From c467b07e275fa1ce85b3ac9168546d0ac98ada37 Mon Sep 17 00:00:00 2001
From: Michal Privoznik <mprivozn@redhat.com>
Date: Mon, 20 Jul 2020 18:01:16 +0200
Subject: [PATCH] qemu_domain_namespace: Check for namespace enablement earlier
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Functions that create a device node after domain startup (used
from hotplug) will get a list of paths they want to create and
eventually call qemuDomainNamespaceMknodPaths() which then checks
whether domain mount namespace is enabled in the first place.
Alternatively, on device hotunplug, we might want to delete a
path inside domain namespace in which case
qemuDomainNamespaceUnlinkPaths() checks whether the namespace is
enabled. While this is not dangerous, it certainly burns a couple
of CPU cycles needlessly.

Check whether mount namespace is enabled upfront.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---
 src/qemu/qemu_namespace.c | 39 +++++++++++++++++++++++++++++++++++----
 1 file changed, 35 insertions(+), 4 deletions(-)

diff --git a/src/qemu/qemu_namespace.c b/src/qemu/qemu_namespace.c
index 1f976886fd..663a542ff2 100644
--- a/src/qemu/qemu_namespace.c
+++ b/src/qemu/qemu_namespace.c
@@ -1481,8 +1481,7 @@ qemuDomainNamespaceMknodPaths(virDomainObjPtr vm,
     int ret = -1;
     size_t i;
 
-    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT) ||
-        !npaths)
+    if (!npaths)
         return 0;
 
     cfg = virQEMUDriverGetConfig(driver);
@@ -1529,8 +1528,7 @@ qemuDomainNamespaceUnlinkPaths(virDomainObjPtr vm,
     size_t i;
     int ret = -1;
 
-    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT) ||
-        !npaths)
+    if (!npaths)
         return 0;
 
     cfg = virQEMUDriverGetConfig(driver);
@@ -1572,6 +1570,9 @@ qemuDomainNamespaceSetupDisk(virDomainObjPtr vm,
     size_t npaths = 0;
     bool hasNVMe = false;
 
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     for (next = src; virStorageSourceIsBacking(next); next = next->backingStore) {
         g_autofree char *tmpPath = NULL;
 
@@ -1655,6 +1656,9 @@ qemuDomainNamespaceSetupHostdev(virDomainObjPtr vm,
 {
     g_autofree char *path = NULL;
 
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     if (qemuDomainGetHostdevPath(hostdev, &path, NULL) < 0)
         return -1;
 
@@ -1687,6 +1691,9 @@ qemuDomainNamespaceTeardownHostdev(virDomainObjPtr vm,
 {
     g_autofree char *path = NULL;
 
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     if (qemuDomainGetHostdevPath(hostdev, &path, NULL) < 0)
         return -1;
 
@@ -1706,6 +1713,9 @@ int
 qemuDomainNamespaceSetupMemory(virDomainObjPtr vm,
                                virDomainMemoryDefPtr mem)
 {
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     if (mem->model != VIR_DOMAIN_MEMORY_MODEL_NVDIMM)
         return 0;
 
@@ -1720,6 +1730,9 @@ int
 qemuDomainNamespaceTeardownMemory(virDomainObjPtr vm,
                                   virDomainMemoryDefPtr mem)
 {
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     if (mem->model != VIR_DOMAIN_MEMORY_MODEL_NVDIMM)
         return 0;
 
@@ -1736,6 +1749,9 @@ qemuDomainNamespaceSetupChardev(virDomainObjPtr vm,
 {
     const char *path;
 
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     if (!(path = virDomainChrSourceDefGetPath(chr->source)))
         return 0;
 
@@ -1757,6 +1773,9 @@ qemuDomainNamespaceTeardownChardev(virDomainObjPtr vm,
 {
     const char *path = NULL;
 
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     if (chr->source->type != VIR_DOMAIN_CHR_TYPE_DEV)
         return 0;
 
@@ -1775,6 +1794,9 @@ qemuDomainNamespaceSetupRNG(virDomainObjPtr vm,
 {
     const char *path = NULL;
 
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     switch ((virDomainRNGBackend) rng->backend) {
     case VIR_DOMAIN_RNG_BACKEND_RANDOM:
         path = rng->source.file;
@@ -1799,6 +1821,9 @@ qemuDomainNamespaceTeardownRNG(virDomainObjPtr vm,
 {
     const char *path = NULL;
 
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     switch ((virDomainRNGBackend) rng->backend) {
     case VIR_DOMAIN_RNG_BACKEND_RANDOM:
         path = rng->source.file;
@@ -1823,6 +1848,9 @@ qemuDomainNamespaceSetupInput(virDomainObjPtr vm,
 {
     const char *path = NULL;
 
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     if (!(path = virDomainInputDefGetPath(input)))
         return 0;
 
@@ -1838,6 +1866,9 @@ qemuDomainNamespaceTeardownInput(virDomainObjPtr vm,
 {
     const char *path = NULL;
 
+    if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
+        return 0;
+
     if (!(path = virDomainInputDefGetPath(input)))
         return 0;
 
-- 
2.47.2