Am 15.02.2017 um 18:30 hat Max Reitz geschrieben: > On 13.02.2017 18:22, Kevin Wolf wrote: > > vvfat is the last remaining driver that can have children, but doesn't > > implement .bdrv_child_perm() yet. The default handlers aren't suitable > > here, so let's implement a very simple driver-specific one that protects > > the internal child from being used by other users as good as our > > permissions permit. > > > > Signed-off-by: Kevin Wolf <[email protected]> > > --- > > block/vvfat.c | 13 +++++++++++++ > > 1 file changed, 13 insertions(+) > > > > diff --git a/block/vvfat.c b/block/vvfat.c > > index c6bf67e..7246432 100644 > > --- a/block/vvfat.c > > +++ b/block/vvfat.c > > @@ -3052,6 +3052,18 @@ err: > > return ret; > > } > > > > +static void vvfat_child_perm(BlockDriverState *bs, BdrvChild *c, > > + const BdrvChildRole *role, > > + uint64_t perm, uint64_t shared, > > + uint64_t *nperm, uint64_t *nshared) > > +{ > > + assert(role == &child_vvfat_qcow); > > + > > + /* This is a private node, nobody should try to attach to it */ > > + *nperm = BLK_PERM_WRITE; > > + *nshared = 0; > > 0 for shared is probably enough to ward every other access off, but > maybe we should still pro forma request consistent read access...?
Makes sense, yes.
But you missed the real bug I hid there for you:
qemu-system-x86_64: block.c:1530: bdrv_check_update_perm: Assertion
`new_shared_perm & BLK_PERM_WRITE_UNCHANGED' failed.
Kevin
> Max
>
> > +}
> > +
> > static void vvfat_close(BlockDriverState *bs)
> > {
> > BDRVVVFATState *s = bs->opaque;
> > @@ -3077,6 +3089,7 @@ static BlockDriver bdrv_vvfat = {
> > .bdrv_file_open = vvfat_open,
> > .bdrv_refresh_limits = vvfat_refresh_limits,
> > .bdrv_close = vvfat_close,
> > + .bdrv_child_perm = vvfat_child_perm,
> >
> > .bdrv_co_preadv = vvfat_co_preadv,
> > .bdrv_co_pwritev = vvfat_co_pwritev,
> >
>
>
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