linux-kernel - Re: frag.sh

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <Zyi8Z7upAZf1sbMN@dread.disaster.area>
Date: Mon, 4 Nov 2024 23:21:59 +1100
From: Dave Chinner <david@...morbit.com>
To: zhangshida <starzhangzsd@...il.com>
Cc: dchinner@...hat.com, djwong@...nel.org, leo.lilong@...wei.com,
	linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
	osandov@...com, wozizhi@...wei.com, xiang@...nel.org,
	zhangjiachen.jaycee@...edance.com, zhangshida@...inos.cn
Subject: Re: frag.sh

On Mon, Nov 04, 2024 at 02:52:14PM +0800, zhangshida wrote:
> From: Shida Zhang <zhangshida@...inos.cn>
> 
> #usage: ./frag.sh $dev $dir $size_k $filename 
> #!/bin/bash
.....
> # Create a big file with allocated space
> xfs_io -f -c "falloc 0 $((TOTAL_SIZE))k" $FILE
> 
> # Calculate total number of punches needed
> NUM_PUNCHES=$(( TOTAL_SIZE / (CHUNK_SIZE * 2) ))
> 
> last_percentage=-1
> # Punch holes alternately to create fragmentation
> for ((i=0; i<NUM_PUNCHES; i++)); do
>     OFFSET=$(( i * CHUNK_SIZE * 2 * 1024 ))
>     xfs_io -c "fpunch $OFFSET ${CHUNK_SIZE}k" $FILE
>     
>     # Calculate current percentage and print if changed
>     PERCENTAGE=$(( (i + 1) * 100 / NUM_PUNCHES ))
>     if [ "$PERCENTAGE" -ne "$last_percentage" ]; then
>         #echo "Processing...${PERCENTAGE}%"
>         last_percentage=$PERCENTAGE
>     fi
> done

Yup, that re-invents fstests::src/punch-alternating.c pretty much
exactly.

The fact that there is a production workload that is generating this
exact operational pattern and running it to ENOSPC repeatedly is
horrifying....

-Dave.
-- 
Dave Chinner
david@...morbit.com