[PATCH 2/5] qemuProcessHandleIOError: Fix logic for lookup of disk

[Peter Krempa <pkrempa@xxxxxxxxxx>]

There are two bugs in the current disk lookup code in
qemuProcessHandleIOError:

 1) The QOM name isn't matched qemuProcessFindDomainDiskByAliasOrQOM()

   We pass NULL as the second argument, but the diskAlias argument can
   be the QOM path for e.g. virtio disks. This means that the IO error
   event doesn't actually contain the disk information:

     event 'io-error' for domain 'cd':  () report due to other: Input/output error

   rather than:

     event 'io-error' for domain 'cd': /dev/mapper/errdev0 (virtio-disk0) report due to other: Input/output error

 2) nodenames are not preferred

   We now do everything based on node names, which also allow you to
   pinpoint a image within the backing chain. With the current code the
   path would always refer to the top image rather than the actual image
   causing the problem.

This patch fixes both issues by re-ordering the lookup to prefer
nodenames and selecting the image path based on the node name and also
populates the third argument of qemuProcessFindDomainDiskByAliasOrQOM().

Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
---
 src/qemu/qemu_process.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 34a755a49a..95d0a40f84 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -833,9 +833,9 @@ qemuProcessHandleIOError(qemuMonitor *mon G_GNUC_UNUSED,
     virObjectEvent *ioErrorEvent = NULL;
     virObjectEvent *ioErrorEvent2 = NULL;
     virObjectEvent *lifecycleEvent = NULL;
-    const char *srcPath;
-    const char *devAlias;
-    virDomainDiskDef *disk;
+    virStorageSource *errsrc = NULL;
+    const char *srcPath = "";
+    const char *devAlias = "";

     virObjectLock(vm);
     priv = QEMU_DOMAIN_PRIVATE(vm);
@@ -843,19 +843,21 @@ qemuProcessHandleIOError(qemuMonitor *mon G_GNUC_UNUSED,
     if (*diskAlias == '\0')
         diskAlias = NULL;

-    if (diskAlias)
-        disk = qemuProcessFindDomainDiskByAliasOrQOM(vm, diskAlias, NULL);
-    else if (nodename)
-        disk = qemuDomainDiskLookupByNodename(vm->def, NULL, nodename, NULL);
-    else
-        disk = NULL;
+    if (nodename) {
+        virDomainDiskDef *disk = qemuDomainDiskLookupByNodename(vm->def, priv->backup, nodename, &errsrc);

-    if (disk) {
-        srcPath = virDomainDiskGetSource(disk);
-        devAlias = disk->info.alias;
-    } else {
-        srcPath = "";
-        devAlias = "";
+        if (errsrc->path)
+            srcPath = errsrc->path;
+
+        if (disk)
+            devAlias = disk->info.alias;
+    } else if (diskAlias) {
+        virDomainDiskDef *disk = qemuProcessFindDomainDiskByAliasOrQOM(vm, diskAlias, diskAlias);
+
+        if (disk) {
+            srcPath = virDomainDiskGetSource(disk);
+            devAlias = disk->info.alias;
+        }
     }

     ioErrorEvent = virDomainEventIOErrorNewFromObj(vm, srcPath, devAlias, action);
-- 
2.48.1