[Xen-changelog] [qemu-upstream-unstable] aio: Fix return value of aio_poll()

[patchbot@xxxxxxx]

commit 9d173df5538a73cb8be53684ab19ea201c783663
Author:     Kevin Wolf <kwolf@xxxxxxxxxx>
AuthorDate: Wed Jan 16 19:25:51 2013 +0100
Commit:     Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon Jan 21 13:23:52 2013 -0600

    aio: Fix return value of aio_poll()
    
    aio_poll() must return true if any work is still pending, even if it
    didn't make progress, so that bdrv_drain_all() doesn't stop waiting too
    early. The possibility of stopping early occasionally lead to a failed
    assertion in bdrv_drain_all(), when some in-flight request was missed
    and the function didn't really drain all requests.
    
    In order to make that change, the return value as specified in the
    function comment must change for blocking = false; fortunately, the
    return value of blocking = false callers is only used in test cases, so
    this change shouldn't cause any trouble.
    
    Cc: qemu-stable@xxxxxxxxxx
    Signed-off-by: Kevin Wolf <kwolf@xxxxxxxxxx>
    Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
    (cherry picked from commit 2ea9b58f0bc62445b7ace2381b4c4db7d5597e19)
    
    Signed-off-by: Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
---
 aio-posix.c      |    3 ++-
 aio-win32.c      |    3 ++-
 qemu-aio.h       |    6 ++----
 tests/test-aio.c |    4 ++--
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/aio-posix.c b/aio-posix.c
index 05cc84e..13d4572 100644
--- a/aio-posix.c
+++ b/aio-posix.c
@@ -264,5 +264,6 @@ bool aio_poll(AioContext *ctx, bool blocking)
         }
     }
 
-    return progress;
+    assert(progress || busy);
+    return true;
 }
diff --git a/aio-win32.c b/aio-win32.c
index cec4646..7886e98 100644
--- a/aio-win32.c
+++ b/aio-win32.c
@@ -214,5 +214,6 @@ bool aio_poll(AioContext *ctx, bool blocking)
         events[ret - WAIT_OBJECT_0] = events[--count];
     }
 
-    return progress;
+    assert(progress || busy);
+    return true;
 }
diff --git a/qemu-aio.h b/qemu-aio.h
index 3889fe9..2b6bdbc 100644
--- a/qemu-aio.h
+++ b/qemu-aio.h
@@ -177,16 +177,14 @@ bool aio_pending(AioContext *ctx);
  * aio as a result of executing I/O completion or bh callbacks.
  *
  * If there is no pending AIO operation or completion (bottom half),
- * return false.  If there are pending bottom halves, return true.
+ * return false.  If there are pending AIO operations of bottom halves,
+ * return true.
  *
  * If there are no pending bottom halves, but there are pending AIO
  * operations, it may not be possible to make any progress without
  * blocking.  If @blocking is true, this function will wait until one
  * or more AIO events have completed, to ensure something has moved
  * before returning.
- *
- * If @blocking is false, this function will also return false if the
- * function cannot make any progress without blocking.
  */
 bool aio_poll(AioContext *ctx, bool blocking);
 
diff --git a/tests/test-aio.c b/tests/test-aio.c
index f53c908..096a6e8 100644
--- a/tests/test-aio.c
+++ b/tests/test-aio.c
@@ -315,13 +315,13 @@ static void test_wait_event_notifier_noflush(void)
     event_notifier_set(&data.e);
     g_assert(aio_poll(ctx, false));
     g_assert_cmpint(data.n, ==, 1);
-    g_assert(!aio_poll(ctx, false));
+    g_assert(aio_poll(ctx, false));
     g_assert_cmpint(data.n, ==, 1);
 
     event_notifier_set(&data.e);
     g_assert(aio_poll(ctx, false));
     g_assert_cmpint(data.n, ==, 2);
-    g_assert(!aio_poll(ctx, false));
+    g_assert(aio_poll(ctx, false));
     g_assert_cmpint(data.n, ==, 2);
 
     event_notifier_set(&dummy.e);
--
generated by git-patchbot for /home/xen/git/qemu-upstream-unstable.git

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