[libvirt] [PATCHv2 1/2] Split qemuDomainChrInsert into two parts

[Ján Tomko]

Do the allocation first, then add the actual device.
The second part should never fail. This is good
for live hotplug where we don't want to remove the device
on OOM after the monitor command succeeded.

The only change in behavior is that on failure, the
vmdef->consoles array is freed, not just the first console.
---
 src/conf/domain_conf.c   | 18 +++++++++++++---
 src/conf/domain_conf.h   |  7 +++++--
 src/libvirt_private.syms |  3 ++-
 src/qemu/qemu_hotplug.c  | 54 +++++++++++++++++++++++++++++++++++++++++-------
 4 files changed, 68 insertions(+), 14 deletions(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 10dbabd..3c6b77d 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -12027,15 +12027,27 @@ virDomainChrGetDomainPtrs(const virDomainDef *vmdef,
 
 
 int
-virDomainChrInsert(virDomainDefPtr vmdef,
-                   virDomainChrDefPtr chr)
+virDomainChrPreAlloc(virDomainDefPtr vmdef,
+                     virDomainChrDefPtr chr)
+{
+    virDomainChrDefPtr **arrPtr = NULL;
+    size_t *cntPtr = NULL;
+
+    virDomainChrGetDomainPtrsInternal(vmdef, chr->deviceType, &arrPtr, &cntPtr);
+
+    return VIR_REALLOC_N(*arrPtr, *cntPtr + 1);
+}
+
+void
+virDomainChrInsertPreAlloced(virDomainDefPtr vmdef,
+                             virDomainChrDefPtr chr)
 {
     virDomainChrDefPtr **arrPtr = NULL;
     size_t *cntPtr = NULL;
 
     virDomainChrGetDomainPtrsInternal(vmdef, chr->deviceType, &arrPtr, &cntPtr);
 
-    return VIR_APPEND_ELEMENT(*arrPtr, *cntPtr, chr);
+    ignore_value(VIR_APPEND_ELEMENT_INPLACE(*arrPtr, *cntPtr, chr));
 }
 
 virDomainChrDefPtr
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 563c18b..93f2314 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -2652,8 +2652,11 @@ bool
 virDomainChrEquals(virDomainChrDefPtr src,
                    virDomainChrDefPtr tgt);
 int
-virDomainChrInsert(virDomainDefPtr vmdef,
-                   virDomainChrDefPtr chr);
+virDomainChrPreAlloc(virDomainDefPtr vmdef,
+                     virDomainChrDefPtr chr);
+void
+virDomainChrInsertPreAlloced(virDomainDefPtr vmdef,
+                             virDomainChrDefPtr chr);
 virDomainChrDefPtr
 virDomainChrRemove(virDomainDefPtr vmdef,
                    virDomainChrDefPtr chr);
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 75a6d83..bd7870f 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -153,7 +153,8 @@ virDomainChrDefNew;
 virDomainChrEquals;
 virDomainChrFind;
 virDomainChrGetDomainPtrs;
-virDomainChrInsert;
+virDomainChrInsertPreAlloced;
+virDomainChrPreAlloc;
 virDomainChrRemove;
 virDomainChrSerialTargetTypeFromString;
 virDomainChrSerialTargetTypeToString;
diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index 1dbcc5d..2ea30f5 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -1403,9 +1403,9 @@ int qemuDomainAttachRedirdevDevice(virQEMUDriverPtr driver,
 
 }
 
-int
-qemuDomainChrInsert(virDomainDefPtr vmdef,
-                    virDomainChrDefPtr chr)
+static int
+qemuDomainChrPreInsert(virDomainDefPtr vmdef,
+                       virDomainChrDefPtr chr)
 {
     if (chr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_CONSOLE &&
         chr->targetType == VIR_DOMAIN_CHR_CONSOLE_TARGET_TYPE_SERIAL) {
@@ -1420,25 +1420,63 @@ qemuDomainChrInsert(virDomainDefPtr vmdef,
         return -1;
     }
 
-    if (virDomainChrInsert(vmdef, chr) < 0)
+    if (virDomainChrPreAlloc(vmdef, chr) < 0)
         return -1;
 
     /* Due to some crazy backcompat stuff, the first serial device is an alias
      * to the first console too. If this is the case, the definition must be
      * duplicated as first console device. */
-    if (vmdef->nserials == 1 && vmdef->nconsoles == 0) {
-        if ((!vmdef->consoles && VIR_ALLOC(vmdef->consoles) < 0) ||
-            VIR_ALLOC(vmdef->consoles[0]) < 0) {
-            virDomainChrRemove(vmdef, chr);
+    if (vmdef->nserials == 0 && vmdef->nconsoles == 0 &&
+        chr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_SERIAL) {
+        if (!vmdef->consoles && VIR_ALLOC(vmdef->consoles) < 0)
+            return -1;
+
+        if (VIR_ALLOC(vmdef->consoles[0]) < 0) {
+            VIR_FREE(vmdef->consoles);
             return -1;
         }
+        vmdef->nconsoles++;
+    }
+    return 0;
+}
+
+static void
+qemuDomainChrInsertPreAlloced(virDomainDefPtr vmdef,
+                              virDomainChrDefPtr chr)
+{
+    virDomainChrInsertPreAlloced(vmdef, chr);
+    if (vmdef->nserials == 1 && vmdef->nconsoles == 0 &&
+        chr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_SERIAL) {
         vmdef->nconsoles = 1;
 
         /* Create an console alias for the serial port */
         vmdef->consoles[0]->deviceType = VIR_DOMAIN_CHR_DEVICE_TYPE_CONSOLE;
         vmdef->consoles[0]->targetType = VIR_DOMAIN_CHR_CONSOLE_TARGET_TYPE_SERIAL;
     }
+}
+
+static void
+qemuDomainChrInsertPreAllocCleanup(virDomainDefPtr vmdef,
+                                   virDomainChrDefPtr chr)
+{
+    /* Remove the stub console added by qemuDomainChrPreInsert */
+    if (vmdef->nserials == 0 && vmdef->nconsoles == 1 &&
+        chr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_SERIAL) {
+        VIR_FREE(vmdef->consoles[0]);
+        VIR_FREE(vmdef->consoles);
+        vmdef->nconsoles = 0;
+    }
+}
 
+int
+qemuDomainChrInsert(virDomainDefPtr vmdef,
+                    virDomainChrDefPtr chr)
+{
+    if (qemuDomainChrPreInsert(vmdef, chr) < 0) {
+        qemuDomainChrInsertPreAllocCleanup(vmdef, chr);
+        return -1;
+    }
+    qemuDomainChrInsertPreAlloced(vmdef, chr);
     return 0;
 }
 
-- 
2.0.5