From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 ; 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 ; 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 ; 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 ; 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 , Proxmox VE development discussion References: <20221128155509.142996-1-f.ebner@proxmox.com> From: Fiona Ebner In-Reply-To: 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 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-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 >> --- >> >> 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.