Fix launching of VMs on when only logind part of systemd is present

Debian systems may run the 'systemd-logind' daemon, which causes the
/sys/fs/cgroup/systemd  mount to be setup, but no other cgroup
controllers are created. While the LXC driver considers cgroups to
be mandatory, the QEMU driver is supposed to accept them as optional.

We detect whether they are present by looking in /proc/mounts for
any mounts of type 'cgroups', but this is not sufficient. We need to
skip any named mounts (as seen by a name=XXX string in the mount
options), so that we only detect actual resource controllers.

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=721979

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

src/util/vircgroup.c

@@ -91,7 +91,10 @@ virCgroupAvailable(void)
         return false;
 
     while (getmntent_r(mounts, &entry, buf, sizeof(buf)) != NULL) {
-        if (STREQ(entry.mnt_type, "cgroup")) {
+        /* We're looking for at least one 'cgroup' fs mount,
+         * which is *not* a named mount. */
+        if (STREQ(entry.mnt_type, "cgroup") &&
+            !strstr(entry.mnt_opts, "name=")) {
             ret = true;
             break;
         }

tests/vircgroupmock.c

@@ -124,6 +124,27 @@ const char *proccgroupsallinone =
     "devices  6   1  1\n"
     "blkio    6   1  1\n";
 
+const char *procmountslogind =
+    "none /not/really/sys/fs/cgroup tmpfs rw,rootcontext=system_u:object_r:sysfs_t:s0,seclabel,relatime,size=4k,mode=755 0 0\n"
+    "systemd /not/really/sys/fs/cgroup/systemd cgroup rw,nosuid,nodev,noexec,relatime,name=systemd 0 0\n";
+
+const char *procselfcgroupslogind =
+    "1:name=systemd:/\n";
+
+const char *proccgroupslogind =
+    "#subsys_name    hierarchy       num_cgroups     enabled\n"
+    "cpuset    0  1  1\n"
+    "cpu       0  1  1\n"
+    "cpuacct   0  1  1\n"
+    "memory    0  1  0\n"
+    "devices   0  1  1\n"
+    "freezer   0  1  1\n"
+    "net_cls   0  1  1\n"
+    "blkio     0  1  1\n"
+    "perf_event  0  1  1\n";
+
+
+
 static int make_file(const char *path,
                      const char *name,
                      const char *value)
@@ -400,18 +421,25 @@ static void init_sysfs(void)
 FILE *fopen(const char *path, const char *mode)
 {
     const char *mock;
-    bool allinone = false;
+    bool allinone = false, logind = false;
     init_syms();
 
     mock = getenv("VIR_CGROUP_MOCK_MODE");
-    if (mock && STREQ(mock, "allinone"))
+    if (mock) {
-        allinone = true;
+        if (STREQ(mock, "allinone"))
+            allinone = true;
+        else if (STREQ(mock, "logind"))
+            logind = true;
+    }
 
     if (STREQ(path, "/proc/mounts")) {
         if (STREQ(mode, "r")) {
             if (allinone)
                 return fmemopen((void *)procmountsallinone,
                                 strlen(procmountsallinone), mode);
+            else if (logind)
+                return fmemopen((void *)procmountslogind,
+                                strlen(procmountslogind), mode);
             else
                 return fmemopen((void *)procmounts, strlen(procmounts), mode);
         } else {
@@ -424,6 +452,9 @@ FILE *fopen(const char *path, const char *mode)
             if (allinone)
                 return fmemopen((void *)proccgroupsallinone,
                                 strlen(proccgroupsallinone), mode);
+            else if (logind)
+                return fmemopen((void *)proccgroupslogind,
+                                strlen(proccgroupslogind), mode);
             else
                 return fmemopen((void *)proccgroups, strlen(proccgroups), mode);
         } else {
@@ -436,6 +467,9 @@ FILE *fopen(const char *path, const char *mode)
             if (allinone)
                 return fmemopen((void *)procselfcgroupsallinone,
                                 strlen(procselfcgroupsallinone), mode);
+            else if (logind)
+                return fmemopen((void *)procselfcgroupslogind,
+                                strlen(procselfcgroupslogind), mode);
             else
                 return fmemopen((void *)procselfcgroups, strlen(procselfcgroups), mode);
         } else {

tests/vircgrouptest.c

@@ -109,6 +109,16 @@ const char *mountsAllInOne[VIR_CGROUP_CONTROLLER_LAST] = {
     [VIR_CGROUP_CONTROLLER_BLKIO] = "/not/really/sys/fs/cgroup",
     [VIR_CGROUP_CONTROLLER_SYSTEMD] = NULL,
 };
+const char *mountsLogind[VIR_CGROUP_CONTROLLER_LAST] = {
+    [VIR_CGROUP_CONTROLLER_CPU] = NULL,
+    [VIR_CGROUP_CONTROLLER_CPUACCT] = NULL,
+    [VIR_CGROUP_CONTROLLER_CPUSET] = NULL,
+    [VIR_CGROUP_CONTROLLER_MEMORY] = NULL,
+    [VIR_CGROUP_CONTROLLER_DEVICES] = NULL,
+    [VIR_CGROUP_CONTROLLER_FREEZER] = NULL,
+    [VIR_CGROUP_CONTROLLER_BLKIO] = NULL,
+    [VIR_CGROUP_CONTROLLER_SYSTEMD] = "/not/really/sys/fs/cgroup/systemd",
+};
 
