[pve-devel] [PATCH qemu 03/23] PVE backup: factor out setting up snapshot access for fleecing

[Fiona Ebner]

Avoids some line bloat in the create_backup_jobs_bh() function and is
in preparation for setting up the snapshot access independently of
fleecing, in particular that will be useful for providing access to
the snapshot via NBD.

Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---
 pve-backup.c | 95 ++++++++++++++++++++++++++++++++--------------------
 1 file changed, 58 insertions(+), 37 deletions(-)

diff --git a/pve-backup.c b/pve-backup.c
index c4178758b3..051ebffe48 100644
--- a/pve-backup.c
+++ b/pve-backup.c
@@ -525,6 +525,62 @@ static int coroutine_fn pvebackup_co_add_config(
     goto out;
 }
 
+/*
+ * Setup a snapshot-access block node for a device with associated fleecing image.
+ */
+static int setup_snapshot_access(PVEBackupDevInfo *di, Error **errp)
+{
+    Error *local_err = NULL;
+
+    if (!di->fleecing.bs) {
+        error_setg(errp, "no associated fleecing image");
+        return -1;
+    }
+
+    QDict *cbw_opts = qdict_new();
+    qdict_put_str(cbw_opts, "driver", "copy-before-write");
+    qdict_put_str(cbw_opts, "file", bdrv_get_node_name(di->bs));
+    qdict_put_str(cbw_opts, "target", bdrv_get_node_name(di->fleecing.bs));
+
+    if (di->bitmap) {
+        /*
+         * Only guest writes to parts relevant for the backup need to be intercepted with
+         * old data being copied to the fleecing image.
+         */
+        qdict_put_str(cbw_opts, "bitmap.node", bdrv_get_node_name(di->bs));
+        qdict_put_str(cbw_opts, "bitmap.name", bdrv_dirty_bitmap_name(di->bitmap));
+    }
+    /*
+     * Fleecing storage is supposed to be fast and it's better to break backup than guest
+     * writes. Certain guest drivers like VirtIO-win have 60 seconds timeout by default, so
+     * abort a bit before that.
+     */
+    qdict_put_str(cbw_opts, "on-cbw-error", "break-snapshot");
+    qdict_put_int(cbw_opts, "cbw-timeout", 45);
+
+    di->fleecing.cbw = bdrv_insert_node(di->bs, cbw_opts, BDRV_O_RDWR, &local_err);
+
+    if (!di->fleecing.cbw) {
+        error_setg(errp, "appending cbw node for fleecing failed: %s",
+                   local_err ? error_get_pretty(local_err) : "unknown error");
+        return -1;
+    }
+
+    QDict *snapshot_access_opts = qdict_new();
+    qdict_put_str(snapshot_access_opts, "driver", "snapshot-access");
+    qdict_put_str(snapshot_access_opts, "file", bdrv_get_node_name(di->fleecing.cbw));
+
+    di->fleecing.snapshot_access =
+        bdrv_open(NULL, NULL, snapshot_access_opts, BDRV_O_RDWR | BDRV_O_UNMAP, &local_err);
+    if (!di->fleecing.snapshot_access) {
+        error_setg(errp, "setting up snapshot access for fleecing failed: %s",
+                   local_err ? error_get_pretty(local_err) : "unknown error");
+        return -1;
+    }
+
+    return 0;
+}
+
 /*
  * backup_job_create can *not* be run from a coroutine, so this can't either.
  * The caller is responsible that backup_mutex is held nonetheless.
@@ -569,49 +625,14 @@ static void create_backup_jobs_bh(void *opaque) {
         const char *job_id = bdrv_get_device_name(di->bs);
         bdrv_graph_co_rdunlock();
         if (di->fleecing.bs) {
-            QDict *cbw_opts = qdict_new();
-            qdict_put_str(cbw_opts, "driver", "copy-before-write");
-            qdict_put_str(cbw_opts, "file", bdrv_get_node_name(di->bs));
-            qdict_put_str(cbw_opts, "target", bdrv_get_node_name(di->fleecing.bs));
-
-            if (di->bitmap) {
-                /*
-                 * Only guest writes to parts relevant for the backup need to be intercepted with
-                 * old data being copied to the fleecing image.
-                 */
-                qdict_put_str(cbw_opts, "bitmap.node", bdrv_get_node_name(di->bs));
-                qdict_put_str(cbw_opts, "bitmap.name", bdrv_dirty_bitmap_name(di->bitmap));
-            }
-            /*
-             * Fleecing storage is supposed to be fast and it's better to break backup than guest
-             * writes. Certain guest drivers like VirtIO-win have 60 seconds timeout by default, so
-             * abort a bit before that.
-             */
-            qdict_put_str(cbw_opts, "on-cbw-error", "break-snapshot");
-            qdict_put_int(cbw_opts, "cbw-timeout", 45);
-
-            di->fleecing.cbw = bdrv_insert_node(di->bs, cbw_opts, BDRV_O_RDWR, &local_err);
-
-            if (!di->fleecing.cbw) {
-                error_setg(errp, "appending cbw node for fleecing failed: %s",
-                           local_err ? error_get_pretty(local_err) : "unknown error");
-                bdrv_drained_end(di->bs);
-                break;
-            }
-
-            QDict *snapshot_access_opts = qdict_new();
-            qdict_put_str(snapshot_access_opts, "driver", "snapshot-access");
-            qdict_put_str(snapshot_access_opts, "file", bdrv_get_node_name(di->fleecing.cbw));
-
-            di->fleecing.snapshot_access =
-                bdrv_open(NULL, NULL, snapshot_access_opts, BDRV_O_RDWR | BDRV_O_UNMAP, &local_err);
-            if (!di->fleecing.snapshot_access) {
+            if (setup_snapshot_access(di, &local_err) < 0) {
                 error_setg(errp, "setting up snapshot access for fleecing failed: %s",
                            local_err ? error_get_pretty(local_err) : "unknown error");
                 cleanup_snapshot_access(di);
                 bdrv_drained_end(di->bs);
                 break;
             }
+
             source_bs = di->fleecing.snapshot_access;
             discard_source = true;
 
-- 
2.39.2