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| 1 | +// +build freebsd |
| 2 | + |
| 3 | +/* |
| 4 | + Copyright The containerd Authors. |
| 5 | +
|
| 6 | + Licensed under the Apache License, Version 2.0 (the "License"); |
| 7 | + you may not use this file except in compliance with the License. |
| 8 | + You may obtain a copy of the License at |
| 9 | +
|
| 10 | + http://www.apache.org/licenses/LICENSE-2.0 |
| 11 | +
|
| 12 | + Unless required by applicable law or agreed to in writing, software |
| 13 | + distributed under the License is distributed on an "AS IS" BASIS, |
| 14 | + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 15 | + See the License for the specific language governing permissions and |
| 16 | + limitations under the License. |
| 17 | +*/ |
| 18 | + |
| 19 | +package mount |
| 20 | + |
| 21 | +import ( |
| 22 | + "os" |
| 23 | + "os/exec" |
| 24 | + "time" |
| 25 | + |
| 26 | + "github.com/pkg/errors" |
| 27 | + "golang.org/x/sys/unix" |
| 28 | +) |
| 29 | + |
| 30 | +var ( |
| 31 | + // ErrNotImplementOnUnix is returned for methods that are not implemented |
| 32 | + ErrNotImplementOnUnix = errors.New("not implemented under unix") |
| 33 | +) |
| 34 | + |
| 35 | +// Mount to the provided target path. |
| 36 | +func (m *Mount) Mount(target string) error { |
| 37 | + // The "syscall" and "golang.org/x/sys/unix" packages do not define a Mount |
| 38 | + // function for FreeBSD, so instead we execute mount(8) and trust it to do |
| 39 | + // the right thing |
| 40 | + return m.mountWithHelper(target) |
| 41 | +} |
| 42 | + |
| 43 | +func (m *Mount) mountWithHelper(target string) error { |
| 44 | + // target: "/foo/target" |
| 45 | + // command: "mount -o ro -t nullfs /foo/source /foo/merged" |
| 46 | + // Note: FreeBSD mount(8) is particular about the order of flags and arguments |
| 47 | + var args []string |
| 48 | + for _, o := range m.Options { |
| 49 | + args = append(args, "-o", o) |
| 50 | + } |
| 51 | + args = append(args, "-t", m.Type) |
| 52 | + args = append(args, m.Source, target) |
| 53 | + |
| 54 | + infoBeforeMount, err := Lookup(target) |
| 55 | + if err != nil { |
| 56 | + return err |
| 57 | + } |
| 58 | + |
| 59 | + // cmd.CombinedOutput() may intermittently return ECHILD because of our signal handling in shim. |
| 60 | + // See #4387 and wait(2). |
| 61 | + const retriesOnECHILD = 10 |
| 62 | + for i := 0; i < retriesOnECHILD; i++ { |
| 63 | + cmd := exec.Command("mount", args...) |
| 64 | + out, err := cmd.CombinedOutput() |
| 65 | + if err == nil { |
| 66 | + return nil |
| 67 | + } |
| 68 | + if !errors.Is(err, unix.ECHILD) { |
| 69 | + return errors.Wrapf(err, "mount [%v] failed: %q", args, string(out)) |
| 70 | + } |
| 71 | + // We got ECHILD, we are not sure whether the mount was successful. |
| 72 | + // If the mount ID has changed, we are sure we got some new mount, but still not sure it is fully completed. |
| 73 | + // So we attempt to unmount the new mount before retrying. |
| 74 | + infoAfterMount, err := Lookup(target) |
| 75 | + if err != nil { |
| 76 | + return err |
| 77 | + } |
| 78 | + if infoAfterMount.ID != infoBeforeMount.ID { |
| 79 | + _ = unmount(target, 0) |
| 80 | + } |
| 81 | + } |
| 82 | + return errors.Errorf("mount [%v] failed with ECHILD (retired %d times)", args, retriesOnECHILD) |
| 83 | +} |
| 84 | + |
| 85 | +// Unmount the provided mount path with the flags |
| 86 | +func Unmount(target string, flags int) error { |
| 87 | + if err := unmount(target, flags); err != nil && err != unix.EINVAL { |
| 88 | + return err |
| 89 | + } |
| 90 | + return nil |
| 91 | +} |
| 92 | + |
| 93 | +func unmount(target string, flags int) error { |
| 94 | + for i := 0; i < 50; i++ { |
| 95 | + if err := unix.Unmount(target, flags); err != nil { |
| 96 | + switch err { |
| 97 | + case unix.EBUSY: |
| 98 | + time.Sleep(50 * time.Millisecond) |
| 99 | + continue |
| 100 | + default: |
| 101 | + return err |
| 102 | + } |
| 103 | + } |
| 104 | + return nil |
| 105 | + } |
| 106 | + return errors.Wrapf(unix.EBUSY, "failed to unmount target %s", target) |
| 107 | +} |
| 108 | + |
| 109 | +// UnmountAll repeatedly unmounts the given mount point until there |
| 110 | +// are no mounts remaining (EINVAL is returned by mount), which is |
| 111 | +// useful for undoing a stack of mounts on the same mount point. |
| 112 | +// UnmountAll all is noop when the first argument is an empty string. |
| 113 | +// This is done when the containerd client did not specify any rootfs |
| 114 | +// mounts (e.g. because the rootfs is managed outside containerd) |
| 115 | +// UnmountAll is noop when the mount path does not exist. |
| 116 | +func UnmountAll(mount string, flags int) error { |
| 117 | + if mount == "" { |
| 118 | + return nil |
| 119 | + } |
| 120 | + if _, err := os.Stat(mount); os.IsNotExist(err) { |
| 121 | + return nil |
| 122 | + } |
| 123 | + |
| 124 | + for { |
| 125 | + if err := unmount(mount, flags); err != nil { |
| 126 | + // EINVAL is returned if the target is not a |
| 127 | + // mount point, indicating that we are |
| 128 | + // done. It can also indicate a few other |
| 129 | + // things (such as invalid flags) which we |
| 130 | + // unfortunately end up squelching here too. |
| 131 | + if err == unix.EINVAL { |
| 132 | + return nil |
| 133 | + } |
| 134 | + return err |
| 135 | + } |
| 136 | + } |
| 137 | +} |
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