Patchwork [v3,3/7] block: implement reference count for BlockDriverState

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Submitter Fam Zheng
Date July 31, 2013, 10:13 a.m.
Message ID <1375265640-27307-4-git-send-email-famz@redhat.com>
Download mbox | patch
Permalink /patch/263732/
State New
Headers show

Comments

Fam Zheng - July 31, 2013, 10:13 a.m.
Introduce bdrv_ref/bdrv_unref to manage the lifecycle of
BlockDriverState. They are unused for now but will used to replace
bdrv_delete() later.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block.c                   | 21 +++++++++++++++++++++
 include/block/block.h     |  2 ++
 include/block/block_int.h |  1 +
 3 files changed, 24 insertions(+)
Wayne Xia - Aug. 2, 2013, 7:36 a.m.
Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>

> Introduce bdrv_ref/bdrv_unref to manage the lifecycle of
> BlockDriverState. They are unused for now but will used to replace
> bdrv_delete() later.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>   block.c                   | 21 +++++++++++++++++++++
>   include/block/block.h     |  2 ++
>   include/block/block_int.h |  1 +
>   3 files changed, 24 insertions(+)
>

Patch

diff --git a/block.c b/block.c
index c77cfd1..8f0d646 100644
--- a/block.c
+++ b/block.c
@@ -306,6 +306,7 @@  BlockDriverState *bdrv_new(const char *device_name)
     bdrv_iostatus_disable(bs);
     notifier_list_init(&bs->close_notifiers);
     notifier_with_return_list_init(&bs->before_write_notifiers);
+    bs->refcnt = 1;
 
     return bs;
 }
@@ -1518,6 +1519,9 @@  static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
     /* dirty bitmap */
     bs_dest->dirty_bitmap       = bs_src->dirty_bitmap;
 
+    /* reference count */
+    bs_dest->refcnt             = bs_src->refcnt;
+
     /* job */
     bs_dest->in_use             = bs_src->in_use;
     bs_dest->job                = bs_src->job;
@@ -4392,6 +4396,23 @@  int64_t bdrv_get_dirty_count(BlockDriverState *bs)
     }
 }
 
+/* Get a reference to bs */
+void bdrv_ref(BlockDriverState *bs)
+{
+    bs->refcnt++;
+}
+
+/* Release a previously grabbed reference to bs.
+ * If after releasing, reference count is zero, the BlockDriverState is
+ * deleted. */
+void bdrv_unref(BlockDriverState *bs)
+{
+    assert(bs->refcnt > 0);
+    if (--bs->refcnt == 0) {
+        bdrv_delete(bs);
+    }
+}
+
 void bdrv_set_in_use(BlockDriverState *bs, int in_use)
 {
     assert(bs->in_use != in_use);
diff --git a/include/block/block.h b/include/block/block.h
index 742fce5..b33ef62 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -356,6 +356,8 @@  int64_t bdrv_get_dirty_count(BlockDriverState *bs);
 void bdrv_enable_copy_on_read(BlockDriverState *bs);
 void bdrv_disable_copy_on_read(BlockDriverState *bs);
 
+void bdrv_ref(BlockDriverState *bs);
+void bdrv_unref(BlockDriverState *bs);
 void bdrv_set_in_use(BlockDriverState *bs, int in_use);
 int bdrv_in_use(BlockDriverState *bs);
 
diff --git a/include/block/block_int.h b/include/block/block_int.h
index e45f2a0..1f85cfb 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -294,6 +294,7 @@  struct BlockDriverState {
     BlockDeviceIoStatus iostatus;
     char device_name[32];
     HBitmap *dirty_bitmap;
+    int refcnt;
     int in_use; /* users other than guest access, eg. block migration */
     QTAILQ_ENTRY(BlockDriverState) list;