Re: Write to the degraded raid5 will trigger the call trace dump when skip_copy is enabled

On Fri, Apr 29, 2016 at 06:54:10PM +0800, Joey Liao wrote:

Hi all,

For improving the I/O performance, we try to enable the raid 5
skip_copy feature by default. It indeed has some benefit, however, it
will always (not a random issue) dump the following call trace
repeatedly when we try to write the raid 5 block device. It is related
to the following codes in handle_stripe_clean_event() in raid5.c.

WARN_ON(test_bit(R5_SkipCopy, &dev->flags));
WARN_ON(dev->page != dev->orig_page);

Is it a known bug for skip_copy feature?
Does it do harm to the data integrity?
If we would like to prevent this call trace, for your suggestion how
should we do to modify the source code?

Looks the two WARN_ON should be deleted. if the dev has R5_LOCKED, it's legit
the dev has SkipCopy set and page != orig_page. I'll delete the code. This will
not harm to data integrity.

Thanks,
Shaohua