From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59256) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VF1Uy-0003Hv-IX for qemu-devel@nongnu.org; Thu, 29 Aug 2013 08:38:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VF1Us-00063r-Ie for qemu-devel@nongnu.org; Thu, 29 Aug 2013 08:38:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:26244) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VF1Us-00063g-B4 for qemu-devel@nongnu.org; Thu, 29 Aug 2013 08:38:46 -0400 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r7TCcj8o022497 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 29 Aug 2013 08:38:45 -0400 Message-ID: <521F40D3.8000302@redhat.com> Date: Thu, 29 Aug 2013 14:38:43 +0200 From: Max Reitz MIME-Version: 1.0 References: <1377771363-5198-1-git-send-email-mreitz@redhat.com> <20130829123343.GH2961@dhcp-200-207.str.redhat.com> In-Reply-To: <20130829123343.GH2961@dhcp-200-207.str.redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] qcow2-refcount: Snapshot update for zero clusters List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: qemu-devel@nongnu.org, Stefan Hajnoczi Am 29.08.2013 14:33, schrieb Kevin Wolf: > Am 29.08.2013 um 12:16 hat Max Reitz geschrieben: >> Do not try to update the refcount for zero clusters in >> qcow2_update_snapshot_refcount. >> >> Signed-off-by: Max Reitz >> --- >> block/qcow2-refcount.c | 16 +++++++++++++--- >> 1 file changed, 13 insertions(+), 3 deletions(-) > Please don't forget to add a test case for v2. Okay. >> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c >> index 1244693..7555242 100644 >> --- a/block/qcow2-refcount.c >> +++ b/block/qcow2-refcount.c >> @@ -863,9 +863,13 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs, >> for(j = 0; j < s->l2_size; j++) { >> offset = be64_to_cpu(l2_table[j]); >> if (offset != 0) { >> + uint64_t cluster_index; >> + >> old_offset = offset; >> offset &= ~QCOW_OFLAG_COPIED; >> - if (offset & QCOW_OFLAG_COMPRESSED) { >> + >> + switch (qcow2_get_cluster_type(offset)) { >> + case QCOW2_CLUSTER_COMPRESSED: >> nb_csectors = ((offset >> s->csize_shift) & >> s->csize_mask) + 1; >> if (addend != 0) { >> @@ -880,8 +884,10 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs, >> } >> /* compressed clusters are never modified */ >> refcount = 2; >> - } else { >> - uint64_t cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits; >> + break; >> + >> + case QCOW2_CLUSTER_NORMAL: >> + cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits; >> if (addend != 0) { >> refcount = update_cluster_refcount(bs, cluster_index, addend, >> QCOW2_DISCARD_SNAPSHOT); >> @@ -893,6 +899,10 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs, >> ret = refcount; >> goto fail; >> } >> + break; > I think this part isn't quite right. Even zero clusters can have an > allocated offset, so I think what's really needed is that the same code > runs from QCOW2_CLUSTER_ZERO. However, add an if (cluster_index == 0) > case for the unallocated case. So then it would be enough to change: - if (offset != 0) { + if ((offset & L2E_OFFSET_MASK) != 0) { and just execute the same code for QCOW2_CLUSTER_NORMAL and QCOW2_CLUSTER_ZERO? >> + >> + default: >> + refcount = 0; > Other places enumerate the enum values explicitly and have a default > label that simply abort()s. This will help catching forgotten places > when a new value is added. Okay. >> } >> >> if (refcount == 1) { > Kevin Max