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[Qemu-devel] Re: [PATCH 1/4] block: clarify the meaning of BDRV_O_NOCACH
[Qemu-devel] Re: [PATCH 1/4] block: clarify the meaning of BDRV_O_NOCACHE
Thu, 17 Mar 2011 09:18:36 +0000
On Thu, Mar 17, 2011 at 9:07 AM, Kevin Wolf <address@hidden> wrote:
> Am 16.03.2011 18:00, schrieb Stefan Hajnoczi:
>> On Wed, Mar 16, 2011 at 2:08 PM, Christoph Hellwig <address@hidden> wrote:
>>> On Wed, Mar 16, 2011 at 09:42:37AM +0000, Stefan Hajnoczi wrote:
>>>> - writethrough = ((flags & BDRV_O_CACHE_MASK) == 0);
>>>> + writethrough = ((flags & (BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH)) == 0);
>>> or rather
>>> writethrough = ((flags & (BDRV_O_CACHE_WB) != );
>>> but yes, this code had sneaked in since my initial version.
>> My intention was that if we don't care about honoring flushes then we
>> might as well use Qcow2Cache. But yes, just checking for cache mode
>> is the clearest.
> You mean for a possible writethrough mode with BDRV_O_NO_FLUSH set? Such
> a mode doesn't make a lot of sense to me.
Yeah, I guess you're right, we can never have BDRV_O_NO_FLUSH without
BDRV_O_CACHE_WB today. I wasn't thinking end-to-end, just looking at
the BDRV_O_* flag bits.
[Qemu-devel] [PATCH 2/4] block: add a helper to change writeback mode on the fly, Christoph Hellwig, 2011/03/15
[Qemu-devel] [PATCH, RFC] virtio_blk: add cache control support, Christoph Hellwig, 2011/03/15