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vircgroupv2: properly detect placement of running VM

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When libvirtd starts a VM it internally stores a path to the main
cgroup. When we restart libvirtd we should get to the same state.

When we start a VM on host with systemd the cgroup is created for us and
the process is already placed into that cgroup and we detect the path
created by systemd using /proc/$PID/cgroup. After that we create
sub-cgroups and move all threads there.

Once libvirtd is restarted we again detect the cgroup path using
/proc/$PID/cgroup, but in this case we will get a different path because
the main thread was moved to a "emulator" cgroup.

Instead of ignoring the "emulator" directory when validating cgroups
remove it completely when detecting cgroup otherwise cgroups will not
work properly when libvirtd is restarted.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
This commit is contained in:
Pavel Hrdina 2020-10-13 13:29:43 +02:00
parent e85cfb095a
commit 902c6644a8
1 changed files with 10 additions and 7 deletions
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17
src/util/vircgroupv2.c
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@ -122,12 +122,6 @@ virCgroupV2ValidateMachineGroup(virCgroupPtr group,
if (!(tmp = strrchr(group->unified.placement, '/')))
return false;
if (STREQ(tmp, "/emulator")) {
*tmp = '\0';
if (!(tmp = strrchr(group->unified.placement, '/')))
return false;
}
tmp++;
if (STRNEQ(tmp, partmachinename) &&
@ -198,6 +192,9 @@ virCgroupV2DetectPlacement(virCgroupPtr group,
const char *controllers,
const char *selfpath)
{
g_autofree char *placement = g_strdup(selfpath);
char *tmp = NULL;
if (group->unified.placement)
return 0;
@ -208,12 +205,18 @@ virCgroupV2DetectPlacement(virCgroupPtr group,
if (STRNEQ(controllers, ""))
return 0;
/* Running VM will have the main thread placed in emulator cgroup
* but we need to get the main cgroup. */
tmp = g_strrstr(placement, "/emulator");
if (tmp)
*tmp = '\0';
/*
* selfpath == "/" + path="" -> "/"
* selfpath == "/libvirt.service" + path == "" -> "/libvirt.service"
* selfpath == "/libvirt.service" + path == "foo" -> "/libvirt.service/foo"
*/
group->unified.placement = g_strdup_printf("%s%s%s", selfpath,
group->unified.placement = g_strdup_printf("%s%s%s", placement,
(STREQ(selfpath, "/") || STREQ(path, "") ? "" : "/"), path);
return 0;