[Qemu-devel] [PATCH v2 2/5] Fix migration in case of scsi-generic

[Dimitris Aragiorgis]

During migration, QEMU uses fsync()/fdatasync() on the open file
descriptor for read-write block devices to flush data just before
stopping the VM.

However, fsync() on a scsi-generic device returns -EINVAL which
causes the migration to fail. This patch skips flushing data in case
of an SG device, since submitting SCSI commands directly via an SG
character device (e.g. /dev/sg0) bypasses the page cache completely,
anyway.

Remove the bdrv_is_sg() test from iscsi_co_flush() since this is
now redundant (we flush the underlying protocol at the end
of bdrv_co_flush() which, with this patch, we never reach).

Signed-off-by: Dimitris Aragiorgis <address@hidden>
---
 block/io.c    |    2 +-
 block/iscsi.c |    4 ----
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/block/io.c b/block/io.c
index 1ce62c4..d248a4d 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2231,7 +2231,7 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
 {
     int ret;
 
-    if (!bs || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
+    if (!bs || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs) || 
bdrv_is_sg(bs)) {
         return 0;
     }
 
diff --git a/block/iscsi.c b/block/iscsi.c
index 502a81f..965978b 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -627,10 +627,6 @@ static int coroutine_fn iscsi_co_flush(BlockDriverState 
*bs)
     IscsiLun *iscsilun = bs->opaque;
     struct IscsiTask iTask;
 
-    if (bdrv_is_sg(bs)) {
-        return 0;
-    }
-
     if (!iscsilun->force_next_flush) {
         return 0;
     }
-- 
1.7.10.4