On Mon, Nov 24, 2014 at 10:29:38PM +0800, Ming Lei wrote:
> Previously -EAGAIN is simply ignored for !s->io_q.plugged case,
> and sometimes it is easy to cause -EIO to VM, such as NVME device.
>
> This patch handles -EAGAIN by io queue for !s->io_q.plugged case,
> and it will be retried in following aio completion cb.
>
> Suggested-by: Paolo Bonzini <pbonz...@redhat.com>
> Signed-off-by: Ming Lei <ming....@canonical.com>
> ---
> block/linux-aio.c | 28 ++++++++++++++++++----------
> 1 file changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/block/linux-aio.c b/block/linux-aio.c
> index 70312a4..0cb098d 100644
> --- a/block/linux-aio.c
> +++ b/block/linux-aio.c
> @@ -282,12 +282,17 @@ static int ioq_enqueue(struct qemu_laio_state *s,
> struct iocb *iocb)
> s->io_q.iocbs[idx++] = iocb;
> s->io_q.idx = idx;
>
> - /* submit immediately if queue depth is above 2/3 */
> - if (idx > s->io_q.size * 2 / 3) {
> - return ioq_submit(s);
> + /*
> + * This is reached in two cases: queue not plugged but io_submit
> + * returned -EAGAIN, or queue plugged. In the latter case, start
> + * submitting some I/O if the queue is getting too full. In the
> + * former case, instead, wait until an I/O operation is completed.
> + */
> + if (!s->io_q.plugged || likely(idx < s->io_q.size * 2 / 3)) {
> + return 0;
> }
>
> - return 0;
> + return ioq_submit(s);Same as in the previous patch, the ioq_submit() return value is not meaningful to ioq_enqueue() callers. It should not be returned.
pgpnWNYiPt970.pgp
Description: PGP signature
