On 12.10.20 19:43, Andrey Shinkevich wrote: > Limit COR operations by the base node in the backing chain when the > overlay base node name is given. It will be useful for a block stream > job when the COR-filter is applied. The overlay base node is passed as > the base itself may change due to concurrent commit jobs on the same > backing chain. > > Signed-off-by: Andrey Shinkevich <[email protected]> > --- > block/copy-on-read.c | 39 +++++++++++++++++++++++++++++++++++++-- > 1 file changed, 37 insertions(+), 2 deletions(-) > > diff --git a/block/copy-on-read.c b/block/copy-on-read.c > index c578b1b..dfbd6ad 100644 > --- a/block/copy-on-read.c > +++ b/block/copy-on-read.c > @@ -122,8 +122,43 @@ static int coroutine_fn > cor_co_preadv_part(BlockDriverState *bs, > size_t qiov_offset, > int flags) > { > - return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset, > - flags | BDRV_REQ_COPY_ON_READ); > + int64_t n = 0; > + int64_t size = offset + bytes; > + int local_flags; > + int ret; > + BDRVStateCOR *state = bs->opaque; > + > + if (!state->base_overlay) { > + return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, > qiov_offset, > + flags | BDRV_REQ_COPY_ON_READ); > + } > + > + while (offset < size) { > + local_flags = flags; > + > + /* In case of failure, try to copy-on-read anyway */ > + ret = bdrv_is_allocated(bs->file->bs, offset, bytes, &n); > + if (!ret) {
In case of failure, a negative value is going to be returned, we won’t
go into this conditional block, and local_flags isn’t going to contain
BDRV_REQ_COPY_ON_READ.
So the idea of CORing in case of failure sounds sound to me, but it
doesn’t look like that’s done.
> + ret = bdrv_is_allocated_above(bdrv_cow_bs(bs->file->bs),
I think this should either be bdrv_backing_chain_next() or we must rule
out the possibility of bs->file->bs being a filter somewhere. I think
I’d prefer the former.
> + state->base_overlay, true, offset,
> + n, &n);
> + if (ret) {
“ret == 1 || ret < 0” would be more explicit (and in line with the “!ret
|| ret < 0” probably needed above), but correct either way.
Max
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