From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1Xguvm-0002kR-9Q for mharc-qemu-trivial@gnu.org; Wed, 22 Oct 2014 08:22:22 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46493) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xguvg-0002Z6-2N for qemu-trivial@nongnu.org; Wed, 22 Oct 2014 08:22:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Xguvb-0001rF-EK for qemu-trivial@nongnu.org; Wed, 22 Oct 2014 08:22:15 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:56675) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XguvR-0001lJ-Ib; Wed, 22 Oct 2014 08:22:02 -0400 Received: from 172.24.2.119 (EHLO szxeml456-hub.china.huawei.com) ([172.24.2.119]) by szxrg01-dlp.huawei.com (MOS 4.3.7-GA FastPath queued) with ESMTP id CDF52408; Wed, 22 Oct 2014 20:21:43 +0800 (CST) Received: from [127.0.0.1] (10.177.19.102) by szxeml456-hub.china.huawei.com (10.82.67.199) with Microsoft SMTP Server id 14.3.158.1; Wed, 22 Oct 2014 20:21:39 +0800 Message-ID: <5447A151.2050000@huawei.com> Date: Wed, 22 Oct 2014 20:21:37 +0800 From: Gonglei User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:11.0) Gecko/20120327 Thunderbird/11.0.1 MIME-Version: 1.0 To: Max Reitz References: <201410221945053926307@sangfor.com> <54479C3E.1070803@huawei.com> <54479C8A.9000407@redhat.com> <54479CE5.7040406@redhat.com> In-Reply-To: <54479CE5.7040406@redhat.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.19.102] X-CFilter-Loop: Reflected X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.4.x-2.6.x [generic] X-Received-From: 119.145.14.64 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 12:22:20 -0000 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. I don't know whether l1_size2 can be zero or not. Best regards, -Gonglei > Therefore, just "if (l1_table == NULL)" is sufficient. > > Max From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46456) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XguvW-0002Iq-PF for qemu-devel@nongnu.org; Wed, 22 Oct 2014 08:22:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XguvS-0001od-7W for qemu-devel@nongnu.org; Wed, 22 Oct 2014 08:22:06 -0400 Message-ID: <5447A151.2050000@huawei.com> Date: Wed, 22 Oct 2014 20:21:37 +0800 From: Gonglei MIME-Version: 1.0 References: <201410221945053926307@sangfor.com> <54479C3E.1070803@huawei.com> <54479C8A.9000407@redhat.com> <54479CE5.7040406@redhat.com> In-Reply-To: <54479CE5.7040406@redhat.com> Content-Type: text/plain; charset="windows-1252" 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: Max Reitz Cc: qemu-trivial , Kevin Wolf , Zhang Haoyu , qemu-devel , Stefan Hajnoczi 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. I don't know whether l1_size2 can be zero or not. Best regards, -Gonglei > Therefore, just "if (l1_table == NULL)" is sufficient. > > Max