Am 07.10.25 um 6:07 PM schrieb Stefan Hajnoczi:
> v2:
> - Simplify condition to if (!s->needs_alignment) in patch 1 [Vladimir]
>
> This series fixes a bug I introduced in commit 5634622bcb33 ("file-posix:
> allow
> BLKZEROOUT with -t writeback"). The Linux fallocate(2) and ioctl(BLKZEROOUT)
> syscalls require logical block size alignment of the offset and length, even
> when the file is opened in buffered I/O mode where read/write operations do
> not
> require alignment.
>
> The fix is to populate the pwrite_zeroes_alignment block limits field and to
> use that limit in create_file_fallback_zero_first_sector().
>
> One issue I want to raise is that pwrite_zeroes_alignment is an "optimal
> alignment" hint. Hence create_file_fallback_zero_first_sector() had to be
> modified to honor the limit explicitly. The block layer doesn't automatically
> apply padding in order to align requests. This is different from how QEMU's
> block layer pwrite/pread works, where it does automatically apply padding and
> read/modify/write as necessary. If you want consistency, please let me know.
>
> Stefan Hajnoczi (3):
> file-posix: populate pwrite_zeroes_alignment
> block: use pwrite_zeroes_alignment when writing first sector
> iotests: add Linux loop device image creation test
>
> include/system/block-backend-io.h | 1 +
> block.c | 3 +-
> block/block-backend.c | 11 ++++
> block/file-posix.c | 16 +++++
> tests/qemu-iotests/tests/loop-create-file | 59 +++++++++++++++++++
> tests/qemu-iotests/tests/loop-create-file.out | 8 +++
> 6 files changed, 97 insertions(+), 1 deletion(-)
> create mode 100755 tests/qemu-iotests/tests/loop-create-file
> create mode 100644 tests/qemu-iotests/tests/loop-create-file.out
>
Thank you for the fix!
Tested-by: Fiona Ebner <[email protected]>
Reviewed-by: Fiona Ebner <[email protected]>
