[Qemu-devel] [PATCH v4 11/15] block: add bdrv_find_backing_image

[Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>]

From: Marcelo Tosatti <mtosatti@redhat.com>

Add bdrv_find_backing_image: given a BlockDriverState pointer, and an id,
traverse the backing image chain to locate the id.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 block.c |   17 +++++++++++++++++
 block.h |    1 +
 2 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/block.c b/block.c
index 5bfaa3a..9b688a0 100644
--- a/block.c
+++ b/block.c
@@ -2614,6 +2614,23 @@ int bdrv_snapshot_load_tmp(BlockDriverState *bs,
     return -ENOTSUP;
 }
 
+BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs, const char *id)
+{
+    if (!bs->drv) {
+        return NULL;
+    }
+
+    if (bs->backing_hd) {
+        if (strcmp(bs->backing_file, id) == 0) {
+            return bs->backing_hd;
+        } else {
+            return bdrv_find_backing_image(bs->backing_hd, id);
+        }
+    }
+
+    return NULL;
+}
+
 #define NB_SUFFIXES 4
 
 char *get_human_readable_size(char *buf, int buf_size, int64_t size)
diff --git a/block.h b/block.h
index 51b90c7..a1d9b56 100644
--- a/block.h
+++ b/block.h
@@ -153,6 +153,7 @@ int coroutine_fn bdrv_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
     int nb_sectors);
 int coroutine_fn bdrv_co_is_allocated(BlockDriverState *bs, int64_t sector_num,
     int nb_sectors, int *pnum);
+BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs, const char *id);
 int bdrv_truncate(BlockDriverState *bs, int64_t offset);
 int64_t bdrv_getlength(BlockDriverState *bs);
 int64_t bdrv_get_allocated_file_size(BlockDriverState *bs);
-- 
1.7.7.3