From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39654) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d3B06-0008OO-A9 for qemu-devel@nongnu.org; Tue, 25 Apr 2017 20:40:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d3B05-0007Am-BX for qemu-devel@nongnu.org; Tue, 25 Apr 2017 20:40:10 -0400 Date: Wed, 26 Apr 2017 08:39:56 +0800 From: Fam Zheng Message-ID: <20170426003956.GB4275@lemon.lan> References: <20170410150542.30376-1-famz@redhat.com> <20170410150542.30376-11-famz@redhat.com> <20170425151610.GC4615@noname.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170425151610.GC4615@noname.redhat.com> Subject: Re: [Qemu-devel] [PATCH for 2.9 v3 10/10] block: Fix bdrv_co_flush early return List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: qemu-devel@nongnu.org, Paolo Bonzini , qemu-block@nongnu.org, Ed Swierk , Max Reitz , Eric Blake , Stefan Hajnoczi 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 > > --- > > 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