Re: [Qemu-devel] [PATCH] block: bdrv_invalidate_cache: invalidate children first

[Max Reitz]

On 31.01.2017 12:23, Vladimir Sementsov-Ogievskiy wrote:
> Current implementation invalidates firstly parent bds and then its
> children. This leads to the following bug:
> 
> after incoming migration, in bdrv_invalidate_cache_all:
> 1. invalidate parent bds - reopen it with BDRV_O_INACTIVE cleared
> 2. child is not yet invalidated
> 3. parent check that its BDRV_O_INACTIVE is cleared
> 4. parent writes to child
> 5. assert in bdrv_co_pwritev, as BDRV_O_INACTIVE is set for child
> 
> This patch fixes it by just changing invalidate sequence: invalidate
> children first.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> 
> v2: I've missed that bdrv_invalidate_cache is already recursive, so we
> can change sequence here. Also v1 doesn't cover the case when
> bdrv_invalidate_cache is called not from bdrv_invalidate_cache_all.
> 
>  block.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)

Reviewed-by: Max Reitz <address@hidden>

I'll wait a bit until I apply this patch (please remind me next week if
I forget it...), though, because migration-related things are not
exactly my forte, so maybe someone else has something to say.

Max

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