[PATCH 0/2] btrfs: allow reflinks into NODATASUM files
Daan De Meyer via B4 Relay <[email protected]>
| Newsgroups | org.kernel.vger.linux-btrfs,org.kernel.feeds.b4-sent,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
The primary use case for this series is building a NOCOW VM image from individual partition images that are COW and checksummed. Today those partitions cannot be cloned into the NODATACOW and NODATASUM destination, so tools fall back to a full copy. This makes provisioning slower and duplicates all of the image data up front. Allow cloning and deduplication from a checksummed file into a NODATASUM file. The VM image can then share extents with the partition images. Existing checksummed extents are COWed once when modified, protecting the source checksums, while newly allocated extents use the destination's normal NOCOW behavior. The reverse direction remains rejected because the destination would expect checksums that do not exist. Patch 1 prevents swap activation from bypassing the COW protection when a NODATASUM file references checksummed extents. Patch 2 relaxes the reflink restriction in the safe direction. The xfstests branch is available at: https://github.com/kdave/xfstests/pull/6 Signed-off-by: Daan De Meyer <[email protected]> --- Daan De Meyer (2): btrfs: reject swapfile activation if any extent has checksums btrfs: allow reflinking from checksummed files into nodatasum files fs/btrfs/inode.c | 29 +++++++++++++++++++++++++++++ fs/btrfs/reflink.c | 18 ++++++++++++++---- 2 files changed, 43 insertions(+), 4 deletions(-) --- base-commit: cab9e339cfbc1a4e075e53e281dfb00391e1a6bb change-id: 20260712-reflink-into-nodatasum-aff962f3794e Best regards, -- Daan De Meyer <[email protected]>