 09:19 PM, Anthony Liguori wrote:
On 08/05/2011 10:43 AM, Kevin Wolf wrote:
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.
Indeed.
We discussed the following so far...
1. How to safely reopen image files
2. Dynamic hostcache change
3. Support for dynamic change of O_DSYNC
Since 2 is independent of 1, shall I go ahead implementing
hostcache change using fcntl.
Implementation for safely reopening image files using "BDRVReopenState"
can be done separately as a pre-requisite before implementing 3
Thanks, Supriya
Regards,
Anthony Liguori
Kevin
