[Qemu-devel] [PATCH 1/7] block: Convert BlockDriverState.in_use to refcount

[Fam Zheng <famz@redhat.com>]

Use numeric value to replace in_use flag in BDS, this will make
lifecycle management with ref count possible. This patch only replaces
existing uses of bdrv_set_in_use, so no logic change here.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block-migration.c               |  4 ++--
 block.c                         | 23 +++++++++++++++--------
 blockjob.c                      |  6 +++---
 hw/block/dataplane/virtio-blk.c |  4 ++--
 include/block/block.h           |  3 ++-
 include/block/block_int.h       |  2 +-
 6 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/block-migration.c b/block-migration.c
index 2fd7699..2efb6c0 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -321,7 +321,7 @@ static void init_blk_migration_it(void *opaque, BlockDriverState *bs)
         bmds->shared_base = block_mig_state.shared_base;
         alloc_aio_bitmap(bmds);
         drive_get_ref(drive_get_by_blockdev(bs));
-        bdrv_set_in_use(bs, 1);
+        bdrv_get_ref(bs);
 
         block_mig_state.total_sector_sum += sectors;
 
@@ -557,7 +557,7 @@ static void blk_mig_cleanup(void)
     blk_mig_lock();
     while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
         QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
-        bdrv_set_in_use(bmds->bs, 0);
+        bdrv_get_ref(bmds->bs);
         drive_put_ref(drive_get_by_blockdev(bmds->bs));
         g_free(bmds->aio_bitmap);
         g_free(bmds);
diff --git a/block.c b/block.c
index 6c493ad..84c3181 100644
--- a/block.c
+++ b/block.c
@@ -1503,8 +1503,10 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
     /* dirty bitmap */
     bs_dest->dirty_bitmap       = bs_src->dirty_bitmap;
 
+    /* ref count */
+    bs_dest->refcount           = bs_src->refcount;
+
     /* job */
-    bs_dest->in_use             = bs_src->in_use;
     bs_dest->job                = bs_src->job;
 
     /* keep the same entry in bdrv_states */
@@ -1534,7 +1536,7 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
     assert(bs_new->dirty_bitmap == NULL);
     assert(bs_new->job == NULL);
     assert(bs_new->dev == NULL);
-    assert(bs_new->in_use == 0);
+    assert(bs_new->refcount == 0);
     assert(bs_new->io_limits_enabled == false);
     assert(bs_new->block_timer == NULL);
 
@@ -1553,7 +1555,7 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
     /* Check a few fields that should remain attached to the device */
     assert(bs_new->dev == NULL);
     assert(bs_new->job == NULL);
-    assert(bs_new->in_use == 0);
+    assert(bs_new->refcount == 0);
     assert(bs_new->io_limits_enabled == false);
     assert(bs_new->block_timer == NULL);
 
@@ -1590,7 +1592,7 @@ void bdrv_delete(BlockDriverState *bs)
 {
     assert(!bs->dev);
     assert(!bs->job);
-    assert(!bs->in_use);
+    assert(!bs->refcount);
 
     /* remove from list, if necessary */
     bdrv_make_anon(bs);
@@ -4360,15 +4362,20 @@ int64_t bdrv_get_dirty_count(BlockDriverState *bs)
     }
 }
 
-void bdrv_set_in_use(BlockDriverState *bs, int in_use)
+void bdrv_put_ref(BlockDriverState *bs)
+{
+    assert(bs->refcount > 0);
+    bs->refcount--;
+}
+
+void bdrv_get_ref(BlockDriverState *bs)
 {
-    assert(bs->in_use != in_use);
-    bs->in_use = in_use;
+    bs->refcount++;
 }
 
 int bdrv_in_use(BlockDriverState *bs)
 {
-    return bs->in_use;
+    return bs->refcount > 0;
 }
 
 void bdrv_iostatus_enable(BlockDriverState *bs)
diff --git a/blockjob.c b/blockjob.c
index ca80df1..a841a66 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -45,7 +45,7 @@ void *block_job_create(const BlockJobType *job_type, BlockDriverState *bs,
         error_set(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
         return NULL;
     }
-    bdrv_set_in_use(bs, 1);
+    bdrv_get_ref(bs);
 
     job = g_malloc0(job_type->instance_size);
     job->job_type      = job_type;
@@ -63,7 +63,7 @@ void *block_job_create(const BlockJobType *job_type, BlockDriverState *bs,
         if (error_is_set(&local_err)) {
             bs->job = NULL;
             g_free(job);
-            bdrv_set_in_use(bs, 0);
+            bdrv_put_ref(bs);
             error_propagate(errp, local_err);
             return NULL;
         }
@@ -79,7 +79,7 @@ void block_job_completed(BlockJob *job, int ret)
     job->cb(job->opaque, ret);
     bs->job = NULL;
     g_free(job);
-    bdrv_set_in_use(bs, 0);
+    bdrv_put_ref(bs);
 }
 
 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 0356665..9893a11 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -431,7 +431,7 @@ bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
     s->blk = blk;
 
     /* Prevent block operations that conflict with data plane thread */
-    bdrv_set_in_use(blk->conf.bs, 1);
+    bdrv_get_ref(blk->conf.bs);
 
     error_setg(&s->migration_blocker,
             "x-data-plane does not support migration");
@@ -450,7 +450,7 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
     virtio_blk_data_plane_stop(s);
     migrate_del_blocker(s->migration_blocker);
     error_free(s->migration_blocker);
-    bdrv_set_in_use(s->blk->conf.bs, 0);
+    bdrv_put_ref(s->blk->conf.bs);
     g_free(s);
 }
 
diff --git a/include/block/block.h b/include/block/block.h
index dd8eca1..77f0f0d 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -353,7 +353,8 @@ 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_set_in_use(BlockDriverState *bs, int in_use);
+void bdrv_put_ref(BlockDriverState *bs);
+void bdrv_get_ref(BlockDriverState *bs);
 int bdrv_in_use(BlockDriverState *bs);
 
 #ifdef CONFIG_LINUX_AIO
diff --git a/include/block/block_int.h b/include/block/block_int.h
index c6ac871..1ea80e7 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -294,7 +294,7 @@ struct BlockDriverState {
     BlockDeviceIoStatus iostatus;
     char device_name[32];
     HBitmap *dirty_bitmap;
-    int in_use; /* users other than guest access, eg. block migration */
+    int refcount;
     QTAILQ_ENTRY(BlockDriverState) list;
 
     QLIST_HEAD(, BdrvTrackedRequest) tracked_requests;
-- 
1.8.3.1