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Re: [Qemu-block] [PATCH for 2.9 v3 10/10] block: Fix bdrv_co_flush early
From: |
Fam Zheng |
Subject: |
Re: [Qemu-block] [PATCH for 2.9 v3 10/10] block: Fix bdrv_co_flush early return |
Date: |
Wed, 26 Apr 2017 08:39:56 +0800 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
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 <address@hidden>
> > ---
> > 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
- [Qemu-block] [PATCH for 2.9 v3 07/10] blockjob: Use bdrv_coroutine_enter to start coroutine, (continued)
- [Qemu-block] [PATCH for 2.9 v3 07/10] blockjob: Use bdrv_coroutine_enter to start coroutine, Fam Zheng, 2017/04/10
- [Qemu-block] [PATCH for 2.9 v3 08/10] qemu-io-cmds: Use bdrv_coroutine_enter, Fam Zheng, 2017/04/10
- [Qemu-block] [PATCH for 2.9 v3 09/10] block: Use bdrv_coroutine_enter to start I/O coroutines, Fam Zheng, 2017/04/10
- [Qemu-block] [PATCH for 2.9 v3 10/10] block: Fix bdrv_co_flush early return, Fam Zheng, 2017/04/10
- Re: [Qemu-block] [PATCH for 2.9 v3 00/10] block: Fixes regarding dataplane and management operations, Stefan Hajnoczi, 2017/04/11
- Re: [Qemu-block] [PATCH for 2.9 v3 00/10] block: Fixes regarding dataplane and management operations, Kevin Wolf, 2017/04/11
- [Qemu-block] [PATCH for 2.9 v3 11/10] block, async: Remove unused *_enter_if_inactive(), Kevin Wolf, 2017/04/11