diff mbox

[v4,1/7] block: add bdrv_common_ancestor()

Message ID 1380542578-2387-2-git-send-email-famz@redhat.com
State New
Headers show

Commit Message

Fam Zheng Sept. 30, 2013, 12:02 p.m. UTC 
This function finds the common ancestor in backing chain of two BDSes.
If there's no common ancestor, NULL is returned.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block.c               | 15 +++++++++++++++
 include/block/block.h |  2 ++
 2 files changed, 17 insertions(+)

Comments

Eric Blake Sept. 30, 2013, 9:40 p.m. UTC | #1 
On 09/30/2013 06:02 AM, Fam Zheng wrote:
> This function finds the common ancestor in backing chain of two BDSes.
> If there's no common ancestor, NULL is returned.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  block.c               | 15 +++++++++++++++
>  include/block/block.h |  2 ++
>  2 files changed, 17 insertions(+)

Reviewed-by: Eric Blake <eblake@redhat.com>
diff mbox

Patch

diff --git a/block.c b/block.c
index ea4956d..db1381d 100644
--- a/block.c
+++ b/block.c
@@ -3036,6 +3036,21 @@  BlockDriverState *bdrv_find(const char *name)
     return NULL;
 }
 
+BlockDriverState *bdrv_common_ancestor(BlockDriverState *bs1,
+                                       BlockDriverState *bs2)
+{
+    /* TODO: higher efficiency with reverse linked backing chain */
+    BlockDriverState *base1, *base2;
+    for (base1 = bs1; base1; base1 = base1->backing_hd) {
+        for (base2 = bs2; base2; base2 = base2->backing_hd) {
+            if (base1 == base2) {
+                return base1;
+            }
+        }
+    }
+    return NULL;
+}
+
 BlockDriverState *bdrv_next(BlockDriverState *bs)
 {
     if (!bs) {
diff --git a/include/block/block.h b/include/block/block.h
index f808550..e095f16 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -321,6 +321,8 @@  void bdrv_lock_medium(BlockDriverState *bs, bool locked);
 void bdrv_eject(BlockDriverState *bs, bool eject_flag);
 const char *bdrv_get_format_name(BlockDriverState *bs);
 BlockDriverState *bdrv_find(const char *name);
+BlockDriverState *bdrv_common_ancestor(BlockDriverState *bs1,
+                                       BlockDriverState *bs2);
 BlockDriverState *bdrv_next(BlockDriverState *bs);
 void bdrv_iterate(void (*it)(void *opaque, BlockDriverState *bs),
                   void *opaque);