Re: [Qemu-devel] [PATCH] block: Update image size in bdrv_invalidate_cache()

["Benoît Canet" <benoit.canet@irqsave.net>]

The Tuesday 11 Mar 2014 à 10:58:39 (+0100), Kevin Wolf wrote :
> After migration has completed, we call bdrv_invalidate_cache() so that
> drivers which cache some data drop their stale copy of the data and
> reread it from the image file to get a new version of data that the
> source modified while the migration was running.
> 
> Reloading metadata from the image file is useless, though, if the size
> of the image file stays stale (this is a value that is cached for all
> image formats in block.c). Reads from (meta)data after the old EOF
> return only zeroes, causing image corruption.
> 
> We need to update bs->total_sectors in all layers that could potentially
> have changed their size (i.e. backing files are not a concern - if they
> are changed, we're in bigger trouble)
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c       | 10 +++++++++-
>  block/qcow2.c |  2 ++
>  block/qed.c   |  3 +++
>  3 files changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/block.c b/block.c
> index f1ef4b0..7b306fb 100644
> --- a/block.c
> +++ b/block.c
> @@ -4776,9 +4776,17 @@ flush_parent:
>  
>  void bdrv_invalidate_cache(BlockDriverState *bs)
>  {
> -    if (bs->drv && bs->drv->bdrv_invalidate_cache) {
> +    if (!bs->drv)  {
> +        return;
> +    }
> +
> +    if (bs->drv->bdrv_invalidate_cache) {
>          bs->drv->bdrv_invalidate_cache(bs);
> +    } else if (bs->file) {
> +        bdrv_invalidate_cache(bs->file);
>      }
> +
> +    refresh_total_sectors(bs, bs->total_sectors);
>  }
>  
>  void bdrv_invalidate_cache_all(void)
> diff --git a/block/qcow2.c b/block/qcow2.c
> index cfe80be..b5b1e8c 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -1176,6 +1176,8 @@ static void qcow2_invalidate_cache(BlockDriverState *bs)
>  
>      qcow2_close(bs);
>  
> +    bdrv_invalidate_cache(bs->file);
> +
>      options = qdict_new();
>      qdict_put(options, QCOW2_OPT_LAZY_REFCOUNTS,
>                qbool_from_int(s->use_lazy_refcounts));
> diff --git a/block/qed.c b/block/qed.c
> index 8802ad3..837accd 100644
> --- a/block/qed.c
> +++ b/block/qed.c
> @@ -1563,6 +1563,9 @@ static void bdrv_qed_invalidate_cache(BlockDriverState *bs)
>      BDRVQEDState *s = bs->opaque;
>  
>      bdrv_qed_close(bs);
> +
> +    bdrv_invalidate_cache(bs->file);
> +
>      memset(s, 0, sizeof(BDRVQEDState));
>      bdrv_qed_open(bs, NULL, bs->open_flags, NULL);
>  }
> -- 
> 1.8.1.4
> 
> 

I have the impression that you are silently fixing other nits;

However:

Reviewed-by: Benoit Canet <benoit@irqsave.net>