From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1Xguxh-0005ff-1E for mharc-qemu-trivial@gnu.org; Wed, 22 Oct 2014 08:24:21 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47074) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xguxb-0005YX-1T for qemu-trivial@nongnu.org; Wed, 22 Oct 2014 08:24:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XguxW-0002jB-HB for qemu-trivial@nongnu.org; Wed, 22 Oct 2014 08:24:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35997) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XguxW-0002j6-9F; Wed, 22 Oct 2014 08:24:10 -0400 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s9MCO3Gk013196 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 22 Oct 2014 08:24:04 -0400 Received: from dresden.str.redhat.com (dhcp-192-247.str.redhat.com [10.33.192.247]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id s9MCO1Bg020651 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Wed, 22 Oct 2014 08:24:02 -0400 Message-ID: <5447A1E1.7030102@redhat.com> Date: Wed, 22 Oct 2014 14:24:01 +0200 From: Max Reitz User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Gonglei References: <201410221945053926307@sangfor.com> <54479C3E.1070803@huawei.com> <54479C8A.9000407@redhat.com> <54479CE5.7040406@redhat.com> <5447A151.2050000@huawei.com> In-Reply-To: <5447A151.2050000@huawei.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: qemu-trivial , Kevin Wolf , Zhang Haoyu , qemu-devel , Stefan Hajnoczi Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH v4] snapshot: use local variable to bdrv_pwrite_sync L1 table X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 22 Oct 2014 12:24:19 -0000 On 2014-10-22 at 14:21, Gonglei wrote: > On 2014/10/22 20:02, Max Reitz wrote: > >> On 2014-10-22 at 14:01, Max Reitz wrote: >>> On 2014-10-22 at 13:59, Gonglei wrote: >>>> On 2014/10/22 19:45, Zhang Haoyu wrote: >>>> >>>>> Use local variable to bdrv_pwrite_sync L1 table, >>>>> needless to make conversion of cached L1 table between >>>>> big-endian and host style. >>>>> >>>>> Signed-off-by: Zhang Haoyu >>>>> Reviewed-by: Max Reitz >>>>> --- >>>>> v3 -> v4: >>>>> - convert local L1 table to host-style before copy it >>>>> back to s->l1_table >>>>> >>>>> v2 -> v3: >>>>> - replace g_try_malloc0 with qemu_try_blockalign >>>>> - copy the latest local L1 table back to s->l1_table >>>>> after successfully bdrv_pwrite_sync L1 table >>>>> >>>>> v1 -> v2: >>>>> - remove the superflous assignment, l1_table = NULL; >>>>> - replace 512 with BDRV_SECTOR_SIZE, and align_offset with ROUND_UP >>>>> - remove needless check of if (l1_table) before g_free(l1_table) >>>>> >>>>> block/qcow2-refcount.c | 28 ++++++++++++---------------- >>>>> 1 file changed, 12 insertions(+), 16 deletions(-) >>>>> >>>>> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c >>>>> index 2bcaaf9..3e4050a 100644 >>>>> --- a/block/qcow2-refcount.c >>>>> +++ b/block/qcow2-refcount.c >>>>> @@ -881,14 +881,17 @@ int >>>>> qcow2_update_snapshot_refcount(BlockDriverState *bs, >>>>> { >>>>> BDRVQcowState *s = bs->opaque; >>>>> uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2; >>>>> - bool l1_allocated = false; >>>>> int64_t old_offset, old_l2_offset; >>>>> int i, j, l1_modified = 0, nb_csectors, refcount; >>>>> int ret; >>>>> l2_table = NULL; >>>>> - l1_table = NULL; >>>>> l1_size2 = l1_size * sizeof(uint64_t); >>>>> + l1_table = qemu_try_blockalign(bs->file, l1_size2); >>>>> + if (l1_size2 && l1_table == NULL) { >>>> I think this check has a logic problem. If l1_size2 != 0 and >>>> l1_table == NULL, >>>> What will happen? >>> Then this condition is met and you return with -ENOMEM...? >> Oh, but I see something different: qemu_try_blockalign() never returns >> NULL, not even when you request 0 bytes. > > Yes. But if l1_size2 is zero, will waste memory or some other problems. > Please see below: > > the original code: > l1_table = g_try_malloc0(align_offset(0, 512)); > -> l1_table = g_try_malloc0(0) > so l1_table == NULL. > > after this patch: > l1_table = qemu_try_blockalign(bs->file, 0) > l1_table will not be NULL. Okay, so you meant "if l1_size2 == 0 and l1_table != NULL". > I don't know whether l1_size2 can be zero or not. Probably not, but if it cannot be zero, testing for that case makes even less sense. Max From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47119) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xguxk-0005kb-7k for qemu-devel@nongnu.org; Wed, 22 Oct 2014 08:24:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Xguxf-0002jz-IX for qemu-devel@nongnu.org; Wed, 22 Oct 2014 08:24:24 -0400 Message-ID: <5447A1E1.7030102@redhat.com> Date: Wed, 22 Oct 2014 14:24:01 +0200 From: Max Reitz MIME-Version: 1.0 References: <201410221945053926307@sangfor.com> <54479C3E.1070803@huawei.com> <54479C8A.9000407@redhat.com> <54479CE5.7040406@redhat.com> <5447A151.2050000@huawei.com> In-Reply-To: <5447A151.2050000@huawei.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v4] snapshot: use local variable to bdrv_pwrite_sync L1 table List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gonglei Cc: qemu-trivial , Kevin Wolf , Zhang Haoyu , qemu-devel , Stefan Hajnoczi On 2014-10-22 at 14:21, Gonglei wrote: > On 2014/10/22 20:02, Max Reitz wrote: > >> On 2014-10-22 at 14:01, Max Reitz wrote: >>> On 2014-10-22 at 13:59, Gonglei wrote: >>>> On 2014/10/22 19:45, Zhang Haoyu wrote: >>>> >>>>> Use local variable to bdrv_pwrite_sync L1 table, >>>>> needless to make conversion of cached L1 table between >>>>> big-endian and host style. >>>>> >>>>> Signed-off-by: Zhang Haoyu >>>>> Reviewed-by: Max Reitz >>>>> --- >>>>> v3 -> v4: >>>>> - convert local L1 table to host-style before copy it >>>>> back to s->l1_table >>>>> >>>>> v2 -> v3: >>>>> - replace g_try_malloc0 with qemu_try_blockalign >>>>> - copy the latest local L1 table back to s->l1_table >>>>> after successfully bdrv_pwrite_sync L1 table >>>>> >>>>> v1 -> v2: >>>>> - remove the superflous assignment, l1_table = NULL; >>>>> - replace 512 with BDRV_SECTOR_SIZE, and align_offset with ROUND_UP >>>>> - remove needless check of if (l1_table) before g_free(l1_table) >>>>> >>>>> block/qcow2-refcount.c | 28 ++++++++++++---------------- >>>>> 1 file changed, 12 insertions(+), 16 deletions(-) >>>>> >>>>> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c >>>>> index 2bcaaf9..3e4050a 100644 >>>>> --- a/block/qcow2-refcount.c >>>>> +++ b/block/qcow2-refcount.c >>>>> @@ -881,14 +881,17 @@ int >>>>> qcow2_update_snapshot_refcount(BlockDriverState *bs, >>>>> { >>>>> BDRVQcowState *s = bs->opaque; >>>>> uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2; >>>>> - bool l1_allocated = false; >>>>> int64_t old_offset, old_l2_offset; >>>>> int i, j, l1_modified = 0, nb_csectors, refcount; >>>>> int ret; >>>>> l2_table = NULL; >>>>> - l1_table = NULL; >>>>> l1_size2 = l1_size * sizeof(uint64_t); >>>>> + l1_table = qemu_try_blockalign(bs->file, l1_size2); >>>>> + if (l1_size2 && l1_table == NULL) { >>>> I think this check has a logic problem. If l1_size2 != 0 and >>>> l1_table == NULL, >>>> What will happen? >>> Then this condition is met and you return with -ENOMEM...? >> Oh, but I see something different: qemu_try_blockalign() never returns >> NULL, not even when you request 0 bytes. > > Yes. But if l1_size2 is zero, will waste memory or some other problems. > Please see below: > > the original code: > l1_table = g_try_malloc0(align_offset(0, 512)); > -> l1_table = g_try_malloc0(0) > so l1_table == NULL. > > after this patch: > l1_table = qemu_try_blockalign(bs->file, 0) > l1_table will not be NULL. Okay, so you meant "if l1_size2 == 0 and l1_table != NULL". > I don't know whether l1_size2 can be zero or not. Probably not, but if it cannot be zero, testing for that case makes even less sense. Max