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Re: [libvirt] [PATCH] qemu: Record timestamp for qemu domain log



On 11/02/2010 06:59 AM, Eric Blake wrote:
On 11/01/2010 06:46 AM, Osier Yang wrote:
Currently only support domain start and domain shutdown, for domain
start, adding timestamp before qemu command line, for domain shutdown,
just say it's shutting down with timestamp.

* src/qemu/qemu_driver.c
---
  src/qemu/qemu_driver.c |   42 +++++++++++++++++++++++++++++++++++++++++-
  1 files changed, 41 insertions(+), 1 deletions(-)

+    } else if (safewrite(logfile, timestamp, strlen(timestamp))<  0) {
+        VIR_FREE(timestamp);
+        VIR_WARN("Unable to write timestamp to logfile: %s",
+                 virStrerror(errno, ebuf, sizeof ebuf));

VIR_FREE might clobber errno.  Swap these two lines.

ok, will update


@@ -4178,6 +4188,31 @@ static void qemudShutdownVMDaemon(struct qemud_driver *driver,
      virErrorPtr orig_err;
      virDomainDefPtr def;
      int i;
+    int logfile = -1;
+    char *timestamp;
+    char ebuf[1024];
+
+    VIR_DEBUG0("Creating domain log file");
+    if ((logfile = qemudLogFD(driver, vm->def->name))<  0) {
+        /* To not break the normal domain shutdown process, skip the
+         * timestamp log writing if failed on opening log file. */
+        VIR_WARN("Unable to open logfile: %s",
+                  virStrerror(errno, ebuf, sizeof ebuf));
+    } else {
+        if ((timestamp = virTimestamp()) == NULL) {
+            virReportOOMError();
+            goto cleanup;

Hmm.  The rest of this function is best-effort cleanup, since there is
no return value.  If you run out of memory while trying to cleanup, you
should STILL try and clean up the rest of the resources freed later in
this function, rather than immediately jumping to your cleanup: handler.

well, actually I just need to VIR_CLOSE the fd, so will not use goto statement in this funtion anymore. but VIR_CLOSE the fd here instead. :-)


+        } else {
+            strcat(timestamp, "shutting down\n");

Ouch. Buffer overflow - you can't guarantee whether timestamp was
overallocated with enough memory for you to blindly strcat() data onto
the end of it.

hum, will update.


+
+            if (safewrite(logfile, timestamp, strlen(timestamp))<  0) {
+                VIR_WARN("Unable to write timestamp to logfile: %s",
+                          virStrerror(errno, ebuf, sizeof ebuf));
+            }
+
+            VIR_FREE(timestamp);
+        }
+    }

      VIR_DEBUG("Shutting down VM '%s' pid=%d migrated=%d",
                vm->def->name, vm->pid, migrated);

Also, I think you want your attempts to write to a log file to occur
after this VIR_DEBUG statement.

yep, after this will be better.


@@ -4315,6 +4350,11 @@ retry:
          virSetError(orig_err);
          virFreeError(orig_err);
      }
+
+cleanup:
+    if (VIR_CLOSE(logfile)<  0)
+        VIR_WARN("Unable to close logfile: %s",
+                 virStrerror(errno, ebuf, sizeof ebuf));
  }



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