[Qemu-devel] [PATCH v4 10/11] block: Eject BDS tree from BB at bdrv_close_all()

[Max Reitz <mreitz@redhat.com>]

When bdrv_close_all() is called, instead of force-closing all root
BlockDriverStates, it is better to just drop the reference from all
BlockBackends and let them be closed automatically. This prevents BDS
from getting closed that are still referenced by other BDS, which may
result in loss of cached data.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block.c                        | 11 +----------
 block/block-backend.c          | 13 +++++++++++++
 include/sysemu/block-backend.h |  1 +
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/block.c b/block.c
index 0b0792c..a2637b6 100644
--- a/block.c
+++ b/block.c
@@ -1941,17 +1941,8 @@ static void bdrv_close(BlockDriverState *bs)
 
 void bdrv_close_all(void)
 {
-    BlockDriverState *bs;
-
     blockdev_close_all_bdrv_states();
-
-    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
-        AioContext *aio_context = bdrv_get_aio_context(bs);
-
-        aio_context_acquire(aio_context);
-        bdrv_close(bs);
-        aio_context_release(aio_context);
-    }
+    blk_remove_all_bs();
 }
 
 /* Check if any requests are in-flight (including throttled requests) */
diff --git a/block/block-backend.c b/block/block-backend.c
index 7e9d53a..2e820fe 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -207,6 +207,19 @@ void blk_unref(BlockBackend *blk)
     }
 }
 
+void blk_remove_all_bs(void)
+{
+    BlockBackend *blk;
+
+    QTAILQ_FOREACH(blk, &blk_backends, link) {
+        AioContext *ctx = blk_get_aio_context(blk);
+
+        aio_context_acquire(ctx);
+        blk_remove_bs(blk);
+        aio_context_release(ctx);
+    }
+}
+
 /*
  * Return the BlockBackend after @blk.
  * If @blk is null, return the first one.
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index e0a2749..ab765a7 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -67,6 +67,7 @@ BlockBackend *blk_new_open(const char *name, const char *filename,
                            Error **errp);
 void blk_ref(BlockBackend *blk);
 void blk_unref(BlockBackend *blk);
+void blk_remove_all_bs(void);
 const char *blk_name(BlockBackend *blk);
 BlockBackend *blk_by_name(const char *name);
 BlockBackend *blk_next(BlockBackend *blk);
-- 
2.1.0