[PATCH] maple_tree: Fix potential NULL pointer dereference if mas_pop_node() fails

[Liam R. Howlett]

* Matthew Wilcox <willy at infradead.org> [251019 16:14]:
> On Sun, Oct 19, 2025 at 07:49:16PM +0800, Huiwen He wrote:
...

> 
> Do not send a v2 until somebody has a substantive comment.  I suspect
> that what you are doing here is wrong, but I lack the understanding to
> explain why it is wrong.

Thanks Matthew.

This is not necessary.

At this point we ALWAYS have enough allocations.

I'm guessing you saw the WARN_ON() and return of NULL and assumed we'd
need to check the return in caller.  This WARN_ON() is in place in case
the calculations are incorrect in some corner case (which has never
happened in mainline), so this will add extra instructions for a
significant amount of calls, especially the mas_wr_node_store() path,
with no chance of catching an error.

In fact, the only time I've seen the tree fail to allocate enough memory
is when syzbot fails allocations - and that will happen in the
preallocation stage, which does check the return.

So, thanks for looking but this patch is unnecessary.

Thanks,
Liam