[PATCH v12 06/14] copy-on-read: pass bottom node name to COR driver

[Andrey Shinkevich via <qemu-devel@nongnu.org>]

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 bottom node name, that is the first non-filter
overlay of the base, to the copy-on-read driver as the 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@virtuozzo.com>
---
 block/copy-on-read.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/block/copy-on-read.c b/block/copy-on-read.c
index 618c4c4..3d8e4db 100644
--- a/block/copy-on-read.c
+++ b/block/copy-on-read.c
@@ -24,18 +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 *bottom_bs;
 } BDRVStateCOR;
 
 
 static int cor_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
+    BlockDriverState *bottom_bs = NULL;
     BDRVStateCOR *state = bs->opaque;
+    /* Find a bottom node name, if any */
+    const char *bottom_node = qdict_get_try_str(options, "bottom");
 
     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
                                BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
@@ -51,7 +57,17 @@ 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 (bottom_node) {
+        bottom_bs = bdrv_lookup_bs(NULL, bottom_node, errp);
+        if (!bottom_bs) {
+            error_setg(errp, QERR_BASE_NOT_FOUND, bottom_node);
+            qdict_del(options, "bottom");
+            return -EINVAL;
+        }
+        qdict_del(options, "bottom");
+    }
     state->active = true;
+    state->bottom_bs = bottom_bs;
 
     /*
      * We don't need to call bdrv_child_refresh_perms() now as the permissions
-- 
1.8.3.1