block: Improve some block-commit, block-stream error messages

block-commit defaults @base-node to the deepest backing image.  When
there is none, it fails with "Base 'NULL' not found".  Improve to
"There is no backing image".

block-commit and block-stream reject a @base argument that doesn't
resolve with "Base 'BASE' not found".  Commit 6b33f3ae8b "qemu-img:
Improve commit invalid base message" improved this message in
qemu-img.  Improve it here, too: "Can't find '%s' in the backing
chain".

QERR_BASE_NOT_FOUND is now unused.  Drop.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20201113082626.2725812-4-armbru@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>

1 files changed, 9 insertions, 6 deletions

diff --git a/blockdev.c b/blockdev.c
index fe6fb5d..d05a874 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2531,7 +2531,7 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
     if (has_base) {
         base_bs = bdrv_find_backing_image(bs, base);
         if (base_bs == NULL) {
-            error_setg(errp, QERR_BASE_NOT_FOUND, base);
+            error_setg(errp, "Can't find '%s' in the backing chain", base);
             goto out;
         }
         assert(bdrv_get_aio_context(base_bs) == aio_context);
@@ -2703,13 +2703,16 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,
         }
     } else if (has_base && base) {
         base_bs = bdrv_find_backing_image(top_bs, base);
+        if (base_bs == NULL) {
+            error_setg(errp, "Can't find '%s' in the backing chain", base);
+            goto out;
+        }
     } else {
         base_bs = bdrv_find_base(top_bs);
-    }
-
-    if (base_bs == NULL) {
-        error_setg(errp, QERR_BASE_NOT_FOUND, base ? base : "NULL");
-        goto out;
+        if (base_bs == NULL) {
+            error_setg(errp, "There is no backimg image");
+            goto out;
+        }
     }
 
     assert(bdrv_get_aio_context(base_bs) == aio_context);