From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37849) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WGEdo-0001M0-0x for qemu-devel@nongnu.org; Wed, 19 Feb 2014 16:25:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WGEdh-0002Xp-K6 for qemu-devel@nongnu.org; Wed, 19 Feb 2014 16:25:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57010) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WGEdh-0002XZ-AY for qemu-devel@nongnu.org; Wed, 19 Feb 2014 16:25:09 -0500 Date: Wed, 19 Feb 2014 16:23:05 -0500 From: Jeff Cody Message-ID: <20140219212305.GB9677@localhost.localdomain> References: <1392817351-22148-1-git-send-email-famz@redhat.com> <1392817351-22148-10-git-send-email-famz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1392817351-22148-10-git-send-email-famz@redhat.com> Subject: Re: [Qemu-devel] [PATCH v14 09/14] stream: Use bdrv_drop_intermediate and drop close_unused_images List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fam Zheng Cc: kwolf@redhat.com, benoit.canet@irqsave.net, rjones@redhat.com, qemu-devel@nongnu.org, armbru@redhat.com, imain@redhat.com, stefanha@redhat.com, pbonzini@redhat.com On Wed, Feb 19, 2014 at 09:42:26PM +0800, Fam Zheng wrote: > This reuses the new bdrv_drop_intermediate. > > Signed-off-by: Fam Zheng > --- > block/stream.c | 30 +----------------------------- > 1 file changed, 1 insertion(+), 29 deletions(-) > > diff --git a/block/stream.c b/block/stream.c > index dd0b4ac..9cdcf0e 100644 > --- a/block/stream.c > +++ b/block/stream.c > @@ -51,34 +51,6 @@ static int coroutine_fn stream_populate(BlockDriverState *bs, > return bdrv_co_copy_on_readv(bs, sector_num, nb_sectors, &qiov); > } > > -static void close_unused_images(BlockDriverState *top, BlockDriverState *base, > - const char *base_id) > -{ > - BlockDriverState *intermediate; > - intermediate = top->backing_hd; > - > - /* Must assign before bdrv_delete() to prevent traversing dangling pointer > - * while we delete backing image instances. > - */ > - top->backing_hd = base; > - > - while (intermediate) { > - BlockDriverState *unused; > - > - /* reached base */ > - if (intermediate == base) { > - break; > - } > - > - unused = intermediate; > - intermediate = intermediate->backing_hd; > - unused->backing_hd = NULL; > - bdrv_unref(unused); > - } > - > - bdrv_refresh_limits(top); > -} > - > static void coroutine_fn stream_run(void *opaque) > { > StreamBlockJob *s = opaque; > @@ -192,7 +164,7 @@ wait: > } > } > ret = bdrv_change_backing_file(bs, base_id, base_fmt); This is redundant if bdrv_drop_intermediate() is used, and can be removed. > - close_unused_images(bs, base, base_id); > + bdrv_drop_intermediate(bs, bs->backing_hd, base); Previously, if base == NULL and base_id == NULL, that meant that we were streaming from the very first backing file all the way up to the active layer. When close_unused_images() was called with base == NULL, the BDS chain was flattened and the active layer became all that was left. By calling bdrv_drop_intermediate() with base == NULL, we get the same behavior, so that is OK. What about if base != NULL here? It still works OK, but now 'base' is really 'bs->backing_hd'. But I don't think we care anymore in this function, or in the streaming block job, so I think it is OK. > } > > qemu_vfree(buf); > -- > 1.8.5.4 > >