qemu: Create multipath targets for PRs

If a disk has persistent reservations enabled, qemu-pr-helper
might open not only /dev/mapper/control but also individual
targets of the multipath device. We are already querying for them
in CGroups, but now we have to create them in the namespace too.
This was brought up in [1].

1: https://bugzilla.redhat.com/show_bug.cgi?id=1711045#c61Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Tested-by: NLin Ma <LMa@suse.com>
Reviewed-by: NJim Fehlig <jfehlig@suse.com>

src/qemu/qemu_domain.c

@@ -62,6 +62,7 @@
 #include "virdomaincheckpointobjlist.h"
 #include "backup_conf.h"
 #include "virutil.h"
+#include "virdevmapper.h"
 
 #ifdef __linux__
 # include <sys/sysmacros.h>
@@ -14623,6 +14624,9 @@ qemuDomainSetupDisk(virQEMUDriverConfigPtr cfg G_GNUC_UNUSED,
     bool hasNVMe = false;
 
     for (next = disk->src; virStorageSourceIsBacking(next); next = next->backingStore) {
+        VIR_AUTOSTRINGLIST targetPaths = NULL;
+        size_t i;
+
         if (next->type == VIR_STORAGE_TYPE_NVME) {
             g_autofree char *nvmePath = NULL;
 
@@ -14641,6 +14645,19 @@ qemuDomainSetupDisk(virQEMUDriverConfigPtr cfg G_GNUC_UNUSED,
 
             if (qemuDomainCreateDevice(next->path, data, false) < 0)
                 return -1;
+
+            if (virDevMapperGetTargets(next->path, &targetPaths) < 0 &&
+                errno != ENOSYS && errno != EBADF) {
+                virReportSystemError(errno,
+                                     _("Unable to get devmapper targets for %s"),
+                                     next->path);
+                return -1;
+            }
+
+            for (i = 0; targetPaths && targetPaths[i]; i++) {
+                if (qemuDomainCreateDevice(targetPaths[i], data, false) < 0)
+                    return -1;
+            }
         }
     }
 
@@ -15656,21 +15673,19 @@ qemuDomainNamespaceSetupDisk(virDomainObjPtr vm,
                              virStorageSourcePtr src)
 {
     virStorageSourcePtr next;
-    char **paths = NULL;
+    VIR_AUTOSTRINGLIST paths = NULL;
     size_t npaths = 0;
     bool hasNVMe = false;
-    g_autofree char *dmPath = NULL;
-    g_autofree char *vfioPath = NULL;
-    int ret = -1;
 
     for (next = src; virStorageSourceIsBacking(next); next = next->backingStore) {
+        VIR_AUTOSTRINGLIST targetPaths = NULL;
         g_autofree char *tmpPath = NULL;
 
         if (next->type == VIR_STORAGE_TYPE_NVME) {
             hasNVMe = true;
 
             if (!(tmpPath = virPCIDeviceAddressGetIOMMUGroupDev(&next->nvme->pciAddr)))
-                goto cleanup;
+                return -1;
         } else {
             if (virStorageSourceIsEmpty(next) ||
                 !virStorageSourceIsLocalStorage(next)) {
@@ -15681,30 +15696,35 @@ qemuDomainNamespaceSetupDisk(virDomainObjPtr vm,
             tmpPath = g_strdup(next->path);
         }
 
-        if (VIR_APPEND_ELEMENT(paths, npaths, tmpPath) < 0)
-            goto cleanup;
+        if (virStringListAdd(&paths, tmpPath) < 0)
+            return -1;
+
+        if (virDevMapperGetTargets(next->path, &targetPaths) < 0 &&
+            errno != ENOSYS && errno != EBADF) {
+            virReportSystemError(errno,
+                                 _("Unable to get devmapper targets for %s"),
+                                 next->path);
+            return -1;
+        }
+
+        if (virStringListMerge(&paths, &targetPaths) < 0)
+            return -1;
     }
 
