linux-ext4 - Re: Random corruption test for e2fsck

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Date:	Wed, 11 Jul 2007 12:33:06 +0530
From:	Kalpak Shah <kalpak@...sterfs.com>
To:	Theodore Tso <tytso@....edu>
Cc:	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: Random corruption test for e2fsck

On Tue, 2007-07-10 at 10:58 -0400, Theodore Tso wrote:
> On Tue, Jul 10, 2007 at 06:37:40PM +0530, Kalpak Shah wrote:
> > Hi,
> > 
> > This is a random corruption test which can be included in the e2fsprogs
> > regression tests. 
> > 1) Create an test fs and format it with ext2/3/4 and random selection of
> > features.
> > 2) Mount it and copy data into it.
> 
> This requires root privileges in order to mount the loop filesystem.
> Any chance you could change it to use debugfs to populate the
> filesystem, so we don't need root privs in order to mount it.
> 
> This will increase the number of people that will actually run the
> test, and more importantly not encourage people from running "make
> check" as root.

That is a good idea. With this script, the mount would just fail without
root privileges and the test would be done on an empty filesystem. I
will make this change and post it.


> > 3) Move around the blocks of the filesystem randomly causing corruption.
> > Also overwrite some random blocks with garbage from /dev/urandom. Create
> > a copy of this corrupted filesystem.
> >
> > 4) Unmount and run e2fsck. If the first run of e2fsck produces any
> > errors like uncorrected errors, library error, segfault, usage error,
> > etc. then it is deemed a bug. But in any case, a second run of e2fsck is
> > done to check if it renders the filesystem clean. 
> 
> Err, you do unmount the filesystem first before you start corrupting
> it, right?  (Checking script; sure looks like it.)
> 

Yes, the filesystem is unmounted before the corruption begins.

> > 5) If the test went by without any errors the test image is deleted and
> > in case of any errors the user is notified that the log of this test run
> > should be mailed to linux-ext4@ and the image should be preserved.
> 
> I certainly like the general concept!!
> 
> I wonder if the code to create a random filesystem and corrupting it
> should be kept as separate shell script, since it can be reused in
> another of interesting ways.  One thought would be to write a test
> script that mounts corrupted filesystems using UML and then does some
> exercises on it (tar cvf on the filesyste, random renames on the
> filesystem, rm -rf of all of the contents of the filesystems), to see
> whether we can provoke a kernel oops.

Well, there is a MOUNT_AFTER_CORRUPTION option in the script which can
be enhanced to do this.

Thanks,
Kalpak.

> Regards,
> 
> 							- Ted
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