Am 30.05.2025 um 17:11 hat Fiona Ebner geschrieben:
> Many write-locked sections are also drained sections. A new
> bdrv_graph_wrunlock_drained() wrapper around bdrv_graph_wrunlock() is
> introduced, which will begin a drained section first. A global
> variable is used so bdrv_graph_wrunlock() knows if it also needs
> to end such a drained section. Both the aio_poll call in
> bdrv_graph_wrlock() and the aio_bh_poll() in bdrv_graph_wrunlock()
> can re-enter a write-locked section. While for the latter, ending the
> drain could be moved to before the call, the former requires that the
> variable is a counter and not just a boolean.
>
> Since the wrapper calls bdrv_drain_all_begin(), which must be called
> with the graph unlocked, mark the wrapper as GRAPH_UNLOCKED too.
>
> The switch to the new helpers was generated with the following
> commands and then manually checked:
> find . -name '*.c' -exec sed -i -z
> 's/bdrv_drain_all_begin();\n\s*bdrv_graph_wrlock();/bdrv_graph_wrlock_drained();/g'
> {} ';'
> find . -name '*.c' -exec sed -i -z
> 's/bdrv_graph_wrunlock();\n\s*bdrv_drain_all_end();/bdrv_graph_wrunlock();/g'
> {} ';'
>
> Suggested-by: Kevin Wolf <kw...@redhat.com>
> Signed-off-by: Fiona Ebner <f.eb...@proxmox.com>
> ---
>
> Changes in v4:
> * Adapt to context changes from earlier patch.
> * Mark the wrapper as GRAPH_UNLOCKED itself
> diff --git a/include/block/graph-lock.h b/include/block/graph-lock.h
> index 2c26c72108..b564cba2c0 100644
> --- a/include/block/graph-lock.h
> +++ b/include/block/graph-lock.h
> @@ -112,10 +112,21 @@ void unregister_aiocontext(AioContext *ctx);
> void no_coroutine_fn TSA_ACQUIRE(graph_lock) TSA_NO_TSA
> bdrv_graph_wrlock(void);
>
> +/*
> + * bdrv_graph_wrlock_drained:
> + * Similar to bdrv_graph_wrlock, but will begin a drained section before
> + * locking.
> + */
> +void no_coroutine_fn TSA_ACQUIRE(graph_lock) TSA_NO_TSA GRAPH_UNLOCKED
> +bdrv_graph_wrlock_drained(void);
GRAPH_UNLOCKED is redundant. TSA_ACQUIRE(graph_lock) already means that
you can't call the function while holding the lock.
Kevin
