commit: Add top-node/base-node options

The block-commit QMP command required specifying the top and base nodes
of the commit jobs using the file name of that node. While this works
in simple cases (local files with absolute paths), the file names
generated for more complicated setups can be hard to predict.

The block-commit command has more problems than just this, so we want to
replace it altogether in the long run, but libvirt needs a reliable way
to address nodes now. So we don't want to wait for a new, cleaner
command, but just add the minimal thing needed right now.

This adds two new options top-node and base-node to the command, which
allow specifying node names instead. They are mutually exclusive with
the old options.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 30 insertions, 2 deletions

diff --git a/blockdev.c b/blockdev.c
index d4b42403df..a8755bd908 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3214,7 +3214,9 @@ out:
 }
 
 void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,
+                      bool has_base_node, const char *base_node,
                       bool has_base, const char *base,
+                      bool has_top_node, const char *top_node,
                       bool has_top, const char *top,
                       bool has_backing_file, const char *backing_file,
                       bool has_speed, int64_t speed,
@@ -3275,7 +3277,20 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,
     /* default top_bs is the active layer */
     top_bs = bs;
 
-    if (has_top && top) {
+    if (has_top_node && has_top) {
+        error_setg(errp, "'top-node' and 'top' are mutually exclusive");
+        goto out;
+    } else if (has_top_node) {
+        top_bs = bdrv_lookup_bs(NULL, top_node, errp);
+        if (top_bs == NULL) {
+            goto out;
+        }
+        if (!bdrv_chain_contains(bs, top_bs)) {
+            error_setg(errp, "'%s' is not in this backing file chain",
+                       top_node);
+            goto out;
+        }
+    } else if (has_top && top) {
         if (strcmp(bs->filename, top) != 0) {
             top_bs = bdrv_find_backing_image(bs, top);
         }
@@ -3288,7 +3303,20 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,
 
     assert(bdrv_get_aio_context(top_bs) == aio_context);
 
-    if (has_base && base) {
+    if (has_base_node && has_base) {
+        error_setg(errp, "'base-node' and 'base' are mutually exclusive");
+        goto out;
+    } else if (has_base_node) {
+        base_bs = bdrv_lookup_bs(NULL, base_node, errp);
+        if (base_bs == NULL) {
+            goto out;
+        }
+        if (!bdrv_chain_contains(top_bs, base_bs)) {
+            error_setg(errp, "'%s' is not in this backing file chain",
+                       base_node);
+            goto out;
+        }
+    } else if (has_base && base) {
         base_bs = bdrv_find_backing_image(top_bs, base);
     } else {
         base_bs = bdrv_find_base(top_bs);