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Re: xfs_logprint segfault with external log

To: Alexander Tsvetkov <alexander.tsvetkov@xxxxxxxxxx>
Subject: Re: xfs_logprint segfault with external log
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 17 Feb 2015 12:38:49 +1100
Cc: Eric Sandee <sandeen@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <54E1F6C2.4060105@xxxxxxxxxx>
References: <54DB5E70.80607@xxxxxxxxxx> <20150211205406.GT4251@dastard> <54DC940D.4030009@xxxxxxxxxx> <20150212230940.GD12722@dastard> <54E1F6C2.4060105@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, Feb 16, 2015 at 04:55:14PM +0300, Alexander Tsvetkov wrote:
> 
> On 02/13/2015 02:09 AM, Dave Chinner wrote:
> >On Thu, Feb 12, 2015 at 02:52:45PM +0300, Alexander Tsvetkov wrote:
> >>On 02/11/2015 11:54 PM, Dave Chinner wrote:
> >>>On Wed, Feb 11, 2015 at 04:51:44PM +0300, Alexander Tsvetkov wrote:
> >>>>Hello,
> >>>>
> >>>>I've obtained corrupted xfs log after some sanity xfs testing:
> >>>>
> >>>>"log=logfile
> >>>>log_size=855
> >>>>
> >>>>dd if=/dev/zero "of=$log" bs=4096 count=$log_size
> >>>>loopdev=$(losetup -f)
> >>>>losetup $loopdev $log
> >>>>
> >>>>mkfs.xfs -f -m crc=1 -llogdev=$loopdev,size=${log_size}b $SCRATCH_DEV
> >>>>mount -t xfs -ologdev=$loopdev $SCRATCH_DEV $SCRATCH_MNT
> >>>>./fdtree.sh  -l 4 -d 4 -C -o $SCRATCH_MNT
> >>>>sync
> >>>>umount $SCRATCH_MNT
> >>>>
> >>>>xfs_logprint -l $loopdev $SCRATCH_DEV"
> >>>>
> >>>>Test makes crc enabled xfs filesystem with the external log of
> >>>>minimal allowed size and then creates on this fs the small directory
> >>>>tree
> >>>>with sub directories and files of fixed depth and size with help of
> >>>>fdtree utility:
> >>>>https://computing.llnl.gov/?set=code&page=sio_downloads
> >>>Just take metadump image and put it somewhere we can down load it.
> >>>
> >>>>After that xfs_logprint stably reports bad data in log:
> >Please try the patch below, it fixes the problem on the image you
> >provided.
> 
> I've restored provided image to filesystem with the same log file,
> applied patch to latest xfsprogs and have stable pass runs
> of xfs_logprint on that filesystem and running with xfsprogs without
> this patch results to xfs_logprint segfaults reported that means
> patch is working.

Good.

> The problem that it is not working for repeated test runs where
> xfs_logprint still continue to report bad log data. It seems it is

xfs_logprint is not a tool that is intended for validation of the
log contents. It's a triage tool that was written in a hurry, and as
such it's neither reliable or maintainable.  Indeed, there's a
comment in the code saying it really needs to be rewritten. ;)

I'll have a look the image, but really spending lots of time on
fixing minor issues with logprint really isn't the best use of my
time right now...

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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