Re: [PATCH 1/2] qcow2: Release read-only bitmaps when inactivated

[Vladimir Sementsov-Ogievskiy]

30.07.2020 15:02, Max Reitz wrote:
> During migration, we release all bitmaps after storing them on disk, as
> long as they are (1) stored on disk, (2) not read-only, and (3)
> consistent.
>
> (2) seems arbitrary, though.  The reason we do not release them is
> because we do not write them, as there is no need to; and then we just
> forget about all bitmaps that we have not written to the file.  However,
> read-only persistent bitmaps are still in the file and in sync with
> their in-memory representation, so we may as well release them just like
> any R/W bitmap that we have updated.

Agree, better to release all image-owned bitmaps on inactivation of the image.

> It leads to actual problems, too: After migration, letting the source
> continue may result in an error if there were any bitmaps on read-only
> nodes (such as backing images), because those have not been released by
> bdrv_inactive_all(), but bdrv_invalidate_cache_all() attempts to reload
> them (which fails, because they are still present in memory).
>
> Signed-off-by: Max Reitz <mreitz@redhat.com>

The patch seems OK to me, thanks!

--
Best regards,
Vladimir