From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Scott Subject: Re: [PATCH] libxl: stat the path for all non-qdisk backends (including unknown) Date: Fri, 10 May 2013 15:09:02 +0100 Message-ID: <518CFF7E.1080408@eu.citrix.com> References: <1366985563-10926-1-git-send-email-ian.campbell@citrix.com> <1366986572.3142.116.camel@zakaz.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: George Dunlap Cc: "xen-devel@lists.xen.org" , Sylvain Munaut , Ian Jackson , Ian Campbell , Roger Pau Monne List-Id: xen-devel@lists.xenproject.org On 10/05/13 14:46, George Dunlap wrote: > On Fri, Apr 26, 2013 at 3:29 PM, Ian Campbell wrote: >> On Fri, 2013-04-26 at 15:17 +0100, Sylvain Munaut wrote: >>>> Since the intention of that commit was to allow for qdisk backends with no >>>> explicit file in dom0 (i.e. network remote backend such as ceph) the lowest >>>> impact fix appears to be to make that explicit. This should probably be >>>> revisited to rationalize the probing. >>> >>> What about the remote disk case of blktap ? blktap2.5 supports NBD >>> already AFAIK >>> and I'm pretty sure I'll hit that same stat issue soon for another >>> remote blktap case. >> >> Right, sounds like I should have gone with my first instinct which was: >> >> 8<------------------------------------------------------------ >> >> From 884beff4a897d785f61705dcfa2f048536982d7c Mon Sep 17 00:00:00 2001 >> From: Ian Campbell >> Date: Fri, 26 Apr 2013 12:41:43 +0100 >> Subject: [PATCH] libxl: stat the path for all non-qdisk backends (including unknown) >> >> The commit a8a1f236a296 "libxl: Only call stat() when adding a disk if we >> expect a device to exist." changed things to only stat the file when the phy >> backend was explicitly requested. This broke the case where we are probing and >> would normally be able to decide on the phy option. > > So at the moment qdisk backends aren't checked at all with this -- > which means that if you give a path to a file that doesn't exist via, > for example, xl cd-insert, things fail in weird ways: > > 1. In qemu-traditional, the command silently completes; the effect is > that the disk currently in the drive is ejected > > 2. in qemu-upstream, qmp returns an error which is reported. The disk > is ejected from the guest, but the xenstore entries are not updated > (still contain the old values) > > It seems like we should probably also at least check if disk_format is RAW. > > OTOH, I don't seen an option for disk_format to be ceph; is it just > listed as "raw" as well? That doesn't seem right... AFAICT a ceph disk is in the "raw" format but it uses a custom network protocol to actually read and write the blocks. I imagine on the ceph servers the disk is stored in a cleverer format, but all qemu/tapdisk see are plain blocks with no fancy encoding, no .vhd or .qcow. Cheers, Dave