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Re: [Qemu-block] [Qemu-devel] [PATCH v4 04/21] stream: Drop reached_end
From: |
John Snow |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH v4 04/21] stream: Drop reached_end for stream_complete() |
Date: |
Wed, 5 Jul 2017 20:05:59 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 |
On 07/05/2017 05:08 PM, Eric Blake wrote:
> stream_complete() skips the work of rewriting the backing file if
> the job was cancelled, if data->reached_end is false, or if there
> was an error detected (non-zero data->ret) during the streaming.
> But note that in stream_run(), data->reached_end is only set if the
> loop ran to completion, and data->ret is only 0 in two cases:
> either the loop ran to completion (possibly by cancellation, but
> stream_complete checks for that), or we took an early goto out
> because there is no bs->backing. Thus, we can preserve the same
> semantics without the use of reached_end, by merely checking for
> bs->backing (and logically, if there was no backing file, streaming
> is a no-op, so there is no backing file to rewrite).
>
> Suggested-by: Kevin Wolf <address@hidden>
> Signed-off-by: Eric Blake <address@hidden>
>
> ---
> v4: new patch
> ---
> block/stream.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/block/stream.c b/block/stream.c
> index 746d525..12f1659 100644
> --- a/block/stream.c
> +++ b/block/stream.c
> @@ -59,7 +59,6 @@ static int coroutine_fn stream_populate(BlockBackend *blk,
>
> typedef struct {
> int ret;
> - bool reached_end;
> } StreamCompleteData;
>
> static void stream_complete(BlockJob *job, void *opaque)
> @@ -70,7 +69,7 @@ static void stream_complete(BlockJob *job, void *opaque)
> BlockDriverState *base = s->base;
> Error *local_err = NULL;
>
> - if (!block_job_is_cancelled(&s->common) && data->reached_end &&
> + if (!block_job_is_cancelled(&s->common) && bs->backing &&
> data->ret == 0) {
> const char *base_id = NULL, *base_fmt = NULL;
> if (base) {
> @@ -211,7 +210,6 @@ out:
> /* Modify backing chain and close BDSes in main loop */
> data = g_malloc(sizeof(*data));
> data->ret = ret;
> - data->reached_end = sector_num == end;
> block_job_defer_to_main_loop(&s->common, stream_complete, data);
> }
>
This seems ever so slightly less intuitive to me, but it is functionally
identical.
Reviewed-by: John Snow <address@hidden>
- [Qemu-block] [PATCH v4 00/21] make bdrv_is_allocated[_above] byte-based, Eric Blake, 2017/07/05
- [Qemu-block] [PATCH v4 03/21] stream: Switch stream_populate() to byte-based, Eric Blake, 2017/07/05
- [Qemu-block] [PATCH v4 01/21] blockjob: Track job ratelimits via bytes, not sectors, Eric Blake, 2017/07/05
- [Qemu-block] [PATCH v4 04/21] stream: Drop reached_end for stream_complete(), Eric Blake, 2017/07/05
- [Qemu-block] [PATCH v4 07/21] commit: Switch commit_run() to byte-based, Eric Blake, 2017/07/05
- [Qemu-block] [PATCH v4 06/21] commit: Switch commit_populate() to byte-based, Eric Blake, 2017/07/05
- [Qemu-block] [PATCH v4 05/21] stream: Switch stream_run() to byte-based, Eric Blake, 2017/07/05
- [Qemu-block] [PATCH v4 02/21] trace: Show blockjob actions via bytes, not sectors, Eric Blake, 2017/07/05
- [Qemu-block] [PATCH v4 08/21] mirror: Switch MirrorBlockJob to byte-based, Eric Blake, 2017/07/05
- [Qemu-block] [PATCH v4 09/21] mirror: Switch mirror_do_zero_or_discard() to byte-based, Eric Blake, 2017/07/05