Am 23.09.2022 um 14:52 hat Hanna Reitz geschrieben:
> blk_get_aio_context() asserts that blk->ctx is always equal to the root
> BDS's context (if there is a root BDS). Therefore,
> blk_do_set_aio_context() must update blk->ctx immediately after the root
> BDS's context has changed.
>
> Without this patch, the next patch would break iotest 238, because
> bdrv_drained_begin() (called by blk_do_set_aio_context()) may then
> invoke bdrv_child_get_parent_aio_context() on the root child, i.e.
> blk_get_aio_context(). However, by this point, blk->ctx would not have
> been updated and thus differ from the root node's context. This patch
> fixes that.
>
> Signed-off-by: Hanna Reitz
> ---
> block/block-backend.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/block/block-backend.c b/block/block-backend.c
> index d4a5df2ac2..abdb5ff5af 100644
> --- a/block/block-backend.c
> +++ b/block/block-backend.c
> @@ -2156,6 +2156,7 @@ static int blk_do_set_aio_context(BlockBackend *blk,
> AioContext *new_context,
> return ret;
> }
> }
> +blk->ctx = new_context;
> if (tgm->throttle_state) {
> bdrv_drained_begin(bs);
> throttle_group_detach_aio_context(tgm);
> @@ -2164,9 +2165,10 @@ static int blk_do_set_aio_context(BlockBackend *blk,
> AioContext *new_context,
> }
>
> bdrv_unref(bs);
> +} else {
> +blk->ctx = new_context;
> }
>
> -blk->ctx = new_context;
> return 0;
> }
Makes sense. Maybe in the first branch a comment wouldn't hurt (like
"make blk->ctx consistent with the root node again before any other
operations like drain").
Reviewed-by: Kevin Wolf
