Emir Beganovic 623af62743 block: Implement write_zeroes and punch_hole for AIO backend ...

The AIO block backend advertises VIRTIO_BLK_F_WRITE_ZEROES
and VIRTIO_BLK_F_DISCARD to guests because the filesystem
probe (supports_sparse_operations) returns true on ext4/XFS.
However, RawFileAsyncAio::write_zeroes() and punch_hole()
return errors because Linux AIO (io_submit) has no IOCB
command for fallocate.

When io_uring is unavailable (e.g. io_uring_disabled=2, a
common security hardening on enterprise Linux), Cloud
Hypervisor falls back to the AIO backend. The guest
negotiates the feature, issues WRITE_ZEROES requests, and
gets I/O errors.

Implement write_zeroes and punch_hole using synchronous
libc::fallocate() calls, matching the pattern used by the
sync backend (RawFileSync). A VecDeque-based completion
list signals results to the caller via the existing eventfd
mechanism.

Unit tests mirror the existing raw_sync.rs test suite.
Integration tests add AIO-specific variants of the discard
and fstrim tests using _disable_io_uring=on.

Signed-off-by: Emir Beganovic <beganovic.emir@gmail.com>

2026-03-12 12:08:01 +00:00

..

src

block: Implement write_zeroes and punch_hole for AIO backend

2026-03-12 12:08:01 +00:00

Cargo.toml

block: qcow: Validate incompatible feature bits

2026-01-23 18:58:56 +00:00