From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LNAbz-0006H6-Mx for qemu-devel@nongnu.org; Wed, 14 Jan 2009 13:37:07 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LNAbx-0006GZ-Ox for qemu-devel@nongnu.org; Wed, 14 Jan 2009 13:37:06 -0500 Received: from [199.232.76.173] (port=53287 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LNAbx-0006GU-Jw for qemu-devel@nongnu.org; Wed, 14 Jan 2009 13:37:05 -0500 Received: from mail2.shareable.org ([80.68.89.115]:58568) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LNAbx-0000O2-87 for qemu-devel@nongnu.org; Wed, 14 Jan 2009 13:37:05 -0500 Date: Wed, 14 Jan 2009 18:37:02 +0000 From: Jamie Lokier Subject: Re: [Qemu-devel] [PATCH] Stop VM on ENOSPC error Message-ID: <20090114183702.GH6431@shareable.org> References: <20090114120358.GS3267@redhat.com> <20090114121147.GI24995@redhat.com> <20090114164617.GB6431@shareable.org> <20090114173044.GS24995@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090114173044.GS24995@redhat.com> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: qemu-devel@nongnu.org Daniel P. Berrange wrote: > > A corrupt VM with data loss sounds much worse than a stopped VM to me. > > You're not corrupting data in current code - you're just unable to finish > new writes, because an IO failure is propagated back to the guest. If the > guest is properly checking for & handling I/O failures, it should be pretty > much OK once the host space problem is resolved - perhaps a reboot + journal > recovery. Think about journalling filesystem writes. If one returns I/O error, some following queued requests must not proceed, otherwise it puts the filesystem in an inconsistent state. That's what I mean by corruption. What that in mind, please name any OS which properly checks for and handles write I/O errors, aside from reporting EIO to apps. I'm pretty sure Linux is not among them. (Heck, even ENOSPC isn't handled well in apps. Why, I remember the time Firefox corrupted by Bookmarks by storing a zero-length file due to ENOSPC... I remember a few times when after Make I had zero-length .o object files, and we're not talking about my personal crappy Makefiles but good quality ones, etc. This seems to be quite common.) -- Jamie