From 6c473bbd42becf52b10677500bb509fbfa077140 Mon Sep 17 00:00:00 2001
From: Fam Zheng <famz@redhat.com>
Date: Fri, 17 Jan 2014 03:07:47 +0100
Subject: [PATCH 04/34] block: implement reference count for BlockDriverState

RH-Author: Fam Zheng <famz@redhat.com>
Message-id: <1389928083-8921-3-git-send-email-famz@redhat.com>
Patchwork-id: 56764
O-Subject: [RHEL-7 qemu-kvm PATCH 02/18] block: implement reference count for BlockDriverState
Bugzilla: 1041301
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.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>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 9fcb025146676ab376e6159b58f5a5ddb67bf03c)
Signed-off-by: Fam Zheng <famz@redhat.com>

Conflicts:
	block.c
        Context conflict because throttling and before_write notifier
        are not backported yet.

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(+)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block.c                   |   21 +++++++++++++++++++++
 include/block/block.h     |    2 ++
 include/block/block_int.h |    1 +
 3 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/block.c b/block.c
index cc7afd4..ddf29d0 100644
--- a/block.c
+++ b/block.c
@@ -301,6 +301,7 @@ BlockDriverState *bdrv_new(const char *device_name)
     }
     bdrv_iostatus_disable(bs);
     notifier_list_init(&bs->close_notifiers);
+    bs->refcnt = 1;
 
     return bs;
 }
@@ -1580,6 +1581,9 @@ 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;
@@ -4754,6 +4758,23 @@ 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 e7f718c..a3b7395 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -421,6 +421,8 @@ 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 d49a317..fbfdab7 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -315,6 +315,7 @@ 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;
 
-- 
1.7.1