Re: zeroes read back more often than appended

[Pat LaVarre <p.lavarre@ieee.org>]

// To recap now, next game suggested is:

CONFIG_DEBUG_KERNEL=y
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_SLAB=y
CONFIG_MAGIC_SYSRQ=y

gdb /usr/src/linux/vmlinux /proc/kcore

// We're motivated to play because when we try
// appending nonzero to files, then we see:

"Two files with mkudffs, reads zeroes from both files ouch."

"One file with mkudffs, ok" if and only if CONFIG_SMP = CONFIG_PREEMPT =
off.

"Two files with mkfs in place of mkudffs, ok."

// To reproduce these results involves such
// steps as the following.
//
// Reliably reproducing this trouble as yet
// requires whole minutes of real time from a PC
// that can rebuild the defconfig kernel in
// about six minutes.

http://sourceforge.net/projects/linux-udf/
ftp://members.aol.com/plscsi/linux/udftools-cvs.2003-11-26.tar.gz

mkdir /mnt/loop0
ln -s /sbin/losetup ~/bin
ln -s $PWD/mkudffs ~/bin

cd ~/bin
patch <http://marc.theaimsgroup.com/?l=linux-fsdevel&m=106675517702950
rm tty.txt
gcc -o whd -Wall whd.c

date; time fswhd 767 1 mkudffs 0xFF 0x10 0x2

date; time fswhd 0 768 mkudffs 0xFF600 0xC8 0x2
date; time fswhd 0 768 mkudffs 0xFF600 0xC8 0x1

//

Pat LaVarre