 const char *links[VIR_CGROUP_CONTROLLER_LAST] = {
     [VIR_CGROUP_CONTROLLER_CPU] = "/not/really/sys/fs/cgroup/cpu",
@@ -132,6 +142,17 @@ const char *linksAllInOne[VIR_CGROUP_CONTROLLER_LAST] = {
     [VIR_CGROUP_CONTROLLER_SYSTEMD] = NULL,
 };
 
+const char *linksLogind[VIR_CGROUP_CONTROLLER_LAST] = {
+    [VIR_CGROUP_CONTROLLER_CPU] = NULL,
+    [VIR_CGROUP_CONTROLLER_CPUACCT] = NULL,
+    [VIR_CGROUP_CONTROLLER_CPUSET] = NULL,
+    [VIR_CGROUP_CONTROLLER_MEMORY] = NULL,
+    [VIR_CGROUP_CONTROLLER_DEVICES] = NULL,
+    [VIR_CGROUP_CONTROLLER_FREEZER] = NULL,
+    [VIR_CGROUP_CONTROLLER_BLKIO] = NULL,
+    [VIR_CGROUP_CONTROLLER_SYSTEMD] = NULL,
+};
+
 
 static int testCgroupNewForSelf(const void *args ATTRIBUTE_UNUSED)
 {
@@ -466,6 +487,48 @@ cleanup:
 }
 
 
+static int testCgroupNewForSelfLogind(const void *args ATTRIBUTE_UNUSED)
+{
+    virCgroupPtr cgroup = NULL;
+    int ret = -1;
+    const char *placement[VIR_CGROUP_CONTROLLER_LAST] = {
+        [VIR_CGROUP_CONTROLLER_CPU] = NULL,
+        [VIR_CGROUP_CONTROLLER_CPUACCT] = NULL,
+        [VIR_CGROUP_CONTROLLER_CPUSET] = NULL,
+        [VIR_CGROUP_CONTROLLER_MEMORY] = NULL,
+        [VIR_CGROUP_CONTROLLER_DEVICES] = NULL,
+        [VIR_CGROUP_CONTROLLER_FREEZER] = NULL,
+        [VIR_CGROUP_CONTROLLER_BLKIO] = NULL,
+        [VIR_CGROUP_CONTROLLER_SYSTEMD] = "/",
+    };
+
+    if (virCgroupNewSelf(&cgroup) < 0) {
+        fprintf(stderr, "Cannot create cgroup for self\n");
+        goto cleanup;
+    }
+
+    ret = validateCgroup(cgroup, "", mountsLogind, linksLogind, placement);
+
+cleanup:
+    virCgroupFree(&cgroup);
+    return ret;
+}
+
+
+static int testCgroupAvailable(const void *args)
+{
+    bool got = virCgroupAvailable();
+    bool want = args == (void*)0x1;
+
+    if (got != want) {
+        fprintf(stderr, "Expected cgroup %savailable, but state was wrong\n",
+                want ? "" : "not ");
+        return -1;
+    }
+
+    return 0;
+}
+
 
 # define FAKESYSFSDIRTEMPLATE abs_builddir "/fakesysfsdir-XXXXXX"
 
@@ -505,9 +568,21 @@ mymain(void)
     if (virtTestRun("New cgroup for domain partition escaped", 1, testCgroupNewForPartitionDomainEscaped, NULL) < 0)
         ret = -1;
 
+    if (virtTestRun("Cgroup available", 1, testCgroupAvailable, (void*)0x1) < 0)
+        ret = -1;
+
     setenv("VIR_CGROUP_MOCK_MODE", "allinone", 1);
     if (virtTestRun("New cgroup for self (allinone)", 1, testCgroupNewForSelfAllInOne, NULL) < 0)
         ret = -1;
+    if (virtTestRun("Cgroup available", 1, testCgroupAvailable, (void*)0x1) < 0)
+        ret = -1;
+    unsetenv("VIR_CGROUP_MOCK_MODE");
+
+    setenv("VIR_CGROUP_MOCK_MODE", "logind", 1);
+    if (virtTestRun("New cgroup for self (logind)", 1, testCgroupNewForSelfLogind, NULL) < 0)
+        ret = -1;
+    if (virtTestRun("Cgroup available", 1, testCgroupAvailable, (void*)0x0) < 0)
+        ret = -1;
     unsetenv("VIR_CGROUP_MOCK_MODE");
 
     if (getenv("LIBVIRT_SKIP_CLEANUP") == NULL)