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[013/156] mirror: fix early wake from sleep due to aio

Message ID 1404839947-1086-14-git-send-email-mdroth@linux.vnet.ibm.com
State New
Headers show

Commit Message

Michael Roth July 8, 2014, 5:16 p.m. UTC 
From: Stefan Hajnoczi <stefanha@redhat.com>

The mirror blockjob coroutine rate-limits itself by sleeping.  The
coroutine also performs I/O asynchronously so it's important that the
aio callback doesn't wake the coroutine early as that breaks
rate-limiting.

Reported-by: Joaquim Barrera <jbarrera@ac.upc.edu>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 7b770c720b28b8ac5b82ae431f2f354b7f8add91)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 block/mirror.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)
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Patch

diff --git a/block/mirror.c b/block/mirror.c
index 9bfc22f..2d9104e 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -95,7 +95,14 @@  static void mirror_iteration_done(MirrorOp *op, int ret)
     }
 
     g_slice_free(MirrorOp, op);
-    qemu_coroutine_enter(s->common.co, NULL);
+
+    /* Enter coroutine when it is not sleeping.  The coroutine sleeps to
+     * rate-limit itself.  The coroutine will eventually resume since there is
+     * a sleep timeout so don't wake it early.
+     */
+    if (s->common.busy) {
+        qemu_coroutine_enter(s->common.co, NULL);
+    }
 }
 
 static void mirror_write_complete(void *opaque, int ret)