block: Introduce bdrv_co_change_backing_file()

bdrv_change_backing_file() is called both inside and outside coroutine
context. This makes it difficult for it to take the graph lock
internally. It also means that driver implementations need to be able to
run outside of coroutines, too. Switch it to the usual model with a
coroutine based implementation and a co_wrapper instead. The new
function is marked GRAPH_RDLOCK.

As the co_wrapper now runs the function in the AioContext of the node
(as it should always have done), this is not GLOBAL_STATE_CODE() any
more.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231027155333.420094-20-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

2 files changed, 98 insertions, 94 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index a1443a31aa..875e613ea9 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3155,8 +3155,9 @@ fail:
     return ret;
 }
 
-static int qcow2_change_backing_file(BlockDriverState *bs,
-    const char *backing_file, const char *backing_fmt)
+static int coroutine_fn GRAPH_RDLOCK
+qcow2_co_change_backing_file(BlockDriverState *bs, const char *backing_file,
+                             const char *backing_fmt)
 {
     BDRVQcow2State *s = bs->opaque;
 
@@ -3816,8 +3817,11 @@ qcow2_co_create(BlockdevCreateOptions *create_options, Error **errp)
             backing_format = BlockdevDriver_str(qcow2_opts->backing_fmt);
         }
 
-        ret = bdrv_change_backing_file(blk_bs(blk), qcow2_opts->backing_file,
-                                       backing_format, false);
+        bdrv_graph_co_rdlock();
+        ret = bdrv_co_change_backing_file(blk_bs(blk), qcow2_opts->backing_file,
+                                          backing_format, false);
+        bdrv_graph_co_rdunlock();
+
         if (ret < 0) {
             error_setg_errno(errp, -ret, "Could not assign backing file '%s' "
                              "with format '%s'", qcow2_opts->backing_file,
@@ -6115,64 +6119,64 @@ static const char *const qcow2_strong_runtime_opts[] = {
 };
 
