Re: [RFC PATCH 19/22] block/export: Move strong user reference to block_exports

[Max Reitz]

On 13.08.20 18:29, Kevin Wolf wrote:
> The reference owned by the user/monitor that is created when adding the
> export and dropped when removing it was tied to the 'exports' list in
> nbd/server.c. Every block export will have a user reference, so move it
> to the block export level and tie it to the 'block_exports' list in
> block/export/export.c instead. This is necessary for introducing a QMP
> command for removing exports.
> 
> Note that exports are present in block_exports even after the user has
> requested shutdown. This is different from NBD's exports where exports
> are immediately removed on a shutdown request, even if they are still in
> the process of shutting down. In order to avoid that the user still
> interacts with an export that is shutting down (and possibly removes it
> a second time), we need to remember if the user actually still owns it.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  include/block/export.h | 8 ++++++++
>  block/export/export.c  | 4 ++++
>  blockdev-nbd.c         | 5 -----
>  nbd/server.c           | 2 --
>  4 files changed, 12 insertions(+), 7 deletions(-)

With this patch, there’s an abort in iotest 281.  Perhaps because
blk_exp_unref() is now done by blk_exp_request_shutdown() outside of
where the AIO context is locked?

Max

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