On Fri 08 Nov 2019 09:53:11 AM CET, Kevin Wolf wrote: > bs->options and bs->explicit_options shouldn't contain any options for > child nodes. bdrv_open_inherited() takes care to remove any options that > match a child name after opening the image and the same is done when > reopening. > > However, we miss the case of 'backing': null, which is a child option, > but results in no child being created. This means that a 'backing': null > remains in bs->options and bs->explicit_options. > > A typical use for 'backing': null is in live snapshots: blockdev-add for > the qcow2 overlay makes sure not to open the backing file (because it is > already opened and blockdev-snapshot will attach it). After doing a > blockdev-snapshot, bs->options and bs->explicit_options become > inconsistent with the actual state (bs has a backing file now, but the > options still say null). On the next occasion that the image is > reopened, e.g. switching it from read-write to read-only when another > snapshot is taken, the option will take effect again and the node > incorrectly loses its backing file. > > Fix bdrv_open_inherited() to remove the 'backing' option from > bs->options and bs->explicit_options even for the case where it > specifies that no backing file is wanted. > > Reported-by: Peter Krempa <pkre...@redhat.com> > Signed-off-by: Kevin Wolf <kw...@redhat.com>
Reviewed-by: Alberto Garcia <be...@igalia.com> Berto