block: Mark bdrv_probe_blocksizes() and callers GRAPH_RDLOCK

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

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231027155333.420094-2-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/block-backend.c

@@ -2666,6 +2666,8 @@ int blk_load_vmstate(BlockBackend *blk, uint8_t *buf, int64_t pos, int size)
 int blk_probe_blocksizes(BlockBackend *blk, BlockSizes *bsz)
 {
     GLOBAL_STATE_CODE();
+    GRAPH_RDLOCK_GUARD_MAINLOOP();
+
     if (!blk_is_available(blk)) {
         return -ENOMEDIUM;
     }

block/raw-format.c

@@ -543,7 +543,8 @@ static int raw_probe(const uint8_t *buf, int buf_size, const char *filename)
     return 1;
 }
 
-static int raw_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
+static int GRAPH_RDLOCK
+raw_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
 {
     BDRVRawState *s = bs->opaque;
     int ret;

include/block/block-global-state.h

@@ -281,7 +281,7 @@ bool bdrv_child_change_aio_context(BdrvChild *c, AioContext *ctx,
 int bdrv_try_change_aio_context(BlockDriverState *bs, AioContext *ctx,
                                 BdrvChild *ignore_child, Error **errp);
 
-int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz);
+int GRAPH_RDLOCK bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz);
 int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo);
 
 void GRAPH_WRLOCK

include/block/block_int-common.h

@@ -386,7 +386,8 @@ struct BlockDriver {
      * On success, store them in @bsz and return zero.
      * On failure, return negative errno.
      */
-    int (*bdrv_probe_blocksizes)(BlockDriverState *bs, BlockSizes *bsz);
+    int GRAPH_RDLOCK_PTR (*bdrv_probe_blocksizes)(
+        BlockDriverState *bs, BlockSizes *bsz);
     /**
      * Try to get @bs's geometry (cyls, heads, sectors)
      * On success, store them in @geo and return 0.