util: Move supported version check to util

as we need to reuse the same code for both cephfs
and rbd moving the supported version check function
to util package, for better readability renamed
the function.

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

internal/util/util.go

@@ -21,6 +21,7 @@ import (
 	"math"
 	"os"
 	"path"
+	"strconv"
 	"strings"
 	"time"
 
@@ -151,6 +152,90 @@ func KernelVersion() (string, error) {
 	return strings.TrimRight(string(utsname.Release[:]), "\x00"), nil
 }
 
+// KernelVersion holds kernel related informations
+type KernelVersion struct {
+	Version      int
+	PatchLevel   int
+	SubLevel     int
+	ExtraVersion int    // prefix of the part after the first "-"
+	Distribution string // component of full extraversion
+	Backport     bool   // backports have a fixed version/patchlevel/sublevel
+}
+
+// CheckKernelSupport checks the running kernel and comparing it to known
+// versions that have support for required features . Distributors of
+// enterprise Linux have backported quota support to previous versions. This
+// function checks if the running kernel is one of the versions that have the
+// feature/fixes backported.
+//
+// `uname -r` (or Uname().Utsname.Release has a format like 1.2.3-rc.vendor
+// This can be slit up in the following components: - version (1) - patchlevel
+// (2) - sublevel (3) - optional, defaults to 0 - extraversion (rc) - optional,
+// matching integers only - distribution (.vendor) - optional, match against
+// whole `uname -r` string
+//
+// For matching multiple versions, the kernelSupport type contains a backport
+// bool, which will cause matching
+// version+patchlevel+sublevel+(>=extraversion)+(~distribution)
+//
+// In case the backport bool is false, a simple check for higher versions than
+// version+patchlevel+sublevel is done.
+func CheckKernelSupport(release string, supportedVersions []KernelVersion) bool {
+	vers := strings.Split(strings.SplitN(release, "-", 2)[0], ".")
+	version, err := strconv.Atoi(vers[0])
+	if err != nil {
+		klog.Errorf("failed to parse version from %s: %v", release, err)
+		return false
+	}
+	patchlevel, err := strconv.Atoi(vers[1])
+	if err != nil {
+		klog.Errorf("failed to parse patchlevel from %s: %v", release, err)
+		return false
+	}
+	sublevel := 0
+	if len(vers) >= 3 {
+		sublevel, err = strconv.Atoi(vers[2])
+		if err != nil {
+			klog.Errorf("failed to parse sublevel from %s: %v", release, err)
+			return false
+		}
+	}
+	extra := strings.SplitN(release, "-", 2)
+	extraversion := 0
+	if len(extra) == 2 {
+		// ignore errors, 1st component of extraversion does not need to be an int
+		extraversion, err = strconv.Atoi(strings.Split(extra[1], ".")[0])
+		if err != nil {
+			// "go lint" wants err to be checked...
+			extraversion = 0
+		}
+	}
+
+	// compare running kernel against known versions
+	for _, kernel := range supportedVersions {
+		if !kernel.Backport {
+			// deal with the default case(s), find >= match for version, patchlevel, sublevel
+			if version > kernel.Version || (version == kernel.Version && patchlevel > kernel.PatchLevel) ||
+				(version == kernel.Version && patchlevel == kernel.PatchLevel && sublevel >= kernel.SubLevel) {
+				return true
+			}
+		} else {
+			// specific backport, match distribution initially
+			if !strings.Contains(release, kernel.Distribution) {
+				continue
+			}
+
+			// strict match version, patchlevel, sublevel, and >= match extraversion
+			if version == kernel.Version && patchlevel == kernel.PatchLevel &&
+				sublevel == kernel.SubLevel && extraversion >= kernel.ExtraVersion {
+				return true
+			}
+		}
+	}
+	klog.Errorf("kernel %s does not support required features", release)
+	return false
+}
+
 // GenerateVolID generates a volume ID based on passed in parameters and version, to be returned
 // to the CO system
 func GenerateVolID(ctx context.Context, monitors string, cr *Credentials, locationID int64, pool, clusterID, objUUID string, volIDVersion uint16) (string, error) {