Re: [libvirt] [PATCH v2 02/53] vircgroup: introduce virCgroupV2Available

On Fri, Oct 05, 2018 at 03:43:50PM +0200, Michal Privoznik wrote: > On 10/05/2018 02:43 PM, Pavel Hrdina wrote: >> We cannot detect only mount points to figure out whether cgroup v2 >> is available because systemd uses cgroup v2 for process tracking and >> all controllers are mounted as cgroup v1 controllers. >> >> To make sure that this is no the situation we need to check >> 'cgroup.controllers' file if it's not empty to make sure that cgroup >> v2 is not mounted only for process tracking. >> >> Signed-off-by: Pavel Hrdina <phrdina(a)redhat.com&gt; >> --- >> src/util/vircgroupv2.c | 59 ++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 59 insertions(+) >> >> diff --git a/src/util/vircgroupv2.c b/src/util/vircgroupv2.c >> index 23bf81dae2..83944602d6 100644 >> --- a/src/util/vircgroupv2.c >> +++ b/src/util/vircgroupv2.c >> @@ -19,6 +19,10 @@ >> */ >> #include <config.h> >> >> +#ifdef __linux__ >> +# include <mntent.h> >> +#endif /* __linux__ */ >> + >> #include "internal.h" >> >> #define __VIR_CGROUP_ALLOW_INCLUDE_PRIV_H__ >> @@ -28,7 +32,9 @@ >> #include "vircgroup.h" >> #include "vircgroupbackend.h" >> #include "vircgroupv2.h" >> +#include "virfile.h" >> #include "virlog.h" >> +#include "virstring.h" >> >> VIR_LOG_INIT("util.cgroup"); >> >> @@ -41,8 +47,61 @@ VIR_ENUM_IMPL(virCgroupV2Controller, VIR_CGROUP_CONTROLLER_LAST, >> >> #ifdef __linux__ > > > How about: > > static bool > virCgroupV2Available(void) > { > bool ret = false; > FILE *mounts = NULL; > struct mntent entry; > char buf[CGROUP_MAX_VAL]; > > if (!(mounts = fopen("/proc/mounts", "r"))) > return false; > > while (getmntent_r(mounts, &entry, buf, sizeof(buf)) != NULL) { > VIR_AUTOFREE(char *) contFile = NULL; > VIR_AUTOFREE(char *) contStr = NULL; > > if (STRNEQ(entry.mnt_type, "cgroup2")) > continue; > > /* Systemd uses cgroup v2 for process tracking but no controller is > * available. We should consider this configuration as cgroup v2 is > * not available. */ > if (virAsprintf(&contFile, "%s/cgroup.controllers", entry.mnt_dir) < 0) > goto cleanup; > > if (virFileReadAll(contFile, 1024 * 1024, &contStr) < 0) > goto cleanup; > > if (STREQ(contStr, "")) > continue; > > ret = true; > break; > } > > cleanup: > VIR_FORCE_FCLOSE(mounts); > return ret; > } Works for me :) I was considering moving it inside the while loop but I was too lazy to do it.