From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39476) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d31xY-00030a-8U for qemu-devel@nongnu.org; Tue, 25 Apr 2017 11:00:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d31xX-00080p-By for qemu-devel@nongnu.org; Tue, 25 Apr 2017 11:00:56 -0400 Received: from mail-wr0-x233.google.com ([2a00:1450:400c:c0c::233]:35950) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1d31xX-0007z0-6c for qemu-devel@nongnu.org; Tue, 25 Apr 2017 11:00:55 -0400 Received: by mail-wr0-x233.google.com with SMTP id l50so36670469wrc.3 for ; Tue, 25 Apr 2017 08:00:54 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20170411122632.14050-11-famz@redhat.com> References: <20170411122632.14050-1-famz@redhat.com> <20170411122632.14050-11-famz@redhat.com> From: Peter Maydell Date: Tue, 25 Apr 2017 16:00:33 +0100 Message-ID: Content-Type: text/plain; charset=UTF-8 Subject: Re: [Qemu-devel] [PULL 10/11] block: Fix bdrv_co_flush early return List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fam Zheng Cc: QEMU Developers On 11 April 2017 at 13:26, Fam Zheng wrote: > 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 > Acked-by: Stefan Hajnoczi > Reviewed-by: Kevin Wolf > Reviewed-by: Paolo Bonzini > --- > 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); > > - int current_gen = bs->write_gen; > + if (!bs || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs) || > + bdrv_is_sg(bs)) { > + goto early_exit; > + } Coverity points out that there's a problem here -- we call bdrv_inc_in_flight(bs), which assumes bs is not NULL, before we do the test for whether bs is NULL. Presumably the NULL check needs to be pulled up earlier in the function? thanks -- PMM