From 8e94512568729c8dfaa9827b5417c7be3d2fb773 Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Thu, 22 Sep 2016 21:45:50 -0400
Subject: [PATCH] block: reintroduce bdrv_flush_all

Commit fe1a9cbc moved the flush_all routine from the bdrv layer to the
block-backend layer. In doing so, however, the semantics of the routine
changed slightly such that flush_all now used blk_flush instead of
bdrv_flush.

blk_flush can fail if the attached device model reports that it is not
"available," (i.e. the tray is open.) This changed the semantics of
flush_all such that it can now fail for e.g. open CDROM drives.

Reintroduce bdrv_flush_all to regain the old semantics without having to
alter the behavior of blk_flush or blk_flush_all, which are already
'doing the right thing.'

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Acked-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 4085f5c7a239567a292876f46cb59d9b19bcf6ac)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 block/io.c            | 25 +++++++++++++++++++++++++
 include/block/block.h |  1 +
 2 files changed, 26 insertions(+)

diff --git a/block/io.c b/block/io.c
index 420944d80d..487755aac6 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1615,6 +1615,31 @@ int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
                            BDRV_REQ_ZERO_WRITE | flags);
 }
 
+/*
+ * Flush ALL BDSes regardless of if they are reachable via a BlkBackend or not.
+ */
+int bdrv_flush_all(void)
+{
+    BdrvNextIterator it;
+    BlockDriverState *bs = NULL;
+    int result = 0;
+
+    for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+        int ret;
+
+        aio_context_acquire(aio_context);
+        ret = bdrv_flush(bs);
+        if (ret < 0 && !result) {
+            result = ret;
+        }
+        aio_context_release(aio_context);
+    }
+
+    return result;
+}
+
+
 typedef struct BdrvCoGetBlockStatusData {
     BlockDriverState *bs;
     BlockDriverState *base;
diff --git a/include/block/block.h b/include/block/block.h
index 11c162d594..acddf3bc42 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -336,6 +336,7 @@ int bdrv_inactivate_all(void);
 /* Ensure contents are flushed to disk.  */
 int bdrv_flush(BlockDriverState *bs);
 int coroutine_fn bdrv_co_flush(BlockDriverState *bs);
+int bdrv_flush_all(void);
 void bdrv_close_all(void);
 void bdrv_drain(BlockDriverState *bs);
 void coroutine_fn bdrv_co_drain(BlockDriverState *bs);