From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1XgvCC-0000bR-42 for mharc-qemu-trivial@gnu.org; Wed, 22 Oct 2014 08:39:20 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49540) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgvC4-0000YJ-TZ for qemu-trivial@nongnu.org; Wed, 22 Oct 2014 08:39:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XgvC0-0007hB-A4 for qemu-trivial@nongnu.org; Wed, 22 Oct 2014 08:39:12 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:54747) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgvBq-0007fp-3M; Wed, 22 Oct 2014 08:38:58 -0400 Received: from 172.24.2.119 (EHLO szxeml418-hub.china.huawei.com) ([172.24.2.119]) by szxrg02-dlp.huawei.com (MOS 4.3.7-GA FastPath queued) with ESMTP id CBC53382; Wed, 22 Oct 2014 20:38:42 +0800 (CST) Received: from [127.0.0.1] (10.177.19.102) by szxeml418-hub.china.huawei.com (10.82.67.157) with Microsoft SMTP Server id 14.3.158.1; Wed, 22 Oct 2014 20:38:36 +0800 Message-ID: <5447A54B.1090701@huawei.com> Date: Wed, 22 Oct 2014 20:38:35 +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> <5447A151.2050000@huawei.com> <5447A1E1.7030102@redhat.com> <5447A374.4070309@huawei.com> <5447A3C0.6070003@redhat.com> In-Reply-To: <5447A3C0.6070003@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: 119.145.14.65 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 12:39:18 -0000 On 2014/10/22 20:32, Max Reitz wrote: > On 2014-10-22 at 14:30, Gonglei wrote: >> On 2014/10/22 20:24, Max Reitz wrote: >> >>> 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". >>> >> Hum, sorry for my typo ;) >> >>>> 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. >>> >> So, can we add a check at the begin of this function? > > We can just omit the "l1_size2 && " from the "if (l1_size2 && l1_table > == NULL)". > Ack. Best regards, -Gonglei From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49514) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgvBv-0000Rp-Cu for qemu-devel@nongnu.org; Wed, 22 Oct 2014 08:39:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XgvBq-0007gF-Q3 for qemu-devel@nongnu.org; Wed, 22 Oct 2014 08:39:03 -0400 Message-ID: <5447A54B.1090701@huawei.com> Date: Wed, 22 Oct 2014 20:38:35 +0800 From: Gonglei MIME-Version: 1.0 References: <201410221945053926307@sangfor.com> <54479C3E.1070803@huawei.com> <54479C8A.9000407@redhat.com> <54479CE5.7040406@redhat.com> <5447A151.2050000@huawei.com> <5447A1E1.7030102@redhat.com> <5447A374.4070309@huawei.com> <5447A3C0.6070003@redhat.com> In-Reply-To: <5447A3C0.6070003@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 20:32, Max Reitz wrote: > On 2014-10-22 at 14:30, Gonglei wrote: >> On 2014/10/22 20:24, Max Reitz wrote: >> >>> 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". >>> >> Hum, sorry for my typo ;) >> >>>> 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. >>> >> So, can we add a check at the begin of this function? > > We can just omit the "l1_size2 && " from the "if (l1_size2 && l1_table > == NULL)". > Ack. Best regards, -Gonglei