Enable uninit_bg (gdt_csum) in ext4 mkfs for fast offline resize - #18
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Patch Photon's do_mkfs to set the gdt_csum feature (uninitialized block groups) on the base ext4 layer. An offline resize2fs grow of a devbox rootfs then marks the new inode tables uninitialized instead of zeroing them — a near-instant grow that writes only metadata into the layered (COW) block format instead of gigabytes of zeros. metadata_csum is deliberately not used: it seeds checksums from s_uuid, which do_mkfs sets after ext2fs_initialize caches the seed, producing an invalid superblock checksum. gdt_csum has no such ordering dependency. Applied to PhotonLibOS v0.6.17 via a CMake FetchContent PATCH_COMMAND in Findphoton.cmake (idempotent reverse-check). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Patch Photon's
do_mkfsto set the ext4gdt_csum(uninitialized block groups) feature on the base layer. A guest-side offlineresize2fsgrow of a devbox rootfs then marks new inode tables uninitialized instead of zeroing them — a near-instant, metadata-only grow into the layered (COW) block format instead of writing gigabytes of zeros.metadata_csumis deliberately not used: it seeds checksums froms_uuid, whichdo_mkfssets afterext2fs_initializecaches the seed, producing an invalid superblock checksum.gdt_csumhas no such ordering dependency.Applied to PhotonLibOS v0.6.17 via a CMake FetchContent
PATCH_COMMANDinFindphoton.cmake(idempotent reverse-check).Released as tag
v0.0.11-runloop; consumed by the runloopai/iac blueprint builder images (v0.9.5).