new "image" mount type

Add a new "image" mount type to `--mount`.  The source of the mount is
the name or ID of an image.  The destination is the path inside the
container.  Image mounts further support an optional `rw,readwrite`
parameter which if set to "true" will yield the mount writable inside
the container.  Note that no changes are propagated to the image mount
on the host (which in any case is read only).

Mounts are overlay mounts.  To support read-only overlay mounts, vendor
a non-release version of Buildah.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

vendor/github.com/prometheus/procfs/schedstat.go

@@ -1,118 +0,0 @@
-// Copyright 2019 The Prometheus Authors
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package procfs
-
-import (
-	"bufio"
-	"errors"
-	"os"
-	"regexp"
-	"strconv"
-)
-
-var (
-	cpuLineRE  = regexp.MustCompile(`cpu(\d+) (\d+) (\d+) (\d+) (\d+) (\d+) (\d+) (\d+) (\d+) (\d+)`)
-	procLineRE = regexp.MustCompile(`(\d+) (\d+) (\d+)`)
-)
-
-// Schedstat contains scheduler statistics from /proc/schedstat
-//
-// See
-// https://www.kernel.org/doc/Documentation/scheduler/sched-stats.txt
-// for a detailed description of what these numbers mean.
-//
-// Note the current kernel documentation claims some of the time units are in
-// jiffies when they are actually in nanoseconds since 2.6.23 with the
-// introduction of CFS. A fix to the documentation is pending. See
-// https://lore.kernel.org/patchwork/project/lkml/list/?series=403473
-type Schedstat struct {
-	CPUs []*SchedstatCPU
-}
-
-// SchedstatCPU contains the values from one "cpu<N>" line
-type SchedstatCPU struct {
-	CPUNum string
-
-	RunningNanoseconds uint64
-	WaitingNanoseconds uint64
-	RunTimeslices      uint64
-}
-
-// ProcSchedstat contains the values from /proc/<pid>/schedstat
-type ProcSchedstat struct {
-	RunningNanoseconds uint64
-	WaitingNanoseconds uint64
-	RunTimeslices      uint64
-}
-
-// Schedstat reads data from /proc/schedstat
-func (fs FS) Schedstat() (*Schedstat, error) {
-	file, err := os.Open(fs.proc.Path("schedstat"))
-	if err != nil {
-		return nil, err
-	}
-	defer file.Close()
-
-	stats := &Schedstat{}
-	scanner := bufio.NewScanner(file)
-
-	for scanner.Scan() {
-		match := cpuLineRE.FindStringSubmatch(scanner.Text())
-		if match != nil {
-			cpu := &SchedstatCPU{}
-			cpu.CPUNum = match[1]
-
-			cpu.RunningNanoseconds, err = strconv.ParseUint(match[8], 10, 64)
-			if err != nil {
-				continue
-			}
-
-			cpu.WaitingNanoseconds, err = strconv.ParseUint(match[9], 10, 64)
-			if err != nil {
-				continue
-			}
-
-			cpu.RunTimeslices, err = strconv.ParseUint(match[10], 10, 64)
-			if err != nil {
-				continue
-			}
-
-			stats.CPUs = append(stats.CPUs, cpu)
-		}
-	}
-
-	return stats, nil
-}
-
-func parseProcSchedstat(contents string) (stats ProcSchedstat, err error) {
-	match := procLineRE.FindStringSubmatch(contents)
-
-	if match != nil {
-		stats.RunningNanoseconds, err = strconv.ParseUint(match[1], 10, 64)
-		if err != nil {
-			return
-		}
-
-		stats.WaitingNanoseconds, err = strconv.ParseUint(match[2], 10, 64)
-		if err != nil {
-			return
-		}
-
-		stats.RunTimeslices, err = strconv.ParseUint(match[3], 10, 64)
-		return
-	}
-
-	err = errors.New("could not parse schedstat")
-	return
-}