If the queue array for io_submit() is already full, but a new request
arrives, we cannot add it to that queue anymore. We can, however, use a
CoQueue, which is implemented as a list and can therefore queue as many
requests as we want.
Signed-off-by: Kevin Wolf <kw...@redhat.com>
---
block/linux-aio.c | 31 ++++++++++++++++++++++++++-----
1 file changed, 26 insertions(+), 5 deletions(-)
diff --git a/block/linux-aio.c b/block/linux-aio.c
index 373ec4b..8e6328b 100644
--- a/block/linux-aio.c
+++ b/block/linux-aio.c
@@ -44,6 +44,7 @@ typedef struct {
int plugged;
unsigned int size;
unsigned int idx;
+ CoQueue waiting;
} LaioQueue;
struct qemu_laio_state {
@@ -160,6 +161,8 @@ static void ioq_init(LaioQueue *io_q)
io_q->size = MAX_QUEUED_IO;
io_q->idx = 0;
io_q->plugged = 0;
+
+ qemu_co_queue_init(&io_q->waiting);
}
static int ioq_submit(struct qemu_laio_state *s)
@@ -201,15 +204,29 @@ static int ioq_submit(struct qemu_laio_state *s)
s->io_q.idx * sizeof(s->io_q.iocbs[0]));
}
+ /* Now there should be room for some more requests */
+ if (!qemu_co_queue_empty(&s->io_q.waiting)) {
+ if (qemu_in_coroutine()) {
+ qemu_co_queue_next(&s->io_q.waiting);
+ } else {
+ qemu_co_enter_next(&s->io_q.waiting);
+
+ }
+ }
+
return ret;
}
static int ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb)
{
unsigned int idx = s->io_q.idx;
+ bool was_waiting = false;
+ int ret = 0;
- if (unlikely(idx == s->io_q.size)) {
- return -EAGAIN;
+ while (unlikely(idx == s->io_q.size)) {
+ /* Wait for iocb slots to become free */
+ qemu_co_queue_wait(&s->io_q.waiting);
+ was_waiting = true;
}
s->io_q.iocbs[idx++] = iocb;
@@ -217,10 +234,14 @@ static int ioq_enqueue(struct qemu_laio_state *s, struct
iocb *iocb)
/* submit immediately if queue is not plugged or full */
if (!s->io_q.plugged || idx == s->io_q.size) {
- return ioq_submit(s);
- } else {
- return 0;
+ ret = ioq_submit(s);
+ } else if (was_waiting) {
+ /* We were just woken up and there's stil room in the queue. Wake up
+ * someone else, too. */
+ qemu_co_queue_next(&s->io_q.waiting);
}
+
+ return ret;
}
void laio_io_plug(BlockDriverState *bs, void *aio_ctx)
--
1.8.3.1
