From 2b23f28639c9ed3d4cdb1262b3e41b6b81be5e0b Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Mon, 29 Jul 2019 12:45:14 +0200 Subject: [PATCH] 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 Reviewed-by: Max Reitz --- block/copy-on-read.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/block/copy-on-read.c b/block/copy-on-read.c index 22f24fd0db..6631f30205 100644 --- a/block/copy-on-read.c +++ b/block/copy-on-read.c @@ -56,16 +56,14 @@ static void cor_child_perm(BlockDriverState *bs, BdrvChild *c, uint64_t perm, uint64_t shared, uint64_t *nperm, uint64_t *nshared) { - if (c == NULL) { - *nperm = (perm & PERM_PASSTHROUGH) | BLK_PERM_WRITE_UNCHANGED; - *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED; - return; - } + *nperm = perm & PERM_PASSTHROUGH; + *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED; - *nperm = (perm & PERM_PASSTHROUGH) | - (c->perm & PERM_UNCHANGED); - *nshared = (shared & PERM_PASSTHROUGH) | - (c->shared_perm & PERM_UNCHANGED); + /* We must not request write permissions for an inactive node, the child + * cannot provide it. */ + if (!(bs->open_flags & BDRV_O_INACTIVE)) { + *nperm |= BLK_PERM_WRITE_UNCHANGED; + } }