On Tue 08 Jan 2019 06:06:52 PM CET, Vladimir Sementsov-Ogievskiy wrote: > @@ -1891,39 +1892,38 @@ static coroutine_fn int > qcow2_co_preadv(BlockDriverState *bs, uint64_t offset, > qemu_iovec_reset(&hd_qiov); > qemu_iovec_concat(&hd_qiov, qiov, bytes_done, cur_bytes); > > + if (ret == QCOW2_CLUSTER_ZERO_PLAIN || > + ret == QCOW2_CLUSTER_ZERO_ALLOC || > + (ret == QCOW2_CLUSTER_UNALLOCATED && !bs->backing)) > + { > + /* No sense in releasing the lock */ > + > + qemu_iovec_memset(&hd_qiov, 0, 0, cur_bytes); > + > + bytes -= cur_bytes; > + offset += cur_bytes; > + bytes_done += cur_bytes; > + continue; > + }
Maybe that was just me, but I got confused by the "No sense in releasing the lock" thinking that it referred to the memset() call. What you're trying to say is that it doesn't make sense to release the lock while you only get zero / unallocated clusters only to lock it again at the next iteration of the loop. I think that comment may make sense when you think about the code changes that you are doing, but when you read the actual resulting code it's fairly obvious that you don't need to touch the lock there. So I'd rather remove that comment. Else the patch looks good. Reviewed-by: Alberto Garcia <be...@igalia.com> Berto