block: Add blk_remove_all_bs()

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.

This patch adds a function for doing that, but does not yet incorporate
it in bdrv_close_all().

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block/block-backend.c b/block/block-backend.c
index 7f5ad59858496970a821c539663723296430adac..ebdf78a11cfcaf721028b5f6eb0deef5daf2fb05 100644 (file)
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -223,6 +223,21 @@ 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);
+        if (blk->bs) {
+            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 ae4efb4138e6362a0ff7a41d9813d8ca58af9614..ec303316bb8b216d229f249d0c4ff4d6ffe7930f 100644 (file)
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -68,6 +68,7 @@ BlockBackend *blk_new_open(const char *name, const char *filename,
 int blk_get_refcnt(BlockBackend *blk);
 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);