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@xxxxxxxxxxxxx>
> ---
> 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;
Just when I hit send I noticed that “end” would be a more fitting name
for this variable.
> + 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) {
(because I got a bit confused looking at this)
(Though dropping @size (or @end) and just checking when @bytes becomes 0
should work, too.)
> + 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) {
> + ret = bdrv_is_allocated_above(bdrv_cow_bs(bs->file->bs),
> + state->base_overlay, true, offset,
> + n, &n);
> + if (ret) {
> + local_flags |= BDRV_REQ_COPY_ON_READ;
> + }
> + }
Furthermore, I just noticed – can the is_allocated functions not return
0 in @n, when @offset is a the EOF? Is that something to look out for?
(I’m not sure.)
Max
> +
> + ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset,
> + local_flags);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + offset += n;
> + qiov_offset += n;
> + bytes -= n;
> + }
> +
> + return 0;
> }
>
>
>
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