On Thu, Sep 26, 2019 at 05:18:40PM -0400, Cole Robinson wrote: > On Fedora 31, starting a 'mock' build alters /proc/$pid/cgroup, > probably due to usage of systemd-nspawn. > > Before: > $ cat /proc/self/cgroup > 0::/user.slice/user-1000.slice/... > > After: > $ cat /proc/self/cgroup > 1:name=systemd:/ > 0::/user.slice/user-1000.slice/... > > The cgroupv2 code mishandles that first line in the second case, which > causes VM startup to fail with: Unable to read from > '/sys/fs/cgroup/machine/cgroup.controllers': No such file or directory > > The kernel docs[1] say that the cgroupv2 path will always start with > '0::', which in the code here controllers="". Only set the v2 placement > path when we see that cgroup file entry. > > [1] https://www.kernel.org/doc/html/v5.3/admin-guide/cgroup-v2.html#processes > > https://bugzilla.redhat.com/show_bug.cgi?id=1751120 > > Signed-off-by: Cole Robinson <crobinso@xxxxxxxxxx> > --- > src/util/vircgroupv2.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/src/util/vircgroupv2.c b/src/util/vircgroupv2.c > index 0663c67190..0cb20e4896 100644 > --- a/src/util/vircgroupv2.c > +++ b/src/util/vircgroupv2.c > @@ -194,12 +194,16 @@ virCgroupV2DetectMounts(virCgroupPtr group, > static int > virCgroupV2DetectPlacement(virCgroupPtr group, > const char *path, > - const char *controllers ATTRIBUTE_UNUSED, > + const char *controllers, > const char *selfpath) > { > if (group->unified.placement) > return 0; > > + /* controllers="" indicates the cgroupv2 controller path */ > + if (STRNEQ_NULLABLE(controllers, "")) > + return 0; Fixes the issue reported by several users and looks reasonable. I would use /* controllers == "" ...*/ to mach the following comment and there is no need to use STRNEQ_NULLABLE as the caller already checks if !controllers. Reviewed-by: Pavel Hrdina <phrdina@xxxxxxxxxx>
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