Replace the qcow specific AlignedBuf along with the pread64/pwrite64
helpers with the new common AlignedBuffer implementation.
Assisted-by: Claude:Opus-4.6
Signed-off-by: Rob Bradford <rbradford@meta.com>
Replace the manual alloc_zeroed/dealloc and pread64/pwrite64 with use of
the new AlignedBuffer structure.
Assisted-by: Claude:Opus-4.6
Signed-off-by: Rob Bradford <rbradford@meta.com>
The block code repeatedly open-codes O_DIRECT alignment calculations and
bounce-buffer allocation at each I/O site. Add an AlignedBuffer struct
that handles the alignment and allocation in one place, using FileExt
(read_exact_at and write_all_at) for the I/O (so no need for custom libc
wrappers).
The caller creates an AlignedBuffer with an offset, length and
alignment, then uses read_from and write_to for aligned I/O and as_slice
and as_mut_slice to access the logical data portion within the aligned
region.
This is a lot like the AlignedBuf that was already existing in the QCOW2
code but is a more generalised version.
Assisted-by: Claude:Opus-4.6
Signed-off-by: Rob Bradford <rbradford@meta.com>
