Patchwork [3/3] block: fix bdrv_flush() ordering in bdrv_close()

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Submitter Stefan Hajnoczi
Date July 5, 2013, 11:32 a.m.
Message ID <1373023972-3587-4-git-send-email-stefanha@redhat.com>
Download mbox | patch
Permalink /patch/257159/
State New
Headers show

Comments

Stefan Hajnoczi - July 5, 2013, 11:32 a.m.
Since 80ccf93b we flush the block device during close.  The
bdrv_drain_all() call should come before bdrv_flush() to ensure guest
write requests have completed.  Otherwise we may miss pending writes
when flushing.

Call bdrv_drain_all() again for safety as the final step after
bdrv_flush().  This should not be necessary but we can be paranoid here
in case bdrv_flush() left I/O pending.

Cc: qemu-stable@nongnu.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Patch

diff --git a/block.c b/block.c
index 6c493ad..183fec8 100644
--- a/block.c
+++ b/block.c
@@ -1358,11 +1358,12 @@  void bdrv_reopen_abort(BDRVReopenState *reopen_state)
 
 void bdrv_close(BlockDriverState *bs)
 {
-    bdrv_flush(bs);
     if (bs->job) {
         block_job_cancel_sync(bs->job);
     }
-    bdrv_drain_all();
+    bdrv_drain_all(); /* complete I/O */
+    bdrv_flush(bs);
+    bdrv_drain_all(); /* in case flush left pending I/O */
     notifier_list_notify(&bs->close_notifiers, bs);
 
     if (bs->drv) {