This reverts commit df9a681dc9.
Note that commit df9a681dc9 included some
unrelated hunks, possibly due to a merge failure or an overlooked
squash. This only reverts the qed .bdrv_drain() implementation.
The qed .bdrv_drain() implementation is unsafe and can lead to a double
request completion.
Paolo Bonzini reports:
"The problem is that bdrv_qed_drain calls qed_plug_allocating_write_reqs
unconditionally, but this is not correct if an allocating write is
queued. In this case, qed_unplug_allocating_write_reqs will restart the
allocating write and possibly cause it to complete. The aiocb however
is still in use for the L2/L1 table writes, and will then be completed
again as soon as the table writes are stable."
For QEMU 2.6 we can simply revert this commit. A full solution for the
qed need check timer may be added if the bdrv_drain() implementation is
extended.
Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1457431876-8475-1-git-send-email-stefanha@redhat.com
1f3ddfcb25