[PATCH 1/2] block/export: Free ignored Error

[Max Reitz <mreitz@redhat.com>]

When invoking block-export-add with some iothread and
fixed-iothread=false, and changing the node's iothread fails, the error
is supposed to be ignored.

However, it is still stored in *errp, which is wrong.  If a second error
occurs, the "*errp must be NULL" assertion in error_setv() fails:

  qemu-system-x86_64: ../util/error.c:59: error_setv: Assertion
  `*errp == NULL' failed.

So the error from bdrv_try_set_aio_context() must be freed when it is
ignored.

Fixes: f51d23c80af73c95e0ce703ad06a300f1b3d63ef
       ("block/export: add iothread and fixed-iothread options")
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/export/export.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/export/export.c b/block/export/export.c
index fec7d9f738..ce5dd3e59b 100644
--- a/block/export/export.c
+++ b/block/export/export.c
@@ -68,6 +68,7 @@ static const BlockExportDriver *blk_exp_find_driver(BlockExportType type)
 
 BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
 {
+    ERRP_GUARD();
     bool fixed_iothread = export->has_fixed_iothread && export->fixed_iothread;
     const BlockExportDriver *drv;
     BlockExport *exp = NULL;
@@ -127,6 +128,9 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
             ctx = new_ctx;
         } else if (fixed_iothread) {
             goto fail;
+        } else {
+            error_free(*errp);
+            *errp = NULL;
         }
     }
 
-- 
2.30.2