From: John Snow <js...@redhat.com> in blockdev_backup_prepare, we check to make sure that the target is associated with a compatible aio context. However, do_blockdev_backup is called later and has some logic to move the target to a compatible aio_context. The transaction version will fail certain commands needlessly early as a result.
Allow blockdev_backup_prepare to simply call do_blockdev_backup, which will ultimately decide if the contexts are compatible or not. Note: the transaction version has always disallowed this operation since its initial commit bd8baecd (2014), whereas the version of qmp_blockdev_backup at the time, from commit c29c1dd312f, tried to enforce the aio_context switch instead. It's not clear, and I can't see from the mailing list archives at the time, why the two functions take a different approach. It wasn't until later in efd7556708b (2016) that the standalone version tried to determine if it could set the context or not. Reported-by: aihua liang <ali...@redhat.com> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1683498 Signed-off-by: John Snow <js...@redhat.com> Message-id: 20190523170643.20794-2-js...@redhat.com Reviewed-by: Max Reitz <mre...@redhat.com> Signed-off-by: Max Reitz <mre...@redhat.com> --- blockdev.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/blockdev.c b/blockdev.c index 3f44b891eb..fdafa173cc 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1876,10 +1876,6 @@ static void blockdev_backup_prepare(BlkActionState *common, Error **errp) } aio_context = bdrv_get_aio_context(bs); - if (aio_context != bdrv_get_aio_context(target)) { - error_setg(errp, "Backup between two IO threads is not implemented"); - return; - } aio_context_acquire(aio_context); state->bs = bs; -- 2.21.0