On Wed, Nov 23, 2016 at 03:22:04PM -0500, Ewan Milne wrote:
[...]
> ---
>
> In other words, this commit made the bad behavior go away in 4.8.
> Need to look at this in more detail, it doesn't appear as if this patch
> was intended to fix such a problem.
>
> -Ewan
Are you sure it did? I can repropduce copy_to_user() errors with 4.8 as well.
Using the very same reproducer. On 4.8 it's just harder to trigger and
doesn't trigger on AHCI as fas as I can telli (maybe I just haven't hit
it hard enough). I can trigger it on QEMUs SCSI CDROM emulation and hpsa
though. I cannot however trigger this with a minimal config inside an initrd.
Here's my test:
--- 8< ---
#!/bin/sh
cleanup()
{
rm -f expect.txt
rm -f test.txt
}
trap cleanup EXIT INT
./sg_mmap_read -d /dev/sg0 -l 0 | od -x > expect.txt
for i in $(seq 1 5000); do
./sg_mmap_read -d /dev/sg0 -l 0 | od -x > test.txt
diff expect.txt test.txt > /dev/null
if [ $? -ne 0 ]; then
echo "FAIL"
exit 1
fi
done
echo "PASS"
--- >8 ---
I added some trace_printk()s to sg.c and try to hunt it down. It'll be good to
know if anyone of you can reproduce it with the above script as well.
Byte,
Johannes
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Johannes Thumshirn Storage
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