fix: retain quorate null versions after newer minorities

Recount only when the existing selection is below quorum and each original nonempty stream has one ordinary null version with identical EC headers. Reuse the existing header grouping and leave history pruning unchanged. Add deterministic signed LIST, complete-metadata permutation, excluded-history, object-read, scanner/heal, Walk and migration-consumer regressions. Signed-off-by: Feng Ruohang <rh@vonng.com> (cherry picked from commit 9804e4deb4d5a18cca640be72bff9b47a415f7de) Signed-off-by: Feng Ruohang <rh@vonng.com>
2026-10-09 03:05:59 +03:00 · 2026-09-16 21:07:17 +08:00
parent fced863036
commit 8d06424b12
3 changed files with 789 additions and 35 deletions
@@ -1941,6 +1941,10 @@ func mergeXLV2Versions(quorum int, strict bool, requestedVersions int, versions
 		// No need for non-strict checks if quorum is 1.
 		strict = true
 	}
+	// Keep the original stream shapes: pruning must not make a versioned object
+	// eligible for the single null-version recount below.
+	originalVersions := versions
+	var checkedSingleNull, singleNull bool
 	// Shallow copy input
 	versions = append(make([][]xlMetaV2ShallowVersion, 0, len(versions)), versions...)

@@ -2015,44 +2019,23 @@ func mergeXLV2Versions(quorum int, strict bool, requestedVersions int, versions
 					// Version IDs match, but otherwise unable to resolve.
 					// We are either strict, or don't have enough information to match.
 					// Switch to a pure counting algo.
-					x := make(map[xlMetaV2VersionHeader]int, len(tops))
-					for _, a := range tops {
-						if a.header.VersionID != ver.header.VersionID {
-							continue
-						}
-						if !strict {
-							// we must match EC, when we are not strict.
-							if !a.header.matchesEC(ver.header) {
-								continue
-							}
-
-							a.header.Signature = [4]byte{}
-						}
-						x[a.header]++
-					}
-					latestCount = 0
-					for k, v := range x {
-						if v < latestCount {
-							continue
-						}
-						if v == latestCount && latest.header.sortsBefore(k) {
-							// Tiebreak, use sort.
-							continue
-						}
-						for _, a := range tops {
-							hdr := a.header
-							if !strict {
-								hdr.Signature = [4]byte{}
-							}
-							if hdr == k {
-								latest = a
-							}
-						}
-						latestCount = v
-					}
+					latest, latestCount = countXLV2Versions(tops, ver.header, latest, strict)
 					break
 				}
 			}
+			if latestCount < quorum {
+				if !checkedSingleNull {
+					singleNull = singleNullVersionStreams(originalVersions)
+					checkedSingleNull = true
+				}
+				if singleNull {
+					// A newer minority at the end can hide an older quorum from
+					// the selection loop. Recount before discarding the null ID.
+					if candidate, count := countXLV2Versions(tops, latest.header, latest, strict); count >= quorum {
+						latest, latestCount = candidate, count
+					}
+				}
+			}
 			if latestCount >= quorum {
 				merged = append(merged, latest)

@@ -2113,6 +2096,70 @@ func mergeXLV2Versions(quorum int, strict bool, requestedVersions int, versions
 	return merged
 }

+// singleNullVersionStreams excludes histories and other version types from the
+// additional recount. Check the original inputs, before any stream is pruned.
+func singleNullVersionStreams(versions [][]xlMetaV2ShallowVersion) bool {
+	var ec xlMetaV2VersionHeader
+	var haveEC bool
+	for _, stream := range versions {
+		if len(stream) == 0 {
+			continue
+		}
+		if len(stream) != 1 {
+			return false
+		}
+		h := stream[0].header
+		if h.VersionID != [16]byte{} || h.Type != ObjectType || h.FreeVersion() {
+			return false
+		}
+		if haveEC && (h.EcN != ec.EcN || h.EcM != ec.EcM) {
+			return false
+		}
+		ec, haveEC = h, true
+	}
+	return haveEC
+}
+
+// countXLV2Versions selects the most frequent compatible header for reference's
+// VersionID, retaining the existing sort tiebreak and last matching entry.
+func countXLV2Versions(tops []xlMetaV2ShallowVersion, reference xlMetaV2VersionHeader, latest xlMetaV2ShallowVersion, strict bool) (xlMetaV2ShallowVersion, int) {
+	x := make(map[xlMetaV2VersionHeader]int, len(tops))
+	for _, a := range tops {
+		if a.header.VersionID != reference.VersionID {
+			continue
+		}
+		if !strict {
+			// we must match EC, when we are not strict.
+			if !a.header.matchesEC(reference) {
+				continue
+			}
+			a.header.Signature = [4]byte{}
+		}
+		x[a.header]++
+	}
+	var latestCount int
+	for k, v := range x {
+		if v < latestCount {
+			continue
+		}
+		if v == latestCount && latest.header.sortsBefore(k) {
+			// Tiebreak, use sort.
+			continue
+		}
+		for _, a := range tops {
+			hdr := a.header
+			if !strict {
+				hdr.Signature = [4]byte{}
+			}
+			if hdr == k {
+				latest = a
+			}
+		}
+		latestCount = v
+	}
+	return latest, latestCount
+}
+
 type xlMetaBuf []byte

 // ToFileInfo converts xlMetaV2 into a common FileInfo datastructure