[PATCH 4/4] rhashtable: fix vmalloc() deadlock in atomic rehash

[Uladzislau Rezki]

> On Thu, Oct 29, 2026 at 10:53:56AM -0400, Liam R. Howlett (Google) wrote:
> >
> > Given where we are in the release, this fixes a real issue that can
> > happen so maybe we take this now and settle the general handling later?
> 
> There is no rush at all since the bug that you found has existed
> since 2025:
> 
> commit c6307674ed82c0c57d6e1e3408e84ac449ab8e94
> Author: Uladzislau Rezki (Sony) <urezki at gmail.com>
> Date:   Tue Oct 7 14:20:35 2025 +0200
> 
>     mm: kvmalloc: add non-blocking support for vmalloc
> 
> Let's take the time to fix this properly.
> 
The problem with spin_lock_irqsave() is that vmalloc() path can take
time to alloc and map pages. I am not sure this is worth to switch to
irq-save locking primitive. So this is the "heaviest" allocator in the
kernel. Callers have to be careful how the call vmalloc().

IMO, this caller has to be fixed.

--
Uladzislau Rezki