     /* qemu-pr-helper might require access to /dev/mapper/control. */
-    if (src->pr) {
-        dmPath = g_strdup(QEMU_DEVICE_MAPPER_CONTROL_PATH);
-        if (VIR_APPEND_ELEMENT_COPY(paths, npaths, dmPath) < 0)
-            goto cleanup;
-    }
+    if (src->pr &&
+        virStringListAdd(&paths, QEMU_DEVICE_MAPPER_CONTROL_PATH) < 0)
+        return -1;
 
-    if (hasNVMe) {
-        vfioPath = g_strdup(QEMU_DEV_VFIO);
-        if (VIR_APPEND_ELEMENT(paths, npaths, vfioPath) < 0)
-            goto cleanup;
-    }
+    if (hasNVMe &&
+        virStringListAdd(&paths, QEMU_DEV_VFIO) < 0)
+        return -1;
 
+    npaths = virStringListLength((const char **) paths);
     if (qemuDomainNamespaceMknodPaths(vm, (const char **) paths, npaths) < 0)
-        goto cleanup;
+        return -1;
 
-    ret = 0;
- cleanup:
-    virStringListFreeCount(paths, npaths);
-    return ret;
+    return 0;
 }
 
 

src/util/virdevmapper.h

@@ -20,6 +20,8 @@
 
 #pragma once
 
+#include "internal.h"
+
 int
 virDevMapperGetTargets(const char *path,
-                       char ***devPaths);
+                       char ***devPaths) G_GNUC_NO_INLINE;

src/util/virutil.h

@@ -120,7 +120,7 @@ bool virValidateWWN(const char *wwn);
 
 int virGetDeviceID(const char *path,
                    int *maj,
-                   int *min);
+                   int *min) G_GNUC_NO_INLINE;
 int virSetDeviceUnprivSGIO(const char *path,
                            const char *sysfs_dir,
                            int unpriv_sgio);

tests/qemuhotplugmock.c

@@ -19,7 +19,24 @@
 #include <config.h>
 
 #include "qemu/qemu_hotplug.h"
+#include "qemu/qemu_process.h"
 #include "conf/domain_conf.h"
+#include "virdevmapper.h"
+#include "virutil.h"
+#include "virmock.h"
+
+static int (*real_virGetDeviceID)(const char *path, int *maj, int *min);
+static bool (*real_virFileExists)(const char *path);
+
+static void
+init_syms(void)
+{
+    if (real_virFileExists)
+        return;
+
+    VIR_MOCK_REAL_INIT(virGetDeviceID);
+    VIR_MOCK_REAL_INIT(virFileExists);
+}
 
 unsigned long long
 qemuDomainGetUnplugTimeout(virDomainObjPtr vm G_GNUC_UNUSED)
@@ -31,3 +48,61 @@ qemuDomainGetUnplugTimeout(virDomainObjPtr vm G_GNUC_UNUSED)
         return 200;
     return 100;
 }
+
+
+int
+virDevMapperGetTargets(const char *path,
+                       char ***devPaths)
+{
+    *devPaths = NULL;
+
+    if (STREQ(path, "/dev/mapper/virt")) {
+        *devPaths = g_new(char *, 4);
+        (*devPaths)[0] = g_strdup("/dev/block/8:0");  /* /dev/sda */
+        (*devPaths)[1] = g_strdup("/dev/block/8:16"); /* /dev/sdb */
+        (*devPaths)[2] = g_strdup("/dev/block/8:32"); /* /dev/sdc */
+        (*devPaths)[3] = NULL;
+    }
+
+    return 0;
+}
+
+
+int
+virGetDeviceID(const char *path, int *maj, int *min)
+{
+    init_syms();
+
+    if (STREQ(path, "/dev/mapper/virt")) {
+        *maj = 254;
+        *min = 0;
+        return 0;
+    }
+
+    return real_virGetDeviceID(path, maj, min);
+}
+
+
+bool
+virFileExists(const char *path)
+{
+    init_syms();
+
+    if (STREQ(path, "/dev/mapper/virt"))
+        return true;
+
+    return real_virFileExists(path);
+}
+
+
+int
+qemuProcessStartManagedPRDaemon(virDomainObjPtr vm G_GNUC_UNUSED)
+{
+    return 0;
+}
+
+
+void
+qemuProcessKillManagedPRDaemon(virDomainObjPtr vm G_GNUC_UNUSED)
+{
+}

