libct/cg/fs2: fix/unify parsing errors

This builds on top of recently introduced fscommon.ParseError.

Errors returned from parsers (mostly ones used by GetStats()) are all
different, and many are incomplete. For example, in many cases errors
from strconv.ParseUint are returned as is, meaning there is no context
telling which file we were reading. Similarly, errors from
fscommon.ParseKeyValue should be wrapped to add more context.
Same is true for scanner.Err().

OTOH, errors from fscommon.GetCgroup* do have enough context and there
is no need to wrap them.

Fix all the above.

While at it, add missing scanner.Err() checks.

[v2: use parseError, not ParseError]

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/cgroups/fs2/cpu.go

@@ -49,7 +49,8 @@ func setCpu(dirPath string, r *configs.Resources) error {
 }
 
 func statCpu(dirPath string, stats *cgroups.Stats) error {
-	f, err := cgroups.OpenFile(dirPath, "cpu.stat", os.O_RDONLY)
+	const file = "cpu.stat"
+	f, err := cgroups.OpenFile(dirPath, file, os.O_RDONLY)
 	if err != nil {
 		return err
 	}
@@ -59,7 +60,7 @@ func statCpu(dirPath string, stats *cgroups.Stats) error {
 	for sc.Scan() {
 		t, v, err := fscommon.ParseKeyValue(sc.Text())
 		if err != nil {
-			return err
+			return &parseError{Path: dirPath, File: file, Err: err}
 		}
 		switch t {
 		case "usage_usec":
@@ -81,5 +82,8 @@ func statCpu(dirPath string, stats *cgroups.Stats) error {
 			stats.CpuStats.ThrottlingData.ThrottledTime = v * 1000
 		}
 	}
+	if err := sc.Err(); err != nil {
+		return &parseError{Path: dirPath, File: file, Err: err}
+	}
 	return nil
 }

libcontainer/cgroups/fs2/fs2.go

@@ -13,6 +13,8 @@ import (
 	"github.com/pkg/errors"
 )
 
+type parseError = fscommon.ParseError
+
 type manager struct {
 	config *configs.Cgroup
 	// dirPath is like "/sys/fs/cgroup/user.slice/user-1001.slice/session-1.scope"

libcontainer/cgroups/fs2/hugetlb.go

@@ -46,7 +46,7 @@ func statHugeTlb(dirPath string, stats *cgroups.Stats) error {
 		fileName := "hugetlb." + pagesize + ".events"
 		value, err = fscommon.GetValueByKey(dirPath, fileName, "max")
 		if err != nil {
-			return errors.Wrap(err, "failed to read stats")
+			return err
 		}
 		hugetlbStats.Failcnt = value
 

libcontainer/cgroups/fs2/io.go

@@ -117,13 +117,14 @@ func readCgroup2MapFile(dirPath string, name string) (map[string][]string, error
 		ret[parts[0]] = parts[1:]
 	}
 	if err := scanner.Err(); err != nil {
-		return nil, err
+		return nil, &parseError{Path: dirPath, File: name, Err: err}
 	}
 	return ret, nil
 }
 
 func statIo(dirPath string, stats *cgroups.Stats) error {
-	values, err := readCgroup2MapFile(dirPath, "io.stat")
+	const file = "io.stat"
+	values, err := readCgroup2MapFile(dirPath, file)
 	if err != nil {
 		return err
 	}
@@ -136,11 +137,11 @@ func statIo(dirPath string, stats *cgroups.Stats) error {
 		}
 		major, err := strconv.ParseUint(d[0], 10, 64)
 		if err != nil {
-			return err
+			return &parseError{Path: dirPath, File: file, Err: err}
 		}
 		minor, err := strconv.ParseUint(d[1], 10, 64)
 		if err != nil {
-			return err
+			return &parseError{Path: dirPath, File: file, Err: err}
 		}
 
 		for _, item := range v {
@@ -177,7 +178,7 @@ func statIo(dirPath string, stats *cgroups.Stats) error {
 
 			value, err := strconv.ParseUint(d[1], 10, 64)
 			if err != nil {
-				return err
+				return &parseError{Path: dirPath, File: file, Err: err}
 			}
 
 			entry := cgroups.BlkioStatEntry{

libcontainer/cgroups/fs2/memory.go

@@ -75,8 +75,8 @@ func setMemory(dirPath string, r *configs.Resources) error {
 }
 
 func statMemory(dirPath string, stats *cgroups.Stats) error {
-	// Set stats from memory.stat.
-	statsFile, err := cgroups.OpenFile(dirPath, "memory.stat", os.O_RDONLY)
+	const file = "memory.stat"
+	statsFile, err := cgroups.OpenFile(dirPath, file, os.O_RDONLY)
 	if err != nil {
 		return err
 	}
@@ -86,10 +86,13 @@ func statMemory(dirPath string, stats *cgroups.Stats) error {
 	for sc.Scan() {
 		t, v, err := fscommon.ParseKeyValue(sc.Text())
 		if err != nil {
-			return errors.Wrapf(err, "failed to parse memory.stat (%q)", sc.Text())
+			return &parseError{Path: dirPath, File: file, Err: err}
 		}
 		stats.MemoryStats.Stats[t] = v
 	}
+	if err := sc.Err(); err != nil {
+		return &parseError{Path: dirPath, File: file, Err: err}
+	}
 	stats.MemoryStats.Cache = stats.MemoryStats.Stats["file"]
 	// Unlike cgroup v1 which has memory.use_hierarchy binary knob,
 	// cgroup v2 is always hierarchical.
@@ -139,13 +142,13 @@ func getMemoryDataV2(path, name string) (cgroups.MemoryData, error) {
 			// swapaccount=0 kernel boot parameter is given.
 			return cgroups.MemoryData{}, nil
 		}
-		return cgroups.MemoryData{}, errors.Wrapf(err, "failed to parse %s", usage)
+		return cgroups.MemoryData{}, err
 	}
 	memoryData.Usage = value
 
 	value, err = fscommon.GetCgroupParamUint(path, limit)
 	if err != nil {
-		return cgroups.MemoryData{}, errors.Wrapf(err, "failed to parse %s", limit)
+		return cgroups.MemoryData{}, err
 	}
 	memoryData.Limit = value
 
@@ -153,7 +156,8 @@ func getMemoryDataV2(path, name string) (cgroups.MemoryData, error) {
 }
 
 func statsFromMeminfo(stats *cgroups.Stats) error {
-	f, err := os.Open("/proc/meminfo")
+	const file = "/proc/meminfo"
+	f, err := os.Open(file)
 	if err != nil {
 		return err
 	}
@@ -190,7 +194,7 @@ func statsFromMeminfo(stats *cgroups.Stats) error {
 		vStr := strings.TrimSpace(strings.TrimSuffix(parts[1], " kB"))
 		*p, err = strconv.ParseUint(vStr, 10, 64)
 		if err != nil {
-			return errors.Wrap(err, "parsing /proc/meminfo "+k)
+			return &parseError{File: file, Err: errors.New("bad value for " + k)}
 		}
 
 		found++
@@ -199,8 +203,8 @@ func statsFromMeminfo(stats *cgroups.Stats) error {
 			break
 		}
 	}
-	if sc.Err() != nil {
-		return sc.Err()
+	if err := sc.Err(); err != nil {
+		return &parseError{Path: "", File: file, Err: err}
 	}
 
 	stats.MemoryStats.SwapUsage.Usage = (swap_total - swap_free) * 1024