Re: [Qemu-devel] [PATCH v2 2/6] file-win32: Switch to byte-based callbacks

[Kevin Wolf <kwolf@redhat.com>]

Am 24.04.2018 um 21:25 hat Eric Blake geschrieben:
> We are gradually moving away from sector-based interfaces, towards
> byte-based.  Make the change for the last few sector-based callbacks
> in the file-win32 driver.
> 
> Note that the driver was already using byte-based calls for
> performing actual I/O, so this just gets rid of a round trip
> of scaling; however, as I don't know if Windows is tolerant of
> non-sector AIO operations, I went with the conservative approach
> of modifying .bdrv_refresh_limits to override the block layer
> defaults back to the pre-patch value of 512.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
> Compile-tested via 'make docker-test-mingw@fedora', but I don't
> have a sane way to test whether it actually works.

Tried to test it, and the only result is that something was broken even
before your patch:

$ ./qemu-img.exe create -f raw /tmp/test.raw 128M
Formatting '/tmp/test.raw', fmt=raw size=134217728
$ ./qemu-io.exe -f raw -c 'read 0 4k' /tmp/test.raw
read failed: Input/output error

For some reason, doing the same with qcow2 works fine. qemu-iotests
for qcow2 starts hanging in 013. Maybe someone should look into this,
qemu-iotests was working fairly well with mingw builds some time ago.
Nothing that will hold up this series, though.

Kevin