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Date:   Sat, 6 Jul 2019 00:02:21 -0400
From:   "Theodore Ts'o" <tytso@mit.edu>
To:     James Bottomley <James.Bottomley@HansenPartnership.com>
Cc:     Matthew Wilcox <willy@infradead.org>, linux-ext4@vger.kernel.org,
        linux-fsdevel@vger.kernel.org,
        Parisc List <linux-parisc@vger.kernel.org>
Subject: Re: Question about ext4 testing: need to produce a high depth extent
 tree to verify mapping code
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On Fri, Jul 05, 2019 at 11:49:02AM -0700, James Bottomley wrote:
> > Create a series of 4kB files numbered sequentially, each 4kB in size
> > until you fill the partition.  Delete the even numbered ones.  Create
> > a 20MB file.
> 
> Well, I know *how* to do it ... I was just hoping, in the interests of
> creative laziness, that someone else had produced a script for this
> before I had to ... particularly one which leaves more randomized gaps.

You mean something like this?  It doesn't do randomized gaps, since
usually I'm trying to stress test block allocations.

#!/bin/bash

DEV=/dev/lambda/scratch
SIZE=10M

mke2fs -Fq -t ext4 -i 4096 -b 4096 $DEV $SIZE
max=$(dumpe2fs -h $DEV 2>/dev/null | awk -F: '/^Free blocks:/{print $2}')
mount $DEV /mnt
cd /mnt
mkdir -p d{0,1,2,3,4,5,6,7,8,9}/{0,1,2,3,4,5,6,7,8,9}
seq 1 $max | sed -E -e 's;^([[:digit:]])([[:digit:]])([[:digit:]]);d\1/\2/\3;' > /tmp/files$$
cat /tmp/files$$ | xargs -n 1 fallocate -l 4096 2>/dev/null
sed -ne 'p;n' < /tmp/files$$ | xargs rm -f
cd /
umount $DEV
rm /tmp/files$$