From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50879) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VX9Ju-0004Ry-74 for qemu-devel@nongnu.org; Fri, 18 Oct 2013 08:38:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VX9Jn-0001Ic-Qj for qemu-devel@nongnu.org; Fri, 18 Oct 2013 08:38:22 -0400 Received: from mail-ea0-x235.google.com ([2a00:1450:4013:c01::235]:36919) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VX9Jn-0001IW-J8 for qemu-devel@nongnu.org; Fri, 18 Oct 2013 08:38:15 -0400 Received: by mail-ea0-f181.google.com with SMTP id d10so1931580eaj.40 for ; Fri, 18 Oct 2013 05:38:14 -0700 (PDT) Date: Fri, 18 Oct 2013 14:38:12 +0200 From: Stefan Hajnoczi Message-ID: <20131018123812.GB19041@stefanha-thinkpad.redhat.com> References: <1381233491-17019-1-git-send-email-pl@kamp.de> <1381233491-17019-15-git-send-email-pl@kamp.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1381233491-17019-15-git-send-email-pl@kamp.de> Subject: Re: [Qemu-devel] [PATCHv4 14/17] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: kwolf@redhat.com, stefanha@redhat.com, qemu-devel@nongnu.org, anthony@codemonkey.ws, pbonzini@redhat.com, ronniesahlberg@gmail.com On Tue, Oct 08, 2013 at 01:58:08PM +0200, Peter Lieven wrote: > this patch does 2 things: > a) only do additional call outs if BDRV_BLOCK_ZERO is not already set. > b) use the newly introduced bdrv_has_discard_zeroes() to return the > zero state of an unallocated block. the used callout to > bdrv_has_zero_init() is only valid right after bdrv_create. > > Reviewed-by: Eric Blake > Signed-off-by: Peter Lieven > --- > block.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/block.c b/block.c > index fc931e3..1be4418 100644 > --- a/block.c > +++ b/block.c > @@ -3247,8 +3247,8 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, > return ret; > } > > - if (!(ret & BDRV_BLOCK_DATA)) { > - if (bdrv_has_zero_init(bs)) { > + if (!(ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO)) { > + if (bdrv_has_discard_zeroes(bs)) { I'm a little unclear about the semantics of bdrv_has_discard_zeroes(). Originally I thought it just meant any blocks discarded will read back as zeroes. But here it implies that any unallocated block reads back as zeroes too? In other words, this patch assumes unallocated blocks behave the same as discarded blocks wrt to zeroes. Stefan