commit f5a3a270fe2b89d1be39f50ebdd15db80d59014b
author Kevin Wolf <kwolf@redhat.com> Fri Oct 27 17:53:12 2023 +0200
committer Kevin Wolf <kwolf@redhat.com> Tue Nov 07 19:14:19 2023 +0100
tree 01874d28f59e8cd8a3322ae104af2f5a6f176fc2
parent 067179868ec8cd467d9810143339e882cb60e388

block: Mark bdrv_filter_bs() and callers GRAPH_RDLOCK

This adds GRAPH_RDLOCK annotations to declare that callers of
bdrv_filter_bs() need to hold a reader lock for the graph because
it calls bdrv_filter_child(), which accesses bs->file/backing.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231027155333.420094-4-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

diff --git a/block.c b/block.c
index 1171f47..d85738b 100644
--- a/block.c
+++ b/block.c
@@ -820,12 +820,17 @@
 int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo)
 {
     BlockDriver *drv = bs->drv;
-    BlockDriverState *filtered = bdrv_filter_bs(bs);
+    BlockDriverState *filtered;
+
     GLOBAL_STATE_CODE();
+    GRAPH_RDLOCK_GUARD_MAINLOOP();
 
     if (drv && drv->bdrv_probe_geometry) {
         return drv->bdrv_probe_geometry(bs, geo);
-    } else if (filtered) {
+    }
+
+    filtered = bdrv_filter_bs(bs);
+    if (filtered) {
         return bdrv_probe_geometry(filtered, geo);
     }
 

block/stream.c

diff --git a/block/stream.c b/block/stream.c
index ddaab7d..b22d9c2 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -268,6 +268,8 @@
         assert(!bottom->drv->is_filter);
         base_overlay = above_base = bottom;
     } else {
+        GRAPH_RDLOCK_GUARD_MAINLOOP();
+
         base_overlay = bdrv_find_overlay(bs, base);
         if (!base_overlay) {
             error_setg(errp, "'%s' is not in the backing chain of '%s'",

include/block/block-io.h

diff --git a/include/block/block-io.h b/include/block/block-io.h
index ad270b6..58c4cf5 100644
--- a/include/block/block-io.h
+++ b/include/block/block-io.h
@@ -183,7 +183,7 @@
 
 const char *bdrv_get_format_name(BlockDriverState *bs);
 
-bool bdrv_supports_compressed_writes(BlockDriverState *bs);
+bool GRAPH_RDLOCK bdrv_supports_compressed_writes(BlockDriverState *bs);
 const char *bdrv_get_node_name(const BlockDriverState *bs);
 
 const char * GRAPH_RDLOCK

include/block/block_int-io.h

diff --git a/include/block/block_int-io.h b/include/block/block_int-io.h
index 34eac72..26bff94 100644
--- a/include/block/block_int-io.h
+++ b/include/block/block_int-io.h
@@ -143,7 +143,8 @@
     return child_bs(bdrv_cow_child(bs));
 }
 
-static inline BlockDriverState *bdrv_filter_bs(BlockDriverState *bs)
+static inline BlockDriverState * GRAPH_RDLOCK
+bdrv_filter_bs(BlockDriverState *bs)
 {
     IO_CODE();
     return child_bs(bdrv_filter_child(bs));

migration/block-dirty-bitmap.c

diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
index 03cb2e7..24347ab 100644
--- a/migration/block-dirty-bitmap.c
+++ b/migration/block-dirty-bitmap.c
@@ -607,6 +607,10 @@
     BlockBackend *blk;
     GHashTable *alias_map = NULL;
 
+    /* Runs in the migration thread, but holds the iothread lock */
+    GLOBAL_STATE_CODE();
+    GRAPH_RDLOCK_GUARD_MAINLOOP();
+
     if (migrate_has_block_bitmap_mapping()) {
         alias_map = construct_alias_map(migrate_block_bitmap_mapping(), true,
                                         &error_abort);