From mboxrd@z Thu Jan 1 00:00:00 1970
Return-Path: <f.ebner@proxmox.com>
Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68])
(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)
key-exchange X25519 server-signature RSA-PSS (2048 bits))
(No client certificate requested)
by lists.proxmox.com (Postfix) with ESMTPS id A0229946A0
for <pve-devel@lists.proxmox.com>; Thu, 12 Jan 2023 09:33:54 +0100 (CET)
Received: from firstgate.proxmox.com (localhost [127.0.0.1])
by firstgate.proxmox.com (Proxmox) with ESMTP id 7C2F72738A
for <pve-devel@lists.proxmox.com>; Thu, 12 Jan 2023 09:33:54 +0100 (CET)
Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com
[94.136.29.106])
(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)
key-exchange X25519 server-signature RSA-PSS (2048 bits))
(No client certificate requested)
by firstgate.proxmox.com (Proxmox) with ESMTPS
for <pve-devel@lists.proxmox.com>; Thu, 12 Jan 2023 09:33:53 +0100 (CET)
Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1])
by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 7FBAB44143
for <pve-devel@lists.proxmox.com>; Thu, 12 Jan 2023 09:33:52 +0100 (CET)
Message-ID: <81b59658-e60d-6899-dc73-4e5b02b151b9@proxmox.com>
Date: Thu, 12 Jan 2023 09:33:51 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
Thunderbird/102.5.0
Content-Language: en-US
To: Thomas Lamprecht <t.lamprecht@proxmox.com>,
Proxmox VE development discussion <pve-devel@lists.proxmox.com>
References: <20221128155509.142996-1-f.ebner@proxmox.com>
<b2ff06be-a653-22bd-224e-5617e367d5d2@proxmox.com>
From: Fiona Ebner <f.ebner@proxmox.com>
In-Reply-To: <b2ff06be-a653-22bd-224e-5617e367d5d2@proxmox.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
X-SPAM-LEVEL: Spam detection results: 0
AWL -0.127 Adjusted score from AWL reputation of From: address
BAYES_00 -1.9 Bayes spam probability is 0 to 1%
KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment
NICE_REPLY_A -0.001 Looks like a legit reply (A)
POISEN_SPAM_PILL 0.1 Meta: its spam
POISEN_SPAM_PILL_1 0.1 random spam to be learned in bayes
POISEN_SPAM_PILL_3 0.1 random spam to be learned in bayes
SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record
SPF_PASS -0.001 SPF: sender matches SPF record
Subject: Re: [pve-devel] [PATCH storage] plugin: file size info: use
fallback for actual size
X-BeenThere: pve-devel@lists.proxmox.com
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Proxmox VE development discussion <pve-devel.lists.proxmox.com>
List-Unsubscribe: <https://lists.proxmox.com/cgi-bin/mailman/options/pve-devel>,
<mailto:pve-devel-request@lists.proxmox.com?subject=unsubscribe>
List-Archive: <http://lists.proxmox.com/pipermail/pve-devel/>
List-Post: <mailto:pve-devel@lists.proxmox.com>
List-Help: <mailto:pve-devel-request@lists.proxmox.com?subject=help>
List-Subscribe: <https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel>,
<mailto:pve-devel-request@lists.proxmox.com?subject=subscribe>
X-List-Received-Date: Thu, 12 Jan 2023 08:33:54 -0000
Am 11.01.23 um 16:46 schrieb Thomas Lamprecht:
> Am 28/11/2022 um 16:55 schrieb Fiona Ebner:
>> The actual-size property is an optional property in the QAPI
>> definition for ImageInfo. If it's not set, simply use the information
>> from stat() as a fallback. This is essentially the same
>> raw_get_allocated_file_size() in QEMU does anyways.
>>
>> Reported in the community forum:
>> https://forum.proxmox.com/threads/118443/post-513421
>>
>> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
>> ---
>>
>> Thanks to Mira for setting up a GlusterFS instance and discussing the
>> issue with me!
>>
>> I'm not sure why QEMU fails here, didn't see much that could go wrong
>> beside the fstat() call failing. But our stat() call in the beginning
>> of file_size_info already succeeded at that point :/ The mysteries of
>> QEMU+GlusterFS.
>>
>> Also, it's a bit strange to call qemu-img info regardless of whether
>> the image is a VM image or not. E.g., this results in the format
>> property for backups to always be raw, rather than the backup format.
>> Should we change that (for 8.0)?
>>
>> PVE/Storage/Plugin.pm | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/PVE/Storage/Plugin.pm b/PVE/Storage/Plugin.pm
>> index 8a41df1..7773ac3 100644
>> --- a/PVE/Storage/Plugin.pm
>> +++ b/PVE/Storage/Plugin.pm
>> @@ -899,6 +899,7 @@ sub file_size_info {
>> }
>>
>> my ($size, $format, $used, $parent) = $info->@{qw(virtual-size format actual-size backing-filename)};
>> + $used ||= $st->blocks * 512;
>
> in general OK, but can we really be sure that blocks are always 512 bytes?
>
Initially, I only checked 'man 2 stat' where this is the case:
> blkcnt_t st_blocks; /* Number of 512B blocks allocated */
But checking again now, 'perldoc -f stat' (File::stat mentions it uses
Perl's builtin stat()) actually states:
> 12 blocks actual number of system-specific blocks allocated
> on disk (often, but not always, 512 bytes each)
Trying to decipher the Perl 5 source code, I /think/ it will just use
stat(2) on Linux (a quick check with strace seems to confirm this) and
I'd say it would be surprising if not, but I'm not 100% sure.
That said, the original issue here was GlusterFS reporting an incorrect
value (see the forum thread). The new fallback introduced by this patch
would only help if 'qemu-img info' fails to determine the size for some
other reason (it also just does st_blocks * 512 in
raw_get_allocated_file_size()), so I'm not sure the patch is even worth
it after all.