Re: [PATCH v7 6/8] config: add check to block layer

[Sam Li]

Stefan Hajnoczi <stefanha@redhat.com> 于2022年8月23日周二 08:54写道：
>
> On Tue, Aug 16, 2022 at 02:25:20PM +0800, Sam Li wrote:
> > Putting zoned/non-zoned BlockDrivers on top of each other is not
> > allowed.
> >
> > Signed-off-by: Sam Li <faithilikerun@gmail.com>
> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> >  block.c                          | 14 ++++++++++++++
> >  block/raw-format.c               |  1 +
> >  include/block/block_int-common.h |  5 +++++
> >  3 files changed, 20 insertions(+)
> >
> > diff --git a/block.c b/block.c
> > index bc85f46eed..affe6c597e 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -7947,6 +7947,20 @@ void bdrv_add_child(BlockDriverState *parent_bs, 
> > BlockDriverState *child_bs,
> >          return;
> >      }
> >
> > +    /*
> > +     * Non-zoned block drivers do not follow zoned storage constraints
> > +     * (i.e. sequential writes to zones). Refuse mixing zoned and non-zoned
> > +     * drivers in a graph.
> > +     */
> > +    if (!parent_bs->drv->supports_zoned_children &&
> > +        child_bs->bl.zoned != BLK_Z_HM) {
>

Should be:
+if (!parent_bs->drv->supports_zoned_children &&
+        child_bs->bl.zoned == BLK_Z_HM)

> Is this logical expression correct:
>
>   If the parent does not support zoned children and the child is not
>   zoned, fail with an error.
>
> ?

No. It should be:

If the parent does not support zoned children and the child is zoned,
fail with an error.  It should handle the case where a filter node is
inserted above a raw block driver with a zoned_host_device child.

There are some QEMU command-line constraints for the zoned devices. I
was wondering where to add such support so that it can print an error
message for users:
1. cache.direct= setting
2. mix zoned/non-zoned drivers

>
> > +        error_setg(errp, "Cannot add a %s child to a %s parent",
> > +                   child_bs->bl.zoned == BLK_Z_HM ? "zoned" : "non-zoned",
> > +                   parent_bs->drv->supports_zoned_children ?
> > +                   "support zoned children" : "not support zoned 
> > children");
> > +        return;
> > +    }
> > +
> >      if (!QLIST_EMPTY(&child_bs->parents)) {
> >          error_setg(errp, "The node %s already has a parent",
> >                     child_bs->node_name);
> > diff --git a/block/raw-format.c b/block/raw-format.c
> > index 6b20bd22ef..9441536819 100644
> > --- a/block/raw-format.c
> > +++ b/block/raw-format.c
> > @@ -614,6 +614,7 @@ static void raw_child_perm(BlockDriverState *bs, 
> > BdrvChild *c,
> >  BlockDriver bdrv_raw = {
> >      .format_name          = "raw",
> >      .instance_size        = sizeof(BDRVRawState),
> > +    .supports_zoned_children = true,
> >      .bdrv_probe           = &raw_probe,
> >      .bdrv_reopen_prepare  = &raw_reopen_prepare,
> >      .bdrv_reopen_commit   = &raw_reopen_commit,
> > diff --git a/include/block/block_int-common.h 
> > b/include/block/block_int-common.h
> > index de44c7b6f4..4c44592b59 100644
> > --- a/include/block/block_int-common.h
> > +++ b/include/block/block_int-common.h
> > @@ -126,6 +126,11 @@ struct BlockDriver {
> >       */
> >      bool is_format;
> >
> > +    /*
> > +     * Set to true if the BlockDriver supports zoned children.
> > +     */
> > +    bool supports_zoned_children;
> > +
> >      /*
> >       * Drivers not implementing bdrv_parse_filename nor bdrv_open should 
> > have
> >       * this field set to true, except ones that are defined only by their
> > --
> > 2.37.1
> >