[dm-devel] [lvm-devel] kernel BUG at drivers/md/persistent-data/dm-space-map-disk.c:178

[Joe Thornber]

On Sat, Dec 28, 2019 at 02:13:07AM +0000, Eric Wheeler wrote:
> On Fri, 27 Dec 2019, Eric Wheeler wrote:

> > Just hit the bug again without mq-scsi (scsi_mod.use_blk_mq=n), all other 
> > times MQ has been turned on. 
> > 
> > I'm trying the -ENOSPC hack which will flag the pool as being out of space 
> > so I can recover more gracefully than a BUG_ON. Here's a first-draft 
> > patch, maybe the spinlock will even prevent the issue.
> > 
> > Compile tested, I'll try on a real system tomorrow.
> > 
> > Comments welcome:

Both sm_ll_find_free_block() and sm_ll_inc() can trigger synchronous IO.  So you
absolutely cannot use a spin lock.

dm_pool_alloc_data_block() holds a big rw semaphore which should prevent anything
else trying to allocate at the same time.

- Joe