[Qemu-devel] [RFC PATCH 3/3] linux-aio: Don't reenter request coroutine recursively

[Kevin Wolf]

When getting an error while submitting requests, we must be careful to
wake up only inactive coroutines. Therefore we must special-case the
currently active coroutine and communicate an error for that request
using the ordinary return value of ioq_submit().

Signed-off-by: Kevin Wolf <address@hidden>
---
 block/linux-aio.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/block/linux-aio.c b/block/linux-aio.c
index 99b259d..fd8f0e4 100644
--- a/block/linux-aio.c
+++ b/block/linux-aio.c
@@ -177,12 +177,19 @@ static int ioq_submit(struct qemu_laio_state *s)
             container_of(s->io_q.iocbs[i], struct qemu_laiocb, iocb);
 
         laiocb->ret = (ret < 0) ? ret : -EIO;
-        qemu_laio_process_completion(s, laiocb);
+        if (laiocb->co != qemu_coroutine_self()) {
+            qemu_coroutine_enter(laiocb->co, NULL);
+        } else {
+            /* The return value is used for the currently active coroutine.
+             * We're always in ioq_enqueue() here, ioq_submit() never runs from
+             * a request's coroutine.*/
+            ret = laiocb->ret;
+        }
     }
     return ret;
 }
 
-static void ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb)
+static int ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb)
 {
     unsigned int idx = s->io_q.idx;
 
@@ -191,7 +198,9 @@ static void ioq_enqueue(struct qemu_laio_state *s, struct 
iocb *iocb)
 
     /* submit immediately if queue is full */
     if (idx == s->io_q.size) {
-        ioq_submit(s);
+        return ioq_submit(s);
+    } else {
+        return 0;
     }
 }
 
@@ -253,11 +262,11 @@ int laio_submit_co(BlockDriverState *bs, void *aio_ctx, 
int fd,
 
     if (!s->io_q.plugged) {
         ret = io_submit(s->ctx, 1, &iocbs);
-        if (ret < 0) {
-            return ret;
-        }
     } else {
-        ioq_enqueue(s, iocbs);
+        ret = ioq_enqueue(s, iocbs);
+    }
+    if (ret < 0) {
+        return ret;
     }
 
     qemu_coroutine_yield();
-- 
1.8.3.1