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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 -+
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| v
| B
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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>
23 lines
1.5 KiB
Text
23 lines
1.5 KiB
Text
{"execute": "blockdev-add", "arguments": {"driver": "null-co", "node-name": "target", "size": 1048576}}
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{"return": {}}
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{"execute": "blockdev-add", "arguments": {"driver": "blkdebug", "image": {"driver": "null-co", "node-name": "base", "size": 1048576}, "node-name": "source"}}
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{"return": {}}
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{"execute": "blockdev-add", "arguments": {"driver": "blkdebug", "image": "base", "node-name": "other", "take-child-perms": ["write"]}}
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{"return": {}}
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{"execute": "blockdev-backup", "arguments": {"device": "source", "sync": "full", "target": "target"}}
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{"error": {"class": "GenericError", "desc": "Cannot set permissions for backup-top filter: Conflicts with use by source as 'image', which does not allow 'write' on base"}}
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=== backup-top should be gone after job-finalize ===
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{"execute": "blockdev-add", "arguments": {"driver": "null-co", "node-name": "source"}}
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{"return": {}}
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{"execute": "blockdev-add", "arguments": {"driver": "null-co", "node-name": "target"}}
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{"return": {}}
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{"execute": "blockdev-backup", "arguments": {"auto-dismiss": false, "auto-finalize": false, "device": "source", "filter-node-name": "backup-filter", "job-id": "backup", "sync": "full", "target": "target"}}
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{"return": {}}
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{"execute": "job-finalize", "arguments": {"id": "backup"}}
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{"return": {}}
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{"execute": "human-monitor-command", "arguments": {"command-line": "qemu-io backup-filter \"write 0 1M\""}}
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{"return": "Error: Cannot find device='' nor node-name='backup-filter'\r\n"}
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{"execute": "job-dismiss", "arguments": {"id": "backup"}}
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{"return": {}}
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