feat(fs): measure APFS and ReFS extent sharing instead of Unknown (0.1.22) - #354
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…nknown (0.1.22) extent_sharing reported Unknown for every file on APFS and ReFS, so a caller that needs proof (zccache#1673) could never credit a freed byte on a Mac or a Dev Drive. - macOS: fgetattrlist ATTR_CMNEXT_PRIVATESIZE gives the bytes a file shares with no clone; a private size below the allocation is Shared, otherwise Exclusive. Volumes that do not report it keep the file system type fallback. - Windows: on ReFS, FSCTL_GET_RETRIEVAL_POINTERS_AND_REFCOUNT reports each extent's reference count; any allocated extent above one is Shared. NTFS/FAT stay Exclusive. - CI formats a ReFS volume on windows-2025 (KERNAL_REFS_TEST_DIR) so the block-clone path is proven, and the macOS tests require a measurement and a clone on APFS. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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…sharing (#1673) kernal-api 0.1.22 (zackees/kernal-api#354) answers extent_sharing on APFS (ATTR_CMNEXT_PRIVATESIZE) and ReFS (per-extent reference counts) instead of Unknown, so retired-store bytes are credited on macOS and Dev Drives again. Comments that said APFS/ReFS always report unknown sharing now describe unqueryable volumes instead. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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…sharing (#1673) (#1679) kernal-api 0.1.22 (zackees/kernal-api#354) answers extent_sharing on APFS (ATTR_CMNEXT_PRIVATESIZE) and ReFS (per-extent reference counts) instead of Unknown, so retired-store bytes are credited on macOS and Dev Drives again. Comments that said APFS/ReFS always report unknown sharing now describe unqueryable volumes instead. Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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Problem
platform::fs::extent_sharing(0.1.21, #353) returnedUnknownfor every file on APFS and ReFS. A caller that needs proof that deleting a file frees its space treatsUnknownas possibly shared, so zccache (zackees/zccache#1673, PR zackees/zccache#1676) could never credit a reclaimed byte on a Mac or a Windows Dev Drive. Its macOS CI fails on exactly that.Changes
fgetattrlistwithATTR_CMNEXT_PRIVATESIZE(FSOPT_ATTR_CMN_EXTENDED, macOS 10.15+) returns the bytes the file shares with no clone or snapshot. Private size < allocated (st_blocks * 512) →Shared, otherwiseExclusive. A volume that does not return the attribute (checked viaATTR_CMN_RETURNED_ATTRS) or rejects the request keeps the existing file-system-type fallback.FSCTL_GET_RETRIEVAL_POINTERS_AND_REFCOUNTreturns each extent's reference count; any allocated extent (Lcn != -1) with a count > 1 →Shared, otherwiseExclusive; paged withERROR_MORE_DATA,ERROR_HANDLE_EOF= nothing allocated. NTFS/FAT stayExclusive; any other volume, or an unsupported ioctl, staysUnknown.windows-2025test job formats a 2 GB ReFS VHDX with diskpart and exportsKERNAL_REFS_TEST_DIR, so the Windows tests require a ReFS block clone to reportSharedand a fresh fileExclusiveinstead of skipping on NTFS. The macOS tests likewise require a private-size measurement and a successfulclonefilewhenever the temp dir is APFS.Verification
-D warnings(lib, libcfg(test),fstests,--features fs) clean for x86_64/aarch64 Windows MSVC, x86_64/aarch64 Apple Darwin, x86_64 Linux.fstests 76/76, extent unit tests 3/3. CI guard unittests (85), release tooling, compilation-boundary and Python package checks pass.PrivateSizeReply4/24/32, refcount header extents at 16, extent 24 bytes).🤖 Generated with Claude Code