| Message ID | 6ec504767392cb91591542c416f0c2ae52f847f8.1547739122.git.berto@igalia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add a 'x-blockdev-reopen' QMP command | expand |
Am 17.01.2019 um 16:33 hat Alberto Garcia geschrieben: > Of all options of type BlockdevRef used to specify children in > BlockdevOptions, 'backing' is the only one that is optional. > > For "x-blockdev-reopen" we want that if an option is omitted then it > must be reset to its default value. The default value of 'backing' > means that QEMU opens the backing file specified in the image > metadata, but this is not something that we want to support for the > reopen operation. > > Because of this the 'backing' option has to be specified during > reopen, pointing to the existing backing file if we want to keep it, > or pointing to a different one (or NULL) if we want to replace it (to > be implemented in a subsequent patch). > > In order to simplify things a bit and not to require that the user > passes the 'backing' option to every single block device even when > it's clearly not necessary, this patch allows omitting this option if > the block device being reopened doesn't have a backing file attached > _and_ no default backing file is specified in the image metadata. > > Signed-off-by: Alberto Garcia <berto@igalia.com> > --- > block.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/block.c b/block.c > index fd51f1cd35..897c8b85cd 100644 > --- a/block.c > +++ b/block.c > @@ -3336,7 +3336,13 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, > > drv_prepared = true; > > - if (reopen_state->backing_missing) { > + /* > + * We must provide the 'backing' option if the BDS has a backing > + * file or if the image file has a backing file name as part of > + * its metadata. Otherwise the 'backing' option can be omitted. > + */ > + if (reopen_state->backing_missing && > + (backing_bs(reopen_state->bs) || reopen_state->bs->backing_file[0])) { > error_setg(errp, "backing is missing for '%s'", > reopen_state->bs->node_name); > ret = -EINVAL; Okay, this should be enough to fix drivers without support for backing files again. Might be worth mentioning in the commit message of this and the previous patch. Normally, I would suggest merging this into the previous patch to keep things bisectable, but keep_old_opts == false isn't used yet, so this isn't a concern in this case. Kevin
diff --git a/block.c b/block.c index fd51f1cd35..897c8b85cd 100644 --- a/block.c +++ b/block.c @@ -3336,7 +3336,13 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, drv_prepared = true; - if (reopen_state->backing_missing) { + /* + * We must provide the 'backing' option if the BDS has a backing + * file or if the image file has a backing file name as part of + * its metadata. Otherwise the 'backing' option can be omitted. + */ + if (reopen_state->backing_missing && + (backing_bs(reopen_state->bs) || reopen_state->bs->backing_file[0])) { error_setg(errp, "backing is missing for '%s'", reopen_state->bs->node_name); ret = -EINVAL;
Of all options of type BlockdevRef used to specify children in BlockdevOptions, 'backing' is the only one that is optional. For "x-blockdev-reopen" we want that if an option is omitted then it must be reset to its default value. The default value of 'backing' means that QEMU opens the backing file specified in the image metadata, but this is not something that we want to support for the reopen operation. Because of this the 'backing' option has to be specified during reopen, pointing to the existing backing file if we want to keep it, or pointing to a different one (or NULL) if we want to replace it (to be implemented in a subsequent patch). In order to simplify things a bit and not to require that the user passes the 'backing' option to every single block device even when it's clearly not necessary, this patch allows omitting this option if the block device being reopened doesn't have a backing file attached _and_ no default backing file is specified in the image metadata. Signed-off-by: Alberto Garcia <berto@igalia.com> --- block.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)