commit dad41997063723eaf5f77bc2015606a5a9bce320 upstream.
The async path cannot use MAY_BACKLOG because it is not meant to
block, which is what MAY_BACKLOG does. On the other hand, both
the sync and async paths can make use of MAY_SLEEP.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>