Am 21.11.2012 09:58, schrieb Christian Borntraeger: > From: Heinz Graalfs <graa...@linux.vnet.ibm.com> > > While testing IPL code (booting) for s390x we faced some problems > with cache=none on dasds (4k block size) on bdrv_preads with length > values != block size. > > This patch makes sure that bdrv_pread and friends work fine with > unaligned access even with cache=none > - propagate alignment value also into bs->file struct > - modify the size in case of no cache to avoid EINVAL on > pread() etc. (file was opened with O_DIRECT). > > This patch seems to cure the problems. > > CC: Kevin Wolf <kw...@redhat.com> > CC: Stefan Hajnoczi <stefa...@redhat.com> > Signed-off-by: Heinz Graalfs <graa...@linux.vnet.ibm.com> > Signed-off-by: Christian Borntraeger <borntrae...@de.ibm.com> > --- > block.c | 3 +++ > block/raw-posix.c | 6 ++++++ > 2 files changed, 9 insertions(+) > > diff --git a/block.c b/block.c > index 854ebd6..f23c562 100644 > --- a/block.c > +++ b/block.c > @@ -4242,6 +4242,9 @@ BlockDriverAIOCB *bdrv_aio_ioctl(BlockDriverState *bs, > void bdrv_set_buffer_alignment(BlockDriverState *bs, int align) > { > bs->buffer_alignment = align; > + 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. > } > > void *qemu_blockalign(BlockDriverState *bs, size_t size) > diff --git a/block/raw-posix.c b/block/raw-posix.c > index f2f0404..baebf1d 100644 > --- a/block/raw-posix.c > +++ b/block/raw-posix.c > @@ -700,6 +700,12 @@ static BlockDriverAIOCB *paio_submit(BlockDriverState > *bs, int fd, > acb->aio_nbytes = nb_sectors * 512; > acb->aio_offset = sector_num * 512; > > + /* O_DIRECT also requires an aligned length */ > + if (bs->open_flags & BDRV_O_NOCACHE) { > + acb->aio_nbytes += acb->bs->buffer_alignment - 1; > + acb->aio_nbytes &= ~(acb->bs->buffer_alignment - 1); > + } Modifying aio_nbytes, but not the iov looks wrong to me. This may work in the handle_aiocb_rw_linear() code path, but not with actual vectored I/O. Kevin