On 05/20/2010 10:24 AM, Paolo Bonzini wrote:
On 05/20/2010 11:32 AM, jes.soren...@redhat.com wrote:
+ if (bdrv_flags & BDRV_O_NOCACHE) {
+ fprintf(stderr, "qemu: failed to open disk image %s as "
+ "nocache (O_DIRECT) retrying as write-back\n",
file);
+ bdrv_flags &= BDRV_O_NOCACHE;
Missing ~ here.
+ bdrv_flags |= BDRV_O_CACHE_WB;
+ if (bdrv_open(dinfo->bdrv, file, bdrv_flags, drv)< 0)
+ goto error_open;
+ } else {
I think the retry should be done silently if no cache= option is
given. That is cache=none will be the default but:
- if it is not specified and not supported by the image, fall back to
writeback with no warning. However, this is just a QoI issue and can
be fixed later.
- if it is specified and not supported by the image, either fall back
to writeback with a warning, or fail altogether. The former would be
a change in behavior, so it has to be documented somewhere if it changes.
Or maybe add BDRV_O_CACHE_WT and let the backend decide the default?
It used to be that we had a CACHE_DEFAULT which allowed qcow2 to do
CACHE_WB by default whereas everything else did CACHE_WT. The same
technique could be used to let physical devices do NOCACHE by default.
Regards,
Anthony Liguori
Paolo
