From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59469) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YxBYS-0002mt-Ia for qemu-devel@nongnu.org; Tue, 26 May 2015 05:53:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YxBYP-0001H0-CN for qemu-devel@nongnu.org; Tue, 26 May 2015 05:53:48 -0400 Date: Tue, 26 May 2015 17:53:41 +0800 From: Fam Zheng Message-ID: <20150526095341.GC27391@ad.nay.redhat.com> References: <1432611383-3779-1-git-send-email-famz@redhat.com> <1432611383-3779-2-git-send-email-famz@redhat.com> <55643B5B.4000905@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55643B5B.4000905@redhat.com> Subject: Re: [Qemu-devel] [PATCH v5 1/8] block: Add bdrv_get_block_status_above List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Kevin Wolf , qemu-block@nongnu.org, Jeff Cody , qemu-devel@nongnu.org, qemu-stable@nongnu.org, Stefan Hajnoczi , jsnow@redhat.com, wangxiaolong@ucloud.cn On Tue, 05/26 11:22, Paolo Bonzini wrote: > > > On 26/05/2015 05:36, Fam Zheng wrote: > > Like bdrv_is_allocated_above, this function follows the backing chain until seeing > > BDRV_BLOCK_ALLOCATED. Base is not included. > > > > Reimplement bdrv_is_allocated on top. > > > > Signed-off-by: Fam Zheng > > --- > > block/io.c | 53 ++++++++++++++++++++++++++++++++++++++++----------- > > include/block/block.h | 4 ++++ > > 2 files changed, 46 insertions(+), 11 deletions(-) > > > > diff --git a/block/io.c b/block/io.c > > index e394d92..a0d9990 100644 > > --- a/block/io.c > > +++ b/block/io.c > > @@ -1560,28 +1560,51 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, > > return ret; > > } > > > > -/* Coroutine wrapper for bdrv_get_block_status() */ > > -static void coroutine_fn bdrv_get_block_status_co_entry(void *opaque) > > +static int64_t coroutine_fn bdrv_co_get_block_status_above(BlockDriverState *bs, > > + BlockDriverState *base, > > + int64_t sector_num, > > + int nb_sectors, > > + int *pnum) > > +{ > > + BlockDriverState *p; > > + int64_t ret; > > + > > + assert(bs != base); > > + for (p = bs; p != base; p = p->backing_hd) { > > + ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, pnum); > > Since pnum is an output parameter only, *pnum will be set by the last > call in the loop. > > This is not what bdrv_is_allocated_above does: you have to set *pnum > (roughly) to the _smallest_ value returned by the calls. Consider this > case (base == NULL, bs->backing_hd->backing_hd == NULL): > > 1 2 3 > 123456789012345678901234567890 > bs ...........AAAAAAAAAAAA....... > bs->backing_hd ...............AAAAAAAAAAAAAAA > > Your code would return *pnum == 15, but the right result is *pnum == 11. Yes, this is the case I missed! Thanks for explaining! Fam