On Tue, 04/25 17:16, Kevin Wolf wrote:
> Am 10.04.2017 um 17:05 hat Fam Zheng geschrieben:
> > bdrv_inc_in_flight and bdrv_dec_in_flight are mandatory for
> > BDRV_POLL_WHILE to work, even for the shortcut case where flush is
> > unnecessary. Move the if block to below bdrv_dec_in_flight, and BTW fix
> > the variable declaration position.
> >
> > Signed-off-by: Fam Zheng <f...@redhat.com>
> > ---
> > block/io.c | 16 +++++++++-------
> > 1 file changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/block/io.c b/block/io.c
> > index 00e45ca..bae6947 100644
> > --- a/block/io.c
> > +++ b/block/io.c
> > @@ -2278,16 +2278,17 @@ static void coroutine_fn bdrv_flush_co_entry(void
> > *opaque)
> >
> > int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
> > {
> > - int ret;
> > -
> > - if (!bs || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs) ||
> > - bdrv_is_sg(bs)) {
> > - return 0;
> > - }
> > + int current_gen;
> > + int ret = 0;
> >
> > bdrv_inc_in_flight(bs);
>
> As Coverity points out, we're now using bs...
>
> > - int current_gen = bs->write_gen;
> > + if (!bs || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs) ||
>
> ...before doing the NULL check.
>
> I'm not sure if we even need to have a NULL check here, but we would have
> to check all callers to make sure that it's unnecessary. Before commit
> 29cdb251, it only checked bs->drv and I don't see how that commit
> introduced a NULL caller, but maybe one was added later.
>
> In any case, bdrv_co_flush() needs a fix, either remove the NULL check
> or do it first.
After auditing the callers and knowing the fact that the above
bdrv_inc_in_flight didn't cause a problem, I think removing the NULL check is
fine.
I'll send a patch.
Thanks.
Fam
>
> > + bdrv_is_sg(bs)) {
> > + goto early_exit;
> > + }
>
> Kevin
