[Sheepdog] [PATCH 2/3] sheepdog: allow cancellation of I/Os which are not processed yet

[MORITA Kazutaka]

We can cancel I/O requests safely if they are not sent to the servers.

Signed-off-by: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>
---
 block/sheepdog.c |   37 +++++++++++++++++++++++++++++++++++++
 1 files changed, 37 insertions(+), 0 deletions(-)

diff --git a/block/sheepdog.c b/block/sheepdog.c
index cedf806..ed98701 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -421,6 +421,43 @@ static void sd_finish_aiocb(SheepdogAIOCB *acb)
 static void sd_aio_cancel(BlockDriverAIOCB *blockacb)
 {
     SheepdogAIOCB *acb = (SheepdogAIOCB *)blockacb;
+    BDRVSheepdogState *s = blockacb->bs->opaque;
+    AIOReq *areq, *next, *oldest_send_req = NULL;
+
+    if (acb->bh) {
+        /*
+         * sd_readv_writev_bh_cb() is not called yet, so we can
+         * release this safely
+         */
+        qemu_bh_delete(acb->bh);
+        acb->bh = NULL;
+        qemu_aio_release(acb);
+        return;
+    }
+
+    QLIST_FOREACH(areq, &s->outstanding_aio_head, outstanding_aio_siblings) {
+        if (areq->state == AIO_SEND_OBJREQ) {
+            oldest_send_req = areq;
+        }
+    }
+
+    QLIST_FOREACH_SAFE(areq, &s->outstanding_aio_head,
+                       outstanding_aio_siblings, next) {
+        if (areq->state == AIO_RECV_OBJREQ) {
+            continue;
+        }
+        if (areq->state == AIO_SEND_OBJREQ && areq == oldest_send_req) {
+            /* the oldest AIO_SEND_OBJREQ request could be being sent */
+            continue;
+        }
+        free_aio_req(s, areq);
+    }
+
+    if (QLIST_EMPTY(&acb->aioreq_head)) {
+        /* there is no outstanding request */
+        qemu_aio_release(acb);
+        return;
+    }
 
     /*
      * Sheepdog cannot cancel the requests which are already sent to
-- 
1.5.6.5