block: Protect bs->backing with graph_lock
Almost all functions that access bs->backing already take the graph
lock now. Add locking to the remaining users and finally annotate the
struct field itself as protected by the graph lock.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231027155333.420094-18-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 cac517a..ed0afdf 100644
--- a/block.c
+++ b/block.c
@@ -3560,10 +3560,14 @@
int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
Error **errp)
{
- BlockDriverState *drain_bs = bs->backing ? bs->backing->bs : bs;
+ BlockDriverState *drain_bs;
int ret;
GLOBAL_STATE_CODE();
+ bdrv_graph_rdlock_main_loop();
+ drain_bs = bs->backing ? bs->backing->bs : bs;
+ bdrv_graph_rdunlock_main_loop();
+
bdrv_ref(drain_bs);
bdrv_drained_begin(drain_bs);
bdrv_graph_wrlock(backing_hd);
@@ -3602,6 +3606,7 @@
Error *local_err = NULL;
GLOBAL_STATE_CODE();
+ GRAPH_RDLOCK_GUARD_MAINLOOP();
if (bs->backing != NULL) {
goto free_exit;
@@ -3643,10 +3648,7 @@
implicit_backing = !strcmp(bs->auto_backing_file, bs->backing_file);
}
- bdrv_graph_rdlock_main_loop();
backing_filename = bdrv_get_full_backing_filename(bs, &local_err);
- bdrv_graph_rdunlock_main_loop();
-
if (local_err) {
ret = -EINVAL;
error_propagate(errp, local_err);
@@ -3677,9 +3679,7 @@
}
if (implicit_backing) {
- bdrv_graph_rdlock_main_loop();
bdrv_refresh_filename(backing_hd);
- bdrv_graph_rdunlock_main_loop();
pstrcpy(bs->auto_backing_file, sizeof(bs->auto_backing_file),
backing_hd->filename);
}
@@ -4750,8 +4750,8 @@
{
BlockDriverState *bs = reopen_state->bs;
BlockDriverState *new_child_bs;
- BlockDriverState *old_child_bs = is_backing ? child_bs(bs->backing) :
- child_bs(bs->file);
+ BlockDriverState *old_child_bs;
+
const char *child_name = is_backing ? "backing" : "file";
QObject *value;
const char *str;
@@ -4797,6 +4797,7 @@
g_assert_not_reached();
}
+ old_child_bs = is_backing ? child_bs(bs->backing) : child_bs(bs->file);
if (old_child_bs == new_child_bs) {
ret = 0;
goto out_rdlock;
@@ -5008,13 +5009,16 @@
* file or if the image file has a backing file name as part of
* its metadata. Otherwise the 'backing' option can be omitted.
*/
+ bdrv_graph_rdlock_main_loop();
if (drv->supports_backing && reopen_state->backing_missing &&
(reopen_state->bs->backing || reopen_state->bs->backing_file[0])) {
error_setg(errp, "backing is missing for '%s'",
reopen_state->bs->node_name);
+ bdrv_graph_rdunlock_main_loop();
ret = -EINVAL;
goto error;
}
+ bdrv_graph_rdunlock_main_loop();
/*
* Allow changing the 'backing' option. The new value can be
@@ -5204,10 +5208,11 @@
QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
bdrv_unref_child(bs, child);
}
- bdrv_graph_wrunlock();
assert(!bs->backing);
assert(!bs->file);
+ bdrv_graph_wrunlock();
+
g_free(bs->opaque);
bs->opaque = NULL;
qatomic_set(&bs->copy_on_read, 0);
@@ -5531,7 +5536,9 @@
GLOBAL_STATE_CODE();
+ bdrv_graph_rdlock_main_loop();
assert(!bs_new->backing);
+ bdrv_graph_rdunlock_main_loop();
old_context = bdrv_get_aio_context(bs_top);
bdrv_drained_begin(bs_top);
@@ -8115,7 +8122,7 @@
/* Note: This function may return false positives; it may return true
* even if opening the backing file specified by bs's image header
* would result in exactly bs->backing. */
-static bool bdrv_backing_overridden(BlockDriverState *bs)
+static bool GRAPH_RDLOCK bdrv_backing_overridden(BlockDriverState *bs)
{
GLOBAL_STATE_CODE();
if (bs->backing) {
