Fam Zheng <f...@redhat.com> 於 2018-09-12 17:34 寫道：
> On Tue, 08/28 11:17, yuchen...@synology.com wrote: > From: yuchenlin
> <yuchen...@synology.com> > > There is a rare case which the size of last
> compressed cluster > is larger than the cluster size, which will cause the
> file is > not aligned at the sector boundary. I don't understand. Doesn't it
> mean that if you force the alignment by truncating out the extra bytes, some
> data is lost?
You can take qcow2_co_pwritev_compressed in block/qcow2.c as an example.
The bdrv_getlength will return the length in bytes which is always a multiple
of BDRV_SECTOR_SIZE.
After truncates this size, the vmdk is extended to align sector size.
> > > Signed-off-by: yuchenlin <yuchen...@synology.com> > --- > block/vmdk.c |
> > > 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git
> > > a/block/vmdk.c b/block/vmdk.c > index a9d0084e36..a8ae7c65d2 100644 > ---
> > > a/block/vmdk.c > +++ b/block/vmdk.c > @@ -1698,6 +1698,24 @@ static int
> > > coroutine_fn > vmdk_co_pwritev_compressed(BlockDriverState *bs, uint64_t
> > > offset, > uint64_t bytes, QEMUIOVector *qiov) > { > + if (bytes == 0) {
> > > Where is this bytes == 0 condition from?
From the end of convert_do_copy in qemu-img.c.
if (s->compressed && !s->ret) {
/* signal EOF to align */
ret = blk_pwrite_compressed(s->target, 0, NULL, 0);
if (ret < 0) {
return ret;
}
}
It signals the EOF to the block driver.
> > + /* align end of file to a sector boundary. */ > + BDRVVmdkState *s =
> > bs->opaque; > + int i, ret; > + int64_t length; > + > + for (i = 0; i <
> > s->num_extents; i++) { > + length = bdrv_getlength(s->extents[i].file->bs);
> > > + if (length < 0) { > + return length; > + } > + ret =
> > bdrv_truncate(s->extents[i].file, length, PREALLOC_MODE_OFF, NULL); > + if
> > (ret < 0) { > + return ret; > + } > + } > + return 0; > + } > return
> > vmdk_co_pwritev(bs, offset, bytes, qiov, 0); > } > > -- > 2.17.0 > Fam
yuchenlin
