block/rbd: report a better error when namespace does not exist

If the namespace does not exist, rbd_create() fails with -ENOENT and
QEMU reports a generic "error rbd create: No such file or directory":

    $ qemu-img create rbd:rbd/namespace/image 1M
    Formatting 'rbd:rbd/namespace/image', fmt=raw size=1048576
    qemu-img: rbd:rbd/namespace/image: error rbd create: No such file or directory

Unfortunately rados_ioctx_set_namespace() does not fail if the namespace
does not exist, so let's use rbd_namespace_exists() in qemu_rbd_connect()
to check if the namespace exists, reporting a more understandable error:

    $ qemu-img create rbd:rbd/namespace/image 1M
    Formatting 'rbd:rbd/namespace/image', fmt=raw size=1048576
    qemu-img: rbd:rbd/namespace/image: namespace 'namespace' does not exist

Reported-by: Tingting Mao <timao@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20220517071012.6120-1-sgarzare@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/block/rbd.c b/block/rbd.c
index 6caf35c..f826410 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -831,6 +831,26 @@ static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
         error_setg_errno(errp, -r, "error opening pool %s", opts->pool);
         goto failed_shutdown;
     }
+
+#ifdef HAVE_RBD_NAMESPACE_EXISTS
+    if (opts->has_q_namespace && strlen(opts->q_namespace) > 0) {
+        bool exists;
+
+        r = rbd_namespace_exists(*io_ctx, opts->q_namespace, &exists);
+        if (r < 0) {
+            error_setg_errno(errp, -r, "error checking namespace");
+            goto failed_ioctx_destroy;
+        }
+
+        if (!exists) {
+            error_setg(errp, "namespace '%s' does not exist",
+                       opts->q_namespace);
+            r = -ENOENT;
+            goto failed_ioctx_destroy;
+        }
+    }
+#endif
+
     /*
      * Set the namespace after opening the io context on the pool,
      * if nspace == NULL or if nspace == "", it is just as we did nothing
@@ -840,6 +860,10 @@ static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
     r = 0;
     goto out;
 
+#ifdef HAVE_RBD_NAMESPACE_EXISTS
+failed_ioctx_destroy:
+    rados_ioctx_destroy(*io_ctx);
+#endif
 failed_shutdown:
     rados_shutdown(*cluster);
 out: