ksmbd: fall back to copy for duplicate extents

FSCTL_DUPLICATE_EXTENTS_TO_FILE currently returns STATUS_NOT_SUPPORTED
when vfs_clone_file_range() cannot clone the requested range. That can
happen on filesystems without reflink support even though the server can
still satisfy the request by copying the bytes.

Validate the requested source range before attempting the operation. If
the destination range extends past EOF, leave the destination size
unchanged and complete the request without copying, matching observed
client expectations for this ioctl.

Reject sparse source to non-sparse destination requests as unsupported.
Keep sparse destination and sparse-to-sparse cases on the normal clone
or copy path.

Reject overlapping same-file ranges as unsupported before attempting
the clone or copy operation.

Return the expected handle status for invalid handles. A closed target
handle fails with STATUS_FILE_CLOSED, while a bad source handle embedded
in the request buffer fails with STATUS_INVALID_HANDLE.

Fall back to vfs_copy_file_range() whenever the clone operation does not
copy the full requested length, and keep reporting an error only if the
fallback also fails or copies a partial range.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

0 files changed, 0 insertions, 0 deletions