mirror of https://gitee.com/openkylin/qemu.git
bd57f8f7f8
Rewrite bdrv_check_perm(), bdrv_abort_perm_update() and bdrv_set_perm()
to update nodes in topological sort order instead of simple DFS. With
topologically sorted nodes, we update a node only when all its parents
already updated. With DFS it's not so.
Consider the following example:
A -+
| |
| v
| B
| |
v |
C<-+
A is parent for B and C, B is parent for C.
Obviously, to update permissions, we should go in order A B C, so, when
we update C, all parent permissions already updated. But with current
approach (simple recursion) we can update in sequence A C B C (C is
updated twice). On first update of C, we consider old B permissions, so
doing wrong thing. If it succeed, all is OK, on second C update we will
finish with correct graph. But if the wrong thing failed, we break the
whole process for no reason (it's possible that updated B permission
will be less strict, but we will never check it).
Also new approach gives a way to simultaneously and correctly update
several nodes, we just need to run bdrv_topological_dfs() several times
to add all nodes and their subtrees into one topologically sorted list
(next patch will update bdrv_replace_node() in this manner).
Test test_parallel_perm_update() is now passing, so move it out of
debugging "if".
We also need to support ignore_children in
bdrv_parent_perms_conflict()
For test 283 order of conflicting parents check is changed.
Note also that in bdrv_check_perm() we don't check for parents conflict
at root bs, as we may be in the middle of permission update in
bdrv_reopen_multiple(). bdrv_reopen_multiple() will be updated soon.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210428151804.439460-14-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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| .. | ||
| acceptance | ||
| bench | ||
| data | ||
| decode | ||
| docker | ||
| fp | ||
| guest-debug | ||
| image-fuzzer | ||
| include | ||
| keys | ||
| migration | ||
| multiboot | ||
| perf/block/qcow2 | ||
| plugin | ||
| qapi-schema | ||
| qemu-iotests | ||
| qtest | ||
| rocker | ||
| tcg | ||
| tsan | ||
| uefi-test-tools | ||
| unit | ||
| vm | ||
| vmstate-static-checker-data | ||
| Makefile.include | ||
| check-block.sh | ||
| dbus-vmstate-daemon.sh | ||
| meson.build | ||
| requirements.txt | ||
| test-qht-par.c | ||
| vhost-user-bridge.c | ||