Re: [Qemu-devel] [PATCH v22 10/30] block/dirty-bitmap: add readonly field to BdrvDirtyBitmap

[Max Reitz]

On 2017-06-28 14:05, Vladimir Sementsov-Ogievskiy wrote:
> It will be needed in following commits for persistent bitmaps.
> If bitmap is loaded from read-only storage (and we can't mark it
> "in use" in this storage) corresponding BdrvDirtyBitmap should be
> read-only.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
>  block/dirty-bitmap.c         | 36 ++++++++++++++++++++++++++++++++++++
>  block/io.c                   |  8 ++++++++
>  blockdev.c                   |  6 ++++++
>  include/block/dirty-bitmap.h |  4 ++++
>  4 files changed, 54 insertions(+)
> 
> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
> index a8fe149c4a..17d3068336 100644
> --- a/block/dirty-bitmap.c
> +++ b/block/dirty-bitmap.c

[...]

> @@ -635,3 +646,28 @@ int64_t bdrv_get_meta_dirty_count(BdrvDirtyBitmap 
> *bitmap)
>  {
>      return hbitmap_count(bitmap->meta);
>  }
> +
> +bool bdrv_dirty_bitmap_readonly(const BdrvDirtyBitmap *bitmap)
> +{
> +    return bitmap->readonly;
> +}
> +
> +/* Called with BQL taken. */
> +void bdrv_dirty_bitmap_set_readonly(BdrvDirtyBitmap *bitmap, bool value)
> +{
> +    qemu_mutex_lock(bitmap->mutex);
> +    bitmap->readonly = value;
> +    qemu_mutex_unlock(bitmap->mutex);
> +}

I find it a bit strange to acquire the mutex if this function is called
with the BQL taken (which I agree it should be) -- but Paolo has given
his OK and I don't think it does harm to acquire the mutex even under BQL.

Max

> +
> +bool bdrv_has_readonly_bitmaps(BlockDriverState *bs)
> +{
> +    BdrvDirtyBitmap *bm;
> +    QLIST_FOREACH(bm, &bs->dirty_bitmaps, list) {
> +        if (bm->readonly) {
> +            return true;
> +        }
> +    }
> +
> +    return false;
> +}

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