paths.go (2769B)
1 /* 2 Copyright The containerd 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 cgroup1 18 19 import ( 20 "errors" 21 "fmt" 22 "path/filepath" 23 ) 24 25 type Path func(subsystem Name) (string, error) 26 27 func RootPath(subsystem Name) (string, error) { 28 return "/", nil 29 } 30 31 // StaticPath returns a static path to use for all cgroups 32 func StaticPath(path string) Path { 33 return func(_ Name) (string, error) { 34 return path, nil 35 } 36 } 37 38 // NestedPath will nest the cgroups based on the calling processes cgroup 39 // placing its child processes inside its own path 40 func NestedPath(suffix string) Path { 41 paths, err := ParseCgroupFile("/proc/self/cgroup") 42 if err != nil { 43 return errorPath(err) 44 } 45 return existingPath(paths, suffix) 46 } 47 48 // PidPath will return the correct cgroup paths for an existing process running inside a cgroup 49 // This is commonly used for the Load function to restore an existing container 50 func PidPath(pid int) Path { 51 p := fmt.Sprintf("/proc/%d/cgroup", pid) 52 paths, err := ParseCgroupFile(p) 53 if err != nil { 54 return errorPath(fmt.Errorf("parse cgroup file %s: %w", p, err)) 55 } 56 return existingPath(paths, "") 57 } 58 59 // ErrControllerNotActive is returned when a controller is not supported or enabled 60 var ErrControllerNotActive = errors.New("controller is not supported") 61 62 func existingPath(paths map[string]string, suffix string) Path { 63 // localize the paths based on the root mount dest for nested cgroups 64 for n, p := range paths { 65 dest, err := getCgroupDestination(n) 66 if err != nil { 67 return errorPath(err) 68 } 69 rel, err := filepath.Rel(dest, p) 70 if err != nil { 71 return errorPath(err) 72 } 73 if rel == "." { 74 rel = dest 75 } 76 paths[n] = filepath.Join("/", rel) 77 } 78 return func(name Name) (string, error) { 79 root, ok := paths[string(name)] 80 if !ok { 81 if root, ok = paths["name="+string(name)]; !ok { 82 return "", ErrControllerNotActive 83 } 84 } 85 if suffix != "" { 86 return filepath.Join(root, suffix), nil 87 } 88 return root, nil 89 } 90 } 91 92 func subPath(path Path, subName string) Path { 93 return func(name Name) (string, error) { 94 p, err := path(name) 95 if err != nil { 96 return "", err 97 } 98 return filepath.Join(p, subName), nil 99 } 100 } 101 102 func errorPath(err error) Path { 103 return func(_ Name) (string, error) { 104 return "", err 105 } 106 }