From 17fe96e6201142b0901f07a2ca7e1c3351b1a394 Mon Sep 17 00:00:00 2001
From: Chris Lu <chris.lu@gmail.com>
Date: Mon, 10 Aug 2026 18:42:53 -0700
Subject: [PATCH] filer: fingerprint every read-relevant chunk field

The layout binding hashed only offset and file id, so a mutation that
kept both - a truncate shrinking chunk.Size, then a sparse extend back
to the original length - passed both the size and fingerprint checks
and served a stale view. Digest size, modification timestamp, cipher
key, compression, manifest status, and SSE type as well.
---
 weed/server/filer_server_format.go      |  8 ++++++--
 weed/server/filer_server_format_test.go | 22 ++++++++++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/weed/server/filer_server_format.go b/weed/server/filer_server_format.go
index 0c91b92fa..d334ccc05 100644
--- a/weed/server/filer_server_format.go
+++ b/weed/server/filer_server_format.go
@@ -45,11 +45,15 @@ const (
 	defaultFormatChunkSizeMB = 4
 )
 
-// formatChunkIdentity digests the chunk list a layout was written against.
+// formatChunkIdentity digests the chunk list a layout was written against,
+// covering every field that changes what a read returns: a FUSE truncate, for
+// one, mutates Size while keeping the chunk's id.
 func formatChunkIdentity(chunks []*filer_pb.FileChunk) []byte {
 	digest := md5.New()
 	for _, chunk := range chunks {
-		fmt.Fprintf(digest, "%d:%s;", chunk.Offset, chunk.GetFileIdString())
+		fmt.Fprintf(digest, "%d:%s:%d:%d:%x:%t:%t:%d;",
+			chunk.Offset, chunk.GetFileIdString(), chunk.Size, chunk.ModifiedTsNs,
+			chunk.CipherKey, chunk.IsCompressed, chunk.IsChunkManifest, chunk.SseType)
 	}
 	return digest.Sum(nil)
 }
diff --git a/weed/server/filer_server_format_test.go b/weed/server/filer_server_format_test.go
index e980d3406..f95d0e596 100644
--- a/weed/server/filer_server_format_test.go
+++ b/weed/server/filer_server_format_test.go
@@ -68,4 +68,26 @@ func TestFormatChunkIdentity(t *testing.T) {
 	if bytes.Equal(identity, formatChunkIdentity(changedOffset)) {
 		t.Fatalf("identity ignored an offset change")
 	}
+	// a truncate mutates Size while keeping the chunk id
+	changedSize := []*filer_pb.FileChunk{
+		{FileId: "1,ab", Offset: 0, Size: 10},
+		{FileId: "2,cd", Offset: 10, Size: 15},
+	}
+	if bytes.Equal(identity, formatChunkIdentity(changedSize)) {
+		t.Fatalf("identity ignored a size change")
+	}
+	changedMtime := []*filer_pb.FileChunk{
+		{FileId: "1,ab", Offset: 0, Size: 10},
+		{FileId: "2,cd", Offset: 10, Size: 20, ModifiedTsNs: 7},
+	}
+	if bytes.Equal(identity, formatChunkIdentity(changedMtime)) {
+		t.Fatalf("identity ignored a modification timestamp change")
+	}
+	changedManifest := []*filer_pb.FileChunk{
+		{FileId: "1,ab", Offset: 0, Size: 10},
+		{FileId: "2,cd", Offset: 10, Size: 20, IsChunkManifest: true},
+	}
+	if bytes.Equal(identity, formatChunkIdentity(changedManifest)) {
+		t.Fatalf("identity ignored a manifest flag change")
+	}
 }