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Re: [Qemu-block] [PATCH 15/16] block: Add and use bdrv_replace_in_backin
From: |
Max Reitz |
Subject: |
Re: [Qemu-block] [PATCH 15/16] block: Add and use bdrv_replace_in_backing_chain() |
Date: |
Wed, 23 Sep 2015 19:08:41 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 |
On 17.09.2015 15:48, Kevin Wolf wrote:
> This cleans up the mess we left behind in the mirror code after the
> previous patch. Instead of using bdrv_swap(), just change pointers.
>
> The interface change of the mirror job that callers must consider is
> that after job completion, their local BDS pointers still point to the
> same node now. qemu-img must change its code accordingly (which makes it
> easier to understand); the other callers stays unchanged because after
> completion they don't do anything with the BDS, but just with the job,
> and the job is still owned by the source BDS.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
> block.c | 32 +++++++++++++++++++++++++++++++-
> block/mirror.c | 23 +++++++----------------
> include/block/block.h | 4 +++-
> qemu-img.c | 16 ++++++++--------
> 4 files changed, 49 insertions(+), 26 deletions(-)
>
> diff --git a/block.c b/block.c
> index 98fc17c..7c21659 100644
> --- a/block.c
> +++ b/block.c
> @@ -1095,7 +1095,7 @@ static BdrvChild *bdrv_attach_child(BlockDriverState
> *parent_bs,
> return child;
> }
>
> -void bdrv_detach_child(BdrvChild *child)
> +static void bdrv_detach_child(BdrvChild *child)
> {
> QLIST_REMOVE(child, next);
> QLIST_REMOVE(child, next_parent);
> @@ -2228,6 +2228,36 @@ void bdrv_append(BlockDriverState *bs_new,
> BlockDriverState *bs_top)
> bdrv_unref(bs_new);
> }
>
> +void bdrv_replace_in_backing_chain(BlockDriverState *old, BlockDriverState
> *new)
> +{
> + assert(!bdrv_requests_pending(old));
> + assert(!bdrv_requests_pending(new));
> +
> + bdrv_ref(old);
> +
> + if (old->blk) {
> + /* As long as these fields aren't in BlockBackend, but in the
> top-level
> + * BlockDriverState, it's not possible for a BDS to have two BBs.
> + *
> + * We really want to copy the fields from old to new, but we go for a
> + * swap instead so that pointers aren't duplicated and cause trouble.
> + * (Also, bdrv_swap() used to do the same.) */
> + assert(!new->blk);
> + swap_feature_fields(old, new);
> + }
> + change_parent_backing_link(old, new);
> +
> + /* Change backing files if a previously independent node is added to the
> + * chain. For active commit, we replace top by its own (indirect) backing
> + * file and don't do anything here so we don't build a loop. */
> + if (new->backing == NULL && !bdrv_chain_contains(backing_bs(old), new)) {
> + bdrv_set_backing_hd(new, backing_bs(old));
> + bdrv_set_backing_hd(old, NULL);
Wouldn't we want @old to keep its backing file?
Then bdrv_append() would basically be a special case of this function,
with it additionally decrementing the refcount of @bs_new.
Max
> + }
> +
> + bdrv_unref(old);
> +}
> +
> static void bdrv_delete(BlockDriverState *bs)
> {
> assert(!bs->job);
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- Re: [Qemu-block] [PATCH 13/16] block: Implement bdrv_append() without bdrv_swap(), (continued)
Re: [Qemu-block] [PATCH 13/16] block: Implement bdrv_append() without bdrv_swap(), Max Reitz, 2015/09/23
[Qemu-block] [PATCH 14/16] blockjob: Store device name at job creation, Kevin Wolf, 2015/09/17
[Qemu-block] [PATCH 12/16] block: Introduce parents list, Kevin Wolf, 2015/09/17
[Qemu-block] [PATCH 15/16] block: Add and use bdrv_replace_in_backing_chain(), Kevin Wolf, 2015/09/17
- Re: [Qemu-block] [PATCH 15/16] block: Add and use bdrv_replace_in_backing_chain(),
Max Reitz <=
[Qemu-block] [PATCH 16/16] block: Remove bdrv_swap(), Kevin Wolf, 2015/09/17
Re: [Qemu-block] [PATCH 00/16] block: Get rid of bdrv_swap(), Alberto Garcia, 2015/09/18
Re: [Qemu-block] [PATCH 00/16] block: Get rid of bdrv_swap(), Alberto Garcia, 2015/09/24