Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

# gpg: Signature made Tue 12 Apr 2016 09:29:54 BST using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/block-pull-request:
  MAINTAINERS: Add Fam Zheng as a co-maintainer of block I/O path
  mirror: Replace bdrv_drain(bs) with bdrv_co_drain(bs)
  block: Fix bdrv_drain in coroutine

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

4 files changed, 48 insertions, 1 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 9277fbf128..d26141277d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -998,6 +998,7 @@ T: git git://repo.or.cz/qemu/kevin.git block
 
 Block I/O path
 M: Stefan Hajnoczi <stefanha@redhat.com>
+M: Fam Zheng <famz@redhat.com>
 L: qemu-block@nongnu.org
 S: Supported
 F: async.c
diff --git a/block/io.c b/block/io.c
index c4869b96c5..a7dbf85b19 100644
--- a/block/io.c
+++ b/block/io.c
@@ -253,6 +253,47 @@ static void bdrv_drain_recurse(BlockDriverState *bs)
     }
 }
 
+typedef struct {
+    Coroutine *co;
+    BlockDriverState *bs;
+    QEMUBH *bh;
+    bool done;
+} BdrvCoDrainData;
+
+static void bdrv_co_drain_bh_cb(void *opaque)
+{
+    BdrvCoDrainData *data = opaque;
+    Coroutine *co = data->co;
+
+    qemu_bh_delete(data->bh);
+    bdrv_drain(data->bs);
+    data->done = true;
+    qemu_coroutine_enter(co, NULL);
+}
+
+void coroutine_fn bdrv_co_drain(BlockDriverState *bs)
+{
+    BdrvCoDrainData data;
+
+    /* Calling bdrv_drain() from a BH ensures the current coroutine yields and
+     * other coroutines run if they were queued from
+     * qemu_co_queue_run_restart(). */
+
+    assert(qemu_in_coroutine());
+    data = (BdrvCoDrainData) {
+        .co = qemu_coroutine_self(),
+        .bs = bs,
+        .done = false,
+        .bh = aio_bh_new(bdrv_get_aio_context(bs), bdrv_co_drain_bh_cb, &data),
+    };
+    qemu_bh_schedule(data.bh);
+
+    qemu_coroutine_yield();
+    /* If we are resumed from some other event (such as an aio completion or a
+     * timer callback), it is a bug in the caller that should be fixed. */
+    assert(data.done);
+}
+
 /*
  * Wait for pending requests to complete on a single BlockDriverState subtree,
  * and suspend block driver's internal I/O until next request arrives.
@@ -269,6 +310,10 @@ void bdrv_drain(BlockDriverState *bs)
     bool busy = true;
 
     bdrv_drain_recurse(bs);
+    if (qemu_in_coroutine()) {
+        bdrv_co_drain(bs);
+        return;
+    }
     while (busy) {
         /* Keep iterating */
          bdrv_flush_io_queue(bs);
diff --git a/block/mirror.c b/block/mirror.c
index f64db1a69b..c2cfc1a5ef 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -650,7 +650,7 @@ static void coroutine_fn mirror_run(void *opaque)
              * mirror_populate runs.
              */
             trace_mirror_before_drain(s, cnt);
-            bdrv_drain(bs);
+            bdrv_co_drain(bs);
             cnt = bdrv_get_dirty_count(s->dirty_bitmap);
         }
 
diff --git a/include/block/block.h b/include/block/block.h
index 6a39f946f5..3a731377db 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -372,6 +372,7 @@ int bdrv_flush(BlockDriverState *bs);
 int coroutine_fn bdrv_co_flush(BlockDriverState *bs);
 void bdrv_close_all(void);
 void bdrv_drain(BlockDriverState *bs);
+void coroutine_fn bdrv_co_drain(BlockDriverState *bs);
 void bdrv_drain_all(void);
 
 int bdrv_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors);