[libvirt] [PATCH v4 06/14] qemu_ns: Allow /dev/mapper/control for PR

[Michal Privoznik]

If qemu-pr-helper is compiled with multipath support the first
thing it does is opening /dev/mapper/control. Since we're going
to be running it inside qemu namespace we need to create it
there. Unfortunately, we don't know if it was compiled with or
without multipath so we have to create it anyway.

BTW: This might be the ugliest piece of code I've ever written
but @devMapperControl really needs to be type of char * otherwise
some crazy check in VIR_APPEND_ELEMENT fails.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/qemu/qemu_domain.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 0856f04406..6fe4eb57e1 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -108,6 +108,7 @@ VIR_ENUM_IMPL(qemuDomainNamespace, QEMU_DOMAIN_NS_LAST,
 #define PROC_MOUNTS "/proc/mounts"
 #define DEVPREFIX "/dev/"
 #define DEV_VFIO "/dev/vfio/vfio"
+#define DEVICE_MAPPER_CONTROL_PATH "/dev/mapper/control"
 
 
 struct _qemuDomainLogContext {
@@ -10269,6 +10270,11 @@ qemuDomainSetupDisk(virQEMUDriverConfigPtr cfg ATTRIBUTE_UNUSED,
             goto cleanup;
     }
 
+    /* qemu-pr-helper might require access to /dev/mapper/control. */
+    if (virStoragePRDefIsEnabled(disk->src->pr) &&
+        qemuDomainCreateDevice(DEVICE_MAPPER_CONTROL_PATH, data, true) < 0)
+        goto cleanup;
+
     ret = 0;
  cleanup:
     VIR_FREE(dst);
@@ -11281,6 +11287,9 @@ qemuDomainNamespaceSetupDisk(virDomainObjPtr vm,
     const char **paths = NULL;
     size_t npaths = 0;
     int ret = -1;
+    /* This is very nasty but we need it to work around some
+     * stupid checks in VIR_APPEND_ELEMENT macro. */
+    char *devMapperControl = (char *) DEVICE_MAPPER_CONTROL_PATH;
 
     if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
         return 0;
@@ -11296,6 +11305,11 @@ qemuDomainNamespaceSetupDisk(virDomainObjPtr vm,
             goto cleanup;
     }
 
+    /* qemu-pr-helper might require access to /dev/mapper/control. */
+    if (virStoragePRDefIsEnabled(src->pr) &&
+        VIR_APPEND_ELEMENT_COPY(paths, npaths, devMapperControl) < 0)
+        goto cleanup;
+
     if (qemuDomainNamespaceMknodPaths(vm, paths, npaths) < 0)
         return -1;
 
-- 
2.16.1