* fix(mount): count manifest sizes in merge condition to prevent manifest accumulation
shouldMergeChunks only counted non-manifest chunk sizes toward the bloat
threshold, so overlapping manifests accumulated undetected across flush
cycles.
During sustained random writes (e.g. fio), each metadata flush compacts
non-manifest chunks and may group them into a new manifest via
MaybeManifestize, while carrying forward all existing manifests. Since
the merge condition only checked non-manifest totals against 2x file
size, the growing pile of redundant manifests never triggered a merge.
In a real workload: 4 GB file, 25 manifests each covering ~4 GB
(107 GB manifest data on volume servers), but shouldMergeChunks saw only
4.2 GB of non-manifest chunks vs the 8.6 GB threshold -- no merge.
Fix: include manifest coverage sizes in totalChunkSize. This correctly
detects the 111 GB total vs 8.6 GB threshold and triggers the merge,
which re-reads the file as clean chunks and lets the filer's MinusChunks
(which resolves manifests) garbage-collect all redundant sub-chunks.
* test(mount,filer): add manifest chunk correctness tests
Filer-level tests (filechunk_manifest_test.go):
- TestManifestRoundTripPreservesChunks: create -> serialize -> deserialize
preserves fileId, offset, size, and timestamp for all sub-chunks
- TestCompactResolvedOverlappingManifests: two manifests covering the same
range, older sub-chunks correctly identified as garbage after compaction
- TestDoMinusChunksWithResolvedManifests: old manifest sub-chunks detected
as garbage when compared against new clean chunks (mirrors filer cleanup)
- TestManifestizeSmallBatchWithRemainder: batch=3 with 7 chunks produces
2 manifests + 1 remainder, all data recoverable after resolve
- TestCompactMultipleOverlappingManifestGenerations: 5 generations of
full-file manifests, compaction keeps only the newest generation
- TestManifestBloatDetection: with N overlapping manifests, merge triggers
at N >= 2 (stored > 2x file size)
Mount-level test (weedfs_file_sync_test.go):
- TestFlushCycleManifestAccumulation: simulates the flushMetadataToFiler
pipeline over multiple cycles with a small manifest batch (5 chunks).
Verifies merge triggers at cycle 2 when accumulated manifests exceed
the 2x threshold. Uses SeparateManifestChunks + CompactFileChunks +
shouldMergeChunks to mirror the real code path.