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