[PATCH v11 04/13] copy-on-read: pass overlay base node name to COR driver

[Andrey Shinkevich <andrey.shinkevich@xxxxxxxxxxxxx>]

We are going to use the COR-filter for a block-stream job.
To limit COR operations by the base node in the backing chain during
stream job, pass the name of overlay base node to the copy-on-read
driver as base node itself may change due to possible concurrent jobs.
The rest of the functionality will be implemented in the patch that
follows.

Signed-off-by: Andrey Shinkevich <andrey.shinkevich@xxxxxxxxxxxxx>
---
 block/copy-on-read.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/block/copy-on-read.c b/block/copy-on-read.c
index bcccf0f..c578b1b 100644
--- a/block/copy-on-read.c
+++ b/block/copy-on-read.c
@@ -24,19 +24,24 @@
 #include "block/block_int.h"
 #include "qemu/module.h"
 #include "qapi/error.h"
+#include "qapi/qmp/qerror.h"
 #include "qapi/qmp/qdict.h"
 #include "block/copy-on-read.h"
 
 
 typedef struct BDRVStateCOR {
     bool active;
+    BlockDriverState *base_overlay;
 } BDRVStateCOR;
 
 
 static int cor_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
+    BlockDriverState *base_overlay = NULL;
     BDRVStateCOR *state = bs->opaque;
+    /* We need the base overlay node rather than the base itself */
+    const char *base_overlay_node = qdict_get_try_str(options, "base");
 
     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
                                BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
@@ -52,7 +57,16 @@ static int cor_open(BlockDriverState *bs, QDict *options, int flags,
         ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
             bs->file->bs->supported_zero_flags);
 
+    if (base_overlay_node) {
+        qdict_del(options, "base");
+        base_overlay = bdrv_lookup_bs(NULL, base_overlay_node, errp);
+        if (!base_overlay) {
+            error_setg(errp, QERR_BASE_NOT_FOUND, base_overlay_node);
+            return -EINVAL;
+        }
+    }
     state->active = true;
+    state->base_overlay = base_overlay;
 
     /*
      * We don't need to call bdrv_child_refresh_perms() now as the permissions
-- 
1.8.3.1