diff mbox

[09/11] migration: add missed aio_context_acquire for state writing/reading

Message ID 1446657582-21619-10-git-send-email-den@openvz.org
State New
Headers show

Commit Message

Denis V. Lunev Nov. 4, 2015, 5:19 p.m. UTC 
aio_context should be locked in the similar way as was done in QMP
snapshot creation in the other case there are a lot of possible
troubles if native AIO mode is enabled for disk.

qemu_fopen_bdrv and bdrv_fclose are used in real snapshot operations only
along with block drivers. This change should influence only HMP snapshot
operations.

AioContext lock is reqursive. Thus nested locking should not be a problem.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
---
 migration/savevm.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

Comments

Stefan Hajnoczi Nov. 6, 2015, 3:37 p.m. UTC | #1 
On Wed, Nov 04, 2015 at 08:19:40PM +0300, Denis V. Lunev wrote:
> aio_context should be locked in the similar way as was done in QMP
> snapshot creation in the other case there are a lot of possible
> troubles if native AIO mode is enabled for disk.
> 
> qemu_fopen_bdrv and bdrv_fclose are used in real snapshot operations only
> along with block drivers. This change should influence only HMP snapshot
> operations.
> 
> AioContext lock is reqursive. Thus nested locking should not be a problem.

hmp_savevm() and load_vmstate() look up the BlockDriverState and perform
other operations on it.  So the natural place to call acquire/release is
in hmp_savevm() and load_vmstate().  They need that anyway since they
also perform other operations.

qemu_fopen_bdrv() and bdrv_fclose() don't need to worry about
AioContext.
diff mbox

Patch

diff --git a/migration/savevm.c b/migration/savevm.c
index 9339f2e..f8c727d 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -153,7 +153,11 @@  static ssize_t block_get_buffer(void *opaque, uint8_t *buf, int64_t pos,
 
 static int bdrv_fclose(void *opaque)
 {
-    return bdrv_flush(opaque);
+    BlockDriverState *bs = (BlockDriverState *)opaque;
+    int ret = bdrv_flush(bs);
+
+    aio_context_release(bdrv_get_aio_context(bs));
+    return ret;
 }
 
 static const QEMUFileOps bdrv_read_ops = {
@@ -169,10 +173,18 @@  static const QEMUFileOps bdrv_write_ops = {
 
 static QEMUFile *qemu_fopen_bdrv(BlockDriverState *bs, int is_writable)
 {
+    QEMUFile *file;
+
     if (is_writable) {
-        return qemu_fopen_ops(bs, &bdrv_write_ops);
+        file = qemu_fopen_ops(bs, &bdrv_write_ops);
+    } else {
+        file = qemu_fopen_ops(bs, &bdrv_read_ops);
+    }
+
+    if (file != NULL) {
+        aio_context_acquire(bdrv_get_aio_context(bs));
     }
-    return qemu_fopen_ops(bs, &bdrv_read_ops);
+    return file;
 }