From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51534) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XTRqe-0006GU-56 for qemu-devel@nongnu.org; Mon, 15 Sep 2014 04:41:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XTRqH-0000nd-Pf for qemu-devel@nongnu.org; Mon, 15 Sep 2014 04:41:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:21697) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XTRqH-0000nX-I8 for qemu-devel@nongnu.org; Mon, 15 Sep 2014 04:41:01 -0400 From: Markus Armbruster References: <1410620427-20089-1-git-send-email-armbru@redhat.com> <1410620427-20089-20-git-send-email-armbru@redhat.com> <20140915073051.GD29999@fam-t430.nay.redhat.com> Date: Mon, 15 Sep 2014 10:40:56 +0200 In-Reply-To: <20140915073051.GD29999@fam-t430.nay.redhat.com> (Fam Zheng's message of "Mon, 15 Sep 2014 15:30:51 +0800") Message-ID: <87y4tlmg2v.fsf@blackfin.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v2 19/23] blockdev: Drop DriveInfo member enable_auto_del List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fam Zheng Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, benoit.canet@nodalink.com Fam Zheng writes: > On Sat, 09/13 17:00, Markus Armbruster wrote: >> Commit 2d246f0 introduced DriveInfo member enable_auto_del to >> distinguish DriveInfo created via drive_new() from DriveInfo created >> via qmp_blockdev_add(). The latter no longer exist. Drop >> enable_auto_del. >> >> Signed-off-by: Markus Armbruster >> --- >> blockdev.c | 11 +++-------- >> include/sysemu/blockdev.h | 1 - >> 2 files changed, 3 insertions(+), 9 deletions(-) >> >> diff --git a/blockdev.c b/blockdev.c >> index 0d99be0..e218c59 100644 >> --- a/blockdev.c >> +++ b/blockdev.c >> @@ -90,16 +90,14 @@ void blockdev_mark_auto_del(BlockBackend *blk) >> DriveInfo *dinfo = blk_legacy_dinfo(blk); >> BlockDriverState *bs = blk_bs(blk); >> >> - if (dinfo && !dinfo->enable_auto_del) { >> + if (!dinfo) { >> return; >> } >> >> if (bs->job) { >> block_job_cancel(bs->job); >> } >> - if (dinfo) { >> - dinfo->auto_del = 1; >> - } >> + dinfo->auto_del = 1; >> } > > Looks good. > > Based on the explanation in the commit message of patch 18, previouly, > dinfo is always non-NULL, so enable_auto_del distinguishes whether the > device is created by drive_new() or qmp_blockdev_add(). Correct. > Now dinfo is NULL iff created by qmp_blockdev_add(), so > enable_auto_del is not necessary any more. Correct again. > If I'm reading correctly, the dropped two "if (dinfo.."'s are also redundant. Yes. Let me explain why. The two cases to distinguish are "created by drive_new()" and "created by qmp_blockdev_add()". Commit 2d246f0 introduced DriveInfo member enable_auto_del to exactly that. The code tests for "created by qmp_blockdev_add()" like this: dinfo && !dinfo->enable_auto_del Before PATCH 18, this was actually unnecessarily careful, because dinfo could never be null, but that's okay. PATCH 18 changes the "created by qmp_blockdev_add() case: now dinfo is null there. The test remains correct, only now its second rather than first part is unnecessary: dinfo now implies dinfo->enable_auto_del. Before PATCH 18 dinfo != NULL !dinfo->enable_auto_del && by drive_new() true false false by qmp_blockdev_add() true true true After PATCH 18 dinfo != NULL !dinfo->enable_auto_del && by drive_new() true false false by qmp_blockdev_add() false N/A false Oops. After PATCH 19 dinfo !dinfo by drive_new() true false by qmp_blockdev_add() false true Looks like I need to squash PATCH 19 into PATCH 18... Thanks for making me think! [...]