[PATCH 2/5] qemu: Avoid using stale data in virDomainGetBlockInfo

[Jiri Denemark <jdenemar@xxxxxxxxxx>]

Generally, every API that is going to begin a job should do that before
fetching data from vm->def. However, qemuDomainGetBlockInfo does not
know whether it will have to start a job or not before checking vm->def.
To avoid using disk alias that might have been freed while we were
waiting for a job, we use its copy. In case the disk was removed in the
meantime, we will fail with "cannot find statistics for device '...'"
error message.

Signed-off-by: Jiri Denemark <jdenemar@xxxxxxxxxx>
---
 src/qemu/qemu_driver.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 8823187..9db0c49 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -9780,10 +9780,12 @@ cleanup:
 }
 
 
-static int qemuDomainGetBlockInfo(virDomainPtr dom,
-                                  const char *path,
-                                  virDomainBlockInfoPtr info,
-                                  unsigned int flags) {
+static int
+qemuDomainGetBlockInfo(virDomainPtr dom,
+                       const char *path,
+                       virDomainBlockInfoPtr info,
+                       unsigned int flags)
+{
     virQEMUDriverPtr driver = dom->conn->privateData;
     virDomainObjPtr vm;
     int ret = -1;
@@ -9795,6 +9797,7 @@ static int qemuDomainGetBlockInfo(virDomainPtr dom,
     int idx;
     int format;
     virQEMUDriverConfigPtr cfg = NULL;
+    char *alias = NULL;
 
     virCheckFlags(0, -1);
 
@@ -9901,13 +9904,16 @@ static int qemuDomainGetBlockInfo(virDomainPtr dom,
         virDomainObjIsActive(vm)) {
         qemuDomainObjPrivatePtr priv = vm->privateData;
 
+        if (VIR_STRDUP(alias, disk->info.alias) < 0)
+            goto cleanup;
+
         if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_QUERY) < 0)
             goto cleanup;
 
         if (virDomainObjIsActive(vm)) {
             qemuDomainObjEnterMonitor(driver, vm);
             ret = qemuMonitorGetBlockExtent(priv->mon,
-                                            disk->info.alias,
+                                            alias,
                                             &info->allocation);
             qemuDomainObjExitMonitor(driver, vm);
         } else {
@@ -9921,6 +9927,7 @@ static int qemuDomainGetBlockInfo(virDomainPtr dom,
     }
 
 cleanup:
+    VIR_FREE(alias);
     virStorageFileFreeMetadata(meta);
     VIR_FORCE_CLOSE(fd);
     if (vm)
-- 
1.8.5.2

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