Il 21/11/2012 10:15, Kevin Wolf ha scritto:
>> > + if ((bs->open_flags & BDRV_O_NOCACHE)) {
>> > + bs->file->buffer_alignment = align;
>> > + }
> Any reason to restrict this to BDRV_O_NOCACHE?
>
> There have been patches to change the BDRV_O_NOCACHE flag from the
> monitor, in which case bdrv_set_buffer_alignment() wouldn't be called
> anew and O_DIRECT requests start to fail again.
>
bdrv_set_buffer_alignment() is completely broken. It should set host
alignment, but in fact it is passed the guest alignment.
In practice, we only support logical_block_size matching the host's or
bigger (which is unsafe due to torn writes, but works).
So I suggest that we just look at writes outside the device models, and
"fix" them to always read a multiple of 4k.
Paolo
