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Re: [libvirt] [PATCH v2] virsh: avoid missing zero value judgement in cmdBlkiotune



On 28.07.2011 11:04, Alex Jia wrote:
* tools/virsh.c: avoid missing zero value judgement in cmdBlkiotune, when
   weight is equal to 0, the cmdBlkiotune will not raise any error information
   when judge weight value first time, and execute else branch to judge weight
   value again, strncpy(temp->field, VIR_DOMAIN_BLKIO_WEIGHT, sizeof(temp->field))
   will be not executed for ever. However, if and only if param->field is equal
   to VIR_DOMAIN_BLKIO_WEIGHT, underlying qemuDomainSetBlkioParameters function
   will check whether weight value is in range [100, 1000].

* how to reproduce?

   % virsh blkiotune ${guestname} --weight 0

Signed-off-by: Alex Jia<ajia redhat com>
---
  tools/virsh.c |   11 +++++------
  1 files changed, 5 insertions(+), 6 deletions(-)


I liked the first verion more than this. Although it is not shown in this snippet,
nparams is initialized to zero

diff --git a/tools/virsh.c b/tools/virsh.c
index 8bd22dc..512f2c6 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -4037,14 +4037,13 @@ cmdBlkiotune(vshControl * ctl, const vshCmd * cmd)
          goto cleanup;
      }

-    if (weight) {
-        nparams++;
-        if (weight<  0) {
-            vshError(ctl, _("Invalid value of %d for I/O weight"), weight);
-            goto cleanup;
-        }
+    if (weight<= 0) {
+        vshError(ctl, _("Invalid value of %d for I/O weight"), weight);
+        goto cleanup;
      }

and therefore doing this
+    nparams++;
+
will invalidate this test.
      if (nparams == 0) {
          /* get the number of blkio parameters */
          if (virDomainGetBlkioParameters(dom, NULL,&nparams, flags) != 0) {

The better way of dealing with this issue IMO is to switch from
if (weight) {
to test if 'weight' parameter was given (vshCommandOptInt() returns >0) and after this check for impermissible values. And after the latter test (still inside 'weight argument
given') increment nparams:

if (weight_given) {
    if (weight<=0) {
        report error; goto cleanup;
    nparams++;
}


Michal


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