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block: Fix order in bdrv_replace_child()

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We have to start by applying the permission restrictions to new_bs
before we can loosen them on old_bs.  See the comment for the
explanation.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2019-05-22 19:03:49 +02:00 committed by Kevin Wolf
parent a193ad3b3b
commit 87ace5f8b6
1 changed files with 13 additions and 5 deletions
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18
block.c
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@ -2240,6 +2240,19 @@ static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs)
bdrv_replace_child_noperm(child, new_bs);
/*
* Start with the new node's permissions. If @new_bs is a (direct
* or indirect) child of @old_bs, we must complete the permission
* update on @new_bs before we loosen the restrictions on @old_bs.
* Otherwise, bdrv_check_perm() on @old_bs would re-initiate
* updating the permissions of @new_bs, and thus not purely loosen
* restrictions.
*/
if (new_bs) {
bdrv_get_cumulative_perm(new_bs, &perm, &shared_perm);
bdrv_set_perm(new_bs, perm, shared_perm);
}
if (old_bs) {
/* Update permissions for old node. This is guaranteed to succeed
* because we're just taking a parent away, so we're loosening
@ -2252,11 +2265,6 @@ static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs)
* node moves back to the main AioContext */
bdrv_try_set_aio_context(old_bs, qemu_get_aio_context(), NULL);
}
if (new_bs) {
bdrv_get_cumulative_perm(new_bs, &perm, &shared_perm);
bdrv_set_perm(new_bs, perm, shared_perm);
}
}
/*