On 09/22/2011 01:33 PM, Oskari Saarenmaa wrote:
QEMU 0.13 introduced cache=unsafe for -drive, this patch exposes
it in the libvirt layer.
* Introduced a new QEMU capability flag ($prefix_CACHE_UNSAFE),
as even if $prefix_CACHE_V2 is set, we can't known if unsafe
s/known/know/
is supported.
* Improved the reliability of qemu cache type detection.
---
Updated patch based on Eric Blake's comments and rebased it to c4111bd0
+++ b/docs/formatdomain.html.in
@@ -996,10 +996,15 @@
<li>
The optional<code>cache</code> attribute controls the
cache mechanism, possible values are "default", "none",
- "writethrough", "writeback", and "directsync". "directsync"
- is like "writethrough", but it bypasses the host page
- cache.
-<span class="since">Since 0.6.0</span>
+ "writethrough", "writeback", "directsync" (like
+ "writethrough", but it bypasses the host page cache) and
+ "unsafe" (host may cache all disk io and sync requests from
s/io and/io, and/
@@ -912,12 +914,16 @@ qemuCapsComputeCmdFlags(const char *help,
else if (strstr(help, "-domid"))
qemuCapsSet(flags, QEMU_CAPS_DOMID);
if (strstr(help, "-drive")) {
+ const char *cache = strstr(help, "cache=");
+
qemuCapsSet(flags, QEMU_CAPS_DRIVE);
- if (strstr(help, "cache=")&&
- !strstr(help, "cache=on|off")) {
- qemuCapsSet(flags, QEMU_CAPS_DRIVE_CACHE_V2);
- if (strstr(help, "directsync"))
+ if (cache&& (p = strchr(cache, ']'))) {
+ if (memmem(cache, p - cache, "on|off", sizeof("on|off") - 1) == NULL)
+ qemuCapsSet(flags, QEMU_CAPS_DRIVE_CACHE_V2);
+ if (memmem(cache, p - cache, "directsync", sizeof("directsync") - 1))
qemuCapsSet(flags, QEMU_CAPS_DRIVE_CACHE_DIRECTSYNC);
+ if (memmem(cache, p - cache, "unsafe", sizeof("unsafe") - 1))
+ qemuCapsSet(flags, QEMU_CAPS_DRIVE_CACHE_UNSAFE);
Nice! And indeed, unsafe but not directsync is present in qemu 0.14.0,
so this does need another capability bit.
ACK and pushed.
--
Eric Blake eblake@xxxxxxxxxx +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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