[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-block] [PATCH 3/9] block: Remove child references from bs->{op
From: |
Max Reitz |
Subject: |
Re: [Qemu-block] [PATCH 3/9] block: Remove child references from bs->{options, explicit_options} |
Date: |
Wed, 29 Aug 2018 12:43:06 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
On 2018-08-26 16:09, Alberto Garcia wrote:
> Block drivers allow opening their children using a reference to an
> existing BlockDriverState. These references remain stored in the
> 'options' and 'explicit_options' QDicts, but we don't need to keep
> them once everything is open.
>
> What is more important, these values can become wrong if the children
> change:
>
> $ qemu-img create -f qcow2 hd0.qcow2 10M
> $ qemu-img create -f qcow2 hd1.qcow2 10M
> $ qemu-img create -f qcow2 hd2.qcow2 10M
> $ $QEMU -drive if=none,file=hd0.qcow2,node-name=hd0 \
> -drive if=none,file=hd1.qcow2,node-name=hd1,backing=hd0 \
> -drive file=hd2.qcow2,node-name=hd2,backing=hd1
>
> After this hd2 has hd1 as its backing file. Now let's remove it using
> block_stream:
>
> (qemu) block_stream hd2 0 hd0.qcow2
>
> Now hd0 is the backing file of hd2, but hd2's options QDicts still
> contain backing=hd1.
>
> Signed-off-by: Alberto Garcia <address@hidden>
> ---
> block.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
Also, the question is, why would we discard the child options, but keep
the references (which we do not add, so we only have the ones specified
by the user).
> diff --git a/block.c b/block.c
> index 0dbb1fcc7b..2f2484965d 100644
> --- a/block.c
> +++ b/block.c
> @@ -2763,12 +2763,15 @@ static BlockDriverState *bdrv_open_inherit(const char
> *filename,
> }
> }
>
> - /* Remove all children options from bs->options and bs->explicit_options
> */
> + /* Remove all children options and references
> + * from bs->options and bs->explicit_options */
> QLIST_FOREACH(child, &bs->children, next) {
> char *child_key_dot;
> child_key_dot = g_strdup_printf("%s.", child->name);
> qdict_extract_subqdict(bs->explicit_options, NULL, child_key_dot);
> qdict_extract_subqdict(bs->options, NULL, child_key_dot);
> + qdict_del(bs->explicit_options, child->name);
> + qdict_del(bs->options, child->name);
> g_free(child_key_dot);
> }
>
> @@ -3289,6 +3292,7 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
> {
> BlockDriver *drv;
> BlockDriverState *bs;
> + BdrvChild *child;
> bool old_can_write, new_can_write;
>
> assert(reopen_state != NULL);
> @@ -3313,6 +3317,12 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
> bs->open_flags = reopen_state->flags;
> bs->read_only = !(reopen_state->flags & BDRV_O_RDWR);
>
> + /* Remove child references from bs->options and bs->explicit_options */
> + QLIST_FOREACH(child, &bs->children, next) {
> + qdict_del(bs->explicit_options, child->name);
> + qdict_del(bs->options, child->name);
> + }
> +
Why don't you remove the child options as well?
Max
> bdrv_refresh_limits(bs, NULL);
>
> bdrv_set_perm(reopen_state->bs, reopen_state->perm,
>
signature.asc
Description: OpenPGP digital signature
- [Qemu-block] [PATCH 8/9] block: Allow changing 'detect-zeroes' on reopen, (continued)
- [Qemu-block] [PATCH 8/9] block: Allow changing 'detect-zeroes' on reopen, Alberto Garcia, 2018/08/26
- [Qemu-block] [PATCH 4/9] block: Don't look for child references in append_open_options(), Alberto Garcia, 2018/08/26
- [Qemu-block] [PATCH 9/9] block: Allow changing 'force-share' on reopen, Alberto Garcia, 2018/08/26
- [Qemu-block] [PATCH 7/9] block: Allow changing 'discard' on reopen, Alberto Garcia, 2018/08/26
- [Qemu-block] [PATCH 3/9] block: Remove child references from bs->{options, explicit_options}, Alberto Garcia, 2018/08/26
- Re: [Qemu-block] [PATCH 3/9] block: Remove child references from bs->{options, explicit_options},
Max Reitz <=
[Qemu-block] [PATCH 6/9] file-posix: Forbid trying to change unsupported options during reopen, Alberto Garcia, 2018/08/26