migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_…

…coroutine()' failed.

bdrv_activate_all() should not be called from the coroutine context, move
it to the QEMU thread colo_process_incoming_thread() with the bql_lock
protected.

The backtrace is as follows:
 #4  0x0000561af7948362 in bdrv_graph_rdlock_main_loop () at ../block/graph-lock.c:260
 #5  0x0000561af7907a68 in graph_lockable_auto_lock_mainloop (x=0x7fd29810be7b) at /patch/to/qemu/include/block/graph-lock.h:259
 #6  0x0000561af79167d1 in bdrv_activate_all (errp=0x7fd29810bed0) at ../block.c:6906
 #7  0x0000561af762b4af in colo_incoming_co () at ../migration/colo.c:935
 #8  0x0000561af7607e57 in process_incoming_migration_co (opaque=0x0) at ../migration/migration.c:793
 #9  0x0000561af7adbeeb in coroutine_trampoline (i0=-106876144, i1=22042) at ../util/coroutine-ucontext.c:175
 #10 0x00007fd2a5cf21c0 in  () at /lib64/libc.so.6

Cc: qemu-stable@nongnu.org
Cc: Fabiano Rosas <farosas@suse.de>
Closes: https://gitlab.com/qemu-project/qemu/-/issues/2277
Fixes: 2b3912f ("block: Mark bdrv_first_blk() and bdrv_is_root_node() GRAPH_RDLOCK")
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Zhang Chen <chen.zhang@intel.com>
Tested-by: Zhang Chen <chen.zhang@intel.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240417025634.1014582-1-lizhijian@fujitsu.com
Signed-off-by: Peter Xu <peterx@redhat.com>
(cherry picked from commit 2cc637f)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(Mjt: fixup bql_lock() => qemu_mutex_lock_iothread() for v8.2.0-444-g195801d700c0
 "system/cpus: rename qemu_mutex_lock_iothread() to bql_lock()")

migration/colo.c

@@ -830,6 +830,16 @@ static void *colo_process_incoming_thread(void *opaque)
         return NULL;
     }
 
+    /* Make sure all file formats throw away their mutable metadata */
+    qemu_mutex_lock_iothread();
+    bdrv_activate_all(&local_err);
+    if (local_err) {
+        qemu_mutex_unlock_iothread();
+        error_report_err(local_err);
+        return NULL;
+    }
+    qemu_mutex_unlock_iothread();
+
     failover_init_state();
 
     mis->to_src_file = qemu_file_get_return_path(mis->from_src_file);
@@ -917,7 +927,6 @@ static void *colo_process_incoming_thread(void *opaque)
 int coroutine_fn colo_incoming_co(void)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
-    Error *local_err = NULL;
     QemuThread th;
 
     assert(qemu_mutex_iothread_locked());
@@ -926,13 +935,6 @@ int coroutine_fn colo_incoming_co(void)
         return 0;
     }
 
-    /* Make sure all file formats throw away their mutable metadata */
-    bdrv_activate_all(&local_err);
-    if (local_err) {
-        error_report_err(local_err);
-        return -EINVAL;
-    }
-
     qemu_thread_create(&th, "COLO incoming", colo_process_incoming_thread,
                        mis, QEMU_THREAD_JOINABLE);