block: Mark bdrv_set_backing_hd_drained() GRAPH_WRLOCK

Instead of taking the writer lock internally, require callers to already
hold it when calling bdrv_set_backing_hd_drained(). Basically everthing
in the function needs the lock and its callers may already want to hold
the graph lock and so wouldn't be able to call functions that take it
internally.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231027155333.420094-14-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block.c b/block.c
index 499b147315bc6adc473968e41af65ebdfcb8ac41..d79a6f41f92e122bbfa0e120c04ab49d4b9ca57f 100644 (file)
--- a/block.c
+++ b/block.c
@@ -3557,7 +3557,6 @@ int bdrv_set_backing_hd_drained(BlockDriverState *bs,
     if (bs->backing) {
         assert(bs->backing->bs->quiesce_counter > 0);
     }
-    bdrv_graph_wrlock(backing_hd);
 
     ret = bdrv_set_backing_noperm(bs, backing_hd, tran, errp);
     if (ret < 0) {
@@ -3567,7 +3566,6 @@ int bdrv_set_backing_hd_drained(BlockDriverState *bs,
     ret = bdrv_refresh_perms(bs, tran, errp);
 out:
     tran_finalize(tran, ret);
-    bdrv_graph_wrunlock();
     return ret;
 }
 
@@ -3580,7 +3578,9 @@ int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
 
     bdrv_ref(drain_bs);
     bdrv_drained_begin(drain_bs);
+    bdrv_graph_wrlock(backing_hd);
     ret = bdrv_set_backing_hd_drained(bs, backing_hd, errp);
+    bdrv_graph_wrunlock();
     bdrv_drained_end(drain_bs);
     bdrv_unref(drain_bs);
 

diff --git a/block/stream.c b/block/stream.c
index 3f5d773535c22686aeec2b2a884809cc6067f61d..0b92410c00c9ea0ff572a6a4807e53083785d2c1 100644 (file)
--- a/block/stream.c
+++ b/block/stream.c
@@ -99,7 +99,9 @@ static int stream_prepare(Job *job)
             }
         }
 
+        bdrv_graph_wrlock(base);
         bdrv_set_backing_hd_drained(unfiltered_bs, base, &local_err);
+        bdrv_graph_wrunlock();
 
         /*
          * This call will do I/O, so the graph can change again from here on.

diff --git a/include/block/block-global-state.h b/include/block/block-global-state.h
index 9a33bd7ef9556e0d40dcd1d782bfc8d75975edc8..a1fd70ec9742a3490a0bcc3fc4439a7d6399da96 100644 (file)
--- a/include/block/block-global-state.h
+++ b/include/block/block-global-state.h
@@ -101,9 +101,10 @@ bdrv_co_open_blockdev_ref(BlockdevRef *ref, Error **errp);
 
 int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
                         Error **errp);
-int bdrv_set_backing_hd_drained(BlockDriverState *bs,
-                                BlockDriverState *backing_hd,
-                                Error **errp);
+int GRAPH_WRLOCK
+bdrv_set_backing_hd_drained(BlockDriverState *bs, BlockDriverState *backing_hd,
+                            Error **errp);
+
 int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
                            const char *bdref_key, Error **errp);