[PATCH v8 4/7] copy-on-read: pass base file name to COR driver

[Andrey Shinkevich]

To limit the guest's COR operations by the base node in the backing
chain during stream job, pass the base file name to the copy-on-read
driver. 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 | 41 ++++++++++++++++++++++++++++++++++++++++-
 block/copy-on-read.h |  1 +
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/block/copy-on-read.c b/block/copy-on-read.c
index 0ede7aa..1f858bb 100644
--- a/block/copy-on-read.c
+++ b/block/copy-on-read.c
@@ -24,19 +24,45 @@
 #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_bs;
 } BDRVStateCOR;
 
+/*
+ * Non-zero pointers are the caller's responsibility.
+ */
+static BlockDriverState *get_base_by_name(BlockDriverState *bs,
+                                          const char *base_name, Error **errp)
+{
+    BlockDriverState *base_bs = NULL;
+    AioContext *aio_context;
+
+    base_bs = bdrv_find_backing_image(bs, base_name);
+    if (base_bs == NULL) {
+        error_setg(errp, QERR_BASE_NOT_FOUND, base_name);
+        return NULL;
+    }
+
+    aio_context = bdrv_get_aio_context(bs);
+    aio_context_acquire(aio_context);
+    assert(bdrv_get_aio_context(base_bs) == aio_context);
+    aio_context_release(aio_context);
+
+    return base_bs;
+}
 
 static int cor_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
+    BlockDriverState *base_bs = NULL;
     BDRVStateCOR *state = bs->opaque;
+    const char *base_name = 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 +78,15 @@ 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_name) {
+        qdict_del(options, "base");
+        base_bs = get_base_by_name(bs, base_name, errp);
+        if (!base_bs) {
+            return -EINVAL;
+        }
+    }
     state->active = true;
+    state->base_bs = base_bs;
 
     /*
      * We don't need to call bdrv_child_refresh_perms() now as the permissions
@@ -190,6 +224,7 @@ static void bdrv_copy_on_read_init(void)
 
 
 static BlockDriverState *create_filter_node(BlockDriverState *bs,
+                                            const char *base_name,
                                             const char *filter_node_name,
                                             Error **errp)
 {
@@ -197,6 +232,9 @@ static BlockDriverState 
*create_filter_node(BlockDriverState *bs,
 
     qdict_put_str(opts, "driver", "copy-on-read");
     qdict_put_str(opts, "file", bdrv_get_node_name(bs));
+    if (base_name) {
+        qdict_put_str(opts, "base", base_name);
+    }
     if (filter_node_name) {
         qdict_put_str(opts, "node-name", filter_node_name);
     }
@@ -206,13 +244,14 @@ static BlockDriverState 
*create_filter_node(BlockDriverState *bs,
 
 
 BlockDriverState *bdrv_cor_filter_append(BlockDriverState *bs,
+                                         const char *base_name,
                                          const char *filter_node_name,
                                          Error **errp)
 {
     BlockDriverState *cor_filter_bs;
     Error *local_err = NULL;
 
-    cor_filter_bs = create_filter_node(bs, filter_node_name, errp);
+    cor_filter_bs = create_filter_node(bs, base_name, filter_node_name, errp);
     if (cor_filter_bs == NULL) {
         error_prepend(errp, "Could not create filter node: ");
         return NULL;
diff --git a/block/copy-on-read.h b/block/copy-on-read.h
index 1686e4e..6a7c8bb 100644
--- a/block/copy-on-read.h
+++ b/block/copy-on-read.h
@@ -28,6 +28,7 @@
 #include "block/block_int.h"
 
 BlockDriverState *bdrv_cor_filter_append(BlockDriverState *bs,
+                                         const char *base_name,
                                          const char *filter_node_name,
                                          Error **errp);
 void bdrv_cor_filter_drop(BlockDriverState *cor_filter_bs);
-- 
1.8.3.1