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pkg/cri/server: optimizations in unmountRecursive()

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Use a PrefixFilter() to get only the mounts we're interested in,
which removes the need to manually filter mounts from the mountinfo
results.

Additional optimizations can be made, as:

> ... there's a little known fact that `umount(MNT_DETACH)` is actually
> recursive in Linux, IOW this function can be replaced with
> `unix.Umount(target, unix.MNT_DETACH)` (or `mount.UnmountAll(target, unix.MNT_DETACH)`
>  (provided that target itself is a mount point).

e8fb2c392f (r535450446)

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This commit is contained in:
Sebastiaan van Stijn
2020-12-07 11:37:29 +01:00
parent 7572919201
commit 2374178c9b
1 changed files with 5 additions and 16 deletions
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21
pkg/cri/server/helpers_linux.go
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@@ -166,34 +166,23 @@ func openLogFile(path string) (*os.File, error) {
// unmountRecursive unmounts the target and all mounts underneath, starting with
// the deepest mount first.
func unmountRecursive(ctx context.Context, target string) error {
mounts, err := mountinfo.GetMounts(nil)
toUnmount, err := mountinfo.GetMounts(mountinfo.PrefixFilter(target))
if err != nil {
return err
}
var toUnmount []string
for _, m := range mounts {
p, err := filepath.Rel(target, m.Mountpoint)
if err != nil {
return err
}
if !strings.HasPrefix(p, "..") {
toUnmount = append(toUnmount, m.Mountpoint)
}
}
// Make the deepest mount be first
sort.Slice(toUnmount, func(i, j int) bool {
return len(toUnmount[i]) > len(toUnmount[j])
return len(toUnmount[i].Mountpoint) > len(toUnmount[j].Mountpoint)
})
for i, mountPath := range toUnmount {
if err := mount.UnmountAll(mountPath, unix.MNT_DETACH); err != nil {
for i, m := range toUnmount {
if err := mount.UnmountAll(m.Mountpoint, unix.MNT_DETACH); err != nil {
if i == len(toUnmount)-1 { // last mount
return err
}
// This is some submount, we can ignore this error for now, the final unmount will fail if this is a real problem
log.G(ctx).WithError(err).Debugf("failed to unmount submount %s", mountPath)
log.G(ctx).WithError(err).Debugf("failed to unmount submount %s", m.Mountpoint)
}
}
return nil