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);
}
void laio_io_plug(BlockDriverState *bs, void *aio_ctx)
@@ -348,15 +353,18 @@ 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) {
- goto out_free_aiocb;
- }
- } else {
- if (ioq_enqueue(s, iocbs) < 0) {
+ /* Switch to queue mode until -EAGAIN is handled */
+ if (!s->io_q.plugged && !s->io_q.idx) {
+ int ret = io_submit(s->ctx, 1, &iocbs);
+ if (ret >= 0) {
+ return &laiocb->common;
+ } else if (ret != -EAGAIN) {
goto out_free_aiocb;
}
}
+ if (ioq_enqueue(s, iocbs) < 0) {
+ goto out_free_aiocb;
+ }
return &laiocb->common;
out_free_aiocb:
--
1.7.9.5