 BlockDriver bdrv_qcow2 = {
-    .format_name        = "qcow2",
-    .instance_size      = sizeof(BDRVQcow2State),
-    .bdrv_probe         = qcow2_probe,
-    .bdrv_open          = qcow2_open,
-    .bdrv_close         = qcow2_close,
-    .bdrv_reopen_prepare  = qcow2_reopen_prepare,
-    .bdrv_reopen_commit   = qcow2_reopen_commit,
-    .bdrv_reopen_commit_post = qcow2_reopen_commit_post,
-    .bdrv_reopen_abort    = qcow2_reopen_abort,
-    .bdrv_join_options    = qcow2_join_options,
-    .bdrv_child_perm      = bdrv_default_perms,
-    .bdrv_co_create_opts  = qcow2_co_create_opts,
-    .bdrv_co_create       = qcow2_co_create,
-    .bdrv_has_zero_init   = qcow2_has_zero_init,
-    .bdrv_co_block_status = qcow2_co_block_status,
-
-    .bdrv_co_preadv_part    = qcow2_co_preadv_part,
-    .bdrv_co_pwritev_part   = qcow2_co_pwritev_part,
-    .bdrv_co_flush_to_os    = qcow2_co_flush_to_os,
-
-    .bdrv_co_pwrite_zeroes  = qcow2_co_pwrite_zeroes,
-    .bdrv_co_pdiscard       = qcow2_co_pdiscard,
-    .bdrv_co_copy_range_from = qcow2_co_copy_range_from,
-    .bdrv_co_copy_range_to  = qcow2_co_copy_range_to,
-    .bdrv_co_truncate       = qcow2_co_truncate,
-    .bdrv_co_pwritev_compressed_part = qcow2_co_pwritev_compressed_part,
-    .bdrv_make_empty        = qcow2_make_empty,
-
-    .bdrv_snapshot_create   = qcow2_snapshot_create,
-    .bdrv_snapshot_goto     = qcow2_snapshot_goto,
-    .bdrv_snapshot_delete   = qcow2_snapshot_delete,
-    .bdrv_snapshot_list     = qcow2_snapshot_list,
-    .bdrv_snapshot_load_tmp = qcow2_snapshot_load_tmp,
-    .bdrv_measure           = qcow2_measure,
-    .bdrv_co_get_info       = qcow2_co_get_info,
-    .bdrv_get_specific_info = qcow2_get_specific_info,
-
-    .bdrv_co_save_vmstate   = qcow2_co_save_vmstate,
-    .bdrv_co_load_vmstate   = qcow2_co_load_vmstate,
-
-    .is_format                  = true,
-    .supports_backing           = true,
-    .bdrv_change_backing_file   = qcow2_change_backing_file,
-
-    .bdrv_refresh_limits        = qcow2_refresh_limits,
-    .bdrv_co_invalidate_cache   = qcow2_co_invalidate_cache,
-    .bdrv_inactivate            = qcow2_inactivate,
-
-    .create_opts         = &qcow2_create_opts,
-    .amend_opts          = &qcow2_amend_opts,
-    .strong_runtime_opts = qcow2_strong_runtime_opts,
-    .mutable_opts        = mutable_opts,
-    .bdrv_co_check       = qcow2_co_check,
-    .bdrv_amend_options  = qcow2_amend_options,
-    .bdrv_co_amend       = qcow2_co_amend,
-
-    .bdrv_detach_aio_context  = qcow2_detach_aio_context,
-    .bdrv_attach_aio_context  = qcow2_attach_aio_context,
+    .format_name                        = "qcow2",
+    .instance_size                      = sizeof(BDRVQcow2State),
+    .bdrv_probe                         = qcow2_probe,
+    .bdrv_open                          = qcow2_open,
+    .bdrv_close                         = qcow2_close,
+    .bdrv_reopen_prepare                = qcow2_reopen_prepare,
+    .bdrv_reopen_commit                 = qcow2_reopen_commit,
+    .bdrv_reopen_commit_post            = qcow2_reopen_commit_post,
+    .bdrv_reopen_abort                  = qcow2_reopen_abort,
+    .bdrv_join_options                  = qcow2_join_options,
+    .bdrv_child_perm                    = bdrv_default_perms,
+    .bdrv_co_create_opts                = qcow2_co_create_opts,
+    .bdrv_co_create                     = qcow2_co_create,
+    .bdrv_has_zero_init                 = qcow2_has_zero_init,
+    .bdrv_co_block_status               = qcow2_co_block_status,
+
+    .bdrv_co_preadv_part                = qcow2_co_preadv_part,
+    .bdrv_co_pwritev_part               = qcow2_co_pwritev_part,
+    .bdrv_co_flush_to_os                = qcow2_co_flush_to_os,
+
+    .bdrv_co_pwrite_zeroes              = qcow2_co_pwrite_zeroes,
+    .bdrv_co_pdiscard                   = qcow2_co_pdiscard,
+    .bdrv_co_copy_range_from            = qcow2_co_copy_range_from,
+    .bdrv_co_copy_range_to              = qcow2_co_copy_range_to,
+    .bdrv_co_truncate                   = qcow2_co_truncate,
+    .bdrv_co_pwritev_compressed_part    = qcow2_co_pwritev_compressed_part,
+    .bdrv_make_empty                    = qcow2_make_empty,
+
+    .bdrv_snapshot_create               = qcow2_snapshot_create,
+    .bdrv_snapshot_goto                 = qcow2_snapshot_goto,
+    .bdrv_snapshot_delete               = qcow2_snapshot_delete,
+    .bdrv_snapshot_list                 = qcow2_snapshot_list,
+    .bdrv_snapshot_load_tmp             = qcow2_snapshot_load_tmp,
+    .bdrv_measure                       = qcow2_measure,
+    .bdrv_co_get_info                   = qcow2_co_get_info,
+    .bdrv_get_specific_info             = qcow2_get_specific_info,
+
+    .bdrv_co_save_vmstate               = qcow2_co_save_vmstate,
+    .bdrv_co_load_vmstate               = qcow2_co_load_vmstate,
+
+    .is_format                          = true,
+    .supports_backing                   = true,
+    .bdrv_co_change_backing_file        = qcow2_co_change_backing_file,
+
+    .bdrv_refresh_limits                = qcow2_refresh_limits,
+    .bdrv_co_invalidate_cache           = qcow2_co_invalidate_cache,
+    .bdrv_inactivate                    = qcow2_inactivate,
+
+    .create_opts                        = &qcow2_create_opts,
+    .amend_opts                         = &qcow2_amend_opts,
+    .strong_runtime_opts                = qcow2_strong_runtime_opts,
+    .mutable_opts                       = mutable_opts,
+    .bdrv_co_check                      = qcow2_co_check,
+    .bdrv_amend_options                 = qcow2_amend_options,
+    .bdrv_co_amend                      = qcow2_co_amend,
+
+    .bdrv_detach_aio_context            = qcow2_detach_aio_context,
+    .bdrv_attach_aio_context            = qcow2_attach_aio_context,
 
     .bdrv_supports_persistent_dirty_bitmap =
             qcow2_supports_persistent_dirty_bitmap,
diff --git a/block/qed.c b/block/qed.c
index 686ad711f7..996aa384fe 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -1498,9 +1498,9 @@ bdrv_qed_co_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
     return 0;
 }
 
