From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Novotny Subject: Re: [PATCH] Introduce dom0-min-space configuration option Date: Wed, 21 Jul 2010 05:52:17 +0200 Message-ID: <4C466EF1.1070002@redhat.com> References: <4C3B59FE.2060201@redhat.com> <19516.43557.723062.885082@mariner.uk.xensource.com> <4C3D9E22.3030302@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4C3D9E22.3030302@redhat.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ian Jackson Cc: "'xen-devel@lists.xensource.com'" List-Id: xen-devel@lists.xenproject.org Ian, what do you think about this? Michal On 07/14/2010 01:23 PM, Michal Novotny wrote: > On 07/13/2010 08:02 PM, Ian Jackson wrote: >> Michal Novotny writes ("[Xen-devel] [PATCH] Introduce dom0-min-space >> configuration option"): >>> This is the patch to introduce configuration option called >>> dom0-min-space since there were some issues with data inflation >>> because of invalid input data stream for zlib decompression. >>> The issue occured because of insufficient free space on the dom0 so >>> this patch checks the free available space for /var/lib/xen >>> and refuses to start up any guests when the space is below >>> specified value. Setting up the value to 0 disables the check >>> which preserves the behaviour before this patch applied and >>> this is the default value for this option. >> Thanks for the patch, but I'm not sure I entirely follow. >> >> What "issues with data inflation because of invalid input data stream >> for zlib decompression" were there and how do they relate to lack of >> space on /var/lib/xen ? > > Ian, the problem is when pygrub extracts the vmlinuz and initrd for PV > guests but there's insufficient space on the dom0, there's no error > message but the error is being raised from Xend itself, libxc to be > precise since there's the zStream inflation code but since the input > data are not valid (i.e. they're just partial, let's say only 50 KiB > was extracted to /var/lib/xen since after those 50 KiBs the dom0 had > no space available) the zStream (zlib decompression) fails with > Z_BUF_ERROR and then it outputs annoying and nothing saying message to > standalone users (non-developers) to doesn't do investigation on their > own. This patch would prevent going into those issues since there > would be always at least specified amount of free space available for > PV images to be extracted to /var/lib/xen . >> Is this just for the situation where the dom0 filesystem hasn't enough >> space to contain the uncompressed version of the domU kernel and >> initrd which are to be loaded ? > > Well, this is for compressed version being extracted from the guest > image files. This is being saved to /var/lib/xen and if there's not > enough space to save it the deflation fails with -5 (Z_BUF_ERROR) > which says nothing to standalone users. > >> Your patch just raises an error. Why does the situation in which the >> patch is needed not already raise an appropriate error ? Perhaps it >> would be better to arrange that it does. > > Well, the reason is that there should be multiple reasons that could > make the decompression (gunzip) fail. Also, having the dom0 with no > space could cause some other (non-Xen) related errors so having this > option could prevent user running into those issues - mainly if the > user's saving images to the default location, i.e. > /var/lib/xen/images, he/she can get running out of free space on dom0 > very easily. > > Michal > -- Michal Novotny, RHCE Virtualization Team (xen userspace), Red Hat