On Wed, Mar 02, 2022 at 03:33:35PM -0800, Bart Van Assche wrote:

Thanks for having published a merge of block-for-next and the branch with 
this patch series. That makes it easy for me to replicate your kernel tree. 
I can reproduce the null-ptr-deref with the freeze-for-next branch but not 
with Jens' block-for-next branch (commit e70f36e84f9b ("Merge branch 
'for-5.18/block' into for-next")). This is what appears in the kernel log 
on my test setup for the freeze-for-next branch (commit acac349e5516 
("block: move rq_qos_exit() into disk_release()"):

BUG: KASAN: null-ptr-deref in __blk_account_io_start+0x28/0xa0

Maybe we are using different kernel configurations? I'm using 
CONFIG_NVME_MULTIPATH=n. I guess that you are using 
CONFIG_NVME_MULTIPATH=y?

Your testcases errors out when CONFIG_NVME_MULTIPATH=y is set, and
also requires various things to be built modular which wasted a lot
of my time yesterday trying to get that test to run.  My .config
is below.  Maybe you can try to figure out what derefernce causes
the null-ptr-deref, and what kind of command causes this?  Also
I suspect this is the first patch in the series, so it would be
great to verify the problem with just that.