tests/qemuhotplugtest.c

@@ -87,6 +87,8 @@ qemuHotplugCreateObjects(virDomainXMLOptionPtr xmlopt,
     virQEMUCapsSet(priv->qemuCaps, QEMU_CAPS_VNC);
     virQEMUCapsSet(priv->qemuCaps, QEMU_CAPS_SPICE);
     virQEMUCapsSet(priv->qemuCaps, QEMU_CAPS_SPICE_FILE_XFER_DISABLE);
+    virQEMUCapsSet(priv->qemuCaps, QEMU_CAPS_PR_MANAGER_HELPER);
+    virQEMUCapsSet(priv->qemuCaps, QEMU_CAPS_SCSI_BLOCK);
 
     if (qemuTestCapsCacheInsert(driver.qemuCapsCache, priv->qemuCaps) < 0)
         return -1;
@@ -750,6 +752,17 @@ mymain(void)
                    "device_del", QMP_DEVICE_DELETED("scsi3-0-5-6") QMP_OK,
                    "human-monitor-command", HMP(""));
 
+    DO_TEST_ATTACH("base-live", "disk-scsi-multipath", false, true,
+                   "object-add", QMP_OK,
+                   "human-monitor-command", HMP("OK\\r\\n"),
+                   "device_add", QMP_OK);
+    DO_TEST_DETACH("base-live", "disk-scsi-multipath", true, true,
+                   "device_del", QMP_OK,
+                   "human-monitor-command", HMP(""));
+    DO_TEST_DETACH("base-live", "disk-scsi-multipath", false, false,
+                   "device_del", QMP_DEVICE_DELETED("scsi0-0-0-0") QMP_OK,
+                   "human-monitor-command", HMP(""));
+
     DO_TEST_ATTACH("base-live", "qemu-agent", false, true,
                    "chardev-add", QMP_OK,
                    "device_add", QMP_OK);

tests/qemuhotplugtestdevices/qemuhotplug-disk-scsi-multipath.xml

+<disk type='block' device='lun'>
+    <driver name='qemu' type='raw'/>
+    <source dev='/dev/mapper/virt'>
+        <reservations managed='yes'/>
+    </source>
+    <target dev='sda' bus='scsi'/>
+  <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+</disk>

tests/qemuhotplugtestdomains/qemuhotplug-base-live+disk-scsi-multipath.xml

+<domain type='kvm' id='7'>
+  <name>hotplug</name>
+  <uuid>d091ea82-29e6-2e34-3005-f02617b36e87</uuid>
+  <memory unit='KiB'>4194304</memory>
+  <currentMemory unit='KiB'>4194304</currentMemory>
+  <vcpu placement='static'>4</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <features>
+    <acpi/>
+    <apic/>
+    <pae/>
+  </features>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>restart</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu-system-x86_64</emulator>
+    <disk type='block' device='lun'>
+      <driver name='qemu' type='raw'/>
+      <source dev='/dev/mapper/virt'>
+        <reservations managed='yes'>
+          <source type='unix' path='/tmp/lib/domain-7-hotplug/pr-helper0.sock' mode='client'/>
+        </reservations>
+      </source>
+      <backingStore/>
+      <target dev='sda' bus='scsi'/>
+      <alias name='scsi0-0-0-0'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'>
+      <alias name='usb'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
+    </controller>
+    <controller type='ide' index='0'>
+      <alias name='ide'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
+    </controller>
+    <controller type='scsi' index='0' model='virtio-scsi'>
+      <alias name='scsi0'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
+    </controller>
+    <controller type='pci' index='0' model='pci-root'>
+      <alias name='pci'/>
+    </controller>
+    <controller type='virtio-serial' index='0'>
+      <alias name='virtio-serial0'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
+    </controller>
+    <input type='mouse' bus='ps2'>
+      <alias name='input0'/>
+    </input>
+    <input type='keyboard' bus='ps2'>
+      <alias name='input1'/>
+    </input>
+    <memballoon model='none'/>
+  </devices>
+  <seclabel type='none' model='none'/>
+</domain>