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 | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/block/linux-aio.c b/block/linux-aio.c
index f66e8ad..f5ca41d 100644
--- a/block/linux-aio.c
+++ b/block/linux-aio.c
@@ -263,6 +263,11 @@ static int ioq_enqueue(struct qemu_laio_state *s, struct
iocb *iocb)
s->io_q.iocbs[idx++] = iocb;
s->io_q.idx = idx;
+ /* don't submit until next completion for -EAGAIN of non plug case */
+ if (unlikely(!s->io_q.plugged)) {
+ return 0;
+ }
+
/* submit immediately if queue depth is above 2/3 */
if (idx > s->io_q.size * 2 / 3) {
return ioq_submit(s, true);
@@ -330,10 +335,25 @@ BlockAIOCB *laio_submit(BlockDriverState *bs, void
*aio_ctx, int fd,
io_set_eventfd(&laiocb->iocb, event_notifier_get_fd(&s->e));
if (!s->io_q.plugged) {
- if (io_submit(s->ctx, 1, &iocbs) < 0) {
+ int ret;
+
+ if (!s->io_q.idx) {
+ ret = io_submit(s->ctx, 1, &iocbs);
+ } else {
+ ret = -EAGAIN;
+ }
+ /*
+ * Switch to queue mode until -EAGAIN is handled, we suppose
+ * there is always uncompleted I/O, so try to enqueue it first,
+ * and will be submitted again in following aio completion cb.
+ */
+ if (ret == -EAGAIN) {
+ goto enqueue;
+ } else if (ret < 0) {
goto out_free_aiocb;
}
} else {
+ enqueue:
if (ioq_enqueue(s, iocbs) < 0) {
goto out_free_aiocb;
}
--
1.7.9.5
