On 03/09/2011 07:38 PM, Anthony Liguori wrote:
On 03/09/2011 11:27 AM, Christoph Hellwig wrote:
On Wed, Mar 09, 2011 at 05:15:53PM +0100, Kevin Wolf wrote:
Quoting the bug report:
qemu ensures that guest writes and qemu metadata writes hit the
disk
when necessary to prevent data corruption. However, if an image
was
in host pagecache prior to starting qemu, for example after
running
qemu-img convert, then nothing prevents writes from reaching the
disk out of order, potentially causing corruption.
I'm not entirely sure if there is a realistic case where we would get
corruption, but it's probably a case of better safe than sorry.
Except for SCSI with ordered tags (which we don't support) there are not
ordering guarantees in the storage protocols, and as such the above
explanation
doesn't make any sense at all.
Even if there was, a guest shouldn't be relying on the ordering of a
write that comes from a non-guest.
I don't understand the failure scenario here.
$ cp x.img y.img
$ qemu -drive file=y.img,cache=writeback
<read something from disk, send it over the network>
<no guest flushes>
<host crash>
The guest may expect that any or none of its writes hit the disk, but
that anything that it read from the disk, stays there.
--
error compiling committee.c: too many arguments to function
