* David Howells <dhowells@xxxxxxxxxx> [240319 14:09]:
> Hi Liam,
>
> I managed to trigger a bug in the maple-tree. I don't know that it's
> definitely your bug as I had a process stuck in the D state, but I don't
> believe it was doing anything that modified maple trees at the time, just
> waiting for PG_writeback on a folio. Anyway, I was running the generic/130
> xfstest and pressed ctrl-C and got a bunch of oopses (see attached).
>
> Unfortunately, I can't do anything to try and get more information as anything
> that tries to clone() gets another oops.
>
> The RIP is mas_alloc_nodes+0x55/0x16e:
>
> mas_set_alloc_req(mas, 0);
> if (mas->mas_flags & MA_STATE_PREALLOC) {
> if (allocated)
> return;
> BUG_ON(!allocated); <------- 1237
> WARN_ON(!allocated);
> }
>
> The base kernel is at commit bf3a69c6861f plus some of my patches, none of
> which alter the maple-tree code or MM code.
>
How can we be stuck in D state on a BUG_ON()?
If this is a maple tree bug, then it's in the calculations done for
preallocation. The last time that changed was in December in commit
4249f13c11be8b8b7bf93204185e150c3bdc968d. Could you try reverting this
change?
>From the trace, this is failing on loading a binary. Could you please
try changing BUG_ON() to MAS_BUG_ON(mas, !allocated) to get more
information?
I ran generic/130 here and it worked in my testing. Does this happen
without your patches? Maybe the changes you make are causing something
to happen more frequently?
Thanks,
Liam
