From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43496) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uh9ab-0006iB-TR for qemu-devel@nongnu.org; Mon, 27 May 2013 22:24:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Uh9aW-000257-UE for qemu-devel@nongnu.org; Mon, 27 May 2013 22:24:41 -0400 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:49130) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uh9aW-00024v-AH for qemu-devel@nongnu.org; Mon, 27 May 2013 22:24:36 -0400 Received: from /spool/local by e28smtp06.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 28 May 2013 07:48:06 +0530 Received: from d28relay02.in.ibm.com (d28relay02.in.ibm.com [9.184.220.59]) by d28dlp03.in.ibm.com (Postfix) with ESMTP id 7CB2D1258053 for ; Tue, 28 May 2013 07:56:32 +0530 (IST) Received: from d28av02.in.ibm.com (d28av02.in.ibm.com [9.184.220.64]) by d28relay02.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r4S2OPXD3604860 for ; Tue, 28 May 2013 07:54:25 +0530 Received: from d28av02.in.ibm.com (loopback [127.0.0.1]) by d28av02.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r4S2OTqC019596 for ; Tue, 28 May 2013 12:24:29 +1000 Message-ID: <51A4155A.9090009@linux.vnet.ibm.com> Date: Tue, 28 May 2013 10:24:26 +0800 From: Wenchao Xia MIME-Version: 1.0 References: <1369451385-23452-1-git-send-email-xiawenc@linux.vnet.ibm.com> <1369451385-23452-2-git-send-email-xiawenc@linux.vnet.ibm.com> <20130527152516.GF2373@dhcp-200-207.str.redhat.com> In-Reply-To: <20130527152516.GF2373@dhcp-200-207.str.redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH V3 1/4] block: drop bs_snapshots global variable List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: phrdina@redhat.com, stefanha@gmail.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, Stefan Hajnoczi , pbonzini@redhat.com, armbru@redhat.com 于 2013-5-27 23:25, Kevin Wolf 写道: > Am 25.05.2013 um 05:09 hat Wenchao Xia geschrieben: >> From: Stefan Hajnoczi >> >> The bs_snapshots global variable points to the BlockDriverState which >> will be used to save vmstate. This is really a savevm.c concept but was >> moved into block.c:bdrv_snapshots() when it became clear that hotplug >> could result in a dangling pointer. >> >> While auditing the block layer's global state I came upon bs_snapshots >> and realized that a variable is not necessary here. Simply find the >> first BlockDriverState capable of internal snapshots each time this is >> needed. >> >> The behavior of bdrv_snapshots() is preserved across hotplug because new >> drives are always appended to the bdrv_states list. This means that >> calling the new find_vmstate_bs() function is idempotent - it returns >> the same BlockDriverState unless it was hot-unplugged. >> >> Signed-off-by: Stefan Hajnoczi >> Reviewed-by: Eric Blake >> Reviewed-by: Wenchao Xia >> Signed-off-by: Wenchao Xia >> --- >> block.c | 28 ---------------------------- >> include/block/block.h | 1 - >> savevm.c | 19 +++++++++++++++---- >> 3 files changed, 15 insertions(+), 33 deletions(-) >> >> diff --git a/block.c b/block.c >> index 3f87489..478a3b2 100644 >> --- a/block.c >> +++ b/block.c >> @@ -99,9 +99,6 @@ static QTAILQ_HEAD(, BlockDriverState) bdrv_states = >> static QLIST_HEAD(, BlockDriver) bdrv_drivers = >> QLIST_HEAD_INITIALIZER(bdrv_drivers); >> >> -/* The device to use for VM snapshots */ >> -static BlockDriverState *bs_snapshots; >> - >> /* If non-zero, use only whitelisted block drivers */ >> static int use_bdrv_whitelist; >> >> @@ -1357,9 +1354,6 @@ void bdrv_close(BlockDriverState *bs) >> notifier_list_notify(&bs->close_notifiers, bs); >> >> if (bs->drv) { >> - if (bs == bs_snapshots) { >> - bs_snapshots = NULL; >> - } >> if (bs->backing_hd) { >> bdrv_delete(bs->backing_hd); >> bs->backing_hd = NULL; >> @@ -1591,7 +1585,6 @@ void bdrv_delete(BlockDriverState *bs) >> >> bdrv_close(bs); >> >> - assert(bs != bs_snapshots); >> g_free(bs); >> } >> >> @@ -1635,9 +1628,6 @@ void bdrv_set_dev_ops(BlockDriverState *bs, const BlockDevOps *ops, >> { >> bs->dev_ops = ops; >> bs->dev_opaque = opaque; >> - if (bdrv_dev_has_removable_media(bs) && bs == bs_snapshots) { >> - bs_snapshots = NULL; >> - } > > This hunk isn't replaced by any other code. If I understand correctly > what it's doing, it prevented you from saving the VM state to a > removable device, which would be allowed after this patch. > > Is this a change we want to make? Why isn't it described in the commit > message? How about adding it back in find_vmstate_bs()? > > Kevin > -- Best Regards Wenchao Xia