cgroups_linux.go

Documentation: k8s.io/kubernetes/pkg/kubelet/cm/util

     1  /*
     2  Copyright 2016 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package util
    18  
    19  import (
    20  	"path/filepath"
    21  
    22  	libcontainercgroups "github.com/opencontainers/runc/libcontainer/cgroups"
    23  	libcontainerutils "github.com/opencontainers/runc/libcontainer/utils"
    24  )
    25  
    26  const (
    27  	// CgroupRoot is the base path where cgroups are mounted
    28  	CgroupRoot = "/sys/fs/cgroup"
    29  )
    30  
    31  // GetPids gets pids of the desired cgroup
    32  // Forked from opencontainers/runc/libcontainer/cgroup/fs.Manager.GetPids()
    33  func GetPids(cgroupPath string) ([]int, error) {
    34  	dir := ""
    35  
    36  	if libcontainercgroups.IsCgroup2UnifiedMode() {
    37  		path, err := filepath.Rel("/", cgroupPath)
    38  		if err != nil {
    39  			return nil, err
    40  		}
    41  		dir = filepath.Join(CgroupRoot, path)
    42  	} else {
    43  		var err error
    44  		dir, err = getCgroupV1Path(cgroupPath)
    45  		if err != nil {
    46  			return nil, err
    47  		}
    48  	}
    49  	return libcontainercgroups.GetPids(dir)
    50  }
    51  
    52  // getCgroupV1Path gets the file path to the "devices" subsystem of the desired cgroup.
    53  // cgroupPath is the path in the cgroup hierarchy.
    54  func getCgroupV1Path(cgroupPath string) (string, error) {
    55  	cgroupPath = libcontainerutils.CleanPath(cgroupPath)
    56  
    57  	mnt, root, err := libcontainercgroups.FindCgroupMountpointAndRoot(cgroupPath, "devices")
    58  	// If we didn't mount the subsystem, there is no point we make the path.
    59  	if err != nil {
    60  		return "", err
    61  	}
    62  
    63  	// If the cgroup name/path is absolute do not look relative to the cgroup of the init process.
    64  	if filepath.IsAbs(cgroupPath) {
    65  		// Sometimes subsystems can be mounted together as 'cpu,cpuacct'.
    66  		return filepath.Join(root, mnt, cgroupPath), nil
    67  	}
    68  
    69  	parentPath, err := getCgroupV1ParentPath(mnt, root)
    70  	if err != nil {
    71  		return "", err
    72  	}
    73  
    74  	return filepath.Join(parentPath, cgroupPath), nil
    75  }
    76  
    77  // getCgroupV1ParentPath gets the parent filepath to this cgroup, for resolving relative cgroup paths.
    78  func getCgroupV1ParentPath(mountpoint, root string) (string, error) {
    79  	// Use GetThisCgroupDir instead of GetInitCgroupDir, because the creating
    80  	// process could in container and shared pid namespace with host, and
    81  	// /proc/1/cgroup could point to whole other world of cgroups.
    82  	initPath, err := libcontainercgroups.GetOwnCgroup("devices")
    83  	if err != nil {
    84  		return "", err
    85  	}
    86  	// This is needed for nested containers, because in /proc/self/cgroup we
    87  	// see paths from host, which don't exist in container.
    88  	relDir, err := filepath.Rel(root, initPath)
    89  	if err != nil {
    90  		return "", err
    91  	}
    92  	return filepath.Join(mountpoint, relDir), nil
    93  }
    94
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