From 64631f368115a332bdca32553a430568ecc7761d Mon Sep 17 00:00:00 2001 From: Vladimir Sementsov-Ogievskiy Date: Thu, 2 Sep 2021 12:37:54 +0300 Subject: block: drop BLK_PERM_GRAPH_MOD First, this permission never protected a node from being changed, as generic child-replacing functions don't check it. Second, it's a strange thing: it presents a permission of parent node to change its child. But generally, children are replaced by different mechanisms, like jobs or qmp commands, not by nodes. Graph-mod permission is hard to understand. All other permissions describe operations which done by parent node on its child: read, write, resize. Graph modification operations are something completely different. The only place where BLK_PERM_GRAPH_MOD is used as "perm" (not shared perm) is mirror_start_job, for s->target. Still modern code should use bdrv_freeze_backing_chain() to protect from graph modification, if we don't do it somewhere it may be considered as a bug. So, it's a bit risky to drop GRAPH_MOD, and analyzing of possible loss of protection is hard. But one day we should do it, let's do it now. One more bit of information is that locking the corresponding byte in file-posix doesn't make sense at all. Signed-off-by: Vladimir Sementsov-Ogievskiy Message-Id: <20210902093754.2352-1-vsementsov@virtuozzo.com> Signed-off-by: Kevin Wolf --- qapi/block-core.json | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) (limited to 'qapi') diff --git a/qapi/block-core.json b/qapi/block-core.json index bd0b285..9a5a364 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -1878,14 +1878,11 @@ # # @resize: This permission is required to change the size of a block node. # -# @graph-mod: This permission is required to change the node that this -# BdrvChild points to. -# # Since: 4.0 ## { 'enum': 'BlockPermission', - 'data': [ 'consistent-read', 'write', 'write-unchanged', 'resize', - 'graph-mod' ] } + 'data': [ 'consistent-read', 'write', 'write-unchanged', 'resize' ] } + ## # @XDbgBlockGraphEdge: # -- cgit v1.1