commit 4da97120d51a4383aa96d741a2b837f8c4bbcd0b
author Stefan Hajnoczi <stefanha@redhat.com> Wed Aug 09 17:02:11 2017 +0100
committer Stefan Hajnoczi <stefanha@redhat.com> Thu Aug 10 14:33:43 2017 +0100
tree 1338896c20d3bee4ee1fe9326b3b32ee6f893d54
parent b38df311c174c98ef8cce7dec9f46603b083018e

IDE: Do not flush empty CDROM drives

The block backend changed in a way that flushing empty CDROM drives now
crashes.  Amend IDE to avoid doing so until the root problem can be
addressed for 2.11.

Original patch by John Snow <jsnow@redhat.com>.

Reported-by: Kieron Shorrock <kshorrock@paloaltonetworks.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20170809160212.29976-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

hw/ide/core.c

diff --git a/hw/ide/core.c b/hw/ide/core.c
index 0b48b64..bea3953 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -1063,7 +1063,15 @@
     s->status |= BUSY_STAT;
     ide_set_retry(s);
     block_acct_start(blk_get_stats(s->blk), &s->acct, 0, BLOCK_ACCT_FLUSH);
-    s->pio_aiocb = blk_aio_flush(s->blk, ide_flush_cb, s);
+
+    if (blk_bs(s->blk)) {
+        s->pio_aiocb = blk_aio_flush(s->blk, ide_flush_cb, s);
+    } else {
+        /* XXX blk_aio_flush() crashes when blk_bs(blk) is NULL, remove this
+         * temporary workaround when blk_aio_*() functions handle NULL blk_bs.
+         */
+        ide_flush_cb(s, 0);
+    }
 }
 
 static void ide_cfata_metadata_inquiry(IDEState *s)