-static int bdrv_qed_change_backing_file(BlockDriverState *bs,
-                                        const char *backing_file,
-                                        const char *backing_fmt)
+static int coroutine_fn GRAPH_RDLOCK
+bdrv_qed_co_change_backing_file(BlockDriverState *bs, const char *backing_file,
+                                const char *backing_fmt)
 {
     BDRVQEDState *s = bs->opaque;
     QEDHeader new_header, le_header;
@@ -1562,7 +1562,7 @@ static int bdrv_qed_change_backing_file(BlockDriverState *bs,
     }
 
     /* Write new header */
-    ret = bdrv_pwrite_sync(bs->file, 0, buffer_len, buffer, 0);
+    ret = bdrv_co_pwrite_sync(bs->file, 0, buffer_len, buffer, 0);
     g_free(buffer);
     if (ret == 0) {
         memcpy(&s->header, &new_header, sizeof(new_header));
@@ -1636,34 +1636,34 @@ static QemuOptsList qed_create_opts = {
 };
 
 static BlockDriver bdrv_qed = {
-    .format_name              = "qed",
-    .instance_size            = sizeof(BDRVQEDState),
-    .create_opts              = &qed_create_opts,
-    .is_format                = true,
-    .supports_backing         = true,
-
-    .bdrv_probe               = bdrv_qed_probe,
-    .bdrv_open                = bdrv_qed_open,
-    .bdrv_close               = bdrv_qed_close,
-    .bdrv_reopen_prepare      = bdrv_qed_reopen_prepare,
-    .bdrv_child_perm          = bdrv_default_perms,
-    .bdrv_co_create           = bdrv_qed_co_create,
-    .bdrv_co_create_opts      = bdrv_qed_co_create_opts,
-    .bdrv_has_zero_init       = bdrv_has_zero_init_1,
-    .bdrv_co_block_status     = bdrv_qed_co_block_status,
-    .bdrv_co_readv            = bdrv_qed_co_readv,
-    .bdrv_co_writev           = bdrv_qed_co_writev,
-    .bdrv_co_pwrite_zeroes    = bdrv_qed_co_pwrite_zeroes,
-    .bdrv_co_truncate         = bdrv_qed_co_truncate,
-    .bdrv_co_getlength        = bdrv_qed_co_getlength,
-    .bdrv_co_get_info         = bdrv_qed_co_get_info,
-    .bdrv_refresh_limits      = bdrv_qed_refresh_limits,
-    .bdrv_change_backing_file = bdrv_qed_change_backing_file,
-    .bdrv_co_invalidate_cache = bdrv_qed_co_invalidate_cache,
-    .bdrv_co_check            = bdrv_qed_co_check,
-    .bdrv_detach_aio_context  = bdrv_qed_detach_aio_context,
-    .bdrv_attach_aio_context  = bdrv_qed_attach_aio_context,
-    .bdrv_drain_begin         = bdrv_qed_drain_begin,
+    .format_name                    = "qed",
+    .instance_size                  = sizeof(BDRVQEDState),
+    .create_opts                    = &qed_create_opts,
+    .is_format                      = true,
+    .supports_backing               = true,
+
+    .bdrv_probe                     = bdrv_qed_probe,
+    .bdrv_open                      = bdrv_qed_open,
+    .bdrv_close                     = bdrv_qed_close,
+    .bdrv_reopen_prepare            = bdrv_qed_reopen_prepare,
+    .bdrv_child_perm                = bdrv_default_perms,
+    .bdrv_co_create                 = bdrv_qed_co_create,
+    .bdrv_co_create_opts            = bdrv_qed_co_create_opts,
+    .bdrv_has_zero_init             = bdrv_has_zero_init_1,
+    .bdrv_co_block_status           = bdrv_qed_co_block_status,
+    .bdrv_co_readv                  = bdrv_qed_co_readv,
+    .bdrv_co_writev                 = bdrv_qed_co_writev,
+    .bdrv_co_pwrite_zeroes          = bdrv_qed_co_pwrite_zeroes,
+    .bdrv_co_truncate               = bdrv_qed_co_truncate,
+    .bdrv_co_getlength              = bdrv_qed_co_getlength,
+    .bdrv_co_get_info               = bdrv_qed_co_get_info,
+    .bdrv_refresh_limits            = bdrv_qed_refresh_limits,
+    .bdrv_co_change_backing_file    = bdrv_qed_co_change_backing_file,
+    .bdrv_co_invalidate_cache       = bdrv_qed_co_invalidate_cache,
+    .bdrv_co_check                  = bdrv_qed_co_check,
+    .bdrv_detach_aio_context        = bdrv_qed_detach_aio_context,
+    .bdrv_attach_aio_context        = bdrv_qed_attach_aio_context,
+    .bdrv_drain_begin               = bdrv_qed_drain_begin,
 };
 
 static void bdrv_qed_init(void)