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block/copy-on-read: Fix permissions for inactive node 

The copy-on-read drive must not request the WRITE_UNCHANGED permission
for its child if the node is inactive, otherwise starting a migration
destination with -incoming will fail because the child cannot provide
write access yet:

  qemu-system-x86_64: -blockdev copy-on-read,file=img,node-name=cor: Block node is read-only

Earlier QEMU versions additionally ran into an abort() on the migration
source side: bdrv_inactivate_recurse() failed to update permissions.
This is silently ignored today because it was only supposed to loosen
restrictions. This is the symptom that was originally reported here:

  https://bugzilla.redhat.com/show_bug.cgi?id=1733022

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Kevin Wolf 2019-07-29 12:45:14 +02:00
parent 251071e0c0
commit 2b23f28639
1 changed files with 7 additions and 9 deletions
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16
block/copy-on-read.c
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@ -56,16 +56,14 @@ static void cor_child_perm(BlockDriverState *bs, BdrvChild *c,
uint64_t perm, uint64_t shared, uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared) uint64_t *nperm, uint64_t *nshared)
{ {
if (c == NULL) { *nperm = perm & PERM_PASSTHROUGH;
*nperm = (perm & PERM_PASSTHROUGH) | BLK_PERM_WRITE_UNCHANGED; *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
*nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
return;
}
*nperm = (perm & PERM_PASSTHROUGH) | /* We must not request write permissions for an inactive node, the child
(c->perm & PERM_UNCHANGED); * cannot provide it. */
*nshared = (shared & PERM_PASSTHROUGH) | if (!(bs->open_flags & BDRV_O_INACTIVE)) {
(c->shared_perm & PERM_UNCHANGED); *nperm |= BLK_PERM_WRITE_UNCHANGED;
}
} }