[linux-lvm] Kernel panic while snapshotting.

[Jay Weber]

This was on 2.2.18 based kernel it includes several (and I mean several)
other patches as well in this case.  I just reproduced the problem without
the IO in the background and I'm thinking the removal of LockPage or the
iobuf->locked=0 bit is whats causing this.  I'll report back shortly with
some more results.

On Fri, 19 Jan 2001, Jay Weber wrote:

> Date: Fri, 19 Jan 2001 07:56:26 -0800 (PST)
> From: Jay Weber <jweber at valinux.com>
> Reply-To: linux-lvm at sistina.com
> To: linux-lvm at sistina.com
> Subject: [linux-lvm] Kernel panic while snapshotting.
>
> Hi,
>
> I just got a kernel panic while snapshotting with 0.9.1beta2.  I wonder if
> anybody has seen any similar issues or I possibly fubar'd the patch on my
> end?
>
> Panic was:
>
> 	Kernel panic: brw_kiovec: iobuf not locked for I/O
>
> This occured while simultanously copying 20 tarballs back and forth
> between two dirs on the source volume and performing a snapshot at that
> time.  It appears to have hung my lvcreate (snapshot) command shell.
> Oh, this was also using loop device for the source volume on my laptop in
> this case.  Hmm, actually could this panic be related to the following
> change in lvm.c?  It did work prior in 0.9.1beta1.
>
> @@ -492,7 +488,7 @@
>                 goto out;
>
>         err = -ENOMEM;
> -       iobuf->locked = 1;
> +       iobuf->locked = 0;
>         iobuf->nr_pages = 0;
>         for (i = 0; i < nr_pages; i++)
>         {
>
>
> I haven't seen this one before myself, but in testing on our bigger scsi
> based boxes in the back while snapshots are active and heavy IO is
> performed on the source volume, the box tends to hang.  I gather this is
> related to having to journal all source volume changes to the snapshot and
> when you throw massive IO at it, things get slow. Any thoughts on this one
> as well?
>
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