block: Call .drain_begin only once in bdrv_drain_all_begin()

bdrv_drain_all_begin() used to call the .bdrv_co_drain_begin() driver
callback inside its polling loop. This means that how many times it got
called for each node depended on long it had to poll the event loop.

This is obviously not right and results in nodes that stay drained even
after bdrv_drain_all_end(), which calls .bdrv_co_drain_begin() once per
node.

Fix bdrv_drain_all_begin() to call the callback only once, too.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 2da9b7d456278bccc6ce889ae350f2867155d7e8)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/block/io.c b/block/io.c
index 096468b76164d899dfb061b11898ef34547a86f2..603f5b059e618e6b2234c04e5fe0e4cae799838a 100644 (file)
--- a/block/io.c
+++ b/block/io.c
@@ -355,6 +355,7 @@ void bdrv_drain_all_begin(void)
         aio_context_acquire(aio_context);
         bdrv_parent_drained_begin(bs);
         aio_disable_external(aio_context);
+        bdrv_drain_invoke(bs, true);
         aio_context_release(aio_context);
 
         if (!g_slist_find(aio_ctxs, aio_context)) {
@@ -377,8 +378,6 @@ void bdrv_drain_all_begin(void)
             aio_context_acquire(aio_context);
             for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
                 if (aio_context == bdrv_get_aio_context(bs)) {
-                    /* FIXME Calling this multiple times is wrong */
-                    bdrv_drain_invoke(bs, true);
                     waited |= bdrv_drain_recurse(bs, true);
                 }
             }