Re: [Qemu-devel] [PATCH 2/4] migration/savevm: use migration_is_blocked to validate

From: Daniel Henrique Barboza <danielhb413@gmail.com>
To: Wei Yang <richardw.yang@linux.intel.com>, qemu-devel@nongnu.org
Cc: dgilbert@redhat.com, quintela@redhat.com
Subject: Re: [Qemu-devel] [PATCH 2/4] migration/savevm: use migration_is_blocked to validate
Date: Thu, 25 Apr 2019 17:55:15 -0300	[thread overview]
Message-ID: <0eb5e5a5-593e-f4a2-7e2d-a9fed481ab6c@gmail.com> (raw)
In-Reply-To: <20190424004700.12766-3-richardw.yang@linux.intel.com>

On 4/23/19 9:46 PM, Wei Yang wrote:
> migration_is_blocked() is used in migrate_prepare() and
> save_snapshot(), this is more proper to use this instead of
> qemu_savevm_state_blocked() in qemu_loadvm_state().

migration_is_blocked() does an additional verification:

"if (migration_blockers)"

comparing to what was previously done in qemu_loadvm_state.

I've checked what migration_blockers does and it is a GList used
for callers to block the migration process. This is used via
'migration_add_blocker', from migration.c.

'migration_add_blocker' is called all over the place, most notably
in  _realize() functions  and _open() functions from block.

Thus, I am not sure if this change will impact the use of
qemu_loadvm_state() from load_snapshot() (i.e. can load_snapshot
be called with migration_blockers?). It's better to someone
with a better understanding of this code to comment on that.

DHB

> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> ---
>   migration/savevm.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 2eea604624..6c61056cde 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2406,7 +2406,7 @@ int qemu_loadvm_state(QEMUFile *f)
>       unsigned int v;
>       int ret;
>   
> -    if (qemu_savevm_state_blocked(&local_err)) {
> +    if (migration_is_blocked(&local_err)) {
>           error_report_err(local_err);
>           return -EINVAL;
>       }