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Re: [Qemu-devel] [PATCH] Stop VM on ENOSPC error
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] [PATCH] Stop VM on ENOSPC error |
Date: |
Wed, 14 Jan 2009 18:37:02 +0000 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
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
Re: [Qemu-devel] [PATCH] Stop VM on ENOSPC error, Jamie Lokier, 2009/01/14