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Substract source mount from cgroup dir 

This is needed because for nested containers cgroups. Without this patch
they creating unnecessary intermediate cgroup like:
/sys/fs/cgroup/memory/system.slice/docker-9409d9f0b68fb9e9d7d532d5b3f35e7c7f9cca1312af392ae3b28436f1f2998f.scope/system.slice/docker-9409d9f0b68fb9e9d7d532d5b3f35e7c7f9cca1312af392ae3b28436f1f2998f.scope/docker/908ebcc9c13584a14322ec070bd971e0de62f126c0cd95c079acdb99990ad3a3

It is because in /proc/self/cgroup we see paths from host, and they don't
exist in container.

Signed-off-by: Alexander Morozov <lk4d4@docker.com>
This commit is contained in:
Alexander Morozov 2015-07-17 11:41:54 -07:00
parent 2598484b97
commit fc31076c23
2 changed files with 30 additions and 4 deletions
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12
libcontainer/cgroups/fs/apply_raw.go
View File

@ -235,16 +235,20 @@ func getCgroupData(c *configs.Cgroup, pid int) (*data, error) {
}, nil
}
func (raw *data) parent(subsystem, mountpoint string) (string, error) {
func (raw *data) parent(subsystem, mountpoint, src string) (string, error) {
initPath, err := cgroups.GetInitCgroupDir(subsystem)
if err != nil {
return "", err
}
return filepath.Join(mountpoint, initPath), nil
relDir, err := filepath.Rel(src, initPath)
if err != nil {
return "", err
}
return filepath.Join(mountpoint, relDir), nil
}
func (raw *data) path(subsystem string) (string, error) {
mnt, err := cgroups.FindCgroupMountpoint(subsystem)
mnt, src, err := cgroups.FindCgroupMountpointAndSource(subsystem)
// If we didn't mount the subsystem, there is no point we make the path.
if err != nil {
return "", err
@ -255,7 +259,7 @@ func (raw *data) path(subsystem string) (string, error) {
return filepath.Join(raw.root, subsystem, raw.cgroup), nil
}
parent, err := raw.parent(subsystem, mnt)
parent, err := raw.parent(subsystem, mnt, src)
if err != nil {
return "", err
}

22
libcontainer/cgroups/utils.go
View File

@ -42,6 +42,28 @@ func FindCgroupMountpoint(subsystem string) (string, error) {
return "", NewNotFoundError(subsystem)
}
func FindCgroupMountpointAndSource(subsystem string) (string, string, error) {
f, err := os.Open("/proc/self/mountinfo")
if err != nil {
return "", "", err
}
scanner := bufio.NewScanner(f)
for scanner.Scan() {
txt := scanner.Text()
fields := strings.Split(txt, " ")
for _, opt := range strings.Split(fields[len(fields)-1], ",") {
if opt == subsystem {
return fields[4], fields[3], nil
}
}
}
if err := scanner.Err(); err != nil {
return "", "", err
}
return "", "", NewNotFoundError(subsystem)
}
func FindCgroupMountpointDir() (string, error) {
mounts, err := mount.GetMounts()
if err != nil {