[Qemu-stable] [PATCH v2 1/1] block-backend: allow flush on devices with open tray

[John Snow]

If a device still has an attached BDS because the medium has not yet
been removed, we will be unable to migrate to a new host because
blk_flush will return an error for that backend.

Replace the call to blk_is_available to blk_is_inserted to weaken
the check and allow flushes from the backend to work, while still
disallowing flushes from the frontend/device model to work.

This fixes a regression present in 2.6.0 caused by the following commit:
fe1a9cbc339bb54d20f1ca4c1e8788d16944d5cf
block: Move some bdrv_*_all() functions to BB

Signed-off-by: John Snow <address@hidden>
---
 block/block-backend.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index effa038..36a32c3 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1058,7 +1058,7 @@ BlockAIOCB *blk_aio_pwritev(BlockBackend *blk, int64_t 
offset,
 BlockAIOCB *blk_aio_flush(BlockBackend *blk,
                           BlockCompletionFunc *cb, void *opaque)
 {
-    if (!blk_is_available(blk)) {
+    if (!blk_is_inserted(blk)) {
         return blk_abort_aio_request(blk, cb, opaque, -ENOMEDIUM);
     }
 
@@ -1118,7 +1118,7 @@ int blk_co_pdiscard(BlockBackend *blk, int64_t offset, 
int count)
 
 int blk_co_flush(BlockBackend *blk)
 {
-    if (!blk_is_available(blk)) {
+    if (!blk_is_inserted(blk)) {
         return -ENOMEDIUM;
     }
 
@@ -1127,7 +1127,7 @@ int blk_co_flush(BlockBackend *blk)
 
 int blk_flush(BlockBackend *blk)
 {
-    if (!blk_is_available(blk)) {
+    if (!blk_is_inserted(blk)) {
         return -ENOMEDIUM;
     }
 
-- 
2.7.4