commit 6d7e73d62fa32813b6f6a3575db2e9b5e0d43387
author Fam Zheng <famz@redhat.com> Thu May 15 19:22:06 2014 +0800
committer Stefan Hajnoczi <stefanha@redhat.com> Wed Jun 04 09:56:12 2014 +0200
tree 23ecafea16541ce74c3cd4f1ff327488ff862ea8
parent db519cba8713fb49aa5233e8debe61dccdd3a57f

virtio-blk: Allow config-wce in dataplane

Dataplane now uses block layer. Protect bdrv_set_enable_write_cache with
aio_context_acquire and aio_context_release, so we can enable config-wce
to allow guest to modify the write cache online.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

hw/block/virtio-blk.c

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 8a568e5..5e9433d 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -523,7 +523,10 @@
     struct virtio_blk_config blkcfg;
 
     memcpy(&blkcfg, config, sizeof(blkcfg));
+
+    aio_context_acquire(bdrv_get_aio_context(s->bs));
     bdrv_set_enable_write_cache(s->bs, blkcfg.wce != 0);
+    aio_context_release(bdrv_get_aio_context(s->bs));
 }
 
 static uint32_t virtio_blk_get_features(VirtIODevice *vdev, uint32_t features)
@@ -582,7 +585,10 @@
      * s->bs would erroneously be placed in writethrough mode.
      */
     if (!(features & (1 << VIRTIO_BLK_F_CONFIG_WCE))) {
-        bdrv_set_enable_write_cache(s->bs, !!(features & (1 << VIRTIO_BLK_F_WCE)));
+        aio_context_acquire(bdrv_get_aio_context(s->bs));
+        bdrv_set_enable_write_cache(s->bs,
+                                    !!(features & (1 << VIRTIO_BLK_F_WCE)));
+        aio_context_release(bdrv_get_aio_context(s->bs));
     }
 }