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Re: [libvirt] [PATCH] qemu: Fix a regression of attaching device



于 2011年07月13日 23:03, Eric Blake 写道:
On 07/13/2011 09:17 AM, Osier Yang wrote:
qemuDomainModifyDeviceFlags: Changing "ret" to "0", but don't
reset it to "-1" on failure, it's not good idea to change the value
of "ret" in the codes to do some condition checking. This patch
fix it.
Can you identify which commit introduced the regression, and what
behavior actually broke as a result?  The commit message will be more
useful with that information.

---
  src/qemu/qemu_driver.c |    6 +++---
  1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 0a6b48e..ae11c68 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -4892,10 +4892,10 @@ qemuDomainModifyDeviceFlags(virDomainPtr dom, const char *xml,
                              _("unknown domain modify action %d"), action);
              break;
          }
-    } else
-        ret = 0;
+    }

-    if (!ret&&  (flags&  VIR_DOMAIN_AFFECT_LIVE)) {
+    if (!(flags&  VIR_DOMAIN_AFFECT_CONFIG)&&
+        (flags&  VIR_DOMAIN_AFFECT_LIVE)) {
I'm not sure I agree with this change.  The logic flow before this patch is:

if config
   make the change in a copy, or record that the change failed
if live, and either no config or change to config copy is happy
   make the change live, or record that change failed
if config, and either no live or change to live is happy
   commit the changed copy made earlier

Your proposed change makes it so that we can now change live even if we
are going to fail to change the config, which is not a good idea.

Yes, I didn't follow with the complete meaning of commit da1eba6b
pointed by Wen, a updated patch is following.

Why not instead do:

if config {
   make change in a copy
   if ret<  0
     goto error
}
if live {
   make change in live
   if ret<  0
     goto error
}
if config
   commit the changed copy made earlier



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