Commit 2b23f286 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

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: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>
parent 251071e0

block/copy-on-read.c

+7 −9
Original line number Diff line number Diff line
@@ -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;

    *nperm = perm & PERM_PASSTHROUGH;

    *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;

        return;

    }



    *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;

    }

}