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 <andrey.shinkevich@virtuozzo.com> --- 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